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Egyptian Board Neurosurgery study materials
Egyptian Board Neurosurgery study resources

Egyptian Board Neurosurgery: Neuroimaging and Diagnostic Workup

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

All guide sections

Neuroimaging and Diagnostic Workup

Questions here ask you to choose the right study, order it at the right time, and interpret it against the clinical timeline.

Choosing the study

  • Non-contrast CT first for trauma, acute stroke and suspected haemorrhage. Acute blood measures 60 to 80 Hounsfield units.
  • CTA for aneurysm, dissection and large vessel occlusion; source images show the thrombus and its extent.
  • MRI: DWI turns positive within minutes of infarction while FLAIR turns positive after about 6 hours, so DWI-FLAIR mismatch dates a stroke to under 4.5 hours. GRE or SWI shows microbleeds, haemorrhage and venous thrombosis; T1 with gadolinium shows barrier breakdown.
  • MR spectroscopy shows raised choline, reduced NAA and a lipid-lactate peak in tumour, but cannot reliably separate glioblastoma from metastasis.
  • Perfusion: Tmax above 6 seconds marks tissue at risk; core is CBF below 30 percent.
  • DSA remains the reference standard for vascular malformations and for subarachnoid haemorrhage with a negative CTA.

Worked example: timing in subarachnoid haemorrhage

A 40-year-old with a thunderclap headache. Non-contrast CT within 6 hours has over 98 percent sensitivity. If CT at 12 hours is negative, proceed to lumbar puncture for xanthochromia, which becomes reliable about 12 hours after the ictus and persists up to two weeks; an earlier tap can be falsely negative. If CT is positive, do CTA, and if CTA is negative repeat DSA.

Reading the report

  • In trauma, note basal cistern effacement, midline shift over 5 mm and the Rotterdam components: cisterns, shift, epidural mass, subarachnoid blood.
  • A ring-enhancing lesion: thin smooth wall with restricted diffusion in the core favours abscess; thick irregular wall with high perfusion favours neoplasm.
  • Check renal function, pregnancy and metal or device history before contrast.

Traps

  • Missing a posterior fossa lesion hidden by beam hardening.
  • Calling a CT normal in a patient within the thrombolysis window.
  • Reading DWI without confirming on the ADC map.
  • Forgetting to image the whole neuraxis in tumours that drop metastases.