Neuro-oncology and Neurosurgical Neurology
Expect a ring-enhancing lesion with a question about the differential and the next step, plus tumour markers that predict treatment response.
Intrinsic tumours (WHO 2021)
- Glioblastoma, IDH-wildtype, grade 4: adults, necrotic ring-enhancing mass, treated with maximal safe resection then radiotherapy with temozolomide. MGMT promoter methylation predicts benefit from temozolomide.
- Astrocytoma, IDH-mutant, and oligodendroglioma, IDH-mutant with 1p/19q codeletion, which is chemotherapy sensitive.
- Pilocytic astrocytoma, grade 1: children, cerebellar cyst with mural nodule, BRAF fusion.
- Medulloblastoma: children, vermis, risk of drop metastases, needs craniospinal irradiation.
Extrinsic and metastatic tumours
Meningioma shows a dural tail and hyperostosis; vestibular schwannoma occupies the cerebellopontine angle; pituitary adenoma causes bitemporal hemianopia; craniopharyngioma is calcified and common in children. Metastases are multiple and at the grey-white junction.
Primary CNS lymphoma
Periventricular, homogeneously enhancing, restricts diffusion, and may be steroid responsive. Obtain a biopsy before giving corticosteroids, because steroids can make the tumour vanish and destroy the diagnosis.
Worked example
A 65-year-old has three weeks of headache and left hemiparesis. MRI shows a ring-enhancing right frontal lesion with surrounding oedema and midline shift. The differential includes high-grade glioma, metastasis, abscess and lymphoma. Give dexamethasone for oedema, obtain imaging of the chest and abdomen, and proceed to biopsy or resection rather than empirical antituberculous therapy.
Traps
Steroids before lymphoma biopsy; ignoring herniation risk; starting prophylactic anticonvulsants routinely, which is not indicated in primary brain tumours without seizures.