In a hemispheric stroke, deficits are due to lesion-related pressure on which structures?

In a hemispheric stroke, deficits are due to lesion-related pressure on which structures?

• A. Spinal tracts.
• B. Cranial nerves near the lesion and corticospinal tracts.
• C. Cerebellar peduncles.
• D. Brainstem nuclei.

Answer: (B)

When a stroke affects a cerebral hemisphere, the deficits come from the mass effect of the lesion pressing on structures that run right through or beside that region. The most important of these are the corticospinal tract fibers, which carry voluntary motor commands from the cortex down through the internal capsule and brainstem. If the lesion compresses these fibers, you get motor weakness on the opposite side of the body. In addition, nearby cranial nerve fibers that originate or pass near the lesioned cortex can be irritated or compressed, producing corresponding cranial nerve signs. Spinal tracts lie in the spinal cord, brainstem nuclei are located in the brainstem itself, and cerebellar peduncles connect the cerebellum to the brainstem; these are not the structures typically compressed by a focal hemispheric cortical stroke unless the swelling extends well beyond the hemisphere. Hence, pressure on the corticospinal tracts and nearby cranial nerve fibers best explains the deficits seen with a hemispheric stroke.

When a stroke affects a cerebral hemisphere, the deficits come from the mass effect of the lesion pressing on structures that run right through or beside that region. The most important of these are the corticospinal tract fibers, which carry voluntary motor commands from the cortex down through the internal capsule and brainstem. If the lesion compresses these fibers, you get motor weakness on the opposite side of the body. In addition, nearby cranial nerve fibers that originate or pass near the lesioned cortex can be irritated or compressed, producing corresponding cranial nerve signs.

Spinal tracts lie in the spinal cord, brainstem nuclei are located in the brainstem itself, and cerebellar peduncles connect the cerebellum to the brainstem; these are not the structures typically compressed by a focal hemispheric cortical stroke unless the swelling extends well beyond the hemisphere. Hence, pressure on the corticospinal tracts and nearby cranial nerve fibers best explains the deficits seen with a hemispheric stroke.