RD7.3 | CT Brain in Stroke — Summary & Reflection

KEY TAKEAWAYS

CT Brain in Stroke — Key Points

• Non-contrast CT (NCCT) head is mandatory first-line in ALL suspected acute stroke, ordered immediately — purpose is to EXCLUDE haemorrhage before thrombolysis. CT cannot be withheld because the diagnosis 'feels clinically obvious'.
• CT is NOT sensitive for early ischaemia (first 1–2 h) but is exquisitely sensitive for haemorrhage. A normal CT does not rule out ischaemic stroke.
• Key early CT signs of ischaemia: loss of grey-white differentiation (insular ribbon sign), hyperdense MCA sign (thrombus in proximal MCA, indicates LVO), ASPECTS score (10-point scale; ≤6 = large core, high haemorrhagic risk).
• Haemorrhagic stroke CT: ICH = hyperdense parenchymal collection (putamen = hypertensive); SAH = hyperdense blood in basal cisterns and sulci; SDH = crescentic, crosses sutures; EDH = biconvex, does not cross sutures.
• Thrombolysis (IV alteplase): onset ≤4.5 hours + no haemorrhage on CT + BP <185/110 + other eligibility criteria. Dose 0.9 mg/kg IV.
• Mechanical thrombectomy: requires CTA to confirm LVO (M1 MCA, ICA, basilar); standard window ≤6 h; extended to 24 h (DAWN) or 16 h (DEFUSE 3) only when CT perfusion or MRI-DWI shows favourable core–penumbra mismatch.
• MRI-DWI: more sensitive than CT for early infarct but slower — reserve for subacute, posterior-fossa stroke, and extended-window thrombectomy selection; NOT required before giving alteplase.
• CT does NOT show posterior-fossa well (beam-hardening artefact); MRI preferred for cerebellar and brainstem stroke.

REFLECT

When you are next on call, and a patient arrives with sudden focal neurology, notice the speed with which the CT brain is ordered (or not ordered) and what happens in the time between arrival and imaging. Ask the senior: Was the thrombolysis window discussed? Was a CTA done after the NCCT, and why or why not? What were the CT findings, and did they match the clinical expectation? Consciously linking the imaging decision to the treatment decision — not as an abstract protocol but as a living chain of clinical reasoning — is what transforms medical knowledge into clinical competence.