Which sign is associated with upper motor neuron lesions?

• A. Tremor
• B. Atrophy
• C. Hyperreflexia
• D. Paresthesia

Answer: (C)

Hyperreflexia is the sign associated with upper motor neuron lesions. Upper motor neurons normally exert inhibitory control over the spinal reflex arcs via the corticospinal tract. When this input is disrupted, the reflex circuits become disinhibited, producing exaggerated deep tendon reflexes. This often comes with spasticity and weakness with relatively preserved early muscle bulk. Tremor isn’t specific to UMN damage and can arise from other systems; atrophy points more toward lower motor neuron involvement or disuse, and paresthesias are sensory, not motor signs.