Pure motor stroke most commonly localizes to which brain structure?

• A. Posterior limb of the internal capsule
• B. Caudate nucleus
• C. Cerebellar hemisphere
• D. Frontal operculum

Answer: (A)

Pure motor strokes come from damage to the corticospinal tract as it travels through the posterior limb of the internal capsule. This compact bundle carries motor signals to the opposite side of the body, so a small lacunar infarct here selectively disrupts these fibers and produces contralateral weakness of the face, arm, and leg without affecting sensation, language, or coordination. Hypertensive small-vessel disease commonly hits the posterior limb, which is why this location is the classic cause of pure motor deficits.

The other structures would produce different problems: the caudate nucleus (basal ganglia) typically causes movement disorders like chorea or rigidity and cognitive changes; the cerebellar hemisphere causes ipsilateral ataxia and incoordination; the frontal operculum can affect language areas (and related face weakness) rather than causing a pure motor hemiparesis.