Which sign indicates upper motor neuron involvement in spastic cerebral palsy?

• A. Hyperactive deep tendon reflexes
• B. Hyporeflexia
• C. Normal reflexes
• D. Fibrillations

Answer: (A)

Signs of upper motor neuron involvement arise from loss of inhibitory input from the brain to the spinal reflex circuits, which makes reflexes more easily activated. In spastic cerebral palsy, this UMN disruption leads to hyperactive deep tendon reflexes, reflecting increased excitability of the stretch reflex due to reduced cortical inhibition. Hyporeflexia or fibrillations point to lower motor neuron or peripheral issues, and normal reflexes don’t indicate UMN dysfunction. So, hyperactive deep tendon reflexes best indicate upper motor neuron involvement in spastic CP.