Which deficit is most characteristic of an internal capsule stroke?

Which deficit is most characteristic of an internal capsule stroke?

• A. Contralateral sensory loss including face
• B. Dysarthria without aphasia
• C. Pure motor weakness of face, arm, and leg
• D. Visual field defect

Answer: (C)

The main idea is that the internal capsule contains the corticospinal and corticobulbar tracts that run from the motor cortex to the brainstem and spinal cord. A small vessel lacunar stroke in the posterior limb of the internal capsule disrupts these motor pathways, producing contralateral weakness that involves the face, arm, and leg. This is called pure motor hemiparesis because sensory function and higher cortical functions are typically spared. That pattern—weakness on the opposite side affecting the face, arm, and leg with little to no sensory loss or language disturbance—is the hallmark of an internal capsule motor stroke. Other deficits, like sensory loss including the face or a visual field defect, point to involvement of different structures (sensory thalamus or optic radiations, respectively) and are not characteristic of a pure internal capsule motor syndrome. Dysarthria can occur when bulbar fibers are involved, but the defining feature remains the contralateral pure motor weakness.

The main idea is that the internal capsule contains the corticospinal and corticobulbar tracts that run from the motor cortex to the brainstem and spinal cord. A small vessel lacunar stroke in the posterior limb of the internal capsule disrupts these motor pathways, producing contralateral weakness that involves the face, arm, and leg. This is called pure motor hemiparesis because sensory function and higher cortical functions are typically spared.

That pattern—weakness on the opposite side affecting the face, arm, and leg with little to no sensory loss or language disturbance—is the hallmark of an internal capsule motor stroke. Other deficits, like sensory loss including the face or a visual field defect, point to involvement of different structures (sensory thalamus or optic radiations, respectively) and are not characteristic of a pure internal capsule motor syndrome. Dysarthria can occur when bulbar fibers are involved, but the defining feature remains the contralateral pure motor weakness.