= sudden intracranial insult that leaves a permanent neurological residual

Incidence:

• 3^rd leading cause of death in USA (after heart disease + cancer); 2^nd leading cause of death due to cardiovascular disease in USA; 2^nd leading cause of death in patients >75 years of age; ~ 800,000 new cases per year (USA 2006); leading cause of death in Orient

Age:>55 years (12% occur in young adults); M÷F = 2÷1

Risk factors: heredity, hypertension (50%), smoking, diabetes (15%), obesity, familial hypercholesterolemia, myocardial infarction, atrial fibrillation, congestive heart failure, alcoholic excess, substance abuse, oral contraceptives, pregnancy, high anxiety + stress

Etiology:

1. NONVASCULAR (5%): eg, tumor, hypoxia
2. VASCULAR (95%)
   1. Brain infarction = ischemic stroke (80%)
      1. Occlusive atheromatous disease of extracranial (35%) / intracranial (10%) arteries = large vessel disease between aorta + penetrating arterioles
         • critical stenosis, thrombosis,
         • plaque hemorrhage / ulceration / embolism
      2. Small vessel disease of penetrating arteries (25%) = lacunar infarct
      3. Cardiogenic emboli (6–15–23%)
         • Ischemic heart disease with mural thrombus
           • acute myocardial infarction (3% risk/year)
           • cardiac arrhythmia
         • Valvular heart disease
           • postinflammatory (rheumatic) valvulitis
           • infective endocarditis (20% risk/year)
           • nonbacterial thrombotic endocarditis (30% risk/year)
           • mitral valve prolapse (low risk)
           • mitral stenosis (20% risk/year)
           • prosthetic valves (1–4% risk/year)
         • Nonvalvular atrial fibrillation (6% risk/year)
         • Left atrial myxoma (27–55% risk/year)
      4. Nonatheromatous disease (5%)
         • arterial elongation, coil, kinks (up to 20%)
         • fibromuscular dysplasia (typically spares origin + proximal segment of ICA)
         • aneurysm (rare) may occur in cervical / petrous portion / intracranially
         • dissection: traumatic / spontaneous (2%); up to 15% of strokes in young adults
         • cerebral arteritis (Takayasu, collagen disease, lymphoid granulomatosis, temporal arteritis, Behçet disease, chronic meningitis, syphilis)
         • postendarterectomy thrombosis / embolism / restenosis
      5. Overactive coagulation (5%)
   2. Hemorrhagic stroke (20%)
      1. Primary intracerebral hemorrhage (15%)
         • Hypertensive hemorrhage 45%
         • Amyloid angiopathy 7–17%
         • Anticoagulants 10%
         • Tumor 5–10%
         • Drug use 6%
         • Vascular malformation, aneurysm 5%
         • Bleeding diathesis (eg, hemophilia) <1%
         • Severe migraine
         • Surgery (carotid endarterectomy, heart)
      2. Vasospasm due to nontraumatic SAH (4%)
         • Ruptured aneurysm 75–80%
         • Vascular malformation 10–15%
         • “Nonaneurysmal” SAH 5–15%
      3. Venoocclusive disease (1%): sinus thrombosis

• May be preceded by TIA:
  • 10–14% of all strokes are preceded by TIA!
  • 60% of all strokes ascribed to carotid disease are preceded by TIA!

Prognosis:

1. Death during hospitalization (25%): alteration in consciousness, gaze preference, dense hemiplegia have a 40% mortality rate
   • Hypodensity involving >50% of MCA territory has a fatal outcome in 85%!
2. Survival with varying degrees of neurologic deficit (75%)
3. Good functional recovery (40%)

Role of imaging:

1. Confirm clinical diagnosis
   • Clinical diagnosis is inaccurate in 13%!
2. Identify primary intracerebral hemorrhage
3. Detect structural lesions mimicking stroke:
   tumor, vascular malformation, subdural hematoma
4. Detect early complications of stroke:
   cerebral herniation, hemorrhagic transformation

Indications for cerebrovascular testing:

1. TIA = transient ischemic attack
2. Progression of carotid disease to 95–98% stenosis
3. Cardiogenic cerebral emboli

Temporal classification:

1. TIA = transient ischemic attack
   • lasts 5 to 30 minutes + clears within 24 hours
2. RIND = reversible ischemic neurologic deficit
   = fully reversible prolonged ischemic event resulting in minor neurologic dysfunction
   • >24 hours and <8 weeks with eventual total recovery
     Incidence: 16÷100,000 population / year
3. Progressing stroke / intermittent progressive stroke
   = stepwise / gradually progressing accumulative neurologic deficit evolving over hours / days
4. Slow stroke
   = rare clinical syndrome presenting as developing neuronal fatigue with weakness in lower / proximal upper extremity after exercise; occurs in patients with occluded ICA
5. Completed stroke
   = severe + persistent stable neurologic deficit = cerebral infarction (death of neuronal tissue) as end stage of prolonged ischemia >21 days
   • level of consciousness correlates well with size of infarct
   
   Prognosis: 6–11% recurrent stroke rate