Presentation and Initial Course

Weakness (100%), sensory loss (89%), back pain at onset (82%), and urinary complaints requiring catheterization (75%) were the most common symptoms of cord ischemia at the time of presentation in a prospectively collected series (Masson et al., 2004). In retrospective series, the same major symptoms are observed, though with minor differences in observed frequency (Kumral et al., 2010; Nedeltchev et al., 2004; Novy et al., 2006). The most common location to be affected is the mid- to low thoracic spine. Lower cervical lesions are less common, and upper thoracic spinal infarcts are rare. Quadriparesis is present in only 20% to 25% of all cases of spinal infarction.

Pain and sensory changes occur first in most cases, followed by weakness within minutes or hours. Over 80% of the back pain with spinal infarction follows a radicular pattern (Novy et al., 2006), but in cases of acute aortic disease, pain may have a more visceral character. Maximum motor disability is observed within 12 hours of onset in a majority of patients, with a trend toward longer intervals when dysfunction was less severe. Urinary retention is typical in the acute phase, but involuntary voiding or defecation may be associated with the onset of the ischemic insult.

Examination Findings

Weakness most commonly affects both legs. Examination typically reveals flaccid paresis accompanied by diminished superficial and tendon reflexes below the level of the lesion. Preservation of strength and reflexes suggests posterior spinal artery territory infarction. Sensory changes, when present, nearly always affect spinothalamic modalities. Isolated proprioceptive loss is rare.

Investigations

Magnetic resonance imaging (MRI) is the diagnostic procedure of choice for detecting spinal cord ischemia, although the results can be normal in up to one-third of patients (Novy et al., 2006). In the acute phase of spinal cord infarction, high diffusion-weighted imaging signal is noted and matches with low apparent diffusion coefficient signal (Thurnher and Bammer, 2006). Pencil-shaped hyperintense signal on T2-weighted images initially appear within 2 hours to several days, and may be accompanied by gadolinium enhancement (Weidauer et al., 2002). Abnormal signal and contrast enhancement may demonstrate a double-dot (“owl’s eyes”) pattern in the region of the anterior horns, an H-shaped pattern involving the central gray matter, or a more diffuse pattern involving both gray and white matter (Fig. 51E.3). The diffuse pattern may be difficult to distinguish from venous infarction. When cord infarction results from compromise of a segmental artery, branches supplying the ipsilateral half of the vertebral body may also be affected. Vertebral body infarct is best detected on sagittal T2-weighted images, usually appearing as a triangular area of increased signal near the end-plate and/or deep medullary portion of the vertebral body.

Fig. 51E.3 Subacute arterial infarction of the conus medullaris. A 69-year-old man had sudden onset of paraparesis and loss of bowel and bladder function 8 days prior to the magnetic resonance (MR) study. A, T2-weighted, fast-spin echo image shows focal enlargement and hyperintense signal within the conus medullaris. B, Postcontrast T1-weighted axial image (T12 level) shows abnormal enhancement in an H-shaped pattern involving the central gray matter.

(From Bowen, B.C., Saraf-Lavi, E., 2005. Magnetic resonance imaging and magnetic resonance angiography of spinal vascular lesions. In: Latchaw, R.E., Kucharczyk, J., Moseley, M.E. (Eds.), Imaging of the Nervous System. Diagnostic and Therapeutic Applications, vol 2. Mosby, Philadelphia, pp. 1707-1722, with permission.)

Other laboratory and radiographic studies are not diagnostic in noncompressive spinal cord ischemia. Myelography is usually normal. Cerebrospinal fluid (CSF) protein was elevated in 44% of one series, but pleocytosis was not observed (Novy et al., 2006).

The exact cause of spinal ischemia often remains occult and could not be discerned in up to half of prospective and retrospective series (Masson et al., 2004; Novy et al., 2006).

Course

The course of spinal ischemic syndromes is variable. Transient ischemic attacks have been reported to precede up to 10% of cord infarcts (Kumral et al., 2010; Novy et al., 2006). Pain is often persistent and is a major contributor to long-term disability after spinal cord infarction. A slowly progressive myelopathy attributed to chronic constriction of radiculomedullary arteries in the neck has been suggested but not established.

Prognosis

Rates of recovery vary widely among case series, which were collected by different methods. In a prospectively collected series, approximately half of patients had a favorable outcome, defined as the ability to walk with one assistive device (or none) and no need for urinary catheterization at the time of hospital discharge (Masson et al., 2004). Recent retrospective series also suggest that ambulation can be restored in about 50% of patients (Kumral et al., 2010; Novy et al., 2006). Likelihood of recovery is higher when the deficits are less severe at presentation. Over a mean follow-up period of 4 years, more than 90% of patients with the mildest severity of deficit during the acute phase were able to walk independently or with assistive devices; in contrast, nearly one-third of more severely affected patients required a wheelchair (Nedeltchev et al., 2004). Poor outcome is predicted when proprioceptive loss, gait impairment, or urinary dysfunction were present at the time of presentation. Chronic pain can be a disabling consequence of cord ischemia, but it tends to occur only in individuals with spinothalamic sensory impairment early in the course. The duration of motor dysfunction is also useful in determining prognosis. Unless significant motor recovery occurs in the first 24 hours, the likelihood of major improvement is low.

Causes of Spinal Cord Ischemia

In recent series, the cause of spinal cord infarction could not be identified in up to 74% of cases. Among cases with identifiable causes, mechanical triggering movements were most common (Kumral et al., 2010; Novy et al., 2006). A high frequency of concomitant spinal column disease and the pattern of clinical findings suggest compression of radicular arteries in cases with mechanical trigger events. Most infarcts associated with spinal disease (e.g., chronic radicular pain, compression fractures) follow anterior or posterior spinal artery patterns and occur at the level of the mechanical stresses in the spine (Novy et al., 2006). Other typical causes of spinal ischemia are summarized in (Box 51E.1).

In contrast, mechanical triggering events are not associated with central or transverse infarct patterns. Systemic arterial disease was noted more frequently in patients with transverse patterns (Novy et al., 2006). Aortic pathologies with regional hemodynamic compromise accounted for 30% to 40% of cord infarcts in older case series. Complications of aortic surgery represented the largest proportion of those cases. Prolonged clamping of the aorta above the renal arteries (e.g., for more than 20-30 minutes) or operative ligation of lower thoracic intercostal vessels places the cord at risk for ischemia and infarction. Open thoraco-abdominal aortic aneurysm repairs are associated with a 5% to 20% risk of significant neurological deficits. Endovascular techniques appear to be safer, but they do not completely eliminate risks for spinal cord ischemia. Intraoperative interventions like distal aortic perfusion and CSF drainage may also contribute to lower complication rates.

Systemic hypotension also produces cord ischemia, but because encephalopathy is common after resuscitation, isolated spinal cord syndromes are infrequent. Transverse cord infarcts are associated with prolonged hypotension. Localized thoracic cord ischemia may result from disordered autoregulation following percutaneous radiofrequency spinal rhizotomy.

Atherosclerotic plaques in the aorta may overlie the origin of branches to the spinal cord and diminish their blood flow or be a source of embolism. Transesophageal echocardiography may identify such plaques in the descending aorta. Occlusive arterial disease may result in intermittent claudication of the spinal cord, manifested by activity-induced transient symptoms of myelopathy. Intermittent spinal claudication may respond positively to aortobifemoral bypass.

Radiotherapy produces myelopathy associated with occlusive changes in parenchymal spinal cord arterioles. The degree of myelopathy depends on the total radiation dose, dose per fraction, and the length of the irradiated segment of the cord.

Thromboembolism causes both acute and stepwise spinal cord dysfunction. Emboli arising from the mitral valve in rheumatic heart disease and from acute bacterial endocarditis may cause acute paraplegia. Similarly, thromboembolism from an atrial myxoma may cause multiple spinal cord infarcts. Myelopathy associated with decompression sickness (also known as Caisson disease [see Chapter 51A]) results from circulating nitrogen bubbles that block small spinal arteries. Spinal cord ischemia also may complicate therapeutic renal or bronchial artery embolizations.

Fibrocartilaginous emboli from ruptured intervertebral disks are the cause of an ischemic syndrome unique to the spinal cord. Fragments of connective tissue material from the damaged disk are traumatically forced into bone marrow sinusoids by local fracture. The increased tissue pressure at the site of injury allows retrograde entry of emboli into the spinal vertebral plexus as well as into arterial channels, leading to cord infarction (Fig. 51E.4). Approximately half of these events are purely arterial; the rest have mixed arterial and venous involvement. The anterior portion of the cervical cord is affected in up to 70% of such cases. Women are affected twice as often as men.

Fig. 51E.4 Pathological sections from a 19-year-old man who died after cervical fibrocartilaginous embolism. A, Segmental infarction in the posterolateral cord. B, Intraluminal fibrocartilaginous material in the infarcted region.

(From Freyaldenhoven, T.E., Mrak, R.E., 2001. Fibrocartilaginous embolization. Neurology 56, 1354, with permission.)

Vasculitic and thrombotic causes of spinal cord ischemia are well known. Before the antibiotic era, meningovascular syphilis was a common cause of anterior spinal artery ischemic syndromes, and spinal meningitis continues to be occasionally associated with paraplegia of vascular origin. Systemic inflammatory conditions such as Crohn disease, polyarteritis nodosa, and giant cell arteritis may also lead to myelopathy. Sickle cell disease, intrathecal chemical irritants, angiographic contrast material, the postpartum state, and intravascular neoplastic invasion all predispose to thrombosis and spinal cord infarction.

Venous infarction without hemorrhage is clinically indistinguishable from the arterial ischemic syndromes. There may be an associated systemic thrombophlebitis that propagates into the spinal canal via the venous plexus. A subacute necrotizing myelitis (Foix-Alajouanine syndrome) causing stepwise spinal cord dysfunction occurs with extensive spinal cord thrombophlebitis in association with chronic obstructive pulmonary disease or a neoplasm (usually of the lung). This condition may also be the end-stage result of chronic venous hypertension and congestion resulting from dural venous fistula. Polycythemia rubra vera can also lead to noninflammatory spinal venous thrombosis with subsequent cord ischemia.

Treatment

The medical management of spinal cord ischemia focuses on supportive measures and reducing risk for recurrence. Recurrence risk is managed with maintenance of adequate blood pressure, early bed rest, and reversal of proximate causes such as hypovolemia or arrhythmias. Acute thrombolysis has not been systematically studied, but treatment with intravenous recombinant tissue plasminogen activator at usual stroke doses may be beneficial in some patients (Restrepo and Guttin, 2006). The low incidence of spinal cord infarction and the variability of its natural course make systematic treatment trials of thrombolysis and antithrombotic therapies unlikely. Over the longer term, care is directed toward minimizing the complications of autonomic dysfunction and immobility. Physical and occupational therapy are useful in promoting functional recovery.

Distribution and Prevalence

Prior to the widespread use of modern diagnostic imaging, patients with vascular malformations were often classified among patients with manifestations of spinal tumors. The reported frequency of vascular malformations as a subset of spinal tumors ranged from 3% to 11%. The actual frequency of malformations could be higher, since patients with small asymptomatic or misdiagnosed lesions may have been overlooked.

Spinal dural AVF is the most common type of spinal vascular malformation. These usually drain to the dorsal surface of the cord. Spinal dural AVFs are identified most frequently between ages 30 and 70, and there is a 9 : 1 male predominance. When symptoms develop during childhood, the vascular malformation is more likely to be an AVM (type II or III vascular malformation). The predominant locations for vascular malformations are the lower thoracic and lumbar spine regions.

Clinical Presentation and Course

Spinal vascular malformations, especially dural AVFs, are frequently misdiagnosed. The onset of symptoms can be acute or insidious, and the course may include remissions and relapses. The most common complaints at onset are pain, weakness, and sensory symptoms referable to the lower thoracic and lumbar regions. Later, bowel and bladder complaints may evolve. Triggering factors include trauma, exercise, pregnancy, or menstruation. Misdiagnosis, especially as demyelinating disease, was common before MRI of the spine. Nonetheless, the interval between symptom onset and accurate diagnosis may be years. Severe locomotor disability develops in approximately 20% by 6 months after onset of symptoms and in 50% by 3 years. Once leg weakness or gait difficulties emerge, they tend to progress rapidly.

The signs and symptoms of spinal vascular malformations are attributable to mass effect and ischemia. It is unusual for an unruptured spinal AVM to produce sufficient mass effect to cause spinal cord dysfunction. However, epidural, subdural, or intramedullary hemorrhage can arise from the malformation and produce spinal cord compression. Dural arteriovenous fistula rarely produces hemorrhage and typically presents as a slowly progressive myelopathy, which has been attributed to venous hypertension and intramedullary venous congestion that eventually can progress to infarction.

Pain may be local, radicular, diffuse, or any combination of these. Upper motor neuron weakness, lower motor neuron weakness, or both may occur. A spinal bruit is a highly specific (though uncommon) finding that is diagnostic of a spinal AVM. Vascular malformations in the skin or paraspinal muscles are sometimes noted in conjunction with spinal AVMs. In cutaneomeningospinal angiomatosis (Cobb syndrome), a cutaneous angioma appears in the dermatome corresponding to the AVM’s spinal segment. Foix-Alajouanine syndrome (see Causes of Spinal Cord Ischemia earlier in this chapter) has been associated with end-stage dural AVF with thrombosis and venous infarction.

Spinal hemorrhage usually has an abrupt onset and may be associated with the typical symptoms of spinal subarachnoid hemorrhage (SAH), including headache, meningeal infection, and cord and nerve root damage. Even in the absence of SAH, the CSF may be abnormal, with mild pleocytosis and elevated protein.

Vascular malformations (AVMs and dural AVFs) may cause increased local venous pressure, decreased perfusion pressure, decreased tissue perfusion, and finally tissue ischemia. This explains the coexistence of deficits in more than a single arterial territory and the symptomatic improvement that results from ligation of feeding vessels. The sometimes confusing and widely varied presentation of spinal vascular malformations results in a large differential diagnosis that includes neoplasms, herniated discs, multiple sclerosis, intracranial SAH, subacute combined degeneration, meningovascular syphilis, and transverse myelitis (see Chapter 24).

Investigations

In the pretreatment evaluation of vascular malformations, plain radiography is rarely helpful. MRI and magnetic resonance angiography (MRA) have supplanted radiographic myelography in most cases. Myelography requires careful technique to detect the serpentine filling defects caused by abnormal intradural vessels (which can be confused with nerve roots in the lumbar region). The definitive radiological procedure in the pretreatment evaluation of vascular malformations is selective spinal (catheter) angiography using digital subtraction techniques. Many institutions perform this procedure while the patient is intubated and under general anesthesia. Selective spinal angiography is tedious and typically requires that each segmental artery in the region being examined be injected.

MRI can discriminate extramedullary from intramedullary lesions, document thrombosis of the malformation following ligation or embolization of the feeding vessels, and demonstrate changes in the spinal cord (edema, hemorrhage) distinct from, yet due to, the vascular malformation. Routine MRI is also sensitive in detecting intramedullary AVMs (types II and III vascular malformations). The findings include intramedullary low signal with surrounding normal cord tissue, focal cord enlargement at the location of the nidus, and serpentine signal voids within the subarachnoid space in the region of the nidus (Fig. 51E.5). MRA augments the MR study by confirming the location of the nidus and allowing better visualization of the AVM drainage to the coronal venous plexus on the surface of the spinal cord.

Fig. 51E.5 Magnetic resonance imaging (MRI) and contrast-enhanced three-dimensional magnetic resonance angiography (3D MRA) of a cervical intramedullary glomus-type arteriovenous malformation (AVM). A, Precontrast T1-weighted sagittal image shows a focal hypointense intramedullary lesion at C3. The cord is not enlarged. B, Postcontrast T1-weighted axial image confirms the intramedullary location of the lesion. C, T2-weighted, fast-spin echo sagittal image shows serpentine flow voids posterior to the cervical cord from C1 to C3. D-E, Sagittal (D) and coronal (E) targeted magnetic resonance angiograms (MRAs) demonstrate the intramedullary nidus communicating with an enlarged posterior median vein.

(From Bowen, B.C., Saraf-Lavi, E., 2005. Magnetic resonance imaging and magnetic resonance angiography of spinal vascular lesions. In: Latchaw, R.E., Kucharczyk, J., Moseley, M.E. (Eds.), Imaging of the Nervous System. Diagnostic and Therapeutic Applications, vol 2. Mosby, Philadelphia, pp. 1707-1722, with permission.)

In cases of dural AVF (Fig. 51E.6), MR abnormalities involving the spinal cord have been observed with variable frequency: slight enlargement of the cord; cord hypointensity on T1-weighted images and hyperintensity on T2-weighted images, involving the central region of the cord and extending over several levels; scalloping of the cord contours on sagittal images; and enhancement of the cord on postcontrast T1-weighted images. Of these findings, the most consistently observed is hyperintensity within the center of the cord on T2-weighted images. In general, however, these findings are nonspecific and, like the clinical findings, can mimic those of cord neoplasm, infection, or ischemia from arterial occlusive disease. Thus, detection of blood flow–related signal abnormalities in the subarachnoid space is crucial to achieving high diagnostic accuracy for dural AVF. The detection of intradural flow voids on T2-weighted images, and the detection of intradural serpentine enhancement on T1-weighted images extending for more than three contiguous vertebral levels, are each associated with the presence of dural AVF (Saraf-Lavi et al., 2002). Contrast-enhanced three-dimensional (3D) spinal MRA provides more direct and extensive visualization of the abnormal intradural vessels (veins), and when added to standard MRI can improve detection of dural fistulas. MRA improves localization of the vertebral level of the fistula; digital subtraction angiography (DSA) studies performed after MRA required less than 50% of the fluoroscopy time and volume of iodinated contrast when the fistula level and side were identified on pre-DSA MRA (Luetmer et al., 2005).

Fig. 51E.6 Magnetic resonance imaging (MRI) and contrast-enhanced three-dimensional magnetic resonance angiography (3D MRA) of a right T11 dural arteriovenous fistula. At the time of the MRI, this 68-year-old man had a 3-year history of progressive myelopathy. His symptoms began approximately 6 months after radiotherapy and surgical excision of a carcinoma of the right lung apex. His progressive neurological deficits were initially attributed to radiation myelitis of the upper thoracic cord. After surgical obliteration of the fistula, his symptoms improved. A, Fast-spin echo T2-weighted image shows hyperintense cord from T6 to T10 and serpentine flow voids, consistent with enlarged intradural vessels, posterior to the cord from T8 to T10. B, Postcontrast T1-weighted image shows hyperintense vertebral bodies from T4 to T7, as seen in A and consistent with radiation changes. There is patchy enhancement within the cord from T6 to T10. C, MRA (targeted to posterior half of the spinal canal) demonstrates an enlarged tortuous vessel (arrow) extending from the right T11 foramen to the posterior cord surface, where numerous convoluted vessels are seen. The right T11 vessel corresponds to the posterior medullary vein draining the fistula. D, Digital subtraction (catheter) angiogram (anteroposterior view) following injection of the right T11 posterior intercostal artery demonstrates a fistula in the region of the right neural foramen, with drainage into the canal via the medullary vein (arrow).

(From Bowen, B.C., Pattany, P.M., 1999. Vascular anatomy and disorders of the lumbar spine and spinal cord. In: Ross, J. (Ed.), The Lumbar Spine. Magnetic Resonance Imaging Clinics of North America. Saunders, Philadelphia, pp. 555-571, with permission).

Treatment

The treatment of spinal vascular malformations is by surgical resection and/or angiographically directed embolization of the malformation. Iatrogenic emboli promote thrombosis and decrease blood flow. A sequential approach of embolization, followed by definitive surgical therapy, is common.

Subarachnoid Hemorrhage

Spinal SAH accounts for less than 1% of all SAHs. The most common cause is a spinal angioma, but these account for only about 10% of the total. Other associated conditions include coarctation of the aorta, rupture of a spinal artery, mycotic and other aneurysms of the spinal arteries, polyarteritis nodosa, spinal tumors, lumbar puncture, blood dyscrasias, and therapeutic thrombolytics and anticoagulants.

Clinical presentation of spinal SAH is characterized by the sudden onset of severe back pain, which localizes near the level of the hemorrhage. The pain typically becomes diffuse, and signs of meningeal irritation become prominent within minutes. Multiple radiculopathies and myelopathy may be present. Headache, cranial neuropathies, and a decreased level of consciousness are associated with diffusion of blood above the foramen magnum. The CSF is grossly bloody, intracranial pressure is frequently elevated, and papilledema may be present.

Correct diagnosis requires a strong clinical suspicion. The evaluation of spinal SAH frequently follows negative radiological studies of the intracranial structures. History may reveal the initial severe back pain or prior anticoagulant use. Physical examination may reveal a spinal bruit, cutaneous angioma, sensory level, the stigmata of collagen vascular disease, or evidence suggesting septicemia. Radiological studies are discussed under Spinal Vascular Malformations (see earlier discussion). Treatment is directed toward the underlying cause.

Hematomyelia

Intramedullary spinal hemorrhage most often results from trauma. Hematomyelia may follow direct trauma to the spinal column or hyperextension injuries of the cervical spine. Spontaneous hematomyelia most often results from bleeding of a spinal vascular malformation, hemorrhage into a spinal tumor or syrinx, a bleeding diathesis, anticoagulant drugs, or venous infarction. The hemorrhage tends to disrupt spinal gray matter more than white matter. There are no recognized intraspinal counterparts to intracerebral hypertensive hemorrhage and amyloid angiopathy. Hematomyelia most commonly presents as spinal shock associated with the sudden onset of severe back pain, which is often radicular. Later, spasticity develops below the level of the lesion, and fasciculations, atrophy, and areflexia may occur in the myotomes corresponding to the lesion.

MRI is the best imaging modality to detect intramedullary hemorrhage. Lumbar puncture may be consistent with SAH. The initial treatment is supportive. Laminectomy and drainage of the hematoma, followed by resection of the tumor or vascular malformation, can be performed if neurological deficits are incomplete or progressive.

Spinal Epidural and Subdural Hemorrhage

Spinal epidural hemorrhage (SEH) occurs more frequently than spinal subdural hemorrhage (SSH). SEH is more commonly observed in men and has a bimodal distribution, with peaks during childhood and the fifth and sixth decades of life. Cervical lesions are more common in childhood, whereas thoracic and lumbar lesions predominate in adults. Hemorrhages can be spontaneous but often occur following exertion or trauma. SEH is a complication of both lumbar puncture and epidural anesthesia and is more likely in anticoagulated patients. Other causes include blood dyscrasia, thrombocytopenia, neoplasms, and vascular malformations. Pregnancy also appears to increase risk for SEH.

SSH is most common in women. It may occur at any age but tends to predominate in the sixth decade. Most occur in the thoracic and lumbar regions. Hemorrhagic diatheses, including treatment with anticoagulants, blood dyscrasias, and thrombocytopenia, are the precipitating factors most commonly associated with SSH. Other factors include trauma, lumbar puncture, vascular malformation, and spinal surgery.

The clinical presentations of SEH and SSH are indistinguishable. The initial symptom is severe back pain at the level of the bleed. Myelopathy or cauda equina syndrome, with motor and sensory findings corresponding to the level of the lesion, develops over hours to days. The diagnosis should be suspected in patients with disorders of coagulation who have undergone recent lumbar puncture and develop back pain or signs of spinal cord or root dysfunction. Patients with a rapidly decreasing platelet count or less than 20,000 platelets/µL are at particular risk of developing SEH or SSH as a complication of lumbar puncture and should receive a platelet transfusion prior to the procedure. Clotting studies and a platelet count are important in the initial evaluation. In SEH and SSH, the CSF may be normal, xanthochromic, or contain increased protein.

MRI can delineate the size and location of the hematoma. In addition, gadolinium-enhanced MRI and MRA may show an underlying vascular malformation. In patients unable to tolerate MRI or where it is unavailable in the acute phase of the illness, myelography with computed tomography (CT) scanning provides an alternative. Myelography can reveal a partial filling defect or complete blockage to the flow of contrast material at the level of the lesion. However, the myelographic appearances of SEH and SSH may be indistinguishable.

Both SEH and SSH are surgical emergencies. Operative treatment is directed toward relief of local pressure and repair of any underlying defect. Laminectomy with evacuation of the clot should be performed as soon as possible. The prognosis for recovery is better when the preoperative deficits are not severe; timing of surgery appears less important (Börm et al., 2004).