INTRODUCTION

Imaging of spinal canal tumors and tumor-like masses has been revolutionized by the advent of magnetic resonance imaging (MRI), which is a sensitive modality for the identification and characterization of spinal lesions. Radiologic evaluation of these lesions focuses on localizing lesions into extradural, intradural extramedullary, and intramedullary compartments. Although this approach is somewhat artificial, because many lesions transgress compartments or can be found in different compartments, it is very useful for generating an appropriate differential diagnosis for a spinal mass (Table 10-1). Clinical information (in particular patient age) is helpful to further narrow and order the differential diagnosis of spinal lesions. This chapter begins with a brief discussion of imaging techniques used in evaluating spinal masses. This is followed by a discussion of imaging characteristics of the most common lesions that occur in each of the aforementioned categories, including a description of tumors, tumor-like cysts, and non-neoplastic tumor mimics. A discussion of spinal vascular malformations is beyond the scope of this chapter.

Table 10-1 Classification of Spinal Canal Tumors and Tumor-Like Masses

MS, multiple sclerosis; OPLL, ossification of the posterior longitudinal ligament

IMAGING MODALITIES

Radiographs, computed tomography (CT), CT myelography, MRI, and angiography are the modalities available for assessment of spinal canal lesions. Radiographs can be a useful screening test but are limited, demonstrating mainly the secondary effects of spinal lesions on the adjacent bony and paraspinal soft tissues. Expansion of the central canal, bony destruction and/or remodeling (including vertebral body scalloping and neural foraminal widening), thickening of the paraspinal soft tissues, and associated scoliosis are some of the findings that may be seen in the setting of an intraspinal lesion. A normal radiograph does not exclude the presence of an underlying spinal mass. CT demonstrates bony and soft tissue changes with a greater degree of conspicuity, but the intraspinal lesion itself may be subtle or impossible to detect. CT myelography, a technique whereby myelographic contrast is introduced directly into the thecal sac followed by CT imaging, increases sensitivity for detection of intraspinal disease over conventional CT. However, it is still less effective than MRI for assessing intramedullary and extradural disease, and, although equally sensitive to contrast-enhanced MRI for detection of intradural extramedullary spinal masses, it is more invasive.^1–3 CT myelography, therefore, typically is reserved for patients who have contraindications for MRI and sometimes for those with spinal hardware that causes excessive artifact on MRI. CT myelography demonstrates expansion of the cord or mass effect on the cord by spinal lesions but is limited in its ability to characterize the underlying lesion and may be insensitive for intramedullary lesions that have only minimal mass effect. Occasionally, CT myelography is a useful adjunct to MRI for cystic lesions within the spinal canal, where it is used to assess for communication with the cerebrospinal fluid (CSF) space.^4,5 In patients without contraindications, MRI is undoubtedly the modality of choice for evaluation of spinal canal lesions. It is the most sensitive and specific modality for both identifying and characterizing intraspinal lesions. Spinal angiography is reserved for vascular lesions, providing important information for preoperative planning and guiding endovascular treatment.

MRI of the spine involves greater technical challenges than imaging of the brain. The presence of bone housing the spinal canal creates large susceptibility gradients. The small size of the spinal canal and spinal cord limits spatial resolution. In addition, CSF pulsation introduces motion artifacts. MR techniques used in screening for spinal lesions include at least a T1- and T2-weighted sequence. Addition of a gradient echo (GRE) sequence is useful to evaluate for blood products. Intravenous gadolinium improves detection of intradural extramedullary disease and helps to characterize and delineate intramedullary lesions.^3,6 Evaluation in both the sagittal and transverse planes is important to confirm true findings and exclude artifacts. The role of these standard sequences in evaluating spinal masses is described in Table 10-2. Examples of the normal appearance of the spine when imaged with these standard sequences are shown in Figs. 10-1 to 10-3.

Table 10-2 Standard MRI Sequences for the Evaluation of Spinal Tumors

CSF, cerebrospinal fluid.

Fig. 10-1 Normal appearance of the cervical spine with MRI in a 25-year-old woman. A, Sagittal T1WI. The spinal cord is isointense to muscle. CSF is hypointense. B, Sagittal T2WI. The CSF is hyperintense. Apparent linear high signal within the anterior spinal cord is caused by truncation (Gibb’s) artifact. C, Axial GRE image. Susceptibility effects are accentuated with this sequence. However, CSF motion artifact is reduced.

Fig. 10-2 Normal appearance of the thoracic spinal canal in a 24-year-old woman. A, Sagittal T1WI. The spinal cord is intermediate signal intensity (isointense to muscle). CSF is dark on this sequence. Mild endplate irregularity is seen within a lower thoracic vertebral body, consistent with Schmorl’s type changes. B, Sagittal T2-weighted fast spin echo (FSE) image. CSF is bright on this sequence. Areas of reduced signal are seen within the CSF space posterior to the spinal cord in the upper thoracic region as a result of CSF flow artifact. C, Sagittal short tau inversion recovery (STIR) image. This is a fat suppressed T2-weighted sequence. CSF flow artifact is seen on this image, similar to that in B. D, Axial T2-weighted FSE image. The distinction between the intramedullary, intradural extramedullary, and extradural spaces is often best appreciated in the axial plane.

Fig. 10-3 Normal appearance of the thoracic spine in a 42-year-old woman. A, Sagittal T1WI. The bright epidural fat is more prominent than in the previous example. B, Sagittal T2-weighted FSE image. CSF flow artifact is prominent in this case, causing reduced signal within the intradural space. C, Sagittal post-gadolinium T1-weighted fat saturated image. A small amount of normal linear vascular enhancement is present. D, Axial T2-weighted FSE image. CSF flow artifact is much worse in this case than in the prior example. The CSF space appears almost isointense to the cord on this image, making intradural lesions difficult to detect. E, Axial post-gadolinium T1-weighted fat saturated image.

Some newer pulse sequences have been investigated for use in spinal imaging with variable results. These include fluid-attenuation inversion recovery (FLAIR), short tau inversion recovery (STIR), diffusion weighted imaging (DWI), diffusion tensor imaging (DTI), and MR spectroscopy (MRS) (Table 10-3). FLAIR is a heavily T2-weighted sequence that nulls signal from CSF and thus may increase conspicuity of hyperintense lesions in close proximity to CSF. Despite its utility in brain imaging, FLAIR has been less successful in the spine and has shown to be less sensitive than standard T2-weighted sequences in assessment of cord lesions.^7–10 STIR (a fat suppressed T2-weighted sequence) is commonly used to assess for vertebral body involvement in the setting of trauma or infection but also may have useful application in detecting intramedullary disease. Several studies have demonstrated increased sensitivity of STIR for cord disease in multiple sclerosis (MS) relative to other T2-weighted sequences.^10,11 However, STIR is limited by reduced signal to noise ratio and greater sensitivity to motion than standard T2-weighted sequences.⁸ DWI is an MR technique that is sensitive to the random motion of water molecules in tissues over microscopic distances (5–20 microns) and can generate a map of the average apparent diffusion coefficient (ADC). Reduced ADC is seen in acute cerebral stroke and aids early detection of infarcts, improving accuracy over conventional MRI.¹² DWI also has become an invaluable technique for assessing other intracranial diseases, including applications in infection, tumors, and cysts. DWI in the spinal cord and spinal canal has been more difficult to implement than in the brain because of technical factors, in particular susceptibility from the vertebrae and limited spatial resolution. Although DWI is not currently routinely used for spinal cord imaging at most institutions, DWI techniques have been developed that are practical for use in the clinical setting.^13,14 DTI, an application of DWI that measures diffusion anisotropy and thus can be used to trace white matter tracts within the brain and spinal cord using statistical methods, is of great interest in spinal cord tumor imaging. DTI demonstrates a high degree of anisotropy in the normal spinal cord, which is disrupted by spinal cord tumors, a feature that may be helpful to depict the full extent of spinal cord lesions more accurately than conventional imaging and perhaps eventually map out involvement of key spinal cord white matter tracts.^15,16 MRS is a technique that can obtain biochemical information about tissues being studied by creating a spectrum of metabolites within a region of interest. Currently, a number of technical factors preclude use of MRS in the spine, but future advances may make this technique both possible and useful in spinal cord imaging.⁸

Table 10-3 Potential Sequences for Evaluation of Spinal Tumors

MS, multiple sclerosis.

EXTRADURAL LESIONS

Extradural lesions, which by definition are outside of the dura, usually arise from the osseous spinal structures, intervertebral discs, and surrounding soft tissues (including vessels, nerves, fat, and paraspinal muscles). These lesions cause focal displacement of the thecal sac and its contents away from the mass. Radiographs may demonstrate secondary effects of the lesion on the bony structures, including bone destruction or scalloping, expansion of the central spinal canal, and paraspinal extension. CT myelography shows extrinsic compression of the thecal sac and decrease in the ipsilateral CSF space. MRI shows the dura draped over the mass and may show an epidural fat cap (Box 10-1).¹⁷ The most common epidural masses are degenerative, including disc protrusions, osteophytes, and synovial cysts. Infection and hematomas may present as epidural masses. Of neoplastic lesions, metastases to bone with extradural extension are the most common.^17,18 Imaging of lesions of the vertebrae (with and without epidural extension) was discussed in the previous chapter. Here we discuss epidural lesions that were not previously mentioned.

EPIDURAL LIPOMATOSIS

This is a rare condition manifested by excessive deposition of unencapsulated fat in the epidural space, resulting in cord and cauda equina compression with neurologic symptoms. Most cases are seen in association with long-term exogenous steroid use or conditions in which there is elevated endogenous production of steroid (such as in Cushing’s disease). Cases may occur as a result of morbid obesity or with no cause evident.¹⁹ In approximately 60% of cases, involvement of the mid to lower thoracic spine is seen with fat predominantly posterior to the cord. The remaining 40% of cases involve mainly the lower lumbar region with fat surrounding the circumference of the thecal sac (Box 10-2). A combination of thoracic and lumbar involvement is sometimes seen.²⁰ CT and MR demonstrate increased epidural fat and diminished subarachnoid space, with tapering of the thecal sac and a Y-shaped configuration seen in the transverse plane (Fig. 10-4).^21,22 Epidural lipomatosis does not enhance nor does it cause bony erosion.^17,20 Fat suppression is helpful on MRI to confirm the presence of adipose tissue (Box 10-2).

Box 10-2 Epidural Lipomatosis

• Rare condition of excessive deposition of unencapsulated fat in epidural space

• Associated with exogenous or endogenous hypercortisolemia

• Typically a result of chronic steroid use

• May occur in morbid obesity or with no etiology evident

• 60% thoracic, 40% lumbar

• CT and MR demonstrate increased epidural fat and diminished subarachnoid space

• Y configuration of thecal sac, tapering of thecal sac, crowding of nerve roots

Fig. 10-4 Epidural lipomatosis within the lumbar spine. A, Sagittal T1WI. Prominent epidural fat is seen anterior and posterior to the thecal sac, extending from the L3–4 level to the sacrum. Note the accentuated tapering of the thecal sac. B, Axial T1WI at the L4–5 level. Note the Y configuration of the thecal sac.

EPIDURAL HEMATOMA

Extravasation of blood into the epidural compartment of the spine may be caused by trauma or instrumentation but also can occur spontaneously, especially in the setting of anticoagulation or coagulopathy (Box 10-4). An epidural hematoma is rarely the sequelae of hemorrhage from a spinal vascular malformation.^27,28 MR and CT myelography demonstrate an elongated, often multisegment, extra-axial mass encasing or displacing the thecal sac.²⁰ MRI signal characteristics depend on the age of blood products and are usually heterogeneous. Hyperintensity on T1WI, heterogeneity with foci of low signal on T2WI, and susceptibility demonstrated with GRE are helpful features in making the diagnosis (Fig. 10-5).^29,30 Enhancement may be seen, especially along the margins of an epidural hematoma (Box 10-4).^20,30

Box 10-4 Epidural Hematoma

• May be spontaneous as a result of anticoagulation/coagulopathy or instrumentation

• Rarely caused by a vascular malformation

• Long-segment extra-axial mass encasing or displacing cord or cauda equina

• MRI characteristics depend on age of blood products: isointense, hypointense, or hyperintense on T1WI; heterogeneous on T2WI; susceptibility on GRE

• Enhancement along margins of collections

Fig. 10-5 A 58-year-old man who presented with a spontaneous epidural hematoma. A, Sagittal T1WI of the cervical spine. A mildly hyperintense epidural mass is seen extending from C4 to C6 posterior to the spinal cord and compressing it anteriorly. B, Sagittal STIR image. The mass is hyperintense (similar to CSF). The dark, thin dura is displaced anteriorly by the hematoma. C, Sagittal GRE image. Susceptibility from the blood products gives rise to low signal within and around the hematoma that makes it more conspicuous. D, Axial T1WI at the C5 level. The hematoma is seen within the right posterior epidural space. E, Axial GRE image at the C5 level. The margins of the lesion are defined by a thin dark line (as a result of susceptibility from blood products).

EPIDURAL ABSCESS

Epidural spinal infection with abscess formation usually results from hematogenous spread of disease primarily to the intervertebral disc, typically from infection of the skin, urinary tract, or respiratory system. Direct spread from paraspinal infection also may occur but is less common. Predisposing factors include diabetes mellitus, trauma, alcoholism, and intravenous drug abuse (Box 10-5). Epidural anesthesia and analgesia also are associated with increased risk. Pyogenic organisms (most often Staphylococcus aureus) are the most common pathogens.^31,32 MRI is the imaging tool of choice and should include the entire spinal axis to exclude multiple sites of involvement.³² The posterior epidural space may be more commonly involved than the anterior, and the abscess can extend over multiple segments.³³ Abscesses are classically isointense to hypointense to the cord on T1WI, hyperintense on T2WI and STIR images, and demonstrate rim enhancement (Fig. 10-6). Homogeneously or heterogeneously enhancing phlegmon may often be seen in some infections without frank abscess formation (Figs. 10-7 and 10-8).³⁴ Associated findings of spondylodiscitis, including vertebral body endplate erosion and disc space narrowing, are helpful in some cases in making the diagnosis. High signal on DWI with reduced ADC has been demonstrated in spinal epidural abscesses and also may be helpful to confirm the diagnosis.³⁵

Box 10-5 Epidural Abscess

• Predisposing factors: Diabetes mellitus, trauma, alcoholism, intravenous drug use, chronic illness, epidural anesthesia or steroid injections, discitis

• Posterior epidural space more common than anterior epidural space

• Multisegmental

• Look for associated findings of spondylodiscitis with adjacent enhancing epidural phlegmon and peripherally enhancing fluid collection

• Abscess is isointense to hypointense to cord on T1WI, hyperintense on T2WI and STIR, hyperintense on DWI, dark on ADC, and peripherally enhances

Fig. 10-6 A 57-year-old man with a cervical epidural abscess. A, Sagittal T1WI of the cervical spine. An isointense epidural mass/collection is seen posterior to the cord, extending from C4 to T2. B, Sagittal T2WI. The lesion is hyperintense on this sequence. C, Sagittal post-gadolinium T1-weighted fat saturated image. The majority of the lesion enhances with a small, focal, non-enhancing collection at the C6 level. There is no evidence of osseous involvement with osteomyelitis/discitis. D, Axial post-gadolinium T1-weighted fat saturated image at the C6 level. Rim enhancement with central non-enhancing material is consistent with a frank abscess.

Fig. 10-7 A 1-year-old boy who presented with hypotonia and was diagnosed with osteomyelitis/discitis at T12–L1 with a small associated epidural phlegmon. A, Lateral radiograph of the lower spine demonstrates disc space narrowing and endplate irregularity at T12-L1, consistent with osteomyelitis/discitis. B, Anteroposterior radiograph. The findings are more subtle in this projection. C, Sagittal T2-weighted MR image of the lower thoracic and lumbar spine. In addition to disc space narrowing and endplate irregularity, there is high signal within the T12 and L1 vertebral bodies as well as within the intervertebral disc. A small, high signal epidural collection is seen posterior to the T12 and L1 vertebral bodies. D, Sagittal post-gadolinium T1WI. The T12 and L1 vertebral bodies, intervertebral disc, and small epidural phlegmon enhance. A frank rim-enhancing abscess is not seen.

Fig. 10-8 A 20-year-old man with chronic granulomatous disease and atypical infection with Aspergillus, affecting the thoracic and lumbar spine. A, Sagittal T1WI of the thoracic spine. Heterogeneous low signal is seen within the T8 through T10 vertebral bodies without evidence of bony destruction. Sparing of the disc space, as noted here, is seen with atypical infections or neoplasms. Epidural and anterior paraspinal soft tissue is seen at the affected levels with encroachment on the neural foramina. B, Sagittal T1WI lateral to A. The paraspinal component of the mass is demonstrated in this image. C, Sagittal T2WI of the thoracic spine. The affected vertebral bodies are mildly heterogeneous and hyperintense. D, Sagittal post-gadolinium T1-weighted fat saturated image of the thoracic spine. The affected vertebral bodies and the associated paraspinal and epidural phlegmon enhance avidly. E, Sagittal post-gadolinium T1-weighted fat saturated image lateral to D. F, Axial T2WI at the T10 level. The high signal vertebral body and epidural and paraspinal soft tissue are shown. Rib and pleural involvement is also present and is appreciated better in the axial than the sagittal plane. G, Sagittal T1WI of the lumbar spine. Pathological fracture of the L4 vertebral body is present with retropulsion into the spinal canal. A small amount of epidural and paraspinal soft tissue is seen extending above and below the L4 vertebral body. H, Sagittal T2WI of the lumbar spine. High signal is seen extending through the fractured L4 vertebral body. A small amount of high signal also is seen in the L3 vertebral body. I, Sagittal post-gadolinium T1-weighted fat saturated image of the lumbar spine. The affected vertebrae, as well as the epidural and paraspinal involvement, enhance.

SYNOVIAL CYST

Synovial cysts are almost always associated with degenerated facet joints and usually do not present a diagnostic dilemma. The appearance of a round, sharply marginated, posterolateral, extradural cystic mass communicating with the facet joint is characteristic (Fig. 10-9). MRI signal intensity of these lesions varies depending on the protein content and the presence of calcification or hemorrhage (Fig. 10-10). Mild rim enhancement may be seen (Fig. 10-11). These lesions may be difficult to detect on CT unless calcification, intracystic gas, or hemorrhage is present (Box 10-6).^36,37

Fig. 10-9 Synovial cyst at the L4–5 level. A, Sagittal T2WI of the lumbar spine demonstrates a round, well-circumscribed, hyperintense, cystic lesion within the posterior epidural space at the L4–5 level. B, Sagittal T1WI of the lumbar spine. The lesion is slightly higher in signal intensity than the CSF but is subtle and difficult to appreciate on this sequence. C, Sagittal post-gadolinium T1-weighted fat saturated image of the lumbar spine. A thin rim of enhancement is seen surrounding the cyst. D, Axial T2WI at the L4–5 level. The relationship to the adjacent right facet joint is confirmed in the axial plane. There is fluid in both facet joints, and facet hypertrophy is noted, typical of facet degeneration.

Fig. 10-10 A 60-year-old man with prior CT-guided aspiration of a synovial cyst at L4–5 presented for evaluation after his symptoms recurred. A, Sagittal T2WI of the lumbar spine. A uniformly low signal mass is seen within the posterior epidural space at L4–5. B, Axial T2WI confirms that the lesion is adjacent to the right facet joint, consistent with a synovial cyst. The presence of uniform low signal throughout the lesion indicates likely calcification or hemorrhage. C, Axial T1WI. The lesion is isointense to hypointense throughout. D, A CT was performed to assess for the potential of CT-guided aspiration of the synovial cyst. Sagittal CT reconstruction shows that the lesion is heavily calcified and not amenable to aspiration. E, Coronal CT reconstruction. F, Axial CT image at the L4–5 level.

Fig. 10-11 L4–5 synovial cyst that extended outside of spinal canal rather than the more typical epidural location. A, Sagittal T1WI of the lumbar spine. An isointense to hypointense mass is seen in the posterior paraspinal soft tissues posterior to the L4–5 facet joint. Degenerative changes, including disc space narrowing, are present at this level. B, Sagittal T2WI. The lesion is well-circumscribed, hyperintense, and has a thin hypo-intense rim. C, Sagittal STIR. Nulling of signal from fat makes the cyst more conspicuous. D, Sagittal post-gadolinium T1-weighted fat saturated image. A thin rim of enhancement is seen. E, Axial post-gadolinium T1-weighted fat saturated image. Enhancement also is present within the adjacent degenerated facet joint.

Box 10-6 Synovial Cyst

• Posterolateral extradural cystic mass communicating with facet joint

• 90% in lumbar spine, most commonly at L4–5

• Round, sharply marginated

• Difficult to detect with CT unless calcification, hemorrhage, or intracystic gas present

• Mild rim enhancement

• Variable signal characteristics on MR depending on protein content, calcification, hemorrhage

• Almost always associated with facet degeneration

SEQUESTERED DISC FRAGMENT

Protruded disc material may detach and become displaced from the parent disc. The extruded, sequestered disc fragment usually is found in the anterior epidural space but may occasionally migrate posteriorly or through the neural foramen.³⁸ Although peripheral enhancement may be seen, the disc material itself usually does not enhance.^17,38,39 Additional findings of degenerative disc disease are helpful in making the diagnosis (Fig. 10-12).

Fig. 10-12 Disc protrusion with extrusion. A, Sagittal T1WI of the lumbar spine. A posterior disc protrusion is seen at L5–S1 with isointense material extending inferior to the disc space, representing extruded disc material. B, Sagittal T2WI. The dark disc material is more conspicuous against a background of bright CSF. C, Axial/oblique T1WI at the L5–S1 level. The disc material extends down into the left lateral recess. D, Axial T2WI at L5–S1.

EXTRADURAL ARACHNOID CYST

An extradural arachnoid cyst (EAC) is a congenital or acquired CSF-filled outpouching of arachnoid that protrudes through a dural defect (Box 10-7). Most EACs are found in the lower thoracic spine, posterior or posterolateral to the cord.⁵ MRI demonstrates a long-segment extradural mass that follows CSF signal characteristics on all sequences. CT myelography may show communication with the CSF space.^17,40

Box 10-7 Extradural Arachnoid Cyst

• CSF-filled outpouching of arachnoid that protrudes through dural defect

• Congenital or acquired

• Two-thirds are in mid to lower thoracic spine, posterior or posterolateral to thoracic cord; cervical uncommon

• Long-segment CSF–equivalent extradural mass that causes cord compression or myelographic block

• Bony changes caused by mass effect—widened pedicles, scalloping, pedicle erosion

• Differential diagnosis: Traumatic meningocele (usually large extra-spinal component), lateral thoracic meningocele (usually neurofibromatosis type 1), sacral meningocele (Figs. 10-13 to 10-16)

Fig. 10-13 A 9-year-old man who presented with L5 radiculopathy. MRI shows cystic epidural mass that either represents an extradural arachnoid cyst or sacral meningocele. A, Midline sagittal T1WI of the lumbar spine. A well-circumscribed posterior epidural mass is seen within the sacral spinal canal, causing expansion of the bony canal. The mass is isointense to CSF on all imaging sequences. B, Sagittal T1WI to the left of A. C, Midline sagittal T2WI. D, Sagittal T2WI to the left of C. E, Axial T2WI at the S1 level. The cyst is outside the dura and compresses the thecal sac anteriorly and to the right. The bony spinal canal is expanded, indicating a long-standing process. F, Axial T2WI below E. G, Sagittal post-gadolinium T1-weighted fat saturated image. The cyst does not enhance. H, Axial post-gadolinium T1-weighted fat saturated image.

Fig. 10-14 A 62-year-old man who has post-traumatic epidural cyst and tethering of the cord at T5 with focal cord atrophy. The patient had a remote history of trauma. A, Sagittal T1WI of the thoracic spine. A well-circumscribed low signal lesion is seen in the posterior epidural space at T5. The adjacent spinal cord has focal decreased caliber and is tethered posteriorly. B, Sagittal T2WI of the thoracic spine. The lesion is high signal, consistent with a cyst. C, Sagittal post-gadolinium T1-weighted fat saturated image. The cyst does not enhance. D, Axial T2WI at the T5 level shows the cyst and the markedly decreased size of the cord. E, Axial CT myelogram image at the T5 level. The attenuated spinal cord is angulated in configuration and sits right up against the posterior dura. The cyst is present posterior to the dural sac at this level and is higher density than the surrounding epidural fat. F, Sagittal reconstruction of CT myelogram. The cyst is shown to communicate with the CSF space with mild hyperdensity caused by partial filling with myelographic contrast. At the time of trauma a small tear of the dura likely occurred at this level causing this acquired epidural arachnoid cyst and cord tethering with possible cord herniation.

Fig. 10-15 Lateral thoracic meningocele. This single image from a contrast enhanced CT of the chest demonstrates a fluid density lesion extending out from the thoracic spinal canal, causing bony expansion and remodeling consistent with a long-standing lesion. A smooth, thin rim of enhancement is seen.

Fig. 10-16 Patient with neurofibromatosis type 1 (NF-1) and associated dural ectasia and meningoceles. A, Off-midline sagittal T2WI. The T3 to T5 neural foramina are markedly expanded with cystic lesions noted, consistent with meningoceles. B, Posterior vertebral scalloping is noted with a patulous central spinal canal within the upper thoracic spine, consistent with NF-1 and dural ectasia. C, Axial T2WI demonstrates contiguity between the intradural space and the meningocele.

INTRADURAL EXTRAMEDULLARY LESIONS

Intradural extramedullary lesions arise inside the dura but outside of the spinal cord or cauda equina. These lesions tend to displace the spinal cord and enlarge the ipsilateral subarachnoid space with a sharp interface between the undersurface of the mass and the CSF space (Box 10-8). Nerve sheath tumors (schwannomas and neurofibromas) and meningiomas account for the vast majority of intradural lesions. Paragangliomas and CSF-disseminated metastases are relatively rare neoplasms of the intradural space. Tumor-like cysts, including arachnoid cysts, epidermoids, and neurenteric cysts, are non-neoplastic lesions that may be seen in the intradural space and may cause symptoms such as spinal cord or nerve root compression. Lipomas are considered congenital developmental lesions and are associated with a tethered cord but may be an incidental finding and may not present until adulthood.

Box 10-8 Characteristics of Intradural Extramedullary Lesions

• Inside the dura, outside of the spinal cord

• Displace spinal cord

• Enlarge ipsilateral subarachnoid space

• Sharp interface with CSF space—“CSF cap”

SCHWANNOMA

Schwannomas are grossly encapsulated neoplasms of the nerve sheath in the peripheral nervous system that typically arise from the dorsal sensory root. They account for approximately 30% of all spinal tumors and 70% of intraspinal tumors and occur with fairly uniform distribution throughout the spine.¹⁸ Most lesions are sporadic with peak incidence between 30–60 years of age (Box 10-9). Lesions are usually solitary unless associated with an underlying genetic condition such as neurofibromatosis type 2 (NF-2), schwannomatosis, or Carney syndrome.²⁰ Lesions are generally benign, although malignant degeneration may occur.⁴¹ Classically, schwannomas are well-circumscribed, lobulated or dumbbell shaped, enhancing spinal masses that often show cystic degeneration and/or hemorrhage. Approximately 70–75% of lesions are intradural, 15% are completely extradural, and 15% are a combination of intradural and extradural.¹⁷ Intradmedullary schwannomas have been reported but are rare (<1%).^42,43 On CT, lesions are usually isodense to the spinal cord with lower density cystic changes, adjacent bony remodeling (enlarged neural foramen and expanded canal), and either peripheral or solid enhancement.^20,44 Calcification is rare. On MRI, lesions are typically isointense to the cord on T1WI, with the exception of rare melanotic schwannomas, which are hyperintense.^45,46 Most lesions are bright on T2WI, with some lesions demonstrating a “target” appearance with a bright rim and dark center. Enhancement is usually intense and may be homogeneous, heterogeneous, or peripheral (Figs. 10-17 to 10-19).^41,44,45,47 Melanotic schwannomas are a rare variant of schwannomas composed of melanin-producing cells with features of Schwann cells. These lesions have an increased incidence of local recurrence after resection as well as an increased likelihood of metastasis compared with typical schwannomas and require careful long-term follow-up. Melanotic schwannomas also may be challenging to differentiate from malignant melanoma, which has a much worse prognosis.⁴⁸

Box 10-9 Schwannoma

• Slow-growing neoplasm of the nerve sheath in the peripheral nervous system; rarely may undergo malignant degeneration

• Accounts for 70% of intraspinal tumors, 30% of all spinal tumors

• Peak age 30–60 years, male to female ratio even

• 70–75% intradural extramedullary, 15% completely extradural, 15% dumbbell—both intradural and extradural, rarely intramedullary (<1%)

• CT: Sharply marginated lesion, isodense to cord, adjacent bony remodeling

• MRI: Isointense to cord on T1WI (except for melanotic schwannoma), 75% hyperintense on T2WI, 40% cystic change, 10% hemorrhage; occasional target sign—high intensity rim, low intensity center

• Intense enhancement: Uniform, heterogeneous, or peripheral

• Variable vascularity demonstrated with angiography

• All spinal nerve root tumors are neurofibromas in NF-1, schwannomas or mixed tumors in NF-2

• Differential diagnosis: Neurofibroma, meningioma, myxopapillary ependymoma

Fig. 10-17 A 44-year-old with C1 schwannoma. A, Sagittal T2WI of the cervical spine. Expansion of the C1–2 neural foramen is caused by a well-circumscribed, round, hyperintense mass. B, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances avidly and uniformly. C, Axial post-gadolinium T1-weighted fat saturated image at the C1–2 level. The upper cervical cord is displaced to the right by the enhancing mass, which causes bony remodeling and extends out of the neural foramen.

Fig. 10-18 A 32-year-old woman with L5 schwannoma. A, Sagittal T1WI of the lumbar spine. A large, lobulated, well-circumscribed soft tissue intensity mass is seen at the L5–S1 level. The mass causes bony remodeling with scalloping of the posterior aspect of the L5 vertebral body and expansion of the L5–S1 neural foramen. B, Sagittal T2WI of the lumbar spine. The mass is heterogeneously hyperintense with several small cysts within it. C, Sagittal post-gadolinium T1-weighted fat saturated image. The lesion enhances avidly, but heterogeneously. The cystic areas do not enhance. D, Axial post-gadolinium T1-weighted fat saturated image at the L5 level. The relationship to the spinal canal and bony structures is demonstrated well in the axial plane.

Fig. 10-19 A 54-year-old man who presented with left thigh pain. MRI was performed to assess for degenerative disc disease, and an L2–3 schwannoma was discovered. A, Axial T1WI at the L2–3 level. Asymmetry of the nerve roots is seen as they exit the neural foramina. A small round isointense mass is seen arising from the left L2 nerve root. B, Axial T2WI. The mass is isointense to mildly hyperintense to the nerve root. C, Axial post-gadolinium T1-weighted fat saturated image. The mass demonstrates rim-enhancement. D, Sagittal post-gadolinium T1-weighted fat saturated image.

NEUROFIBROMA

Neurofibromas are unencapsulated neoplasms of the nerve sheath. They are less common than schwannomas and have a peak incidence between 20–30 years of age. Most lesions are sporadic, solitary tumors (Box 10-10). However, multiple neurofibromas (especially those of the plexiform type) are typically seen in NF-1. Lesions may be localized, diffuse, or plexiform in morphology.²⁰ Imaging characteristics may be indistinguishable from schwannomas, especially for the localized types. However, hemorrhage and cystic degeneration are less common. A target appearance of peripheral hyperintensity on T2WI with central low to intermediate signal intensity has been described as more common in neurofibromas than in schwannomas.^49,50

Box 10-10 Neurofibroma

• Unencapsulated neoplasm of nerve sheath

• Peak age 20–30 years, less common than schwannomas

• Cervical region most common

• Three patterns: Localized, diffuse, or plexiform

• Similar appearance to schwannomas, but hemorrhage uncommon; target sign more common than schwannomas

• 90% are sporadic solitary tumors

• 13–65% of NF-1 have spinal neurofibromas (Figs. 10-20 and 10-21)

Fig. 10-20 A 3-year-old child with NF-1 and plexiform neurofibroma within the cervical spine and neck. A, Sagittal T1WI of the cervical spine. A soft tissue mass is seen at the C5 to T1 levels within the lateral portion of the spinal canal and causing bony remodeling of the adjacent vertebrae. B, Sagittal T2WI. The mass has heterogeneous signal on this sequence. The spinal cord is displaced and compressed anteriorly and to the right. C, Sagittal T2WI lateral to B. The mass expands and extends through the neural foramina of the cervical spine. The large anterior paraspinal component is appreciated on this image. D, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances heterogeneously. E, Sagittal post-gadolinium T1-weighted fat saturated image lateral to D. F, Coronal post-gadolinium T1-weighted fat saturated image of the chest. The full extent of the paraspinal component of the mass is appreciated in this plane. Bilateral paraspinal involvement is present, left much greater than right. The mass extends to involve the left axilla. G, Axial post-gadolinium T1-weighted fat saturated image at the C5–6 level. The mass does not invade the dura at this level but does compress the thecal sac and cord anteriorly and to the right. The neural foramen is expanded, and the paraspinal component of the mass has an infiltrative, irregular contour.

Fig. 10-21 Patient with NF-1 who has associated scoliosis, dural ectasia with vertebral body scalloping, and a plexiform neurofibroma. A, Coronal T2WI of the lower thoracic and lumbar spine. Thoracolumbar scoliosis is present with a curve convex to the right. A heterogeneous mildly hyperintense infiltrating paraspinal mass is seen with extension into several neural foramina. Dural ectasia and associated vertebral body scalloping are seen. B, Sagittal T2WI. The anterior and posterior extent of the mass are visualized. C, Sagittal post-gadolinium T1-weighted fat saturated image of the lumbar spine. The mass enhances heterogeneously. D, Axial T2WI at the L2 level. Extension into the spinal canal is characterized best in the axial plane. E, Axial post-gadolinium T1-weighted fat saturated image.

MENINGIOMA

Meningiomas are slow-growing benign tumors that arise from arachnoid cap cell rests and are based on the dura. They are the second most common type of intradural lesions, accounting for 25% of spinal tumors, and occur most commonly in the fifth and sixth decades of life, with a female predilection (Box 10-11). Most lesions are solitary and sporadic, but multiple lesions can be seen in the setting of multiple meningiomatosis or NF-2, and some meningiomas may occur as the sequelae of prior radiation.^17,18,41,51 The vast majority of meningiomas (90%) are intradural. The remaining 10% are either extradural or dumbbell-shaped (intradural and extradural), with the rare occurrence of intramedullary or paraspinal meningiomas reported.^52–55 Meningiomas are most commonly found in the thoracic region in a posterolateral location. Cervical meningiomas are more commonly anterior to the cord.⁵⁶ The classic appearance is of a round, well-circumscribed, uniformly enhancing, broad-based mass against the dura with a dural tail. On CT, most meningiomas are isointense to slightly hyperdense to the spinal cord; demonstrate strong, homogeneous enhancement; and have an enhancing dural tail. Variable amounts of calcification may be present within meningiomas, and some are so heavily calcified that enhancement may not be apparent. Cystic change may occur but is rare. Hyperostosis of the adjacent bone is a feature that, if present, is helpful to make the diagnosis. Similar features are demonstrated on MRI. Most lesions are isointense to the spinal cord on T1- and T2-weighted sequences and enhance uniformly, with variation of signal intensity and enhancement dependent on the degree of calcification of the lesion (Figs. 10-22 to 10-25).^{17,18,41,47,57} DWI may demonstrate reduced ADC in some meningiomas and may be helpful in making the diagnosis and determining the likelihood of recurrence.^58,59 Highly vascular meningiomas may demonstrate internal flow voids on MRI.⁶⁰ On angiography, meningiomas demonstrate early capillary blush and remain opacified well into the venous phase—arriving early and staying late—thus inspiring the “mother-in-law” sign.

Box 10-11 Meningioma

• Slow growing, benign tumor based on the dura

• Second most common intradural extramedullary lesion

• 25% of primary spinal tumors

• Occurs most commonly in older patients—fifth and sixth decades of life

• Genetic predisposition in women (4:1); associated with prior radiation

• Most are solitary, sporadic—but may be seen as part of multiple meningiomatosis and NF-2

• 90% intradural, 10% extradural and/or dumbbell shaped, rarely intramedullary or paraspinous

• Round broad-based lesion against the dura with dural tail

• Isodense to hyperdense mass on CT with strong homogeneous enhancement (unless heavily calcified); may be calcified, occasionally cystic

• Associated adjacent hyperostosis is a specific sign, if present

• On MRI, isointense to cord on T1WI, most lesions isointense to cord on T2WI but may be hyperintense or hypointense (if calcification presents), show uniform enhancement; very vascular meningiomas may have flow voids

• Angiogram: Early capillary blush with stain well into venous phase (“mother-in-law sign”)

• Differential diagnosis: Hemangiopericytoma (Fig. 10-26), schwannoma (uncommon to be posterior to cord), lymphoma, extradural masses (e.g., cyst, chordoma)

Fig. 10-26 Hemangiopericytoma of the thoracic spine. Hemangiopericytomas are rare tumors that arise from the same cells as meningiomas but are more aggressive and are known to metastasize. The diagnosis of meningioma was initially favored on the basis of the MRI findings. A, Sagittal T2WI of the thoracic spine demonstrates an isointense to mildly hyperintense intradural mass posterior to the lower spinal cord, compressing it anteriorly. B, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances avidly. A small enhancing dural tail is present. C, Axial post-gadolinium T1-weighted fat saturated image demonstrates the enhancing mass within the right posterolateral aspect of the spinal canal. D, Axial T2WI. Only a small sliver of CSF is present at this level posterior to the cord and to the left of the mass.

Fig. 10-22 A 51-year-old with cervical spine meningioma. A, Sagittal T1WI of the cervical spine demonstrates a well- circumscribed, extramedullary, isointense mass anterior to the cord at C4–5. It has a broad base along the dura. B, Sagittal T2WI. The mass is isointense to the cord on this sequence as well. C, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances homogeneously. A tiny enhancing dural tail is seen extending from the lesion. D, Axial post-gadolinium T1-weighted fat saturated image. The mass indents the anterior aspect of the cord.

Fig. 10-23 Foramen magnum meningioma. A, Sagittal T1WI shows an intradural extramedullary mass anterior to the cervicomedullary junction that is isointense to brain parenchyma and the spinal cord. Compression of the upper cord is present. B, Sagittal T2WI. The mass is isointense to brain and cord on this sequence as well. High signal is seen within the upper cervical cord because of edema from cord compression. C, Sagittal post-gadolinium T1WI. The mass enhances uniformly and brightly with a dural tail, typical of (but not specific for) a meningioma.

Fig. 10-24 A 92-year-old with meningioma at the conus. A, Sagittal T1WI of the lumbar spine. A soft tissue mass is present anterior to the distal cord and conus at T12. The mass is isointense to the cord and blends in with it. B, Sagittal T2WI. The mass is isointense to the cord and nerve roots on this sequence, but it is easier to identify against the background of bright CSF. C, Sagittal post-gadolinium T1-weighted fat saturated image. The mass is well-circumscribed and enhances homogeneously. A dural tail is not appreciated. D, Axial post-gadolinium T1-weighted fat saturated image. The broad base against the dura is appreciated in the axial plane.

Fig. 10-25 Meningioma arising within the lumbar spine after treatment for lymphoma. A, Sagittal T1WI of the lumbar spine. The bone marrow has heterogeneous signal intensity. There is evidence of prior surgery with multi-level lumbar laminectomy. The cauda equina is distorted, and a lobulated isointense intradural mass is seen at L4. B, Sagittal T2WI. The mass is isointense to the cord and cauda equina. C, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances homogeneously. Non-specific enhancement is seen along the surface of the distal cord and nerve roots that may be related to reactive inflammatory changes rather than a neoplastic etiology. D, Axial T2WI at the L4 level. The mass is centered within the left aspect of the thecal sac. E, Axial post-gadolinium T1-weighted fat saturated image at the L4 level.

CEREBROSPINAL FLUID DISSEMINATED METASTASES

Spread of a malignant tumor through the subarachnoid space, also termed leptomeningeal spread of disease, is much less common than vertebral body/extradural involvement. CSF metastases may result from hematogenous spread of primary neoplasms, such as lung, breast, or melanoma, or may be caused by drop metastases of primary CNS tumors, such as anaplastic astrocytoma, glioblastoma (GBM), and ependymoma in adults and primitive neuroectodermal tumor (PNET)/medulloblastoma, germinoma, ependymoma, and choroid plexus papilloma/carcinoma in children.¹⁸ Any point along the CSF pathway may be involved, including the central canal of the spinal cord (Box 10-12). CSF metastases may present as a solitary mass at the bottom of the thecal sac or along the cord surface; as multifocal discrete nodules along the cord, nerve roots, or central canal; or as a diffuse sheet-like coating of the cord and nerve roots, termed leptomeningeal carcinomatosis. Disease may be subtle or impossible to detect on CT.⁶¹ MRI findings reflect the aforementioned patterns of disease. On T1WI, diffuse disease may cause apparent mild increased signal of the CSF space and blurring of the cord and nerve roots. On T2WI, thickening of the nerve roots, small nodules, or a dominant mass may be seen (Figs. 10-27 to 10-29). These are typically isointense to the cord and nerve roots and stand out against the background of bright CSF. However, both T1- and T2-weighted standard sequences may fail to detect disease; however, gadolinium markedly improves sensitivity of MRI, making it the preferred modality (Fig. 10-30).^62–64 Post-contrast images generally demonstrate avid enhancement of lesions and, in diffuse disease, may give a “sugar-coating” appearance to the spinal cord and nerve roots.⁶² One must be careful, however, because diffuse enhancement of the cord surface and nerve roots is nonspecific and can be seen with postoperative reactive changes, inflammatory disorders such as sarcoidosis, and leptomeningeal carcinomatosis.⁶²

Box 10-12 Cerebrospinal Fluid Disseminated Metastases

• May result from hematogenous spread of primary neoplasms such as lung, breast, and melanoma or be caused by drop metastases from CNS primary tumor (anaplastic astrocytoma, GBM, and ependymoma in adults and PNET/medulloblastoma, germinoma, ependymoma, and choroid plexus papilloma/carcinoma in children)

• Any point along CSF pathway can be involved, including central canal

• May see solitary mass at bottom of thecal sac or along cord surface; diffuse, thin, sheet-like coating of cord/roots (carcinomatous meningitis); or multifocal discrete nodules along cord/roots

• CT findings may be normal

• MRI

• T1WI—diffuse disease may appear as mild increase signal of CSF space and “blurring” of cord and nerve roots

• T2WI may show thickening of nerve roots, nodules, or a mass, isointense with cord and roots

• Post-gadolinium T1WI demonstrates enhancement, sugar-coating of cord/roots, single/multiple enhancing nodular masses

• Postoperative enhancement of meninges may mimic leptomeningeal spread of disease

Fig. 10-27 A 72-year-old woman with colon carcinoma and intradural metastases. A, Sagittal T2WI of the lumbar spine. Two isointense intradural masses are seen at the L4 and L5 levels. The masses are well-visualized against the background of bright CSF. There is evidence of prior pelvic radiation with uniform high signal in the L5 vertebral body and sacrum. B, Sagittal T1WI of the lumbar spine. The masses are isointense to the cord and nerve roots but are less obvious against the background of dark CSF. C, Sagittal STIR image. D, Sagittal post-gadolinium T1-weighted fat saturated image. The masses enhance avidly. E, Axial T1WI at the L4–5 level. The larger of the two masses occupies almost the entire intradural space. F, Axial post-gadolinium T1-weighted fat saturated image at L4–5. The nerve roots of the cauda equina are displaced around the mass.

Fig. 10-28 A 29-year-old with intradural metastases from a neuroendocrine primary. A, Sagittal T2WI of the cervical and upper thoracic spine. Two focal intradural masses are seen posterior to the spinal cord at the T1 and T2 levels. These are isointense to the spinal cord. Metallic artifact is seen posterior to the spinal canal at C7. B, Sagittal post-gadolinium T1-weighted fat saturated image. The two masses enhance. Metallic artifact at C7 is accentuated on this sequence. C, Sagittal T2WI of the lower thoracic and lumbar spine. Numerous small isointense nodules/masses are seen along the cauda equina. D, Sagittal post-gadolinium T1-weighted fat saturated sequence of the lower spine. The nodules enhance.

Fig. 10-29 Intradural metastases from leukemia. A, Sagittal post-gadolinium T1WI of the cervical and upper thoracic spine. Mild irregular enhancement is seen along the surface of the cord. B, Sagittal post-gadolinium T1WI of the lower thoracic and lumbar spine. The nerve roots of the cauda equina are thickened and enhance. C, Sagittal T2WI of the lower thoracic and lumbar spine. The nerve roots of the cauda equina are thickened and almost no CSF is visible.

Fig. 10-30 A 52-year-old woman with leptomeningeal carcinomatosis from metastatic ovarian cancer. A, Sagittal T1WI of the lumbar spine. The CSF has a blurred appearance because of increased signal and thickening of the nerve roots of the cauda equina. B, Sagittal T2WI. The nerve roots are thickened and slightly increased in signal intensity. C, Axial T2WI. Decreased CSF is seen surrounding the nerve roots of the cauda equina. D, Axial post-gadolinium T1-weighted fat saturated image. The thickened nerve roots enhance avidly.

PARAGANGLIOMA

Paragangliomas are tumors composed of chromaffin cells, a group of cells associated with the autonomic nervous system. They most commonly arise from the adrenal glands (where they are referred to as pheochromocytomas) and along the sympathetic chain (where they are called glomus tumors). The spine is a rare extra-adrenal site of paragangliomas (Box 10-13).^17,65 Spinal paragangliomas are usually intradural and located at the conus medullaris, cauda equina, or filum terminale, but have been described within the thoracic spine and within extradural locations.^41,66,67 They are well-defined, lobular, vascular masses that often have associated hemorrhage. MRI demonstrates heterogeneous signal on T1WI, high signal on T2WI, and strong enhancement (Fig. 10-31).^{17,41,68–70} Flow voids are commonly seen within lesions.^17,41

Box 10-13 Paraganglioma

• Spine is rare extra-adrenal site

• Usually occurs in conus medullaris, cauda equina, or filum terminale

• Well-defined, lobular, vascular mass

• Heterogeneous signal on T1WI and hyperintense on T2WI, flow voids common

• Commonly see hemorrhage, intratumoral and adjacent vessels, and strong enhancement

• Uptake on l-123 or l-131 meta-iodobenzylguanidine (MIBG) and octreotide

Fig. 10-31 A 46-year-old woman with previously partially resected primary thoracic paraganglioma and spinal metastases. A, Sagittal T2WI of the thoracic spine. Metallic artifact is seen from posterior fixation of the upper thoracic spine. The residual/recurrent mildly hyperintense primary upper thoracic extradural and vertebral paragangliomas are seen at the T4 level between pedicle screws at the level above and below. Metastatic lesions are seen within the T8, T11, and L1 vertebral bodies. Pathological fracture of the T11 vertebral body is present. B, Sagittal T1WI of the thoracic spine. The lesions are mildly heterogeneous. C, Sagittal post-gadolinium T1WI of the thoracic spine. The lesions enhance heterogeneously. D, Sagittal T2WI of the lumbar spine. Hyperintense lesions are seen within all of the lumbar vertebrae. A large lesion is seen at S1 with epidural extension. Linear low signal is seen within several lesions, possibly as a result of flow voids. E, Sagittal T1WI of the lumbar spine. The lesions are mainly isointense to the intervertebral discs but are slightly heterogeneous. F, Sagittal post-gadolinium T1-weighted fat saturated image of the lumbar spine. The lesions enhance. G, Axial post-gadolinium T1-weighted fat saturated image at the S1 level.

INTRADURAL ARACHNOID CYST

Intradural arachnoid cysts are loculated intradural CSF collections that may be congenital or acquired. Primary arachnoid cysts most commonly occur in the dorsal mid-thoracic spine.⁷¹ As one might expect, they are well-circumscribed, nonenhancing lesions that follow CSF characteristics on all imaging modalities and displace the cord and spinal nerve roots (Box 10-14). One may see immediate, delayed, or no filling of an arachnoid cyst with myelographic contrast relative to the CSF space with CT myelography (Figs. 10-32 and 10-33).^72,73 Idiopathic spinal cord herniation, a syndrome in which the thoracic cord is prolapsed through an anterior dural defect, can have similar MR appearance to an intradural arachnoid cyst and is important to recognize because it is a cause of progressive myelopathy and can be treated effectively with surgery. MRI demonstrates focal ventral displacement of the mid-thoracic spinal cord and focal cord atrophy with or without an associated dorsal intradural arachnoid cyst present. CT myelography with thin slices may be helpful to demonstrate the focal dural defect (Fig. 10-34).⁷⁴

Box 10-14 Intradural Arachnoid Cyst

• Loculated intradural CSF collection

• May be congenital or acquired

• Primary arachnoid cyst most commonly found in dorsal mid-thoracic spine

• Anterior location uncommon

• Well-circumscribed, oval, nonenhancing lesion that follows CSF characteristics on all imaging and displaces the cord and spinal nerve roots

• May see delayed filling of arachnoid cyst with myelographic contrast relative to CSF space; therefore obtain immediate and delayed images on CT myelography

• Differential diagnosis: Idiopathic spinal cord herniation (upper to mid-thoracic level most common, focal cord atrophy and ventral deviation, present with progressive myelopathy, and requires surgical intervention), meningocele

Fig. 10-32 Thoracic intradural arachnoid cyst. A, Initial axial image from CT myelogram of the thoracic spine. A round, well-circumscribed filling defect is seen posterior to the thoracic spinal cord, displacing it anteriorly. Myelographic contrast fills the intradural space. B, Delayed axial image from CT myelogram. The arachnoid cyst has filled with contrast and now has only slightly lower attenuation than the opacified CSF space. C, Sagittal T2WI of the thoracic spine. The arachnoid cyst is isointense to CSF but is evident because of mass effect on the spinal cord and absence of CSF pulsation artifact within the cyst.

Courtesy Nancy Fischbein, Stanford University.

Fig. 10-33 Patient with spina bifida and tethered cord with intradural arachnoid cyst vs. intradural meningocele. A, Axial CT myelogram image at the L5 level demonstrates a well-circumscribed intradural lesion to the left of the cauda equina with a “CSF-cap.” The lesion partially fills with myelographic contrast, and a fluid-contrast level is present. B, Sagittal reconstruction of CT-myelogram. The cystic lesion extends from the L4 to S2 level.

Fig. 10-34 A 39-year-old woman who presented with progressive lower extremity weakness. MRI (not shown) raised the question of an arachnoid cyst. CT myelogram demonstrated findings typical of idiopathic spinal cord herniation. A, Sagittal reformat of CT myelogram of the thoracic spine. Focal dural defect is seen with ventral displacement and focal atrophy of the thoracic spinal cord within the upper to mid-thoracic spine. B, Axial CT myelogram image at the involved level. No filling defect is seen within the CSF space. There is no evidence of an intradural arachnoid cyst.

EPIDERMOID

Epidermoids are benign spinal masses composed of cells that embryologically comprise the skin and dermal appendages (hair follicles, sweat glands, and sebaceous glands). These lesions can be congenital or may be acquired from iatrogenically implanted epithelial cells (e.g., as a result of lumbar puncture).⁷⁵ The majority of epidermoids are extramedullary and intradural, but intramedullary lesions have been reported.⁷⁶ On MRI, the signal characteristics of epidermoids are similar but not identical to those of CSF (Box 10-15). They are isointense to mildly hyperintense to CSF on T1WI and T2WI.^76–79 FLAIR and DWI may be helpful to distinguish these lesions from arachnoid cysts, because epidermoids remain hyperintense on FLAIR and demonstrate reduced ADC, unlike arachnoid cysts, which behave identically to CSF.^20,79,80 Epidermoids demonstrate minimal or no enhancement, unless infected (Figs. 10-35 to 10-37).^{17,20,76–79}

Box 10-15 Epidermoid

• Benign spinal tumor composed of cells that embryologically comprise skin and its appendages (hair follicles, sweat glands, sebaceous glands)

• May be congenital or acquired (e.g., as a result of lumbar puncture)

• Acquired type occur almost uniformly at cauda equina

• Minimal or no enhancement unless infected; usually isointense to mildly hyperintense to CSF on T1WI and T2WI

• May be slightly hyperintense on FLAIR (helps to distinguish from arachnoid cyst)

• Restricted diffusion helpful to distinguish from arachnoid cyst

• Differential diagnosis: Arachnoid cyst, neurenteric cyst

Fig. 10-35 Cauda equina epidermoid. A, Sagittal T1WI of the lumbar spine demonstrates a well-circumscribed hyperintense mass at the L1 level. B, Sagittal T2WI. The mass is isointense to cord and nerve roots. The adjacent nerve roots of the cauda equina are splayed around the mass. C, Sagittal post-gadolinium T1-weighted fat saturated image. No drop out of signal is seen, indicating that this is not a lipoma. The mass is uniformly hyperintense but does not demonstrate any enhancement relative to the pre-gadolinium T1WI . D, Axial post-gadolinium T1-weighted fat saturated image.

Fig. 10-36 A 6-year-old man with cauda equina epidermoid and history of prior lumbar puncture. A, Sagittal T1WI of the lumbar spine. A well-circumscribed intradural mass is seen at the L4 level that is isointense to the spinal cord and nerve roots. B, Sagittal STIR image. The mass is hyperintense and almost completely blends in with the adjacent CSF. C, Sagittal post-gadolinium T1-weighted fat saturated image. A thin rim of enhancement is present along the inferior margin of the mass. The mass shows no other enhancement. D, Axial T2WI at the L4 level. The nerve roots of the cauda equina are displaced around the mass.

Fig. 10-37 Intramedullary thoracic epidermoid. A, Sagittal T1WI of the upper thoracic spine. A mildly hyperintense lesion is seen within and expanding the dorsal spinal cord at approximately T6. B, Sagittal T2WI. The lesion is heterogeneous and hyperintense. Focal posterior bulging of the spinal cord contour is seen. C, Axial T1WI at the level of the mass. D, Axial post-gadolinium T1-weighted fat saturated image. The mass does not enhance nor does it demonstrate decreased signal from suppression of fat.

LIPOMA

Spinal lipomas arise from premature separation (dysjunction) of the cutaneous ectoderm from the underlying neuroectoderm during neurulation and therefore are considered developmental rather than neoplastic lesions (Box 10-16). Imaging demonstrates a lobulated mass with characteristics of fat, including low attenuation on CT, high signal on T1-weighted MR images, low signal on fat suppressed images, and lack of enhancement (Figs. 10-38 to 10-40). Lesions may grow during infancy. Associated findings of tethered cord and spinal dysraphism may be seen.^17,20

Box 10-16 Lipoma

• Arises from premature separation (dysjunction) of cutaneous ectoderm from neuroectoderm during neurulation

• Lobulated mass, hypodense on CT; hyperintense on T1WI; suppresses with fat saturation; no enhancement

• May grow during infancy

• Sometimes associated with tethered cord and spinal dysraphism

Fig. 10-38 Cervical spine lipoma. A, Sagittal T1WI of the cervical spine. A large, lobulated, hyperintense mass is seen arising along the posterior margin of the spinal cord, centered at the C3 and C4 levels. B, Sagittal T2WI. The mass is mildly hyperintense, similar to the subcutaneous fat. C, Sagittal post-gadolinium T1-weighted fat saturated image. Signal within the lesion is suppressed, confirming fatty composition. No enhancement is seen. D, Axial T1WI at the C3–4 level. The adjacent spinal cord is small in caliber and irregular in contour, presumably because of abnormal development rather than atrophy. E, Axial T2WI at the C3–4 level.

Fig. 10-39 A 1-year-old man with thoracic spine lipoma. A, Sagittal T1WI of the cervical and upper thoracic spine. A well- circumscribed, uniformly hyperintense mass is seen arising from the dorsal spinal cord at the T8 to T10 levels. B, Sagittal T2WI. The mass follows intensity of the subcutaneous and epidural fat. C, Sagittal post-gadolinium T1-weighted fat saturated image. Drop out of signal is seen because of fat saturation. The mass does not enhance. D, Axial T1WI at the T9 level. The adjacent spinal cord is small and irregular in contour.

Fig. 10-40 Patient with metastatic breast cancer, vertebral body metastases, and filar lipoma. A, Sagittal T1WI of the lumbar spine. The vertebral bodies have a mottled appearance with numerous hypo-intense vertebral body lesions, consistent with bony metastases. A hyperintense elongated mass is seen arising from the filum terminale at the L2 level. B, Sagittal T2WI. The L2 mass is hyperintense, similar to subcutaneous and epidural fat, and blends in with the adjacent CSF. C, Sagittal post-gadolinium T1-weighted fat saturated image. The filar mass demonstrates drop out of signal because of fat saturation and no enhancement, confirming diagnosis of filum lipoma. The vertebral body metastases enhance. D, Axial T1WI at the L2 level demonstrates the hyperintense mass in the expected location of the filum terminale. E, Axial post-gadolinium T1-weighted fat saturated image at the L2 level. F, Axial T2WI at the L2 level. Crescentic high signal along the left margin of the mass is caused by chemical shift artifact from closely apposed fat and fluid.

POLYNEUROPATHIES

A number of conditions may affect multiple spinal nerve roots including trauma, infection, radiation, neurofibromatosis, lymphoma, and hereditary hypertrophic polyneuropathies. An in-depth discussion of these entities is beyond the scope of this chapter. The hereditary hypertrophic polyneuropathies encompass several hereditary disorders characterized by focal or diffuse peripheral nerve enlargement with distal extremity atrophy. Imaging shows the enlarged nerves, which may or may not demonstrate abnormal enhancement and should not be confused with a neoplastic process, such as lymphoma, in the appropriate clinical setting (Fig. 10-41). In the acute stage, high signal may be seen within denervated muscles on T2WI.²⁰

Fig. 10-41 A 42-year-old woman with known diagnosis of Charcot-Marie-Tooth (a hereditary hypertrophic polyneuropathy). A, Off-midline sagittal T1WI of the cervical spine. There is enlargement of all the visualized neural foramina and exiting nerve roots of the cervical spine. B, Off-midline sagittal T2WI. The enlarged nerve roots have normal signal intensity. C, Axial T2WI within the cervical spine. The spinal cord is normal in appearance. The exiting nerve roots demonstrate fusiform enlargement along their entire course.

INTRAMEDULLARY LESIONS

Intramedullary masses are by definition lesions within the spinal cord (Box 10-17). The majority of these lesions are malignant primary neoplasms, most of which are astrocytomas or ependymomas.⁴¹ Gangliogliomas are relatively rare neoplasms in adults but are the second most common intramedullary tumor in children, despite being previously underdiagnosed because of limited or uncertain methods of studying pathological specimens.^81–84 Hemangioblastomas are considered the third most common intramedullary tumor in adults, accounting for approximately 3% of spinal cord tumors and are often associated with von Hippel–Lindau (VHL) disease.^8,18,41 Intramedullary metastases are rare but should be considered in the setting of a known primary tumor. Tumor-like masses, including benign syrinx, multiple sclerosis (MS) plaques, transverse myelitis, and cord infarcts, are important to recognize and to not mistake for neoplasms.

Box 10-17 Characteristics of Intramedullary Lesions

• Cord expansion

• Circumferential decrease of CSF space

ASTROCYTOMA

Astrocytomas are primary neoplasms of astrocytic origin that comprise the second most common type of spinal cord neoplasm in adults and are the most common type in children. Peak incidence is in the third to fourth decades, and lesions most commonly occur in the cervical and upper thoracic spine.^17,18,24 Seventy-five percent of spinal cord astrocytomas are low-grade World Health Organization (WHO) grade I or II lesions (Box 10-18). An even higher proportion of astrocytomas are low-grade lesions in children than in adults.¹⁷ The diffuse fibrillary type of astrocytoma is more common in the spine than pilocytic astrocytomas.⁸⁴ Spinal astrocytomas are typically enhancing, infiltrating masses that expand the cord and secondarily expand the spinal canal. Lesions are often eccentric within the cord or may even be exophytic. Tumor margins may be ill defined but are better characterized and differentiated from associated cysts, syrinx, and edema on post-gadolinium images. Astrocytomas are typically hypointense on T1, hyperintense on T2, and nearly always show a mild to moderate degree of heterogeneous enhancement (Figs. 10-42 to 10-47). Astrocytomas commonly have cystic components, and calcification is rare.^{8,17,18,20,41,85–88}

Box 10-18 Astrocytoma

• Second most common cord neoplasm overall; most common in children

• Peak incidence in the third to fourth decades of life

• 75% low-grade WHO I or II lesions (80–90% in children); diffuse fibrillary type more common than pilocytic

• Most common in cervical and upper thoracic spine

• Enhancing, infiltrating mass expanding the cord—may be eccentric in cord or even exophytic

• Hypointense to isointense on T1WI, hyperintense on T2WI

• Nearly always enhances with mild to moderate, partial enhancement

• Cystic components common

• Calcification rare

• Tumor margins not always clearly defined but better differentiated from edema, cysts, and syringes with administration of intravenous gadolinium; tumor cysts generally surrounded by enhancement, whereas syrinx not surrounded by enhancement

Fig. 10-42 A 8-year-old woman with progressive scoliosis caused by low-grade astrocytoma of the thoracic spinal cord. A, Sagittal T1WI of the cervical and upper thoracic spine. The spinal cord is expanded from the T2 to T5 levels. B, Sagittal T2WI. The upper thoracic spinal cord lesion is mildly hyperintense, and the intramedullary lesion has ill-defined borders. C, Axial T1WI at the T4 level. D, Axial T2WI at the T4 level. Signal intensity within the lesion is somewhat heterogeneous.

Fig. 10-43 A 33-year-old man with low-grade cervical and upper thoracic spinal cord astrocytoma. A, Sagittal T1WI of the cervical and upper thoracic spine. The visualized portion of the spinal cord is expanded. B, Sagittal T2WI. The intramedullary lesion is heterogeneously hyperintense. C, Sagittal post-gadolinium T1-weighted fat saturated image. The lesion involves the entire cervical cord and extends down to at least the T4 level. Only a small amount of enhancement is seen within the lesion at the T3–4 level. D, Axial T1WI within the lower cervical spine. The cord occupies almost the entire central spinal canal, and the canal itself is enlarged. E, Axial post-gadolinium T1-weighted fat saturated image at the T3–4 level demonstrates the enhancing portion of the lesion.

Fig. 10-44 A 2-year-old man with spinal cord pilocytic astrocytoma and associated cord syrinx. A, Sagittal T2WI of the cervical and upper thoracic spine. A hyperintense intramedullary mass is seen within and expanding the thoracic spinal cord. An associated syrinx is present within the cervical cord, expanding the cord above the spinal mass. B, Sagittal post-gadolinium T1-weighted fat saturated image of the cervical and upper thoracic spine. The mass enhances avidly. The syrinx does not enhance. C, Sagittal post-gadolinium T1-weighted fat saturated image of the lower thoracic and lumbar spine. A non-enhancing syrinx also is present below the lower margin of the mass extending to the conus. D, Axial post-gadolinium T1WI through the lower thoracic spine. The enhancing mass occupies the entire expanded central canal.

Fig. 10-45 A 6-year-old woman with thoracic pilocytic astrocytoma and associated syrinx. A, Coronal T2WI of the chest/thoracic spine. A lower thoracic scoliosis convex to the right is seen. A thoracic syrinx is seen expanding the thoracic spinal cord. A hyperintense intramedullary mass is present at about the T10 level, with the syrinx above and below it. B, Sagittal T2WI of the thoracic spine. The entire cord is not seen on this image because of the scoliosis. The T2-hyperintense mass is seen with a syrinx visualized below it. C, Sagittal T2WI of the lower thoracic and lumbar spine. The syrinx is seen extending to the conus. D, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances solidly and avidly as compared with the adjacent syrinx. E, Axial post-gadolinium T1-weighted fat saturated image at the level of the enhancing mass. F, Axial post-gadolinium T1-weighted fat saturated image through the non-enhancing syrinx, below the enhancing mass.

Fig. 10-46 A 54-week-old man child with cervical spinal cord anaplastic glioneuronal tumor. A, Sagittal T1WI of the cervical and upper thoracic spinal cord. The entire spinal cord is expanded. A solid intramedullary mass is present, extending from C7 to T2, with lower signal intensity tumor cysts above and below it. B, Sagittal T2WI. The mass is mildly hyperintense and ill defined. The tumor cysts are well defined and difficult to distinguish from a syrinx without assessing for enhancement. High signal is seen within the lower cord, below the lower tumor cysts. C, Sagittal post-gadolinium T1-weighted fat saturated image. The tumor cysts demonstrate rim enhancement. The solid mass demonstrates heterogeneous irregular enhancement.

Fig. 10-47 A 51-year-old man with hemorrhage into an astrocytoma of the cervical spinal cord. A, Sagittal T1WI of the cervical spine. The entire cervical cord is expanded. A well-circumscribed cystic cord lesion is seen extending from C4 to T1 with intrinsic high signal, consistent with hemorrhage and a fluid-fluid level. A low signal nodule is seen within the anterior portion of the mass at C5 and C6. B, Sagittal T2WI. The cystic lesion with hemorrhage and a fluid-fluid level is again shown. High signal is seen within the cord above and below the cyst as a result of cord edema and/or infiltrating tumor. The solid nodule at C5 and C6 is isointense to the spinal cord. C, Sagittal post-gadolinium T1-weighted fat saturated image. The nodular component within the cyst enhances and is less conspicuous against the background of hyperintense blood product. No other enhancement is seen. D, Axial post-gadolinium T1-weighted fat saturated image through the cystic mass.

EPENDYMOMA

Ependymomas are neoplasms of the ependyma lining the central canal of the spinal cord. They comprise the most common type of primary spinal cord tumor in adults. Peak incidence is in the fourth to fifth decades. Histologically, spinal cord ependymomas are almost always of either the cellular or myxopapillary type.^41,84 The cellular type is most common and typically presents as an intramedullary, well-circumscribed mass within the cervical or thoracic cord that is hypointense on T1WI and hyperintense on T2WI and causes symmetric cord expansion (Figs. 10-48 to 10-50).^41,89–91 Myxopapillary ependymomas constitute approximately 30% of spinal cord ependymomas and are almost exclusively found in the conus and filum terminale (Box 10-19). These lesions tend to be more heterogeneous than the cellular type, and can demonstrate areas of T1 hyperintensity (Figs. 10-51 and 10-52).^20,41,92 Cysts and hemorrhage are common in all types of ependymomas. Calcification is uncommon. Ependymomas typically enhance intensely but may demonstrate heterogeneous or rim enhancement.^{17,18,20,41,89–93} There is significant overlap in the appearances of spinal cord ependymomas and astrocytomas, and imaging is often unable to accurately identify these intramedullary tumors correctly. Certain helpful imaging features are listed in Table 10-4.

Fig. 10-48 A 33-year-old woman with cellular-type ependymoma within the cervical spine. A, Sagittal T1WI demonstrates a mildly hyperintense, well-circumscribed intramedullary mass at the C4 level. B, Sagittal T2WI. The mass is hyperintense and mildly expands the cord. C, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances avidly and uniformly. D, Axial T2WI at the C4 level demonstrates the mass within the right anterior aspect of the spinal cord.

Fig. 10-49 51-year-old with cervical spine ependymoma. A, Sagittal T1WI of the cervical spine. A mildly hyperintense well-circumscribed mass is seen expanding the spinal cord at the C4 level. B, Sagittal T2WI. The mass is mildly hyperintense with a focal cystic component posteriorly. C, Sagittal post-gadolinium T1WI. The mass enhances avidly. D, Axial T2WI through the mass demonstrating the focal cyst. The mass is fairly central within the spinal cord. E, Axial post-gadolinium T1-weighted fat saturated image at the same level shows the enhancing solid portion of the mass and non-enhancing cyst.

Fig. 10-50 Cervicomedullary junction ependymoma. A, Sagittal T1WI. The upper cervical spinal cord and cervicomedullary junction are expanded. Heterogeneous signal intensity is noted within an intramedullary lesion. B, Sagittal T2WI. The mass is heterogeneous and isointense to hyperintense to the spinal cord. Adjacent cysts are present along the superior margin of the mass. A low signal rim is seen along the inferior margin of the mass, consistent with a hemosiderin cap from hemorrhage within the lesion. C, Sagittal post-gadolinium T1-weighted fat saturated image. The mass enhances brightly. The tumor cysts do not enhance. D, Axial T2WI at the C1 level. The well-circumscribed bright tumor cyst is shown with the adjacent solid component of the mass posterior and to the right of it. E, Axial post-gadolinium T1-weighted fat saturated image at the same level. The solid component of the mass enhances. The cystic component does not enhance.

Box 10-19 Ependymoma

• Neoplasm of ependyma lining spinal cord central canal

• Most common primary spinal cord tumor in adults

• Peak incidence in the fourth to fifth decades of life

• May be seen in NF-2 as part of “MIS ME” constellation of findings—multiple inherited schwannomas, meningiomas, and ependymomas (Fig. 10-53)

• Cellular type vs. myxopapillary type

• Most common histology is cellular type—intramedullary and well-circumscribed

• Myxopapillary ependymoma subtype (constitute 30%) almost exclusively occurs in conus and filum

• Cyst formation and hemorrhage common, calcification uncommon

• Usually hyperintense on T2WI

• Myxopapillary type hyperintense on T1WI, other varieties hypointense on T1WI

• Sometimes heterogeneous because of hemorrhage—bleeding occurs less often than in intracranial lesions; may see hemosiderin cap

• Usually enhance intensely, may have heterogeneous or rim enhancement

Fig. 10-53 A 32-year-old woman with manifestations of NF-2. The patient has bilateral acoustic schwannomas as well as intramedullary ependymomas and multiple spinal schwannomas. A, Sagittal T1WI of the cervical spine and craniocervical junction. Intramedullary masses are seen within the cervicomedullary junction/upper cervical spine as well as extending from the C6 to T1 level. The upper mass has a cystic appearance. Both masses expand the cord and are consistent with ependymomas in this clinical setting. B, Sagittal T2WI. The upper mass is hyperintense and cystic in appearance with a dark hemosiderin cap along its inferior margin. High signal is seen within the cord below this lesion, and the two masses may be components of a single larger mass or may represent two separate masses. The lower lesion is heterogeneous and hyperintense. C, Sagittal post-gadolinium T1-weighted fat saturated image. The upper cystic mass demonstrates a thick rim of enhancement with nodular enhancement superiorly. The lower mass enhances more solidly. D, Sagittal post-gadolinium T1-weighted fat saturated image lateral to C. At the upper margin of the image, a solidly enhancing mass is seen within the cerebellopontine angle/internal auditory canal, consistent with an acoustic schwannoma. The patient had a second mass on the contralateral side (not shown). Enhancing masses are seen within the neural foramina at C2–3 and C7–T1, consistent with spinal schwannomas of the C3 and C8 nerve roots. E, Sagittal post-gadolinium T1-weighted fat saturated image lateral to E.

Fig. 10-51 Myxopapillary ependymoma of the filum terminale. A, Sagittal T1WI of the lumbar spine demonstrates an intradural mass immediately below the conus. B, Sagittal T2WI. The mass is well-circumscribed and mildly hyperintense. C, Sagittal post-gadolinium T1WI of the lumbar spine. The mass enhances heterogeneously. D, Axial T2WI. The nerve roots of the cauda equina are displaced around the mass.

Fig. 10-52 A 36-year-old woman with ependymoma of the conus and filum. A, Sagittal T1WI of the lumbar spine. A large isointense mass is seen extending from L1 to L4, arising from the conus/filum. B, Sagittal T2WI. The mass is heterogeneously hyperintense with a dark rim.

Table 10-4 Imaging Features of Spinal Cord Astrocytoma vs. Ependymoma

	Astrocytoma	Ependymoma
Age	Children	Adults
Location	75% cervicothoracic Eccentric	Conus, cauda equina Central cord
Characteristics	Enhancing, infiltrating mass expanding the cord Hemorrhage less common 30% have cystic components	Well-defined Hemosiderin common (may present with subarachnoid hemorrhage) Intense enhancement with sharp borders Cyst formation common

HEMANGIOBLASTOMA

Hemangioblastomas are low-grade vascular neoplasms that may be seen sporadically or in one-third of cases are associated with VHL disease. VHL disease is an autosomal dominant condition with increased incidence of cerebellar and/or spinal hemangioblastomas; retinal angiomatosis; renal cell carcinoma; pheochromocytomas; and cysts in the kidneys, liver, and pancreas. The majority of spinal hemangioblastomas are intramedullary lesions within the posterior aspect of the cord, but extramedullary lesions (both intradural and extradural) are not uncommonly seen.^20,41 Small hemangioblastomas tend to be homogeneously hypointense on T1WI, hyperintense on T2WI, and enhance brightly and homogeneously (Box 10-20). Larger lesions classically demonstrate a tumor cyst with a bright enhancing mural nodule, but appearances are variable and these tumors may be heterogeneous or solid. Associated edema is often seen within the cord surrounding hemangioblastomas (Fig. 10-54).⁹⁴ Because these tumors are so highly vascular, adjacent flow voids caused by feeding arteries or, more often, by draining veins can be seen surrounding the tumor (Fig. 10-55). On angiography, intense tumor stain and prominent venous drainage are seen.^8,20

Box 10-20 Hemangioblastomas

• Low-grade vascular neoplasm seen sporadically or in association with VHL

• Peak incidence in the fourth decade of life

• One-third associated with VHL, an autosomal dominant disease associated with cerebellar and/or spinal hemangioblastomas; retinal angiomatosis; renal cell carcinoma and/or pheochromocytoma; cysts in kidneys, pancreas, and liver (Figs. 10-56 and 10-57)

• Multiple in 20%

• 75% intramedullary but may be extramedullary (intradural or extradural); more often in posterior aspect of cord

• Small lesions tend to be homogeneous hypointense to isointense on T1WI, hyperintense on T2WI, and enhance homogenously

• Larger lesions classically cystic with brightly enhancing mural nodule but may be heterogeneous or solid, often have surrounding edema within cord

• Feeding arteries or, more often, large draining veins can be seen surrounding tumor nidus—angiography shows intense tumor stain and draining veins

Fig. 10-56 A 22-year-old woman with VHL disease and cerebellar and spinal hemangioblastomas demonstrating varying morphology. A, Sagittal T2WI of the cervical spine and craniocervical junction. A cystic lesion is seen within the dorsal cervicomedullary junction. Extensive surrounding edema is present, and prominent edema is seen within the lower cervical cord. B, Sagittal T1WI of the cervical spine. The cyst and edema are less conspicuous, but cord expansion is clearly present. C, Sagittal post-gadolinium T1-weighted fat saturated image. Multiple enhancing nodules are present, revealing multiple hemangioblastomas. A lesion is present within the cerebellum, at the cervicomedullary junction (with the classic cyst and mural nodule appearance), anterior to the cord at C3–4, and along the dorsal surface of the cord at T2. D, Sagittal post-gadolinium T1-weighted fat saturated image lateral to C. An additional two enhancing lesions are seen along the lateral margin of the cord at C2–3 and C5. E, Sagittal post-gadolinium T1WI of the lower thoracic spine. Multiple enhancing nodules are seen dorsal and lateral to the mid to lower thoracic spinal cord. Serpiginous enhancement and flow voids are seen posterior to the cord, which represent prominent feeding vessels and draining veins. F, Axial post-gadolinium T1WI at the C3–4 level demonstrates two small enhancing nodules anterior to the spinal cord. G, Axial T2WI at the C1 level demonstrates the tumor cyst within the lesion at the cervicomedullary junction. H, Axial T2WI at the L1 level. Pancreatic cysts are seen anterior to the left kidney within the field of view.

Fig. 10-57 Patient with VHL disease and associated cerebellar and spinal hemangioblastomas. A, Sagittal T1WI of the cervical spine and cervicomedullary junction. Large cystic lesions are present within the cerebellum and within the craniocervical junction. Cord expansion is present at the C4 to C6 levels and at T2 to T4, suggesting the presence of additional lesions. B, Sagittal T2WI. The tumor cysts are again seen at the cervicomedullary junction and within the cerebellum. Cord edema is present at the C4 to C6 levels and at T2–4. C, Sagittal post-gadolinium T1-weighted fat saturated image. The cervicomedullary lesion demonstrates an enhancing mural nodule. Tiny nodules of enhancement are seen anterior and posterior to the cervical and upper thoracic spinal cord. D, Sagittal post-gadolinium T1-weighted fat saturated image lateral to C. Two focal enhancing lesions are seen lateral to the cord at C2 and C4. E, Axial T2WI at the cervicomedullary junction demonstrates the tumor cyst. F, Axial post-gadolinium T1-weighted fat saturated image at the same level demonstrates the non-enhancing tumor cyst and brightly enhancing mural nodule. G, Coronal post-gadolinium T1WI of the brain. Enhancing nodules are present within the right cerebellar hemisphere and right cerebellar tonsil.

Fig. 10-54 A 18-year-old man tennis player who noticed arm weakness. MRI was performed and an intramedullary mass was discovered, which enlarged on follow-up and was subsequently resected. Diagnosis of hemangioblastoma was made. There was no family history of VHL disease. A, Sagittal T2WI. A cystic mass with a solid nodule at its inferior margin is seen centrally within the spinal cord at the C7 to T1 level. High signal is seen within the cord above and below the lesion, representing edema. B, Sagittal post-gadolinium T1-weighted fat saturated image. The solid mural nodule of the lesion enhances brightly. C, Axial T2WI demonstrates the cystic portion of the mass centrally within the spinal cord. D, Axial post-gadolinium T1-weighted fat saturated image through the enhancing mural nodule. E, Axial post-gadolinium T1-weighted fat saturated image through the non-enhancing tumor cyst.

Fig. 10-55 A 48-year-old woman with VHL disease and spinal hemangioblastoma. A, Sagittal T1WI of the thoracic spine. A low signal intensity lesion is seen centrally within the spinal cord in the mid-thoracic region. B, Sagittal T2WI. The lesion has a cystic appearance. A prominent flow void is noted posterior to the spinal cord at this level. C, Sagittal post-gadolinium T1-weighted fat saturated image. An enhancing mural nodule is seen along the anterior border of the mass. Prominent linear enhancement is seen posterior to the spinal cord at the level of the lesion and above it, consistent with prominent draining veins. D, Axial T2WI at the level of the mass. E, Axial post-gadolinium T1WI at the level of the enhancing mural nodule.

GANGLIOGLIOMA

Gangliogliomas have traditionally been considered rare tumors of the spinal cord, but it is likely that they are more common than originally reported, because many gangliogliomas were misclassified as astrocytomas in the original literature.⁸¹ Gangliogliomas are likely the second most common spinal cord tumor in children.⁸³ Their appearance may be identical to that of spinal cord astrocytomas, but tumor cysts and heterogeneous enhancement may be more common in gangliogliomas (Fig. 10-58).⁸² The upper cord is the most common location (Box 10-21). Associated scoliosis and bony erosion may be seen in up to 50% of cases.^20,82

Fig. 10-58 A 61-week-old man with scoliosis and cervical cord ganglioglioma. A, Coronal T1WI of the chest. A cervicothoracic scoliosis convex to the left is present. The visualized portion of the spinal cord is expanded. B, Sagittal T1WI of the cervical and upper thoracic spine. The cervical and upper thoracic spinal cord is expanded and heterogeneous. C, Sagittal T2WI. The mass is heterogeneous with intermediate to high signal and associated cord edema. D, Sagittal post-gadolinium T1-weighted fat saturated image. Heterogeneous enhancement of the mass is present. E, Axial T2WI demonstrates the mass in cross-section. Little to no CSF space is present surrounding the expanded spinal cord. F, Axial post-gadolinium T1WI without fat saturation.

Box 10-21 Ganglioglioma

• Considered rare tumors, but likely more common than originally supposed because many gangliogliomas were misclassified as astrocytomas in original literature

• Cervical > thoracic > filum

• Scoliosis and bone erosion in approximately 50%

• Appearance may be identical to astrocytoma

• Cysts more common than in astrocytomas and ependymomas

• Contrast enhancement may be absent

METASTASES

Intramedullary metastases are less common than intradural or extradural metastases but are now more often diagnosed as cancer patients survive longer. The context of a known primary malignancy is extremely important for diagnosis. Similar to intradural metastatic spread of disease, metastases may either originate as drop metastases from primary CNS neoplasms or may spread hematogenously from non-neurogenic primary neoplasms (most commonly lung, breast, melanoma, colon, renal, lymphoma, and leukemia). Intramedullary metastatic lesions are typically small at presentation (Box 10-22). The most common appearance is that of a small, avidly enhancing mass with surrounding cord edema out of proportion to the lesion’s size (Fig. 10-59). Spinal cord metastases are rarely associated with cysts.⁸

Box 10-22 Intramedullary Metastases

• Drop metastases: Medulloblastoma/PNET, ependymoma, gliomas

• Non-neurogenic: Lung, breast, melanoma, colon, renal, lymphoma, leukemia

• Usually small at presentation with minimal cord enlargement

• Intense enhancement with associated edema out of proportion to size

• Rarely associated with cysts

• Context of known primary malignancy is important

Fig. 10-59 A 55-year-old woman with metastatic lung cancer and vertebral and intramedullary spinal metastases. A, Sagittal T1WI of the cervical and upper thoracic spine. Multiple low signal lesions are present throughout the vertebrae, consistent with bony metastases. Pathological fracture of T7 is noted. The upper thoracic spinal cord is mildly expanded. B, Sagittal T2WI. Extensive cord edema is present from C4 to T4. A focal, low signal intramedullary mass is present at the T1–2 level. C, Sagittal post-gadolinium T1-weighted fat saturated image. The focal mass at T1–2 enhances avidly. The vertebral body lesions enhance heterogeneously. D, Axial T2WI at the level of the focal lesion. The lesion is isointense to the spinal cord. E, Axial post-gadolinium T1-weighted fat saturated image at the level of the focal lesion. The mass is central within the spinal cord and enhances avidly.

HYDROSYRINGOMYELIA

Hydromyelia refers to expansion of the central cord that is lined by ependyma. Syringomyelia refers to an eccentric cystic space that is lined by gliotic tissue. Because hydromyelia and syringomyelia cannot be distinguished by imaging, the term hydrosyringomyelia is often used to encompass the two conditions. Patients typically develop hydrosyringomyelia in the setting of abnormal CSF flow, such as in Chiari malformation, arachnoiditis, cord injury, or chronic cord compression caused by an intramedullary or extramedullary mass (Box 10-23).^20,95 In some patients, no predisposing factor is found. The favored hypothesis for syrinx formation is that abnormal CSF flow around the cord forces fluid into the cord through abnormal perivascular and extracellular spaces, forming intramedullary microcysts that then expand to become cystic cavities. This hypothesis is supported by the so-called “pre-syrinx state” of intramedullary high T2 signal that may be observed before frank cyst formation.⁹⁶ Because hydrosyringomyelia may be caused by an underlying neoplasm, contrast should be administered when the syrinx is first observed (Fig. 10-60).

Box 10-23 Hydrosyringomyelia

• Hydromyelia: Expansion of central cord lined by ependyma

• Syringomyelia: Eccentric cystic space lined by gliotic tissue

• History of abnormal CSF flow: Chiari malformation, arachnoiditis, injury to cord, chronic compression of cord by extramedullary mass, or intramedullary tumors

• In some patients, no predisposing factor found

• Favored hypothesis: Abnormal CSF flow around cord forces fluid into cord through abnormal perivascular and extracellular spaces, which form intramedullary microcysts that then expand to cystic cavities; hypothesis supported by pre-syrinx state of high T2 signal before cyst formation

• Contrast should be administered to rule out tumor

Fig. 10-60 A 19-year-old with small cervical spine syrinx and no specific known cause. A, Sagittal T1WI of the cervical spine. A low signal cystic cavity is seen centrally within the cord extending from C6 to T1. The cerebellar tonsils are in normal position with no evidence of a Chiari malformation. B, Sagittal STIR image. The syrinx is hyperintense, following CSF signal. C, Sagittal post-gadolinium T1-weighted fat saturated image. No abnormal enhancement is seen. Contrast administration is necessary to rule out an underlying neoplastic lesion. D, Axial T2WI through the cervicothoracic junction demonstrates the central location of the syrinx within the cord.

MULTIPLE SCLEROSIS

Multiple sclerosis (MS) is a primary demyelinating disease of the central nervous system characterized by multiple lesions disseminated in time and space. Only 10-20% of patients with MS have isolated spinal cord disease; therefore, imaging the brain for concomitant intracranial lesions is often helpful in making the diagnosis.^20,97 MS lesions within the spinal cord generally present as well-circumscribed foci of increased T2 signal peripherally within the cord that extend over two or fewer vertebral segments (Box 10-24). Little if any cord expansion is seen, and cord atrophy may be present, especially in the secondary progressive form of the disease.⁹⁸ Enhancement is variable and is only seen during the acute to subacute phase of a lesion, disappearing within 1 to 2 months (Fig. 10-61).^20,99

Box 10-24 Multiple Sclerosis

• More focal than intramedullary neoplasms (one segment rather than several)

• Less mass effect than cord neoplasm

• Imaging of the brain is helpful to look for MS lesions elsewhere

• Follow-up imaging is helpful to demonstrate lesion evolution

Fig. 10-61 A 39-year-old woman with Devic disease (form of MS presenting with optic neuritis and spinal involvement). A, Axial post-gadolinium fat saturated image of the orbits. The right optic nerve demonstrates mild enlargement and abnormal central enhancement, consistent with optic neuritis. Peripheral optic nerve enhancement is seen more posteriorly within the right optic nerve, a slightly atypical pattern for optic neuritis. B, Sagittal T2WI of the cervical and upper thoracic spine. A hyperintense intramedullary lesion is present, extending from the T4 to T5 levels. There is minimal associated cord expansion. C, Sagittal post-gadolinium T1-weighted fat saturated image of the spine. The lesion demonstrates mild enhancement, consistent with an acute/active MS plaque. D, Axial T2WI at the T4 level demonstrates the high signal lesion slightly eccentric within the thoracic spinal cord.

SPINAL CORD INFARCT

Spinal cord infarction is rare in those younger than 50 years of age and is associated with atherosclerotic risk factors, such as diabetes, cigarette smoking, and hypertension. Abrupt onset of symptoms, including weakness or loss of sensation, is helpful to make the diagnosis.²⁰ Focal hyperintensity is seen within the cord on T2WI, usually extending over more than one vertebral body segment and causing mild cord expansion. The signal abnormality may involve only gray matter or may extend to involve the adjacent white matter or even the entire cross-sectional area of the cord.^100,101 Patchy, ill-defined enhancement can be seen in the subacute phase (Fig. 10-62). Associated vertebral body infarct, although uncommon, may help confirm the diagnosis (Box 10-25), presenting as marrow T2 hyperintensity in the anterior vertebral body or in the deep medullary portion near the endplate.¹⁰² Similarly, reduced diffusion demonstrated on DWI supports the diagnosis of spinal cord infarct.¹⁰³

Fig. 10-62 Spinal cord infarct after abdominal aortic aneurysm repair. A, Sagittal T1WI of the thoracic spine. No acute abnormality is seen. B, Sagittal post-gadolinium T1-weighted fat saturated image of the thoracic spine. Enhancement is seen extending along approximately four segments of the lower thoracic spine as a result of a subacute infarct. C, Axial T2WI at the level of the infarct. A high signal lesion is seen within the central and posterior spinal cord, involving both gray and white matter. The cord is normal to minimally increased in caliber. D, Axial post-gadolinium T1WI at the same level. Enhancement of the lesion is shown.

Box 10-25 Spinal Cord Infarct

• Clinical history and regression of findings over 2- to 3-week period helpful

• Associated vertebral body infarct is uncommon but supports diagnosis

• DWI demonstrates reduced diffusion in the acute stage

TRANSVERSE MYELITIS

Transverse myelitis refers to acute inflammation of the spinal cord that may be idiopathic or caused by direct viral infection or post-viral immunological attack. MRI demonstrates diffuse T2 hyperintensity as a result of cord edema with associated fusiform cord enlargement over multiple contiguous segments. On T1WI, central low signal may be seen within the cord similar to a syrinx but with a slightly higher signal than CSF. Variable patchy enhancement of the involved cord can be seen (Fig. 10-63).^20,104,105 Symptoms often peak at 1 week and typically regress over a 4- to 6-week period, although complete recovery is uncommon.²⁰

Fig. 10-63 A 42-year-old man who presented with progressive weakness after a recent viral upper respiratory tract infection. A, Sagittal T1WI of the cervical and upper thoracic spine. The cervical spinal cord is mildly expanded with mildly reduced signal centrally. B, Sagittal T2WI. High signal is seen throughout the cervical spinal cord, and there also is involvement of the thoracic spinal cord to a lesser degree. C, Sagittal post-gadolinium T1-weighted fat saturated image of the cervical and upper thoracic spine. Diffuse mild enhancement of the spinal cord is seen. D, Sagittal post-gadolinium T1-weighted fat saturated image of the lower thoracic and lumbar spine. Diffuse nerve root enhancement is present. E, Axial T2WI within the cervical spine demonstrates central high signal within the spinal cord. F, Axial post-gadolinium T1-weighted fat saturated image within the lumbar spine demonstrates the brightly enhancing nerve roots of the cauda equina. G, Sagittal T2WI of the cervical spine 1 week later. The cervical spinal cord changes have markedly improved and have almost completely resolved.