Ependymomas

RELATED CONDITIONS: Glial tumors and gliomas

DEFINITION: An ependymoma is a central nervous system cancer arising from the ependymal cells that line the fluid-containing ventricles and central canal of the brain and spinal cord. Ependymomas are a type of glial cell tumor. They are collectively derived from the cells that support and nourish neural cells. Ependymomas account for three percent of all glial cell tumors and six to nine percent of all primary central nervous system tumors.

Risk factors: The most salient risk factor relates to a genetically mediated transformation of normal ependymal cells into tumor cells. A history of neurofibromatosis type 2 is associated with the development of spinal ependymomas. Neurofibromatosis type 2, an autosomal dominant syndrome, is caused by a mutation in the NF2 gene manifesting with skin lesionscafé-au-lait spotsand bilateral hearing loss from acoustic nerve tumor growth. Familial occurrences of isolated ependymomas have also been documented.

Etiology and the disease process: Ependymomas originate from the transformation of an ependymal cell. Although no single aberration has been implicated, the involvement of chromosome 22 has been most commonly involved, the same chromosome that bears the NF2 tumor-suppressor gene (22q12). Changes seen in genetic studies include:

• Translocationremoval and subsequent reattachment of a chromosomal segment to another chromosome
• Deletion of the long arm (22q)
• Monosomyabsence of one half of a chromosome pair

One family study has narrowed down this region (22pter-22q11.2), suggesting a tumor-suppressor gene may be responsible. Different studies noted aberrations in several other chromosomes.

Incidence: Ependymomas have two incidence peaks: in early childhood and adulthood. The mean age of ependymoma occurrence in childhood is five years, peaking again during adulthood at a mean age of thirty-four. However, a substantial number of ependymomas in children, 30 percent of all childhood cases, manifest before age three. By location, ependymomas in the brain are seen more commonly in children90 percent of cases. In comparison, spinal, or intramedullary, tumors are more commonly seen in adults60 percent of cases.

Symptoms: Obstruction of cerebrospinal fluid (CSF) flow within the fourth ventricle, with resulting pressure buildup and tissue compression, usually occurs. Brain stem involvement may be seen as irritability or lethargy. Cerebellar symptoms denoting involvement may be seen as frequent loss of balance and dizziness. Occasional cerebrum involvement may manifest as personality and behavioral changes, one-sided body weakness, or paralysis. Symptoms of increased pressure include nausea, vomiting, morning headache, and vision changes. Physical examination findings may include papilledemaswelling of both optic nerveslimb incoordination with voluntary movements, cranial nerve VI to X compression signs such as eye movementnystagmus, lateral gaze weakness or paralysisfacial movement, speech, and swallowing abnormalities, and increase in head circumference in babies younger than two years of age. Spinal cord manifestations correspond with the affected nerve root level, ranging from pain to sensory deficits, weakness, paralysis, loss of reflexes, and muscle wasting.

Screening and diagnosis: There are no routine screening tests available for ependymomas. Clinical history, physical examination, and neuroimaging tests such as magnetic resonance imaging (MRI) or computed tomography (CT) can suggest an ependymoma. These tumors are seen as intraventricular or intramedullary masses that closely match or are darker than surrounding tissue. Clues that may aid in distinguishing a tumor from normal tissue include cystic formations, calcifications, hemorrhage, or necrosis. The final diagnosis of the type of ependymoma is mainly pathological when a tissue sample is examined microscopically and classified according to the World Health Organization classification for ependymal tumors. Grade I includes subependymomas and myxopapillary ependymomas; grade II includes cellular, papillary, and clear-cell ependymomas, and grade III ependymomas are of the anaplasticalignantvariety.

Treatment and therapy: Treatment of ependymomas includes surgical removal, radiation therapy, and chemotherapy. The most critical factor in a good prognosis is surgical removal, in which a gross total resection is done irrespective of tumor location, removing the entire primary tumor. Postoperative radiotherapy and chemotherapy, a regimen of cisplatin, etoposide, carboplatin, vincristine, and mechlorethamine or of ifosfamide, carboplatin, and etoposide (ICE) are carried out to prevent recurrence. Radiotherapy is preferred over chemotherapy, except in malignant cases. Restoration of average cerebrospinal fluid circulation through the ventricles and central canal is a secondary objective if the assessment of cerebrospinal fluid shows poor outflow postoperatively. This may be achieved by adding a device diverting excess cerebrospinal fluid to the abdominal cavityventriculoperitoneal shunt.

Prognosis, prevention, and outcomes: Twenty-two people in 100,000 will contract a central nervous system tumor. The ten-year ependymoma survival rate is more favorable for adults than children. For adults, this rate is 89 percent. For children, this percentage drops to 64 percent. This lower rate is attributed to the typical location of tumors in children. The prognosis depends on several predictors, the most significant being the extent of tumor resection. Other factors include the remaining tumor, tumor grade, age, infratentorial location, local spread to the brain stem, metastases, and recovery rate.

Complications associated with posterior fossacerebellarresection surgery include cerebellar mutismspeech deficits or absence with cerebellar deficitsand long-term neurologic deficits.

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