Ulnar nerve compression syndrome due to an anomalous arch of the ulnar nerve piercing the flexor carpi ulnaris: A case report

Abstract

There have been a number of reports about ulnar nerve compression in the canal of Guyon. We recently treated a patient with an anomalous arch of the nerve piercing the flexor carpi ulnaris 1 centimeter proximal to the pisiform. Resection of the smaller segment of the flexor carpi ulnaris totally relieved the patient's preoperative symptoms. Case Report While under treatment for fractures of the left humerus and right tibia, a 54-year-old woman complained of paresthesias on the ulnar side of her right hand of 10 years' duration. Physical examination revealed some minor sensory and motor abnormalities. An electrodiagnostic study revealed abnormal patterns in the abductor digiti quinti and first dorsal interosseous muscles and the nerve conduction studies showed minimal changes. The area was explored surgically. We found that the ulnar nerve divided 2.5 cm proximal to the pisiform, with one branch following the expected course of a normal ulnar nerve and the other arching through a portion of the flexor carpi ulnaris before rejoining the main trunk of the nerve just proximal to Guyon's canal (Figs. 1, 2). Distal to that point the ulnar nerve was normal and we could find no other area of compression or abnormality. We divided the looped section of the flexor carpi ulnaris. Immediately after the surgery, the ulnar compression symptoms began to subside and were completely gone 1 year after surgery.