Pediatric Supratentorial Intraventricular Tumors

Timothy Mapstone, M.D.,

Disclosures

Neurosurg Focus. 2001;10(6) 

In This Article

Tumors of The Third Ventricle

Primary third ventricular neoplasms are relatively rare regardless of patient age. The vast majority of neoplasms that involve the third ventricle are astrocytomas originating in the wall or the floor of the ventricle and affecting the ventricle by direct extension. Most are low-grade lesions and cause symptoms associated with increased hydrocephalus-induced ICP. Endocrinological deficits and visual disturbances are typically uncommon with tumors arising from within the third ventricle. When visual disturbance is demonstrated, it is usually secondary to extraventricular involvement or optic pathway compression due to ventricular distortion. Mass effect on the hypothalamus or hypothalamic involvement can result in the diencephalic syndrome, which is classically seen in infants and is manifest by emaciation combined with hyperalertness. Lesions located in the posterior segment of the third ventricle can result in mass effect on the pretectal region and/or obstruction of CSF flow.

A variety of tumors can occur in the third ventricle in children, with certain masses more commonly found in the anterior portion compared with the posterior portion of the third ventricle. The more common anterior third ventricular neoplasms are hypothalamic astrocytoma and suprasellar craniopharyngioma. Choroid plexus papilloma, germinoma, teratoma, and ependymoma occasionally are seen in children. Ten percent of CPPs involve the third ventricle and occur primarily in children younger than 5 years of age. Fifteen percent of all supratentorial ependymomas present within the third ventricle. Epidermoid and dermoid tumors occur uncommonly in the anterior third ventricle.

A number of nonneoplastic entities that occur in the anterior body of the third ventricle deserve mention. Colloid cysts represent the most common anterior third ventricular mass demonstrated in adults. These lesions can occur in adolescents and young adults but seldom occur in young children. Both microsurgical and endoscopic procedures have been performed to resect these lesions, and the results have been good. Histiocytosis represents a common anterior third ventricular mass lesion found in children; these lesions tend to arise in the suprasellar region from the floor of the third ventricle and may invade the hypothalamus. Children with these lesions can present with evidence of pituitary-hypothalamic dysfunction and bony skeletal lesions. There appears to be a slight male predominance. The goal of surgical intervention is primarily to obtain a biopsy sample to determine a diagnosis, as these lesions are extremely radiosensitive. Cysticercosis is the most common parasitic infection involving the CNS; it is caused by the intestinal tapeworm Taenia solium and is endemic in some areas of Mexico and certain Third World countries. In the United States, cysticercosis is a rare entity more commonly found in the Western and Southwestern regions. The favored location of cystic lesions is either meningeal or within brain parenchyma. Approximately 12 to 18% are located intraventricularly, possibly gaining access via the choroid plexus. Ventricular involvement is associated with higher patient morbidity and mortality. Cysts may travel via the ventricular system and can cause obstructive hydrocephalus, although the classic clinical presentation in children involves repeated bouts of meningitis rather than hydrocephalus. Treatment of intraventricular cysticercal cysts typically involves three possible options: antihelmintic therapy, CSF diversion, and/or resection of the cysts. Surgery may be necessary to establish a diagnosis or to treat intraventricular lesions that appear to be less responsive to medical therapy. Cerebrospinal fluid diversion for symptomatic hydrocephalus is frequently necessary. Endoscopic management of intraventricular cysticercal cysts, used in combination with third ventriculostomy or septum pellucidotomy in selected cases, has also been described. [10]

Juvenile Pilocytic Astrocytoma. Juvenile pilocytic astrocytomas represent 5 to 10% of all cerebral gliomas and account for approximately one third of glial neoplasms occuring in children. The majority of JPAs are supratentorial, arising from the floor of the third ventricle in the chiasmal-hypothalamic region and extending into the third ventricle. Approximately one third of JPAs are infratentorial, located in the cerebellar vermis or hemispheres. Opticochiasmatic-hypothalamic JPAs are one of the most common supratentorial neoplasms in childhood, with nearly 75% of optic pathway JPAs presenting in patients younger than 12 years of age. [101] Low-grade gliomas are usually indolent, slow-growing neoplasms with symptom presentation and natural history dependent on location. Although these lesions appear macroscopically well defined, they usually infiltrate the optic pathways and hypothalamus. Some of these tumors, however, progress more rapidly or disseminate to the neuraxis. This is especially true for low-grade gliomas involving the hypothalamus and chiasm. [59,72]

Multicentric pilocytic tumors of the optic nerve are particularly common in patients with NF1. As many as 70% of optic pathway tumors are pilocytic astrocytomas associated with NF1. [67] These tumors tend to be very low grade and have a more benign course with favorable prognosis. [103] In a longitudinal study the authors documented that in children with NF1 and isolated optic nerve gliomas disease progression tended not to occur. [66] In fact, a case of spontaneous regression of an optic glioma in a child with NF1 has been reported. [15]

In children in whom the bulk of the tumor occupies the ventricle, the most common clinical presentation involves symptoms of hydrocephalus, but visual disturbance is seldom a predominant complaint. Endocrinological and/or hypothalamic dysfunction tend to occur late in the disease process. In contrast to their cerebellar counterparts, which tend to be cystic masses with a mural nodule, opticochiasmatic- hypothalamic JPAs are usually solid lesions and rarely have associated cysts. Radiographically, they appear iso- to hypodense to brain on CT scans, iso- to hypointense on T 1 -weighted MR images, and hyperintense on T 2 -weighted MR images. These tumors show mild to moderate enhancement with contrast. Treatment is reserved for symptomatic patients, and observation is often recommended especially for children with NF1.

Craniopharyngioma. Craniopharyngiomas represent the most common nonglial neoplasms in children, accounting for 1 to 2% of all intracranial neoplasms and nearly 50% of all suprasellar masses in children. The peak incidence of craniopharyngiomas occurs when the patient is between 5 and 10 years of age. There is a second, smaller peak incidence noted between the fifth and sixth decades. [53] Lesions that involve the third ventricle primarily arise extraventricularly along the infundibular stalk or in the floor of the anterior portion of the third ventricle with ventricular extension. Purely intraventricular craniopharyngiomas are rare, however, with fewer than 30 pediatric cases reported in a recent review. [70] The clinical presentation typically involves a combination of symptoms of raised ICP or manifestations of visual, hypothalamic, or endocrinological dysfunction.

The majority of third ventricular CPs appears to be of the papillary type and accounts for approximately 10% of all craniopharyngiomas. The classic adamantinomatous lesion is typically found in the suprasellar region. The two variants of craniopharyngioma are not only distinct in terms of their morphological features, but also in their age-related incidence, location, radiographic appearance, and prognosis. Papillary craniopharyngiomas are solid, noncalcified masses that are seldom cystic and are more frequently encountered in adults. A dissection plane that separates papillary tumor from the surrounding brain tissue allows for total excision. [1,21] In a review of the Mayo Clinic experience, Duff, et al., [27] found no difference in outcome or recurrence rates between papillary and adamantinomatous tumors. Thus, even though craniopharyngiomas are well circumscribed, they are not encapsulated. Moreover, they tend to become insinuated among and adherent to vital neurovascular structures, making radical resection extremely difficult. This adhesiveness to surrounding neural and vascular structures is a risk factor for poor outcome and/or tumor recurrence. [23,27] Adamantinomatous craniopharyngiomas are more commonly seen in children and tend to be cystic, calcified, suprasellar lesions that are more likely to recur. On MR imaging these lesions have the most heterogeneous signal characteristics of all sellar region masses. The signal is highly variable and dependent on the cyst contents. Craniopharyngiomas enhance strongly but heterogeneously after contrast administration (Fig. 5).

Magnetic resonance imaging studies of suprasellar craniopharyngioma obtained in a patient after placement of a right ventriculoperitoneal shunt for treatment of hydrocephalus. There is a large suprasellar mass that extends into the sella, third ventricle, and into the right middle fossa to the cerebellopontine angle. The lesion displaces the chiasm anteriorly and the upper pons and midbrain dorsally, with compression of the brainstem. Precontrast T 1 - and T 2 -weighted MR images (not shown) demonstrated heterogeneous signal intensity on all sequences with multiple areas of cystic change. There was extensive calcification noted. Following the adminstration of gadolium, axial (A and B), and coronal (C) T 1 -weighted MR images demonstrated heterogeneous enhancment throughout the lesion and rim enhancement in several of the larger cystic regions.

Treatment of these histologically benign but locally aggressive lesions remains controversial. Radical resection has been the mainstay of treatment. Early enthusiasm for radical surgical approaches, however, has been dampened by the recognition that aggressive resection (particularly for retrochiasmatic and giant craniopharyngiomas) was frequently associated with significant morbidity and a relatively high rate of recurrence. [23,35,53,96,122,131] Therefore, efforts have been focused on combining less aggressive resection with adjuvant therapies as a primary treatment, and the reported results are comparable with those of radical resection. [23,36,43,97,106,129] Others have advocated a staged surgical approach and the early incorporation of conservative measures such as stereotactically guided cyst aspiration/ instillations as a strategy to defer the undertaking of external fractionated radiotherapy until a child is old enough. [23,47] The ultimate role of stereotactic radiosurgery for these lesions is currently undefined but appears promising. [18,68,95]

Germinoma. Pure germinomas are the most common primary CNS GCT, accounting for 65% of all CNS GCTs. [128] Although they occur more often in the pineal region, however, suprasellar germinomas can also present in the anterior third ventricle via extension from the infundibular stalk. Occasionally, there is a synchronous pineal region tumor. [118] In rare cases, these tumors arise in the thalamus or basal ganglia. There is a strong male predominance, with most patients presenting between the ages of 10 and 30 years for germinomas involving the pineal region. [64] Both pineal and suprasellar region germinomas occur during the first three decades of life and more often at the onset of puberty. Symptoms depend on the site of growth and the degree of invasion of adjacent structures. Patients with anterior third ventricular germinoma generally present with visual loss, decreased libido, and diabetes insipidus. Diffuse ependymal and subarachnoid seeding is common. Computerized tomography scanning typically reveals a hyperdense lesion. On MR imaging, germinomas tend to be isointense on T 1 - and T 2 -weighted images. They demonstrate homogeneous enhancement after contrast administration.

Because management of CNS GCTs is complicated by the diversity of histological subtypes, accurate diagnosis is paramount to determining the optimal treatment strategy. One key factor is to differentiate pure germinomas from those GCTs that contain an admixture of nongerminomatous elements (choriocarcinoma, endodermal sinus tumor, or embryonal carcinoma). Collectively, the mixed forms are less responsive to adjuvant therapies than pure germinomas. [73] Pure germinomas are typically nonsecreting tumors, whereas nongerminomatous GCTs are secreting tumors, based on elevations of either -fetoprotein or HCGin the serum or the CSF. There is also some evidence to suggest that typical germinomas may occasionally contain foci of syncytiotrophoblastic cells, which are strongly reactive for HCGand human placental lactogen. Placental alkaline phosphatase also appears to be a marker for intracranial germinomas. Although the clinical significance of this variant of HCG-secreting germinoma is not clearly established, as these tumors do not appear to mimic the aggressive malignant behavior of choriocarcinomas, they may be associated with a higher recurrence rate than germinomas without syncytiotrophoblastic components. [132] Other authors have not found any difference in recurrence rates for HCG-secreting germinomas. [105,112] Fortunately, a significant proportion of CNS GCTs can be diagnosed by analysis of tumor markers expressed in the serum or CSF or based on tissue specimens obtained by biopsy sampling or resection. Biopsy sampling of these malignant GCTs carries the inherent risk of histological sampling error, particularly in tumors with mixed elements. Serial analysis of these markers is also essential to determine and monitor treatment response. Tumor marker levels in the serum and CSF must be collected simultaneously, because it is common for normal levels to be observed in the serum while CSF levels are elevated. This finding is especially prevalent in germinomas. [128] In addition, CSF specimens should be obtained from ventricular fluid intraoperatively or within 1 to 2 days postoperatively.

Because pure germinomas are extremely radiosensitive, until recently radiotherapy has remained the cornerstone of treatment. [104,128] A variety of dosing schemes and volumes have been described: whole-ventricle irradiation, [73,113] high-dose whole-brain irradiation, craniospinal irradiation, [45] and/or low-dose irradiation to the craniospinal axis. [46] Others advocate low-dose (20-24 Gy) prophylactic irradiation to the craniospinal axis in patients with positive CSF cytological findings or evidence of dissemination demonstrated on the initial MR images. [110,111] In the past, it was commonplace to assess the radiosensitivity of a lesion by delivering a single fractionated dose to the tumor site, even without initially determining a diagnosis based on examination of tissue specimen. If a radiographic response was demonstrated, the tumor was considered to have germinal origin, and high-dose focal radiotherapy was initiated. [99] Because of the associated long-term sequelae and morbidity of craniospinal radiotherapy in young children, however, recent strategies have been developed to avoid or reduce the role of radiotherapy in the treatment of germinomas. It has become more prevalent to initiate chemotherapy as the primary treatment for patients with CNS GCTs. Pure germinomas demonstrate an 80% complete radiographic response with chemotherapeutic regimens, regardless of the extent of tumor resection. [128] A standard approach for patients in whom CNS GCTs have been diagnosed by the presence of positive tumor markers or by biopsy sample may entail initial chemotherapy followed by radiographic surveillance for residual tumor after completion of two to four cycles. A second-look surgical intervention to resect the lesion or to obtain biopsy sample is reserved for patients in whom an incomplete radiographic response is demonstrated, despite the normalization of tumor markers. [7] Those who have not responded have been found to harbor either fibrotic/ necrotic tissue or a teratomous lesion at second-look surgery. [16] If the teratoma is mature, excision is curative and no further therapy is indicated. If an immature teratoma is confirmed, local-field irradiation is initiated after resection. Some investigators have also suggested that radical resection of nongerminomatous GCTs may offer some survival benefit. [7,73,128]

Colloid Cyst. These histologically benign lesions are typically found in the roof of the third ventricle at the level of the foramen of Monro. Colloid cysts account for 15 to 20% of all intraventricular masses and represent the most common mass lesion found in the anterior portion of the third ventricle. The histogenesis of colloid cysts remains unclear. They are rare in children, with only 1 to 2% occurring in patients younger than 10 years of age. Colloid cysts rarely become symptomatic before the patient reaches 20 years of age and are usually found in adults in the second to fourth decades of life. Clinical behavior is the same in children as adults. Symptoms of intermittent hydrocephalus are common and sudden death secondary to acute obstruction has been reported, although in the majority of cases of sudden death there appeared to be a history of symptoms indicating increasing ICP that preceded the event by weeks to months. Occasionally, acute hemorrhage within the cyst may be the presenting clinical symptom. Imaging characteristics vary depending on the contents of the cyst.

A variety of tumors may arise from the region of the posterior region of the third ventricle, reflecting the varied tissue types that originate in this region. The majority of neoplasms are glial in nature (two thirds of which are usually high grade) and include astrocytomas and, to a lesser extent, ependymomas. A number of tumors arise from the pineal region and have been reviewed in preceding sections. These include the pineal region germinomas and teratomas. Pineal parenchymal tumors such as pineoblastomas, pineocytomas, and other GCTs (embryonal cell carcinomas and choriocarcinomas) are rare tumors that arise in the posterior third ventricle. Regardless of the tumor type, lesions in the posterior third ventricle cause a similar constellation of symptoms related to obstructive hydrocephalus or involvement of the pretectal plate and resulting in Parinaud syndrome.

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