Which lacunar infarct syndrome classically presents with pure motor weakness?

• A. Pure motor stroke due to occlusion of the lenticulostriate arteries (internal capsule/pontine region).
• B. Pure sensory stroke due to thalamic lacune.
• C. Ataxic-hemiparesis.
• D. Dysarthria-clumsy hand syndrome.

Answer: (A)

Lacunar infarcts from small vessel disease cause pure motor weakness when the lesion involves the lenticulostriate arteries supplying the posterior limb of the internal capsule (or basis pontis). The corticospinal fibers there mediate motor output to the face, arm, and leg, so occlusion yields contralateral weakness in these regions without cortical signs such as aphasia, neglect, or cortical sensory loss. This deep, small infarct pattern is the classic pure motor lacunar stroke, often linked to hypertension-driven lipohyalinosis. The other lacunar syndromes describe different signs: a thalamic lacune gives pure sensory loss; an infarct causing ataxic-hemiparesis includes motor weakness with ipsilateral incoordination; a lesion in the ventral pons or genu of the internal capsule can produce dysarthria with a clumsy hand.