What is a Lacunar Stroke?
A lacunar stroke is a small subcortical infarction measuring less than 1.5 cm in diameter caused by occlusion of a single penetrating artery deep in the brain or brainstem, resulting from small vessel disease rather than atherosclerosis. 1
Defining Characteristics
Size and Location:
- The infarct must be <1.5 cm in diameter on neuroimaging (CT or MRI) 1, 2
- Located in subcortical regions: basal ganglia, brainstem, or deep white matter 1
- No cortical involvement should be present 2, 3
- The term "lacunar infarct" is most appropriately reserved for cystic lesions smaller than 1 cm in these deep structures 1
Underlying Pathophysiology
Vascular Mechanism:
- Caused by occlusive arteriopathy of small penetrating arteries deep in the brain or brainstem 4
- Not caused by atherosclerosis like other stroke subtypes, but rather by a distinct small vessel arteriopathy 2, 3
- Strongly associated with chronic hypertension and diabetes mellitus 4, 3, 5
- The name derives from their ability to cavitate and form "little lakes" (Latin: lacune) 6
Clinical Presentation
Classic Lacunar Syndromes:
- Pure motor hemiparesis (most common) 4, 1, 5
- Pure sensory syndrome 5
- Sensorimotor stroke 5
- Ataxic hemiparesis 5
- Dysarthria-clumsy hand syndrome 5
Diagnostic Requirements
Imaging Confirmation:
- MRI with diffusion-weighted imaging (DWI) is preferred over CT for detecting acute lacunar infarcts, as it identifies small acute ischemic lesions that CT may miss 3
- Must demonstrate a small (<1.5 cm) subcortical infarct 1, 2
Essential Exclusions:
- Must exclude potential cardioembolism sources (such as atrial fibrillation) 4, 1, 2
- Must exclude ipsilateral large-artery stenosis (≥50% narrowing) 4, 1, 2
This exclusion process is critical because the presence of either cardiac sources or large vessel disease would reclassify the stroke into a different subtype with different treatment implications 4.
Epidemiology
- Accounts for approximately 25% of all ischemic strokes 4, 5, 7
- Represents a substantial proportion of both symptomatic and asymptomatic ischemic strokes 6
Prognosis: A Paradox
Short-term (Favorable):
- Highest survival rate among stroke subtypes at 85% at 2 years 1, 2, 3
- Low early mortality within 30 days 1
- Reduced functional disability at hospital discharge 5
Long-term (Less Favorable):
- Increased risk of death from cardiovascular causes in the mid- to long-term 5, 8
- Similar risk of recurrent stroke as other stroke types 8
- Increased risk of cognitive decline and dementia 8
- 20-30% of patients experience neurological worsening (progressive lacunar stroke) in hours or days after onset 9
- Asymptomatic progression of small-vessel disease is typical 5
Common Pitfall: Lacunar stroke should not be regarded as a benign disorder despite favorable short-term outcomes; it requires rigorous long-term management and follow-up 5.
Classification Context
Within the TOAST classification system, lacunar stroke represents one of five major ischemic stroke categories: