Brain Tumours — SAQ

Stem

A candidate is asked to manage a classic presentation of Brain Tumours in an exam setting. Use precise definitions, scores, doses, and decision thresholds.

Core knowledge (model answer backbone)

Brain tumours are intracranial neoplasms — primary (arising from glia, meninges, cranial nerves, pituitary or germ cells) or secondary (metastatic, roughly five to ten times commoner than primary). The WHO 2021 classification defines them by integrated histology and molecular markers (IDH mutation, 1p/19q codeletion, MGMT methylation, BRAF, H3 K27). Presentation: raised ICP (morning headache, vomiting, papilloedema), seizures, progressive focal deficit. MRI with gadolinium is the imaging gold standard. Management: maximal safe resection, radiotherapy, chemotherapy (Stupp protocol for glioblastoma — radiotherapy 60 Gy plus concomitant and adjuvant temozolomide), dexamethasone for vasogenic oedema, anticonvulsants for seizures. Glioblastoma median survival is about 15 months with Stupp protocol.

Red flags

• New-onset seizure in an adult — think brain tumour; urgent MRI with contrast
• Headache worse on waking, with Valsalva, plus papilloedema or vomiting — raised ICP; urgent imaging, neurosurgical referral
• Progressive focal neurological deficit over days to weeks — urgent MRI with contrast
• Suspected primary CNS lymphoma — DO NOT give steroids before biopsy (steroids lyse lymphoma and destroy diagnostic tissue)

High-yield structure examiners expect

Cover: Overview & Definition, Classification, Epidemiology & Risk Factors, Pathophysiology, Clinical Presentation, Differential Diagnosis.

Key doses / thresholds (from topic teaching)

• and the characteristic chromosome 7 gain plus chromosome 10 loss (+7/-10)**
• Dexamethasone 10 mg IV bolus, then 4 mg every 6 hours, for
• lorazepam 4 mg IV** (repeat once after 4 minutes), the
• levetiracetam 1500 to 3000 mg IV** or **fosphenytoin 18 mg phenytoin-
• methotrexate 3 to 8 g/m² every 2 to 4 weeks) — often with rit
• Dexamethasone 4 to 16 mg daily** controls peritumoural oedema, w

Questions

a) Define the condition and give the most important classification or severity framework used in exams. (3 marks)

• Clear one-line definition matching standard teaching.
• Named classification / stages / types with discriminating features.
• One sentence on why classification changes management.

b) Outline pathophysiology in a mechanism chain that explains the main clinical features. (3 marks)

• Initiating insult → intermediate pathway → end-organ effect.
• Link at least two symptoms/signs to mechanism.
• Mention one complication pathway (e.g. shock, perforation, herniation, arrhythmia).

c) List discriminating clinical features and bedside assessment. (3 marks)

• Classic presentation plus one atypical group (elderly, pregnancy, child, immunocompromised).
• Named signs/manoeuvres if relevant.
• What must never be missed on exam/bedside (pregnancy test, airway, glucose, etc.).

d) Investigations with thresholds and one named score if applicable. (3 marks)

• First-line tests and what positive findings mean.
• Gold-standard or definitive investigation when needed.
• Score components reproduced exactly if a named score is standard for this topic.

e) Immediate resuscitation and definitive management with doses where standard. (3 marks)

• ABC / time-critical steps first.
• First-line drug(s) with agent + dose + route (or procedure steps).
• Escalation triggers (theatre, ICU, thrombolysis window, antidote, etc.).
• Disposition and safety-netting.

Marking tips

Full marks require specificity (numbers, names, doses) not generic "give antibiotics/fluids." Regional practice (ICMR / NICE / AHA) may be cited as alternative where relevant.