Somatosensory and brainstem auditory evoked responses in sleep-related periodic leg movements.

The pathophysiological mechanisms of sleep-related periodic leg movements (sPLM) and restless legs syndrome are unknown. Evoked potentials have been demonstrated to be abnormal in a variety of episodic movement disorders. In the present study, mixed nerve somatosensory and brainstem auditory evoked responses were examined in patients with polysomnographically documented sPLM who also had restless legs. Normal lower extremity (posterior tibial nerve stimulation) and upper extremity (median nerve stimulation) somatosensory evoked responses were recorded in a group of 10 patients with documented sPLM. Brainstem auditory evoked responses also were normal. These findings do not provide any evidence for a primary afferent sensory disturbance and indirectly support a recently forwarded hypothesis that sPLM is a reflection of suppression of descending inhibitory influences on pyramidal tract function.