A patient sustained an injury to the cerebellar cortex. Which function would be MOST likely diminished?

• A. Initiation of movement
• B. Upper extremity strength
• C. Upper extremity sensation
• D. Rapid alternating arm movements

Answer: (D)

Coordination of rapid, alternating limb movements depends on the cerebellar cortex to time and smooth out each motion. When the cerebellar cortex is injured, this timing is disrupted, leading to dysdiadochokinesia—the inability to perform rapid, alternating movements smoothly.

That’s why rapid alternating arm movements would be diminished with cerebellar cortex injury. Other functions listed aren’t primarily governed by the cerebellum: initiation of movement relies more on motor planning areas and basal ganglia; upper-extremity strength comes from the motor neurons and muscles; and upper-extremity sensation is carried by somatosensory pathways.