Neuro-oncology
What to know
Presenting features reflect location and intracranial pressure: morning headache and vomiting, papilledema, head tilt, ataxia, and nystagmus for posterior fossa tumors; seizures and focal deficits for supratentorial lesions; endocrine and visual complaints for sellar masses.
Medulloblastoma is the most common malignant pediatric brain tumor; it arises in the fourth ventricle, may disseminate through CSF, and is treated with resection, craniospinal radiation, and chemotherapy. Pilocytic astrocytoma is the most common pediatric brain tumor overall; it is a cerebellar cyst with a mural nodule, often BRAF-altered, with excellent prognosis after gross total resection. Ependymoma arises from the fourth ventricular floor and can extrude through foramina; treatment is resection plus local radiation. Diffuse midline glioma (formerly DIPG) is H3K27M-mutant, pontine, unresectable, and treated palliatively with radiation. Craniopharyngioma is a calcified sellar/suprasellar mass causing visual field loss, diabetes insipidus, and obesity. Germ cell tumors arise in the pineal or suprasellar region and secrete AFP or beta-hCG. Optic pathway glioma occurs with NF1 and is often treated with chemotherapy to avoid radiation in young children.
Late effects: radiation causes neurocognitive decline, endocrinopathy, second tumors, and moyamoya; platinum agents cause hearing loss; methotrexate causes leukoencephalopathy.
Traps
Lumbar puncture is contraindicated with raised intracranial pressure. Steroids can shrink lymphoma and confound histology but should not be withheld when pressure is dangerously elevated. Do not call a posterior fossa mass harmless solely because its histology is likely pilocytic.
Rule of thumb
A child with a posterior fossa mass and hydrocephalus needs urgent neurosurgical evaluation; dexamethasone and ventricular drainage precede biopsy.