Which arteries are commonly implicated in lacunar strokes causing pure motor deficits?

• A. Lenticulostriate arteries
• B. Posterior cerebral arteries
• C. Anterior communicating arteries
• D. Middle cerebral arteries

Answer: (A)

Lacunar strokes come from occlusion of small penetrating arteries that supply deep brain structures. A pure motor deficit typically results when a lacunar infarct affects the posterior limb of the internal capsule, where corticospinal fibers pass. The vessels most commonly involved are the lenticulostriate arteries, tiny perforators that arise from the middle cerebral artery and supply the basal ganglia and internal capsule. When these small arteries are blocked—often due to hypertensive-related lipohyalinosis—the resulting tiny infarct produces a pure motor syndrome without cortical signs.

The other arteries listed don’t fit this pattern. The posterior cerebral arteries feed the occipital lobe and parts of the thalamus and temporal cortex, so occlusion tends to cause visual or sensory deficits rather than a pure motor loss. The anterior communicating arteries are a connection in the circle of Willis; issues here affect collateral flow rather than producing a small deep lacunar infarct with isolated motor symptoms. The middle cerebral arteries are large vessels; their major territory occlusions cause broader cortical and subcortical deficits, not the classic small deep infarct that yields a pure motor presentation.