Medulloblastoma

INTRODUCTION

Medulloblastomas are the most common malignant brain tumor of childhood and occur in the cerebellum. The disease is rare after the fourth decade of life.

The epidemiology, clinical presentation, diagnosis, and risk stratification of medulloblastoma in children and adults will be discussed here. The histopathology, molecular pathogenesis, treatment, prognosis, and delayed complications in survivors are discussed separately.

●Epidemiology – Medulloblastoma is the most common malignant brain tumor of childhood, accounting for approximately 10 percent of all primary tumors of the central nervous system among children less than 19 years of age. The peak incidence is in children between five and nine years of age.

●Clinical features – Patients with medulloblastoma present with a combination of signs and symptoms, typically of increased intracranial pressure and cerebellar dysfunction. Common symptoms include nocturnal or morning headaches, nausea, vomiting, and gait ataxia.

On neurologic examination, patients may exhibit papilledema secondary to increased intracranial pressure; cerebellar findings such as head titubation, nystagmus, and ataxia; and cranial nerve dysfunction.

●Neuroimaging – MRI typically demonstrates a midline or paramedian cerebellar mass that enhances after administration of contrast and often compresses the fourth ventricle. Dilation of the ventricles secondary to obstructive hydrocephalus may be seen.

●Differential diagnosis – The differential diagnosis of a cerebellar mass in a child includes other tumors with a predilection for the cerebellum, the most common of which are pilocytic astrocytoma, ependymoma, and atypical teratoid/rhabdoid tumors (ATRT); in adults, extra-central nervous system metastatic tumors should also be considered.

●Diagnosis – The diagnosis of medulloblastoma requires pathological confirmation at the time of surgical resection. Leptomeningeal dissemination is present in approximately one-third of patients at the time of diagnosis and confers a worse prognosis.