Ulnar neuropathy at the elbow due to unusual sleep position

Abnormal strain of the ulnar nerve over the sulcus due to an unusual sleep position is a rare cause of ulnar neuropathy at the elbow. A 57-year-old patient with Mandelung's deformity developed progressive weakness in the flexion of fingers 4 and 5 and in finger straddling on the left side. Additionally, there was slight wasting of the left hypothenar and the left interossei muscles. Motor and sensory nerve conduction studies of the left ulnar nerve showed delayed conduction velocities over the left ulnar sulcus. He preferred to sleep in a left lateral position with his head lying on a headrest roll, his left forearm being flexed at 110 degrees and his hand lying either under his cheek or placed on the roll. Only three weeks after the patient had been advised to change his sleep position and to sleep without the headrest roll, weakness markedly improved. This case shows that sleeping in a lateral position with the head on a headrest roll and the hand placed on the roll or under the cheek may cause ulnar neuropathy at the elbow. Change of such a habitual sleep position promptly resolves the symptoms.