Upper Motor Neuron Lesion (at/above T12) causes:

Upper Motor Neuron Lesion (at/above T12) causes:

• A. Hyperreflexia
• B. Flaccidity
• C. Muscle atrophy
• D. Facial palsy

Answer: (A)

Hyperreflexia is expected with an upper motor neuron lesion at or above T12 because the descending pathways normally inhibit spinal reflex circuits. When this inhibition is lost, reflex arcs become overactive, leading to brisk deep tendon reflexes and increased muscle tone (spasticity) over time. Flaccidity points to lower motor neuron damage or the acute spinal shock phase, not a chronic UMN lesion. Muscle atrophy can occur with disuse but is not a defining UMN sign, and facial palsy would involve cranial nerves or brainstem, not a spinal lesion. So the best indicator of an UMN lesion here is hyperreflexia.

Hyperreflexia is expected with an upper motor neuron lesion at or above T12 because the descending pathways normally inhibit spinal reflex circuits. When this inhibition is lost, reflex arcs become overactive, leading to brisk deep tendon reflexes and increased muscle tone (spasticity) over time. Flaccidity points to lower motor neuron damage or the acute spinal shock phase, not a chronic UMN lesion. Muscle atrophy can occur with disuse but is not a defining UMN sign, and facial palsy would involve cranial nerves or brainstem, not a spinal lesion. So the best indicator of an UMN lesion here is hyperreflexia.