Neurology
Stroke Types
Ischemic vs hemorrhagic — sudden focal neurologic deficit from infarction (87%) or bleeding (13%), where time is brain
Stroke is sudden focal neurologic dysfunction from cerebrovascular cause. Two major types. Ischemic (~87%): occlusion of a cerebral artery cuts blood flow, causing infarction; subtypes are large-artery atherosclerotic, cardioembolic (atrial fibrillation), small-vessel/lacunar, and cryptogenic. Hemorrhagic (~13%): intracerebral hemorrhage (hypertension, amyloid angiopathy) or subarachnoid hemorrhage (ruptured berry aneurysm, AVM). Diagnosis: non-contrast CT first to exclude bleed; CT angiogram and MRI for vessel and parenchymal detail. Time-critical treatment: tPA up to 4.5 hours, mechanical thrombectomy up to 24 hours for large vessel occlusion. Stroke is a leading cause of long-term disability and the 5th leading cause of US death.
- Ischemic share~87% of strokes
- Hemorrhagic share~13% (intracerebral + subarachnoid)
- tPA window4.5 hours from symptom onset
- Thrombectomy windowUp to 24 hours for large vessel occlusion
- Penumbra conceptHypoperfused tissue salvageable if reperfused
- Top modifiable risk factorHypertension
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Why stroke types matter
- Time-critical treatment. tPA and thrombectomy save brain only within hours; "time is brain" — ~1.9 million neurons lost per minute.
- Diagnostic algorithm. Non-contrast CT distinguishes hemorrhage from ischemic; this branches all subsequent management.
- Secondary prevention. Etiology determines therapy: anticoagulation for AF, statin and antiplatelet for atherosclerotic, BP control for lacunar.
- Aneurysm screening. SAH survivors and families with ≥2 affected first-degree relatives may benefit from screening MRA.
- Telestroke networks. Remote neurology consultation extends thrombolysis to rural hospitals.
- Rehabilitation. Early intensive PT/OT/SLT exploits neuroplasticity; outcomes plateau by 6 months but improvement continues.
- Public health. FAST campaign (Face, Arm, Speech, Time) increases bystander recognition and reduces door-to-needle times.
Common misconceptions
- All strokes look the same. Ischemic and hemorrhagic require opposite treatments — confirming with imaging is mandatory.
- Strokes are inevitable with age. 80% are preventable through risk factor control.
- TIAs don't require admission. 10% recur as completed strokes within 90 days; urgent evaluation is standard of care.
- tPA window is 3 hours. Updated to 4.5 hours since 2008; thrombectomy extends to 24 hours in selected cases.
- Aspirin treats acute stroke. Aspirin is started after exclusion of hemorrhage; it does not lyse existing clots.
- Recovery ends at 3 months. Although fastest gains occur early, motor and language recovery continue for years with rehabilitation.
Frequently asked questions
How do you tell ischemic from hemorrhagic stroke?
Symptoms overlap — sudden focal deficit can be either. Non-contrast CT is first imaging because it reliably detects acute hemorrhage as hyperdense blood. Early ischemic changes on CT are subtle (loss of gray-white differentiation, hyperdense MCA sign). MRI diffusion-weighted imaging detects ischemia within minutes. The distinction is critical because tPA is contraindicated in hemorrhage. Hemorrhage often causes more headache, vomiting, decreased consciousness; ischemic strokes more commonly present with focal deficits.
What is tPA and when is it used?
Tissue plasminogen activator (alteplase or tenecteplase) converts plasminogen to plasmin to dissolve fibrin clots. Indication: acute ischemic stroke within 4.5 hours of last known well, no contraindications (recent surgery, active bleeding, severe hypertension >185/110, recent stroke, INR >1.7). Standard dose alteplase 0.9 mg/kg, max 90 mg. Tenecteplase 0.25 mg/kg single bolus is increasingly preferred. Symptomatic hemorrhage rate ~6%. NNT for good outcome ~10 in early-window patients.
How does mechanical thrombectomy work?
Endovascular procedure for large vessel occlusion (internal carotid, M1/M2 MCA, basilar). Catheter advanced via femoral or radial artery; stent retriever or aspiration catheter removes clot. Window extended to 24 hours in selected patients with mismatch on perfusion imaging (DAWN, DEFUSE-3 trials). Effective recanalization rates ~85%. NNT for functional independence ~3-5 — among the most effective interventions in modern medicine.
What causes intracerebral hemorrhage?
Hypertensive: deep penetrating arteries (basal ganglia, thalamus, pons, cerebellum) damaged by chronic hypertension form Charcot-Bouchard microaneurysms that rupture. Cerebral amyloid angiopathy: lobar hemorrhages in elderly from amyloid in vessel walls. Other causes: AVM, cavernous malformation, anticoagulation, tumor, cocaine/amphetamines. Acute management: blood pressure control (target SBP 130-150), reverse anticoagulation (PCC for warfarin, idarucizumab for dabigatran), neurosurgical evacuation in selected cases.
What is subarachnoid hemorrhage?
Bleeding into subarachnoid space, usually from ruptured saccular (berry) aneurysm at circle of Willis branch points (anterior communicating most common). Classic presentation: thunderclap headache, "worst of life," neck stiffness, sometimes loss of consciousness. CT detects ~95% within 6 hours; if CT negative and suspicion high, lumbar puncture for xanthochromia. Mortality ~30-40%. Treatment: aneurysm coiling or clipping, nimodipine to prevent vasospasm, blood pressure control, ICU monitoring.
What are stroke risk factors?
Modifiable: hypertension (most important), diabetes, hyperlipidemia, smoking, atrial fibrillation, obesity, physical inactivity, alcohol excess, sleep apnea. Non-modifiable: age (doubles per decade after 55), male sex, family history, prior stroke/TIA, sickle cell disease. Atrial fibrillation increases stroke risk fivefold; CHA2DS2-VASc score ≥2 in men or ≥3 in women warrants anticoagulation. Statin therapy reduces ischemic stroke risk independent of LDL.
What is a TIA and why does it matter?
Transient ischemic attack: focal neurologic symptoms from temporary ischemia, classically <24 hours and now defined by absence of infarction on imaging. ~10% risk of stroke within 90 days, half within 48 hours — TIA is a medical emergency. Workup: vascular imaging (carotid duplex, CTA), cardiac evaluation (echo, telemetry), risk factor management. Carotid endarterectomy benefits patients with ≥70% symptomatic stenosis. Antiplatelet therapy (aspirin + clopidogrel for 21 days) reduces early recurrence.