Choroid Plexus Tumors

Published on 26/03/2015 by admin

Filed under Neurosurgery

Last modified 22/04/2025

Print this page

This article have been viewed 4050 times

CHAPTER 197 Choroid Plexus Tumors

Bruce A. Kaufman

Clinical Background

As a group, the choroid plexus tumors can be a great challenge to treat. The risks associated with their surgical treatment are increased by their typical location within the ventricles, their significant vascularity, and the frequent presentation in our smallest patients. However, the benign forms are curable, and even the more malignant forms can have successful long-term survival with combined treatments.

Choroid plexus tumors are rather infrequent neoplasms, representing less than 1% of all tumors.¹^–³ However, they are much more frequent in the pediatric population and can represent a sizeable percentage of the tumors in children younger than 1 year of age.⁴^,⁵ Choroid plexus and its tumors are derived from the specialized neuroepithelial cells in the ventricles. The tumors can recapitulate the characteristics of normal choroid plexus in their structure and appearance and in their function, with the overproduction of cerebrospinal fluid resulting in hydrocephalus. There are also more aggressive forms, with clearly anaplastic features that more closely resemble carcinomas. Significant glial characteristics can also be expressed.

Choroid plexus tumors must be included in the differential diagnosis of the young child or adult presenting with an intraventricular mass. Surgical resection has become an essential part of the treatment of these lesions, with the specific approach based on the tumor location and characteristics. Although the outcome is a function of the tumor type and required treatments, cures and long-term survival are quite possible. See Case 197-1 for an illustrative example of evaluation of an intraventricular mass in a 1-year-old child.

Case 197-1

Case provided by Dr. Frederick A. Boop, LeBonheur Children’s Hospital and St. Jude Children’s Cancer Center Research Hospital.

One-Year-Old with an Intraventricular Mass

This case illustrates a typical presentation and evaluation of an infant with an intraventricular tumor. There are difficulties of treatment: in particular, defining a balance between immediate intervention and presurgical adjunctive therapy. The child experienced treatment complications that are significant and indicative of the severe nature of these tumors.

Presentation

This 12-month-old boy presented with typical symptoms and signs of increased intracranial pressure. The child had been irritable, with no focal motor findings, but had a bulging fontanelle and split cranial sutures. He underwent prompt cranial imaging.

Imaging

Magnetic resonance imaging clearly showed generalized hydrocephalus and a left intraventricular mass at the atrium consistent with a choroid plexus tumor (Fig. 197-E1). The mass appears to be completely within the left lateral ventricle, with no obvious brain edema, nor any invasion of the parenchyma. Several flow voids are seen within the tumor suggesting large vessels.

FIGURE 197-E1 Axial T1-weighted magnetic resonance imaging. A large tumor is seen in the body of the left lateral ventricle, with concurrent significant hydrocephalus. There is no edema of the surrounding brain seen in this image, nor any obvious brain invasion.

The tumor enhances brightly with gadolinium, showing a structure along the superior and lateral margins of the mass that resembles normal choroid plexus. However, more medially, there are definite structural differences (Fig. 197-E2). These differences are seen much better on the T2-weighted images (Fig. 197-E3). In addition, there is a small area of increased signal in the lateral wall of the ventricle that is consistent with brain invasion.

FIGURE 197-E2 Gadolinium-enhanced T1-weighted magnetic resonance imaging, coronal (A) and sagittal (B) views. The tumor shows enhancement throughout. In both orientations, the more “papillary” architecture is seen on the top and sides of the tumor. The medial aspects are different from the rest of the mass.

FIGURE 197-E3 A and B, T2-weighted magnetic resonance imaging, coronal views. The different structural components are seen more easily on these images. An area of increased signal extending from the tumor laterally into the brain parenchyma is seen in B, suggesting brain invasion.

The lack of tumor uniformity and the possibility of brain invasion suggested the diagnosis of a choroid plexus carcinoma. This was further supported by the finding of disseminated disease seen on spinal imaging.

Treatment

Chemotherapy was started with the intent of reducing the tumor vascularity before surgical resection. However, the child developed a right gaze preference and a left hemiparesis, prompting insertion of a shunt. He deteriorated further, becoming obtunded and developing quadriparesis.

The child underwent surgery to remove the cranial tumor. Although a gross-total resection was achieved, the child lost 3 blood volumes during surgery. After surgery, the obtundation, gaze preference, and left hemiparesis resolved quickly, whereas the right hemiparesis resolved slowly. Pathology confirmed a choroid plexus carcinoma.

With adjunctive chemotherapy, the child has remained free of disease for at least 5 years but does have significant deficits.

History

Guerard in 1832 provided the first description of a choroid plexus tumor found at autopsy of a 3-year-old girl.⁶ The first surgical resection was reported in 1906, with the first long-term survival in an adult in 1919.⁷^,⁸ Until the 1930s, a number of reports focused on the rarity of these lesions and their association with hydrocephalus.⁸^–¹⁷ Van Wagenen¹⁷ reported excision and good survival of a lateral ventricle tumor in a 3-month-old child in 1930. Dandy¹⁸ reported his transcallosal approach to the third ventricle to remove a choroid plexus tumor in a 14-year-old girl. Masson¹⁹ reported a transfrontal approach to the third ventricle to successfully remove a third ventricular papilloma in 1934.

The focus of more recent reports has been on gross-total surgical resection, even with the malignant forms of these tumors. There has also been the suggestion of a pathologically intermediate form of choroid plexus tumor that resembles the benign papilloma but may behave much more aggressively.

Presentation

Incidence

Choroid plexus tumors may occur during any stage of life and thus represent only 0.5% to 0.6% of all intracranial tumors.^2,^3,²⁰ They are clearly more frequent in the pediatric age range, representing up to 2.9% of all pediatric brain tumors, but account for between 10% and 20% of tumors in infants younger than 1 year.^4,^20,²¹ Considering only choroid plexus tumors, 70% are found in children and 50% in children younger than 2 years.^5,²¹^–²⁶ Congenital examples have been reported, including tumors detected on prenatal ultrasound.^20,²⁷^–³¹ There does not appear to be clear evidence of a sex predilection, with a reported male-to-female ratio of 1.2 : 1.³² Some reports have noted a slight male predominance, whereas others have seen an equal distribution.^1,^21,^25,³³^–³⁵

The malignant forms (choroid plexus carcinoma) account for 15% to 20% of choroid plexus tumors, but 80% of these malignant tumors are found in children.^24,³⁶^–³⁹ Although these tumors tend to have a shorter duration of symptoms, there does not appear to be a difference from the benign tumors with respect to age at presentation, sex, type of symptoms, or location of the tumor. The carcinomas have a marked propensity to metastasize.⁴⁰ Metastasis is the exception for the benign forms, but the satellite lesion retains the benign histology.

Symptoms

Patients with choroid plexus tumors do not have a single typical clinical presentation. Most symptoms are predicated on the location of the tumor, the size of the tumor, or the presence of hydrocephalus. Choroid plexus tumors generally have a shorter duration of symptoms when compared with other pediatric brain tumors, and the malignant forms typically have even shorter symptom duration.

The most common symptoms are associated with increased intracranial pressure (ICP).^20,^22,^26,³⁵ The increased ICP may result directly from the large tumor size or from the tumor location obstructing the outflow of cerebrospinal fluid (CSF) and the development of obstructive hydrocephalus. Interestingly, not all choroid plexus papillomas produce hydrocephalus. In younger children, the signs of increased ICP include the sometimes subtle observations of increased head circumference or split sutures before the more obvious signs of vomiting and lethargy. In adult patients, the symptoms can be ataxia, nausea, and vomiting.

In many cases, there is generalized hydrocephalus with ventricular enlargement, not only from obstruction but also possibly from an overproduction of CSF, with up to 800 mL per hour reported in one case.^22,^23,^26,⁴¹^–⁴⁷ The overproduction of CSF is also supported by electron microscopic morphologic findings consistent with CSF production, with the frequent resolution of hydrocephalus after tumor removal, and with a report of ascites after shunting but before tumor resection.⁴⁸ However, increased rate of CSF production has been actually shown in only a few patients.^42,^43,^46,⁴⁷

Alternative causes for hydrocephalus have been suggested, including the effects of subtle hemorrhage or ventriculitis occurring before any surgery. There is a failure to resolve hydrocephalus after tumor removal in up to 50% of patients, and this could be due to operation-induced hemorrhage or inflammation.^21,^26,^35,^46,^49,⁵⁰ It is likely that there are multiple factors of CSF production and absorption that affect the occurrence and resolution of hydrocephalus.

Some patients will manifest focal neurological signs as a result of hemorrhage or focal invasion. For example, tumors located in the fourth ventricle can present with brainstem and lower cranial nerve symptoms related to direct brainstem or cerebellar compression. Patients with tumors in the third ventricle have been reported with various endocrine disturbances, the bobble-head doll phenomenon, and diencephalic dysfunction.^16,⁵¹^–⁵³

Location

Choroid plexus tumors are generally found where the choroid plexus is located—the lateral ventricle in 40% to 50%, third ventricle in 5% to 10%, fourth ventricle in about 40%, and more than one ventricle in about 5%.^17,^21,^25,^26,^37,^40,^48,⁵⁴^–⁵⁷ Primary extraventricular locations have been rarely described, including the cerebellopontine angle, cerebellomedullary cistern, suprasellar cistern, foramen magnum, and spinal subarachnoid space.⁵⁸^–⁶¹

There is a correlation of ventricular location with age, however, that is without an obvious pathophysiologic cause. The lateral ventricular location is most common and the fourth ventricular location least common in children ^4,^20,^23,^32,^56,^58,^62,⁶³ (Fig. 197-1). In a meta-analysis, the median ages at diagnosis were 1.5 years, 1.5 years, 22.5 years, and 35.5 years for patients with lateral, third, and fourth ventricle and cerebellopontine angle tumors, respectively.³² Bilateral tumors have been reported, but the sheer size of some tumors precludes accurately defining the multifocal origin versus direct extension.^23,^48,⁵⁵

FIGURE 197-1 Comparison of age and tumor location. Most lateral ventricle choroid plexus tumors occur in children. The fourth ventricular tumors are more equally distributed in all age groups, with a slight increase in incidence in the later decades.

(Data adapted from Wolff JEA, Sajedi M, Brant R, et al. Choroid plexus tumours. Br J Cancer. 2002;87:1086-1091.)

The lateral ventricle tumors are typically located at the atrium, although they can be found more anteriorly near the foramen of Monro and in the temporal horn. These tumors are usually very large at presentation, often greater than 4 to 6 cm.²¹ There may be a predilection for lateral ventricle tumors to occur on the left side, but this is an inconsistent finding. The fourth ventricle tumors are usually in the midline. There can be extension into and through the lateral recesses of the ventricle.³²

There are rare reports of metastatic masses derived from the benign forms of choroid plexus tumors. The metastases retain the same pathologic structure and are assumed to be “drop” lesions, disseminating through the CSF.⁶⁴ It is possible that this group of choroid plexus papillomas showing metastases is a unique and more aggressive variant called an atypical choroid plexus papilloma. There has been one case of pulmonary metastasis.⁶⁵ However, metastases are a notable feature in the malignant forms of choroid tumors.

The blood supply to the intraventricular tumors is the same as for normal choroid plexus in that ventricle. The principal arterial supply to the choroid of the lateral and third ventricles comes from the anterior and posterior choroidal arteries.⁶⁶^,⁶⁷ The anterior choroidal artery comes off the internal carotid artery, courses through the choroidal fissure, and supplies the choroid and tumors primarily in the atrium and temporal horn. The posterior choroidal arteries arise from the posterior cerebral artery. The lateral posterior choroidal artery enters the ventricle near the crus of the fornix and supplies the choroidal tissues in the temporal horn, atrium, and body of the lateral ventricle. The medial posterior choroidal artery has a variable supply to the lateral ventricle through the choroidal fissure and foramen of Monro, but it does supply the choroid in the roof of the third ventricle. Thus, tumors of the third ventricle and some in the lateral ventricle can be supplied by branches of this vessel. Because of the significant anastomosis and overlap in arterial supply, both the anterior and posterior choroidal arteries can contribute feeders to these intraventricular tumors.⁶⁶^,⁶⁷ The choroid of the fourth ventricle is supplied by branches from both the posterior inferior cerebellar and the superior cerebellar arteries.

The venous drainage for the lateral ventricular choroid tumors is through subependymal veins into the choroidal fissure, in particular the thalamostriate vein, to the foramen of Monro to the deep cerebral venous system (internal cerebral veins, vein of Rosenthal, vein of Galen). The fourth ventricular tumors can drain into the quadrigeminal and precentral cerebellar veins to the deep system. These anatomic relationships are important for planning the surgical approach.

Diagnosis

Imaging

The evolution of imaging for brain lesions has also affected the diagnosis of choroid plexus lesions. Plain radiography, while done infrequently in the modern era, can show nonspecific calcification within the tumor and nonspecific signs of increased intracranial pressure such as split sutures.^1,^55,^68,⁶⁹ In the past, pneumoencephalography and ventriculograms were used to indirectly demonstrate these tumors but with significant morbidity and mortality.⁵⁰ These studies have been replaced with direct imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) usually obtained for the initial evaluation of symptoms in these patients.

Angiography used to be routinely performed to demonstrate the vascular supply of the tumor. The lateral ventricular tumors would consistently show enlarged anterior or lateral posterior choroidal arteries. The third ventricular tumors would be shown supplied by the medial posterior choroidal arteries. The tumors would have an irregular blush. Raimondi and Gutierrez ⁵⁰ provide excellent examples of these angiographic findings. However, currently, angiography is rarely indicated for diagnostic purposes; the vascular supply to these tumors both is consistent and can be effectively demonstrated on MRI.

CT will show a variable density to these tumors, ranging from isodense to hyperdense relative to the brain.²²^,²⁶ Calcification occurs in about 10%²⁶ (Fig. 197-2). The tumor is usually well demarcated from the brain tissue and has rather dramatic enhancement.²⁶ Areas of cystic degeneration can suggest the more malignant choroid plexus carcinoma.²²

FIGURE 197-2 Computed tomography (without contrast) of choroid plexus papilloma. A, The frontal choroid plexus tumor has caused hydrocephalus with periventricular edema in the frontal lobes. The tumor is isodense to hyperdense relative to brain. B, This fourth ventricular tumor demonstrates calcification and a relative hypodensity to brain.

MRI will provide excellent anatomic delineation of the tumor and surrounding brain. The choroid plexus papilloma appears lobulated and separate from the surrounding brain tissue (Fig. 197-3). They are usually isointense to brain on T1-weighted imaging and enhance uniformly. The T2-weighted images show an intermediate to high signal intensity, and the serpentine vascular supply and drainage can be easily seen as flow voids.⁴⁰^,⁷⁰

FIGURE 197-3 Magnetic resonance imaging of choroid plexus papilloma. A, Sagittal T1-weighted image showing the intraventricular mass at the trigone, well demarcated from the ventricle. B, With administration of gadolinium, the tumor enhances brightly and relatively uniformly, with the lobulated nature more prominently seen.

The distinction between papillomas and carcinomas, however, is not always clear-cut. Some papillomas demonstrate adjacent cerebral edema and invasion, whereas some carcinomas do not (Fig. 197-4). Choroid plexus carcinomas often have lost the lobulated appearance and have invasion of the parenchyma with associated vasogenic edema.⁴⁰^,⁷⁰ There is frequently significant hemosiderin signal change and extensive enhancement with administration of gadolinium-DTPA, although with more variability than seen in papillomas.

FIGURE 197-4 Magnetic resonance imaging: comparison between papilloma and carcinoma. A, T2-weighted, axial section. A papilloma shows significant adjacent cerebral edema. There is some consistent fine structure seen inside the tumor. There may be some brain invasion at the lateral edge of the tumor. B, T2-weighted, axial section. This carcinoma also shows significant adjacent brain edema. The structure within the tumor is much less defined. There may be brain invasion laterally, but the tumor appears generally distinct from the brain. C, T1-weighted, gadolinium-enhanced, axial section. The papilloma enhances nearly uniformly and demonstrates a small lobular structure. The edges are distinct from the surrounding brain. D, T1-weighted, gadolinium-enhanced, axial section. The carcinoma also enhances brightly, but with much less regularity within the tumor. There is a loss of the fine lobules seen in the papilloma. There is not a clear site of brain invasion.

Magnetic resonance spectroscopy has shown consistently a prominent choline peak with an absent N-acetyl aspartate peak. Choroid plexus papillomas appear to have a significantly higher myoinositol signal than both choroid plexus carcinomas and all other brain tumors.⁷¹ The carcinomas had markedly elevated choline peaks.⁷¹^,⁷²

A quality MRI, obtaining images in all three planes using T2 and T1, without and with gadolinium sequences, should allow the complete definition of these tumors, the surrounding and feeding vessels, and the CSF spaces adjacent to the tumor. Magnetic resonance angiography can also add information on the vascular supply and now usually obviates the need for diagnostic angiography, although attempts at embolization can be considered.

All the tumors in the differential diagnosis, including ependymoma, primitive neuroectodermal tumor, astrocytoma, germinoma, teratoma, and meningioma, can have similar imaging characteristics. It can even be difficult to define the difference between the benign choroid plexus papilloma and the malignant choroid plexus carcinoma. Modern imaging cannot yet accurately define the pathologic diagnosis. However, the magnetic resonance spectroscopy findings of papillomas compared with carcinomas suggest that preoperative differentiation is possible. This could have a tremendous effect on planning, with a greater emphasis on embolization or chemotherapy for the identified carcinoma.⁷¹

Pathology

Choroid Plexus Papilloma

Choroid plexus papillomas correlate with World Health Organization (WHO) grade I classification.⁷³ On gross inspection, the choroid plexus papillomas are well circumscribed and globular, with a pink to reddish-gray color. They are frequently described as cauliflower like, and tend to expand and fill the ventricular cavity. There is limited if any direct brain invasion, but the tumors can cause extensive compression of the brain.

Microscopically, the papillomas are easy to identify as they recapitulate the structure of normal choroid plexus tissue ⁷⁴^,⁷⁵ (Fig. 197-5). There is a single layer of cuboidal to columnar cells, usually without cilia or blepharoplasts as in normal choroidal epithelium, covering a stroma of delicate fibrovascular connective tissue. The nuclei are monomorphic and toward the base of the cells, and mitoses are rarely seen in papillomas but if present can signify a more aggressive form. It is sometimes difficult to identify papilloma from normal choroid plexus, but the papillomas tend to have higher cellularity and more cellular and nuclear pleomorphism.⁵⁸ Papillary ependymomas of the ventricle must be distinguished from choroid plexus papillomas. However, the ependymoma has a fibrillary neuroglial stroma that is absent in the papillomas.

FIGURE 197-5 Microscopic pathology (hematoxylin-eosin staining). A, Normal choroid plexus. The cells are monomorphic and evenly placed around a thin fibrovascular stroma. B, Choroid plexus papilloma: the general architecture of the normal choroid is recapitulated, but the cell density is increased, and the cells are not as uniform. C, Choroid plexus carcinoma. The underlying stroma has been lost, and mitotic figures are seen, with much greater cellular variability. Necrosis and parenchymal invasion were seen in other areas of this tumor. D, Choroid plexus carcinoma with brain invasion. The image demonstrates an interface of the tumor (lower right) invading the brain parenchyma, accompanied by lymphocytic infiltration.

If there is also brain invasion, a malignant change to a carcinoma can be considered. There have been reports of papillomas undergoing malignant transformation, but the pathology was also reported to show mitoses and may actually represent a previously unrecognized variant of the tumor (atypical choroid plexus papilloma).⁷⁶^–⁸⁰

Choroid Plexus Carcinoma

Choroid plexus carcinomas correlate with WHO grade III.⁷³ The gross structure of the choroid plexus carcinoma is not similar to normal choroid, and the tumor at surgery is usually friable. There is usually clear-cut invasion of adjacent tissue. The changes on microscopic examination are equally obvious, with loss of the papillary structures into ill-defined patterns, and a loss of the fibrous supporting stroma seen in papillomas (see Fig. 197-5). The cells are variable in size and shape, densely packed or heaped up, with frequent mitoses and nuclear variability.⁷⁴^,⁸¹

The malignant changes in the carcinomas are usually obvious, although in the older literature, there has been debate about which feature is most important in making the diagnosis. Retrospective reviews that applied more recent criteria for diagnosis of a carcinoma identified that only half of the reported cases fit the definition.⁸²^,⁸³ The most consistent histologic criteria for diagnosis of a carcinoma will have a tumor with cellular anaplasia, loss of the papillary fibrous stroma, frequent mitosis and necrosis, and giant cell formation.²¹^,⁴⁰

The presence of brain invasion has been suggested as a required component for the diagnosis of choroid plexus carcinoma (see Fig. 197-5).⁸⁴ However, there can be tumors with otherwise benign histologic features showing some brain invasion, and others with anaplastic features appearing to have circumscribed borders.²¹^,⁸⁵ The technique of surgical resection could obliterate the tumor-brain interface and render that distinction moot.²¹ MRI may give the best indication of brain invasion, but it is does not seem realistic to require the demonstration of brain invasion as the sole diagnostic criterion for choroid plexus carcinoma.

The choroid plexus carcinoma can be confused with metastatic carcinoma in adults or with neuroepithelial embryonal tumors in children.⁵⁸ A combination of cytologic, ultrastructural, and immunohistochemical evaluations can be used to differentiate choroid plexus carcinomas from atypical teratoid/rhabdoid tumors (AT/RT).⁸⁶

Atypical Choroid Plexus Papillomas

Recent attention has been focused on the few patients with tumors that for the most part appear pathologically just like papillomas but behave in a more aggressive fashion with a higher rate of recurrence and demonstrating dissemination.⁸⁰ These have been recognized as atypical choroid plexus papillomas and may represent up to 15% of all choroid plexus papillomas.³⁷ They can have more invasion than expected with papillomas, more cellular pleomorphism, and increased cellularity. The only histologic feature that consistently defines this group of tumors is having 2 or more mitoses per 10 high-power fields.³⁷ These tumors correlate with WHO grade II.⁷³

Choroid Villous Hypertrophy

It is not clear whether there is a distinct pathologic entity of choroid villous hypertrophy. Davis ¹⁰ described this in 1924 as a bilateral choroid plexus lesion. It is hard to determine, however, whether this entity is not really the same as a bilateral papilloma, given the relatively small pathologic difference between normal choroid plexus and papillomas. The overproduction of CSF could occur with either entity. Treatment of these bilateral lesions has resulted in the resolution of CSF overproduction, whether through resection or endoscopic coagulation of the plexus.^46,^87,⁸⁸

Immunohistochemistry and Molecular Biology

The immunohistochemistry of choroid plexus tumors has not shown a clear-cut distinction among the various forms.⁷⁴ The tumors can show both epithelial and glial characteristics. Normal choroidal tissue can demonstrate expression of S-100, low-molecular-weight keratin (CKER), and keratin. S-100 staining is seen in 55% to 90% of papillomas and is found variably in carcinomas.⁷⁴^,⁷⁸ Significant S-100 staining (>50% of cells) has been associated with a more benign histologic appearance and a better outcome. Glial fibrillary acidic protein (GFAP) and cytokeratin are expressed in both papillomas and carcinomas but can also be seen in normal choroid plexus and some carcinomas.⁷⁴^,⁸⁹ GFAP-positive cells are usually absent in normal choroid plexus but can be seen in infant choroidal tissue.⁷⁵ GFAP positivity can be seen in 25% to 55% of papillomas and in up to 20% of carcinomas. Carcinoembryonic antigen positivity has been seen in up to 100% of choroid plexus carcinomas but also in 29% of papillomas. Its presence is associated with a more aggressive behavior.⁷⁴ As might be expected, the cellular proliferation indices (Ki-67, MIB-1) are typically low in papillomas and higher in carcinomas.⁹⁰^,⁹¹

Chromosomal analysis of papillomas and carcinomas by comparative genomic hybridization showed a multitude of chromosomal gains and losses.⁹² However, there was a significant difference in the aberrations in the carcinomas compared with the papillomas. There was also a difference between papillomas in adult and pediatric patients. This supports the theory that these tumors develop from different genetic abnormalities and suggests why malignant degeneration from papilloma to carcinoma seems so rare.

Surgical Treatment and Complications

Surgical treatment of these lesions through the 1980s consistently resulted in high operative mortality and morbidity rates (25% to 65%).^1,^22,^63,^69,⁹³ This was due to the less sophisticated imaging, with difficulty in accurately defining the tumors preoperatively, and to the often very significant blood loss in infants. Modern surgical treatment has improved through the use of enhanced preoperative delineation of the tumors and use of steroids, anesthetic techniques, and microsurgical techniques that provide better direct vision and lighting to the tight confines of intraventricular surgery. The more recent results have been much better, but perioperative death still occurs.^21,^35,^39,⁵⁰

Surgical planning begins at patient presentation, when a decision may need to be made regarding the timing and type of treatment for hydrocephalus in an acutely ill patient. Often a balance must be achieved between treating the hydrocephalus and performing the appropriate diagnostic tests or preoperative intravascular embolization. If the patient’s condition requires urgent treatment of the hydrocephalus, early diversion with an external ventricular drain (EVD) can be used, but maintaining enlarged ventricles can ease the exposure and dissection at surgery. Shunting at presentation is not usually indicated. It may not ultimately be needed, and it does not allow for a measured decompression of the enlarged ventricles. Appropriate imaging should include an MRI, which can define the vascular supply and any brain invasion.

The surgical approach is planned to maximize the exposure of the tumor, with the aim of gaining early access to the vascular supply to the lesion. The goals are to achieve a gross total resection of the lesion and to alleviate any hydrocephalus (temporarily or permanently). The tumor locations within the ventricular system virtually ensure an approach through normal neurological tissue, some inferior fourth ventricular lesions excepted.⁶⁶^,⁶⁷

The standard technique of internal debulking is fraught with danger in these tumors with significant vascularity. An attempt at extensive debulking often results in unacceptable blood loss, morbidity, and the risk for death from rapid exsanguination.³⁹ Early “control of the vascular pedicle” has been stressed but may not be allowed by the required approaches, which often place the vascular pedicle on the opposite side of the tumor from the surgeon.²⁶^,⁶⁹ This has led to recommendations for preoperative embolization, which is more feasible in this age of superselective interventional angiography.²⁶ However, the option for embolization may be limited in very small children and infants because of complications of vascular access.²⁶

A technique of gentle, repetitive bipolar coagulation can be used along the surface of choroid plexus papillomas (Video 197-1). The fibrovascular stroma allows for excellent coagulation and control of bleeding, with significant shrinkage of the tumor bulk. With patient application, the tumor mass can be shrunk to allow for visualization of the vascular pedicle. Small vessels can be coagulated and cut, but the larger ones may require clipping. Manipulation of the tumor must be done carefully to prevent disruption of the vascular pedicles before they can be controlled. This technique is not very successful for choroid plexus carcinomas, which tend to be much more friable, likely because they lack the fibrous stroma that aids coagulation and permits retraction and manipulation of the tumor.

All the standard surgical approaches are useful for choroid tumors of the posterior fossa. An external ventricular drain can be placed for control of the hydrocephalus (if not already in place). A midline craniotomy, or far lateral craniectomy for lesions in the cerebellopontine angle, allows direct access to the tumor. The cerebellar tonsils can be dissected to the side to gain access to the feeding vessels. The velum across the bottom of the cerebellar hemispheres can be divided to gain access to the fourth ventricle, but vermis can be split as needed to gain access to the vessels and attachments dorsally. Care must be taken to look for anomalous venous drainage, such as a deep vein into the floor of the fourth ventricle, although most of these variations should be seen on preoperative MRI. Cerebellopontine angle tumors pose unique challenges. They can have feeding vessels from both the posterior and inferior cerebellar arteries, and they will usually have some approximation with the lower cranial nerves, resulting in the need for tedious and careful microscopic dissection.

All the typical approaches to the third ventricle can be used. The interhemispheric-transcallosal approach, using either transforaminal or interforniceal access to the ventricle, should give prompt access to the feeding and draining vessels. The transcortical-transventricular (through the choroidal fissure) can also give appropriate exposure depending on the exact tumor location.

The best approach to use for choroid tumors of the lateral ventricles is dependent on the tumor location within the lateral ventricle. The chosen approach must take into consideration access to the tumor and to the vascular supply and the potential neurological morbidity of the transgressed tissue. Lesions in the frontal horn may be approached through the middle frontal gyrus or sometimes through a transcallosal approach. Lesions in the trigone can be accessed through a small cerebrotomy in the superior parietal lobule, although this approach on the dominant hemisphere has inherent risks. An approach through the middle temporal gyrus can be used, especially with tumors limited to the temporal horn, although it is limited in the exposure of the vascular supplies. Some will elect to perform dual craniotomies, from an anterior and a posterior approach, to gain access to the vascular supply at either end of the tumor.

As previously discussed, hydrocephalus may persist even after tumor removal, ranging in frequency from 24% to 50%.^21,^26,^39,^49,⁵⁰ It is treated with shunting in a standard fashion. Each surgical approach will entail risks specific to that approach, but in general these include postoperative hematoma formation, developmental and neuropsychological deficits, visual field defects, and cranial nerve deficits. Seizure problems can persist in 25% of papilloma patients after resection. Hemiparesis can remain in another 25%, but 25% will have no morbidity.

The development of large, symptomatic subdural fluid collections occurs regularly with these tumors.^5,^25,²⁶ They occur not as a result of a specific surgical approach but as a function of the suddenly decompressed brain (from hydrocephalus or tumor evacuation).²⁵^,⁵⁷ Shunting does not always resolve the collections but will treat any pressure effects.

Subdural collections may be avoided by use of a modified “brain patch” technique.^25,^26,⁹⁴ A small corticotomy is used, kept at a superior position, allowing the decompressed ventricular cavity to be filled and the brain “floated” with saline. The corticotomy is sealed, either with Gelfoam surrounded by fibrin glue or with pial sutures and sealant. After the tissue sealant has set, a ventricular catheter inserted into the cavity can be used to slowly infuse more saline and “inflate” the brain. The catheter is withdrawn from the brain, the hole is sealed, and the catheter is then used as an externalized subdural drain. Although subdural collections may still form, the tissue sealant closure allows subsequent direct treatment and resolution of only the subdural collection.²⁶

Outcomes

The extent of surgical resection remains the most important factor in determining long-term survival in patients with tumors of the choroid plexus.^21,^22,^26,^32,^39,^56,⁹⁵^–⁹⁸ Adjuvant therapy is used for malignant tumors and those that have shown leptomeningeal spread. Radiation therapy is reasonable in adults and older children, especially in the context of dissemination or residual malignant tumor. It has no significant role in younger children, in whom severe developmental delay would result from such treatment.

Choroid plexus papillomas have an excellent long-term survival after only gross-total resection, ranging from 90% to 100%.^21,^26,⁵⁶ This group of patients may have some major morbidity, with up to 25% having a seizure disorder and 25% having hemiparesis. About 25% will have no significant morbidity.

Patients with choroid plexus carcinomas treated only with surgery have had a very poor outcome: disease progresses rapidly, and patients often die within 1 year.^21,^82,^84,^99,¹⁰⁰ The early use of radiation therapy did extend survival but at a significant developmental cost because most of these patients are younger than 2 years.³²^,³⁸ This result led to the use of combination chemotherapy after surgery, with a notable improvement in survival rate to 26% to 50% at 5 years.^21,^39,^79,^95,^96,^101,¹⁰²

As the combination of improved surgery and aggressive chemotherapy was used consistently on choroid plexus carcinomas, the long-term survival rate began to approach 75%.^26,^84,¹⁰³ In turn, this prompted use of chemotherapy as preoperative adjunctive treatment.^21,^24,^84,^103,¹⁰⁴ A biopsy or subtotal resection of the tumor would confirm the diagnosis, followed by multidrug chemotherapy. After tumor regression on chemotherapy, a second surgery to attempt complete excision would be performed. The tumor vascularity was decreased, which aided resection and correlated with the significant fibrosis seen on pathology.

It appears that the key to long-term survival with choroid plexus carcinoma is the achievement of gross total resection, even if multiple surgeries are required.^21,^26,^39,^95,¹⁰³ Recurrences tend to manifest early.³⁷ It has been controversial whether chemotherapy is required after gross total resection, but generally it has been undertaken owing to the aggressive nature of these tumors.⁷⁹ Chemotherapy without complete resection does not provide the same long-term survival.