Which lacunar stroke syndrome is most typically associated with the lenticulostriate arteries affecting the internal capsule?

• A. Pure sensory stroke is due to occlusion of thalamic arteries.
• B. Pure motor stroke is due to occlusion of the lenticulostriate arteries affecting the internal capsule.
• C. Ataxic-hemiparesis is due to posterior cerebral artery occlusion.
• D. Lacunar strokes show large territorial involvement on MRI.

Answer: (B)

The key idea is that small penetrating arteries, the lenticulostriate arteries, supply deep brain structures including the posterior limb of the internal capsule. When these arteries occlude, the resulting lacunar infarct disrupts the corticospinal tract as it runs through the internal capsule, producing a pure motor deficit on the opposite side without sensory loss or higher cortical signs. That’s why pure motor stroke is the classic lacunar syndrome linked to lenticulostriate artery disease.

Pure sensory stroke, by contrast, comes from occlusion of thalamic perforators feeding the ventral posterior nucleus, not the internal capsule. Ataxic-hemiparesis is another lacunar syndrome involving motor and cerebellar pathways, but it isn’t due to posterior cerebral artery occlusion. And lacunar strokes are small, not large territorial, so they don’t show large areas of involvement on MRI.