NEURORADIOLOGY

Imaging Findings

Study shows infra-tentorial cerebellar mass lesion with CSF metastasis.

Diagnosis

Medulloblastoma with CSF metastasis

Discussion

This tumor usually originates in the cerebellum. It may spread contiguously to the cerebellar peduncle, floor of the fourth ventricle, into the cervical spine, or above the tentorium. In addition, it may spread via the cerebrospinal fluid intracranially and/or to the spinal cord. Every patient with medulloblastoma should be evaluated with diagnostic imaging of the entire neuraxis, and when possible, lumbar cerebrospinal fluid analysis for free- floating tumor cells.

The most sensitive method available for evaluating spinal cord subarachnoid metastasis is spinal magnetic resonance imaging (MRI) performed with gadolinium. Cerebrospinal fluid shunts at the time of surgery have not been shown to increase the risk of leptomeningeal relapse.

Prognosis

Patients with disseminated disease at diagnosis are clearly at highest risk for disease relapse. Other factors that may portend an unfavorable outcome include younger age at diagnosis, brain stem involvement, subtotal resection, and a nonposterior fossa tumor. These prognostic variables must be evaluated in the context of the treatment received.

Subclassifications For Risk

Average risk - Children older than 3 years of age with posterior fossa tumors; tumor is totally or "near-totally" (<1.5 cubic centimeters of residual disease) resected; no dissemination.

Poor risk - Children younger than 3 years of age or those with metastatic disease and/or subtotal resection (>1.5 cubic centimeters of residual disease) and/or nonposterior fossa location.

Further Reading

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