Recognizing Capsular Warning Syndrome: The Diagnostic Challenge of Crescendo Subcortical TIAs

Capsular Warning Syndrome (CWS) is a high-risk clinical presentation characterized by recurrent, stereotyped transient ischemic attacks (TIAs) involving pure motor or sensory-motor deficits. These episodes originate from deep penetrating small-vessel occlusion affecting the internal capsule or adjacent subcortical structures. Clinically, CWS poses a major therapeutic challenge because it frequently portends a high risk of permanent lacunar infarction despite rapid intervention.

Clinical Presentation & Case Highlights

A 52-year-old male with hypertension and a history of smoking presented within 90 minutes of symptom onset following multiple transient episodes of right-sided weakness and facial deviation. The initial events resolved spontaneously within 5 to 10 minutes. Cranial CT and initial neurological examination were completely normal, leading to deferral of systemic thrombolysis (tPA) due to rapid symptom resolution.

• Symptom Profile: Recurrent motor-predominant episodes involving right upper and lower limb weakness accompanied by right UMN facial palsy, with no cortical signs (e.g., aphasia, neglect) or sensory impairment during initial phases.

• Fluctuating Course: Over 4 days, the patient experienced 8 separate stereotyped episodes. Early episodes reached maximum durations of 40 minutes, with NIHSS scores reaching 8 before complete spontaneous recovery.

• Laboratory & Cardiac Workup: Inflammatory markers, lipid panels, cardiac enzymes, telemetry, ECG, and echocardiogram were within normal parameters.

Diagnostic Findings

• MRI Brain (DWI): Revealed a clear restricted diffusion lesion in the left lentiform nucleus/internal capsule region, confirming acute subcortical lacunar ischemia.

• Vascular Imaging: Both 3D Time-of-Flight MRA and CT Angiography were normal, ruling out large-vessel intracranial occlusion or severe carotid stenosis.

Pathophysiology & Management Considerations

Unlike classical crescendo TIAs associated with large-vessel atherosclerosis (>90% carotid stenosis), CWS stems from hemodynamic instability or unstable thrombosis within single lenticulostriate or penetrating arteries.

Clinical Aspect : Primary Site
Crescendo TIA (Large Vessel) : Extracranial or major intracranial arteries
Capsular Warning Syndrome (Small Vessel) : Penetrating arteries (Internal Capsule / Basal Ganglia)

Clinical Aspect : Deficit Pattern
Crescendo TIA (Large Vessel) : Variable; often involves cortical signs
Capsular Warning Syndrome (Small Vessel) : Highly stereotyped; pure motor or sensory-motor

Clinical Aspect : Angiography
Crescendo TIA (Large Vessel) : High-grade large vessel stenosis (>90%)
Capsular Warning Syndrome (Small Vessel) : Normal MRA/CTA (microvascular occlusion)