Which statement correctly links brain region involvement to hypotonia in Down syndrome?

• A. Brainstem and cerebellum involvement contributes to hypotonia
• B. Cerebellum involvement reduces reflexes only
• C. Brainstem involvement increases hypertonicity
• D. Cerebral cortex changes cause scoliosis

Answer: (A)

Central regulation of muscle tone relies on input from the brainstem and cerebellum to the spinal motor neurons. In Down syndrome, underdevelopment or dysfunction of these regions reduces the descending modulatory drive that sets baseline tone, leading to generalized hypotonia and slower motor development. This makes the statement that brainstem and cerebellum involvement contributes to hypotonia the best match to the observed clinical pattern.

The other ideas are less accurate in linking tone to brain regions here: cerebellum involvement isn’t limited to reflex reduction, hypertonicity is not typical in Down syndrome, and cortical changes aren’t the primary driver of scoliosis linked to the tone issues seen in this condition.