Ulnar neuropathy at the wrist: case report and review of literature.

We present a case of pure motor ulnar neuropathy with sparing of the hypothenar muscles and a review of 55 published cases of ulnar neuropathy at the wrist in which the clinicoanatomic correlation was clearly delineated. We propose a classification of ulnar neuropathies at the wrist divided into five types based on clinical findings, electrophysiologic studies, and clinicoanatomic correlations. Type I: a mixed motor and sensory neuropathy, occurring just outside or within the proximal end of Guyon's canal. II: a pure sensory neuropathy, where the lesion involves the superficial branch of the ulnar nerve (UN) at the wrist but distal to the branch to the m. palmaris brevis. III: a pure motor neuropathy due to a lesion of the deep branch of the UN just distal to the superficial branch but proximal to the branch to the hypothenars. IV: a pure motor ulnar neuropathy with sparing of hypothenars; this lesion occurs on the deep branch of the UN distal to the origin of the superficial branch and distal to the branch going to the hypothenars. V: a distal motor neuropathy in which the lesion occurs just proximal to the branches going to the first dorsal interosseus and adductor pollicis muscles.