Pathogenesis and Pathophysiology. There are no known risk factors for these tumors. Ependymomas arise from ependymal cells lining the ventricles and the spinal cord central canal. Histologically, ependymomas are well demarcated from the surrounding structures and are marked by pseudorosettes, often located in the perivascular region. Blepharoplasts, intracellular structures associated with cilia formation, are also present. Anaplastic ependymomas have increasing features of nuclear atypia, necrosis, and mitotic figures. Myxopapillary ependymomas are usually confined to the filum terminale and have a distinctive fibrillary pattern with mucin secretion.y
Epidemiology and Risk Factors. Ependymomas represent less than 5 percent of all intracranial tumors. They occur in younger patients, usually in children, with a slight predominance among young men, although they can present in adults up to 30 years of age. An infratentorial location is more common in children, whereas supratentorial ependymomas are more common in adults. Cerebrospinal fluid dissemination and systemic metastasis can occur.
Clinical Features and Associated Disorders. Patients with ependymomas have symptoms corresponding to the part of the neuroaxis affected by the tumor. For example, tumors arising in the spinal cord can lead to localized back pain, sensory disturbances with a demonstrated dermatomal line, weakness of both legs, or disturbances of bowel or bladder control. Ependymomas arising in the fourth ventricle, brain stem, or lateral ventricles can present with evidence of headaches or other symptoms of hydrocephalus (especially nausea and vomiting), ataxia, and increasing head circumference. Neck pain and behavioral changes also are common presenting complaints in children. Because ependymomas may be present for as long as 3 to 6 months before they come to clinical attention, symptoms may sometimes be labeled chronic.
Differential Diagnosis and Evaluation. The differential diagnosis of these tumors includes other CNS tumors such as medulloblastoma and low-grade glioma. Other more benign lesions such as meningioma do not have similar characteristics on MRI. Patients require surgical intervention when this tumor is diagnosed pathologically. Prior to surgery, the entire neuroaxis should be imaged with gadolinium-MRI to determine involvement of other sites such as "dropped" metastasis. The resection attempt should be as extensive as possible, but occasionally this is not feasible. At least 2 weeks following surgery and before radiotherapy, the cerebrospinal fluid should be evaluated for seeding of the cerebrospinal pathways with tumor cells.
Management. After surgery radiotherapy is the mainstay of treatment for patients with residual tumor. y Craniospinal irradiation is often given to treat clinically undetected
seeding of cerebrospinal spaces. In patients with negative cerebrospinal fluid examination after surgery, this is not indicated because it may hamper future treatment of localized recurrence. Myxopapillary ependymomas can often be cured with complete surgical resection. Chemotherapy has been shown to be of minimal benefit in patients with anaplastic ependymoma, although chemotherapy regimens including carboplatin and etoposide have been shown to prolong survival in several small series. The use of craniospinal irradiation results in extensive treatment of the vertebral bone marrow, leaving little reserve for the cytotoxic chemotherapy. With newer cytokines such as the colony-stimulating factors that stimulate bone marrow function, patients may be able to tolerate more chemotherapy, allowing better appraisal of its use in these patients. Recurrence is usually local, although patients can develop distant metastasis. An increased risk of recurrence is associated with incomplete resection. Surgical resection, if feasible, should be strongly considered when the tumor recurs, followed by conventional radiotherapy to previously nonirradiated areas. Salvage chemotherapy also remains an option at recurrence.
Prognosis and Future Perspectives. Survival may be increased in patients who undergo resection of tumor and radiotherapy. Overall survival is similar to that for low-grade gliomas or oligodendrogliomas. Patient age of less than 5 years and a posterior fossa location of the tumor suggest a worse outcome. No histological predictors of survival are available at this time. Future improvements in therapy can be expected with better understanding of the histological variants, application of radiotherapy and chemotherapy to more malignant subtypes of these tumors, and a better understanding of the molecular basis of tumor pathogenicity.
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