Ischaemic Stroke
Summary
Ischaemic stroke accounts for 85% of all strokes (15% are Haemorrhagic). It is a neurological emergency caused by the occlusion of a cerebral artery by a thrombus (clot formation on plaque) or embolus (clot from heart/carotids). The loss of blood supply leads to a core of irreversible necrosis and a surrounding "penumbra" of potentially salvageable tissue. Rapid reperfusion via Thrombolysis (less than 4.5 hrs) and Mechanical Thrombectomy (less than 6-24 hrs) improves functional outcomes. Management requires organised Stroke Unit care. [1,2]
Key Facts
- Time is Brain: 1.9 million neurons are lost every minute in untreated stroke.
- Bamford Classification (OCSP): Based on clinical features, not scans. Predicts prognosis and vessel involved.
- TACS (Total Anterior): Weakness + Visual Field Loss + Cortical Sign (Dysphasia/Neglect). Worst prognosis.
- PACS (Partial Anterior): 2 of the above, or Higher Cortical function alone.
- LACS (Lacunar): Pure Motor or Pure Sensory (small vessel disease).
- POCS (Posterior): Brainstem/Cerebellar signs (Crossed signs, Hemianopia alone).
- Wake Up Strokes: Timing is calculated from "Time last seen well". If a patient wakes up with a stroke at 08:00, but went to bed at 23:00, the onset is 23:00 (too late for thrombolysis, but maybe not for thrombectomy depending on perfusion imaging).
Clinical Pearls
No Aspirin before CT: You cannot distinguish Ischaemic from Haemorrhagic stroke clinically. Giving Aspirin to a bleed will kill the patient. CT First.
BP Management: Do not treat hypertension acutely unless it is extreme (>220/120) or if the patient is a candidate for Thrombolysis (target less than 185/110). High BP is a compensatory mechanism to perfuse the penumbra.
Swallowing: 50% of stroke patients aspirate. All patients must remain NBM (Nil By Mouth) until a formal dysphagia screen is passed. Aspiration pneumonia is a leading cause of death.
Incidence
- 3rd leading cause of death outcomes globally.
- Risk doubles with every decade after 55.
Risk Factors
- Modifiable: Hypertension (Single biggest risk), Atrial Fibrillation (5-fold risk), Smoking, Diabetes, High Cholesterol.
- Non-modifiable: Age, Ethnicity (Black/South Asian), Male sex.
Mechanism
- Large Artery Atherosclerosis: Carotid stenosis. Rupture of plaque -> platelet aggregation.
- Cardioembolism: AF, Mural thrombus (post-MI), PFO (Patent Foramen Ovale - paradoxical embolus).
- Small Vessel Disease: Lipohyalinosis of penetrating arterioles (Lacunar infarcts).
- Penumbra: Area of brain around the core infarct that is electrically silent but metabolically active. Reperfusion saves this tissue.
FAST
Posterior Circulation (POCS)
- Cardiovascular: Irregular pulse (AF)? Carotid Bruits?
- Neurology:
- TACS: Global deficit. Hemiplegia (face/arm/leg equal), Homonymous hemianopia, Dysphasia (if dominant hemisphere) or Neglect (non-dominant).
- PACS: Brachial-predominant weakness (MCA) + Dysphasia.
- LACS: "Pure Motor Stroke" (Internal Capsule). "Pure Sensory Stroke" (Thalamus). "Ataxic Hemiparesis" (Pons).
- POCS: Cranial nerve palsies (III-XII). Crossed signs (face on one side, body on other).
Immediate
- CT Head (Non-Contrast):
- Ischaemic Check: Rule out blood (Hyperdense/White). Ischaemic changes (Hypodense/Dark) may take 6-12 hours to appear. Look for "Hyperdense MCA sign" (clot in vessel).
- ASPECTS Score: Assessment of early ischaemic changes.
- Blood Glucose: Rule out hypoglycaemia (Brain requires glucose).
For Reperfusion Candidates
- CT Angiogram (CTA): To identify Large Vessel Occlusion (LVO) in ICA/MCA suitable for thrombectomy.
- CT Perfusion: To assess salvageable penumbra (Ischaemic core vs perfusion defect).
Secondary Prevention Workup
- Carotid Doppler: Stenosis >50%?
- ECG / Holter: AF?
- Echocardiogram: Structural heart disease.
Management Algorithm
SUSPECTED STROKE
(FAST Positive)
↓
CT HEAD (Immediate)
↓
┌───────────┴───────────┐
BLEED NO BLEED
(Haemorrhagic) (Ischaemic)
│ │
Neurosurgery? ONSET less than 4.5h?
Reversal? │
┌───────────┴───────────┐
YES NO
↓ ↓
THROMBOLYSIS ASPIRIN 300mg
(Alteplase) (Loading dose)
↓ ↓
LVO on CTA? STROKE UNIT
↓ Physio/SALT
THROMBECTOMY
(Up to 6-24h)
1. Acute Reperfusion
- Thrombolysis (IV Alteplase):
- Indication: Disabling stroke, onset less than 4.5 hours.
- Exclusion: Haemorrhage, Recent surgery (less than 2 weeks), INR >1.7 (Warfarin/DOAC), Previous stroke less than 3 months.
- Mechanical Thrombectomy:
- Stent retriever clot removal.
- Indication: Large Vessel Occlusion (Anterior circulation) + good functional status. Window up to 6 hours (extended to 24h for wake-up strokes with salvageable tissue on perfusion imaging: DAWN/DEFUSE-3 criteria).
2. Acute Medical Management
- Antiplatelet: Aspirin 300mg daily for 2 weeks. (Started 24h after thrombolysis to prevent bleed).
- Statin: Atorvastatin 80mg ON.
- Swallowing: NBM + IV Fluids until SALT assessment. NG tube if unsafe.
- VTE Prophylaxis: Intermittent Pneumatic Compression (IPC). No pharmacological prophylaxis (LMWH) due to bleed risk into brain.
3. Long Term Secondary Prevention
- Antiplatelet: Clopidogrel 75mg Monotherapy is first line. (Aspirin + Dipyridamole is second line).
- Anticoagulation (for AF): Start DOAC (Edoxaban/Apixaban) usually 2 weeks after event (delay depends on infarct size).
- Carotid Endarterectomy: If symptomatic stenosis >50-70%. Ideally within 2 weeks.
- Malignant MCA Syndrome: Massive oedema causes midline shift and coning. Needs Decompressive Hemicraniectomy (taking part of skull off to allow brain to swell outwards).
- Haemorrhagic Transformation: Bleeding into the weak infarct tissue.
- Depression: Post-stroke depression is common.
- Mortality: 20% in first month.
- Disability: 50% of survivors have permanent disability.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| NG128 | NICE (2019) | Admit all directly to hyperacute stroke unit (HASU). Thrombectomy is standard of care for LVO. |
| Stroke | RCP | Aspirin 300mg immediately after exclusion of haemorrhage. |
Landmark Trials
1. MR CLEAN (2015)
- Findings: First RCT to prove Thrombectomy works.
- Impact: NNT (Number Needed to Treat) of 2.6 to reduce disability. One of the most effective treatments in all of medicine.
2. IST-3: Confirmed benefit of Alteplase in over 80s.
What is a Stroke?
It is a "Bran Attack". A blood clot blocks an artery feeding the brain. The brain cells die from lack of oxygen.
Why do you need to act fast?
"Time is Brain". For every minute the artery is blocked, millions of brain cells die. The clot-busting drug (Thrombolysis) only works if given within 4.5 hours while the cells are struggling but not dead yet.
What is the recovery like?
It depends on the size of the stroke. The brain has "plasticity" - it can re-wire itself. Rehabilitation (Physiotherapy, Speech therapy) is the key to teaching undamaged parts of the brain to take over the work of the damaged parts.
Primary Sources
- NICE Guideline NG128. Stroke and transient ischaemic attack in over 16s: diagnosis and initial management. 2019.
- Berkhemer OA, et al. A randomized trial of intraarterial treatment for acute ischemic stroke (MR CLEAN). N Engl J Med. 2015;372:11-20. PMID: 25517348.
- Bamford J, et al. Classification and natural history of clinically identifiable subtypes of cerebral infarction. Lancet. 1991.
Common Exam Questions
- Medicine: "Patient on Warfarin (INR 2.5) has stroke. Can they have Alteplase?"
- Answer: NO. (Risk of fatal haemorrhage). Consider Thrombectomy if LVO.
- Neurology: "Left arm weakness + Right sided face weakness. Where is the lesion?"
- Answer: Brainstem (Crossed signs).
- Pharmacology: "Antiplatelet choice long term?"
- Answer: Clopidogrel (not Aspirin).
- Radiology: "Hyperdense MCA sign?"
- Answer: Visible thrombus in Middle Cerebral Artery on plain CT.
Viva Points
- Permissive Hypertension: Why do we allow BP up to 220/120? Autoregulation is lost in the ischaemic brain. Perfusion becomes pressure-dependent. Dropping BP drops cerebral blood flow to the penumbra.
- Rosier Score: Used in ED to distinguish stroke from mimics (Seizure, Syncope, Sepsis, Sommatisation).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.