- Definition
- Transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia without acute infarction.
- Current Definition (Tissue-based): Clinical symptoms typically lasting <1 hour, with no evidence of infarction on neuroimaging (MRI-DWI).
- Old Definition (Time-based): Symptoms lasting <24 hours (less reliable).
- Significance: TIA is a “warning shot”; high risk of ischemic stroke in the subsequent 48 hours to 90 days.
- Etiology
- Large Artery Atherosclerosis: Embolus from carotid bifurcation (plaque rupture).
- Cardioembolism: Atrial fibrillation (A-fib), valvular vegetations, mural thrombus (post-MI).
- Small Vessel Disease: Lipohyalinosis (HTN, DM).
- Major Mechanisms
- Microembolism (Most Common)
- Artery-to-Artery: Platelet-fibrin clumps break off from ulcerated atherosclerotic plaque (e.g., Carotid bifurcation) and lodge in distal vessels.
- Cardioembolic: Clots from Atrial Fibrillation or valvular vegetations.
- Key Feature: The embolus rapidly fragments or dissolves, allowing reperfusion.
- Hemodynamic “Low Flow”
- Occurs in setting of severe arterial stenosis (e.g., >70% ICA stenosis).
- Triggered by a transient drop in systemic blood pressure.
- Results in ischemia in watershed areas.
- Small Vessel Disease
- Transient occlusion of deep penetrating arterioles due to lipohyalinosis (HTN/DM).
- Clinical
- Amaurosis Fugax: “Curtain coming down” monocular vision loss (ipsilateral carotid stenosis).
- Focal motor/sensory deficits.
- Workup
- CT Head: First step (r/o hemorrhage).
- Carotid Duplex US: Assess for stenosis.
- ECG/Echo: Rule out A-fib or cardiac thrombus.
- Treatment
- Antiplatelet: Aspirin is standard. DAPT (ASA + Clopidogrel) for high-risk.
- Anticoagulation: Warfarin/DOAC only if A-fib/thrombus found.
- Surgery: Carotid Endarterectomy if symptomatic stenosis >70%.
- Prevention: Statin + BP control.