Neuro-oncology - exam-focused guide
Neuro-oncology covers intracranial and spinal tumours, skull base lesions and the molecular information that now drives diagnosis. The exam tests classification, safe resection principles and adjuvant therapy.
Core rules
- WHO 2021 integrates histology with molecular markers. Adult diffuse gliomas are classified by IDH status; IDH-mutant 1p/19q-codeleted tumours are oligodendrogliomas.
- Glioblastoma is IDH-wildtype and typically shows necrosis and microvascular proliferation. MGMT promoter methylation predicts benefit from temozolomide.
- Maximal safe resection is the goal for glioblastoma and many low-grade gliomas; it improves survival and seizure control without causing new deficits.
- Meningiomas are usually dural-based, enhancing and extra-axial; grade and invasion guide follow-up. Vestibular schwannoma arises from the vestibular division of CN VIII at the internal acoustic meatus.
- Pituitary adenomas are classified by size and hormone secretion; prolactinoma is usually treated medically. Metastases are the commonest adult brain tumours and are often multiple at the grey–white junction.
- Spinal tumours: extradural metastases are commonest; intradural extramedullary lesions include meningioma and schwannoma; intramedullary lesions include ependymoma and astrocytoma.
Worked example: A 62-year-old has a ring-enhancing frontal mass with edema. Imaging alone cannot distinguish glioblastoma from abscess, metastasis or lymphoma. If mass effect threatens herniation, steroids are used briefly; otherwise biopsy/resection is arranged. Steroids can shrink lymphoma and obscure histology, so they are not given routinely before biopsy.
Traps: diagnosing tumour grade from imaging; giving steroids before biopsy without indication; using seizure prophylaxis beyond the early postoperative period; forgetting molecular markers; missing spinal cord compression from metastases.