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Egyptian Board Neurosurgery study materials
Egyptian Board Neurosurgery study resources

Egyptian Board Neurosurgery: Neurophysiology and Neuropathology

Egyptian Board Neurosurgery · Work through your exam, one topic at a time.

All guide sections

Neurophysiology and Neuropathology

Physiology questions test whether you can convert a number into a bedside decision. Pathology questions test the current WHO classification and the histological features that separate grades.

Flow, pressure and volume

  • Normal adult CBF is about 50 mL/100 g/min, grey matter 70 to 80, white matter 20 to 30. Electrical failure begins below roughly 20 and membrane failure below 10 to 12; that band is the penumbra.
  • Autoregulation holds CBF constant between MAP 50 and 150 mmHg and is right-shifted in chronic hypertension.
  • CPP equals MAP minus ICP. In severe adult traumatic brain injury aim for CPP 60 to 70 mmHg and treat ICP above 22 mmHg.
  • CO2 reactivity is about 3 percent of CBF per mmHg PaCO2, so hyperventilation to 30 mmHg cuts flow by a quarter and is only a bridge to theatre or an EVD.
  • Monro-Kellie: brain, blood, CSF. CSF production is 0.3 to 0.35 mL/min, roughly 500 mL daily against a 150 mL total volume, so turnover is about three times a day.

Cerebral oedema

Cytotoxic oedema is intracellular, follows ischaemia or toxins, involves grey matter and shows restricted diffusion. Vasogenic oedema is blood-brain barrier breakdown in white matter and responds to steroids. Interstitial oedema is transependymal flow in hydrocephalus; osmotic oedema follows rapid sodium shifts.

Neuropathology essentials

  • Glioblastoma, IDH-wildtype, grade 4: pseudopalisading necrosis and microvascular proliferation.
  • Oligodendroglioma requires IDH mutation plus 1p/19q codeletion.
  • Atypical meningioma, grade 2: at least 4 mitoses per 10 high-power fields or brain invasion; anaplastic, at least 20.
  • Schwannoma: Antoni A with Verocay bodies, Antoni B, S100 positive.
  • Medulloblastoma groups: WNT has the best prognosis, group 3 the worst, group 4 is commonest.

Worked example

An intubated patient has MAP 85 and ICP 25. CPP is 60, the lower limit of target. Exclude a blocked catheter, hypoxia, hypercapnia, head rotation and excessive sedation before escalating. You would not hyperventilate first and you would not give dexamethasone.

Traps

  • Using systolic rather than mean pressure to compute CPP.
  • Treating traumatic vasogenic oedema with steroids.
  • Calling every grade 4 glioma a glioblastoma when it is an IDH-mutant astrocytoma.