- Seen in adults (peak age 60–80 years, though also seen in younger adults aged 20–50 years with arterial dissection or cardioembolism) presenting with sudden-onset focal neurological deficits (unilateral hemiparesis, facial droop, hemisensory loss, acute aphasia, or hemineglect) within hours of onset (last seen well timestamp).
- Caused by thromboembolic or atherothrombotic occlusion of a major intracranial artery (most commonly internal carotid artery [ICA] terminus or middle cerebral artery [MCA] M1/M2 segments), resulting in cessation of cerebral blood flow, cellular energy failure, cytotoxic edema, and progressive ischemic infarction.
Imaging Findings
- Non-Contrast CT (NCCT - Hyperacute 0–6 Hour Findings):
- –Dense Vessel Sign: Hyperattenuating thrombus within the lumen of occluded artery (hyperdense MCA sign [M1], MCA dot sign [M2 in Sylvian fissure], hyperdense basilar artery).
- –Loss of Gray-White Matter Differentiation: Cytotoxic edema causing hypoattenuation of insular cortex ('insular ribbon sign') and obscuration of lentiform nucleus.
- –Sulcal Effacement: Cortical swelling causing compression of regional cerebral sulci.
- –Alberta Stroke Program Early CT Score (ASPECTS - 10-Point Score for MCA Territory): Evaluated across ganglionic and supragalionic levels (10 zones: C, L, IC, I, M1–M6). Score 10 = Normal; Score ≤5–6 indicates large established ischemic core with high hemorrhagic transformation risk.
- CT Angiography (CTA) & Multiphasic CTA (Vascular & Collateral Assessment):
- –Identifies exact site of Large Vessel Occlusion (LVO: ICA terminus, M1, dominant M2, basilar artery).
- –Multi-phase CTA grades pial collateral status (good, intermediate, poor collaterals predict clinical salvageability).
- CT Perfusion (CTP) / MRI Diffusion-Perfusion Mismatch (Tissue Salvageability):
- –Ischemic Core (Irreversible Infarction): Cerebral Blood Flow (CBF) <30% of normal,.
- –Ischemic Penumbra (Potentially Salvageable Tissue): Time to Maximum (Tmax) >6.0 seconds.
- –Mismatch Ratio: Penumbral Volume / Core Volume ≥1.8, and absolute mismatch volume ≥15 mL (qualifies for extended-window thrombectomy up to 24 hours per DEFUSE-3 and DAWN trials).
- –DWI / ADC (Most Sensitive Hyperacute Sequence): Demonstrates true cytotoxic diffusion restriction (markedly hyperintense on DWI with corresponding dark ADC drop <620 × 10⁻⁶ mm²/s) within 15–30 minutes of arterial occlusion.
- –**SWI / T2* GRE ('Susceptibility Vessel Sign'): Erythrocyte-rich acute intravascular thrombus produces tubular blooming artifact exceeding the parent artery diameter on SWI, and SWI is the most sensitive sequence for detecting early hemorrhagic transformation** and cortical petechial bleeding.
Differential Diagnosis
| Differential Diagnosis | Key Distinguishing Features |
|---|---|
Acute Intracranial Hemorrhage | Hyperdense parenchymal or subarachnoid hematoma on NCCT; absolute contraindication to intravenous thrombolysis or anticoagulation. |
Post-Ictal Todd Paresis | Clinical hemiparesis following seizure; normal NCCT/CTA without vessel cutoff; perfusion shows regional hyperperfusion or normal CBF/Tmax without core/penumbra mismatch. |
Hemiplegic Migraine | Transient hemiparesis in young patients with headache history; normal non-contrast CT and normal CTA vessels; absence of true cytotoxic restricted diffusion on DWI. |
Hypoglycemia / Metabolic Encephalopathy | Reversible neurological deficit mimicking stroke; blood glucose <2.8 mmol/L; symmetrical or posterior limb internal capsule DWI hyperintensity; prompt reversal with IV dextrose. |
Important Points to Remember
- Diagnostic Pitfall: Looking only at the brain parenchyma and missing the hyperdense MCA sign or basilar artery occlusion on non-contrast CT! Always inspect the vascular tree systematically. Furthermore, never delay acute mechanical thrombectomy triage: in patients presenting within 0–6 hours with LVO and ASPECTS ≥6, rapid intervention is life-saving; in 6–24 hours, perform CT Perfusion to document core-penumbra mismatch.
- Crucial Review Areas:
- 1.Terminal internal carotid artery and M1/M2 middle cerebral artery for hyperdense vessel sign and abrupt CTA cutoff.
- 2.Insular ribbon and lentiform nucleus for earliest loss of gray-white distinction (subtle cytotoxic edema).
- 3.Posterior circulation: Basilar artery and vertebral arteries (basilar occlusion can cause catastrophic locked-in syndrome or fatal brainstem infarction).
- 4.Calvarium and scalp for signs of subtle trauma or hemorrhagic transformation.
- Case-Specific Radiologist Management:
- 1.Immediate 'Code Stroke' Direct Verbal Notification: Immediate telephone alert to on-call stroke physician and interventional neuroradiology (INR) team within minutes of scan acquisition confirming LVO and ASPECTS score.
- 2.Emergency Thrombolysis / Thrombectomy Triaging: If within 4.5 hours of onset and no hemorrhage or extensive established infarction (ASPECTS >6), clear patient for immediate IV thrombolysis (Alteplase or Tenecteplase); if LVO is present within 0–6 hours (or 6–24 hours with CTP mismatch), transfer immediately to Angio-Suite for Mechanical Thrombectomy.
- 3.Pre-Procedural Blood Pressure Protocol: Document that systolic blood pressure must be maintained <185 mmHg and diastolic <110 mmHg prior to thrombolysis.
- 4.Post-Intervention Surveillance CT at 24 Hours: Protocol mandatory 24-hour non-contrast follow-up CT (or sooner if acute neurological deterioration occurs) to exclude hemorrhagic transformation (ECASS classification: HI1/2 vs PH1/2 parenchymal hematoma).
- 5.Hyperacute Stroke Unit (HASU) & Neuro-Vascular MDT: Immediate admission to dedicated Hyperacute Stroke Unit for cardiac rhythm monitoring (telemetry/Holter for atrial fibrillation), carotid Doppler ultrasound, and secondary antiplatelet/anticoagulation optimization.