The absent reflexes in the legs suggests lower motor neuron involvement. Upper motor neuron involvement, such as myelopathy, would likely result in extensor plantar responses, clonus, and hyperreflexia. However, with an acute spinal lesion above about T12, flaccid paralysis during the initial period of spinal shock can complicate interpretation of physical exam findings. The complete sparing of the cranial nerves and the arms argues against a polyneuropathy, although the legs can be much more affected than the arms in an early polyneuropathy. Motor neuron disease, myopathy, and neuromuscular junction disorders are now very low on the differential, as these disorders spare the sensory system.
Sensory testing is a vital part of the electrodiagnostic evaluation.
When sensory testing reveals a deficit, attention is focused upon those conditions that affect both the motor and sensory systems.