Is an internal capsule stroke in an adult patient with possible underlying cardiovascular risk factors, such as hypertension and diabetes, considered a lacunar stroke?

Is an Internal Capsule Stroke a Lacunar Stroke?

Yes, an internal capsule stroke is typically a lacunar stroke, provided it meets the size criterion of <1.5 cm in diameter and occurs without evidence of a concomitant cortical infarct. 1, 2

Anatomic and Pathophysiologic Basis

The internal capsule is one of the classic locations for lacunar infarcts because it is supplied by small penetrating arteries (lenticulostriate arteries) that arise directly from the middle cerebral artery. 1, 2 These deep penetrating vessels are particularly vulnerable to the small vessel arteriopathy that characterizes lacunar stroke pathophysiology. 3

• Lacunar infarcts are defined as subcortical strokes measuring <1.5 cm in diameter on CT or MRI, located in the basal ganglia, brain stem, or deep white matter—which includes the internal capsule. 1, 2
• The internal capsule is specifically mentioned as a common symptomatic location for lacunar infarcts, particularly in patients presenting with pure motor hemiparesis. 4

Critical Diagnostic Caveat: Size and Mechanism Matter

However, not every internal capsule infarct is automatically a lacunar stroke—the diagnosis requires both imaging confirmation of size AND exclusion of alternative embolic mechanisms. 1, 3

Why This Distinction Is Clinically Critical:

• A patient with atrial fibrillation and a small subcortical internal capsule infarct requires anticoagulation, not just antiplatelet therapy, even though the infarct appears "lacunar" in size and location. 1, 3
• Embolic mechanisms (cardiac or artery-to-artery from carotid disease) can produce small internal capsule infarcts that mimic lacunar strokes clinically but have entirely different treatment implications. 3, 5
• Case reports have documented pure motor hemiplegia from internal capsule infarction occurring during cardiac angiography, proving that emboli can cause classic "lacunar" syndromes. 5

Required Diagnostic Workup

The clinical syndrome alone is insufficient for diagnosis—you must complete a comprehensive evaluation to exclude embolic sources: 1

Mandatory Cardiac Evaluation:

• Transthoracic echocardiography at minimum to assess for cardioembolic sources 1, 3
• Extended cardiac rhythm monitoring to detect paroxysmal atrial fibrillation 1, 3

Mandatory Vascular Assessment:

• Carotid imaging (duplex ultrasound, CTA, or MRA) within 48 hours to exclude ipsilateral large-artery stenosis >50% 1, 3
• Vascular imaging (CTA or MRA) must be obtained urgently to exclude large vessel occlusion, even when lacunar stroke is suspected clinically, because NIHSS scores correlate poorly with large vessel occlusion presence 1

Laboratory Studies:

• Lipid profile and hemoglobin A1c are essential components 1

Management Implications Based on Mechanism

If small vessel disease is confirmed after excluding embolic sources:

• Use antiplatelet therapy with aggressive risk factor modification 1, 3
• Blood pressure target <130 mmHg systolic 1, 3

If atrial fibrillation or high-risk cardiac source is identified:

• Anticoagulation is required regardless of small infarct size—not just antiplatelet therapy 1, 3

If ipsilateral carotid stenosis >50% is found:

• Consider carotid revascularization depending on degree of stenosis 1

Prognosis

When confirmed as true small vessel disease, lacunar strokes have the best prognosis among stroke subtypes, with an 85% survival rate at 2 years and lower early mortality and recurrence rates compared to other ischemic stroke subtypes. 1, 2 However, long-term cardiovascular risk remains elevated even in lacunar stroke patients. 6