Subclinical Ulnar Neuropathy in Carpal Tunnel Syndrome

ABSTRACT

BACKGROUND: When performing routine diagnostic nerve conduction studies in patients with carpal tunnel syndrome(CTS), we sometimes happen to be confronted with patients who have also ulnar nerve abnormality without any clinical symptoms or signs, although not so common. Anatomically, the borders of the carpal tunnel and the Guyon canal share common features, separated from each other by the pisiform bone, and the volar carpal ligament forming both the roof of the carpal tunnel and the floor of the Guyon canal. Therefore, if there is an entrapment syndrome at the carpal tunnel with subsequent electrophysiological changes for the median nerve, the same process could also affect the ulnar nerve in the Guyon canal. METHODS: We analyzed 283 patients who were diagnosed as CTS clinically and electrophysiologically for the past 5 years in this hospital. RESULTS: Of 283 patients(491 hands) with CTS, 15 patients(16 hands) had ulnar nerve involvement(5%). Of 75 patients with unilateral CTS, 2 patients(2%) had ulnar nerve involvement; whereas of 208 patients with bilateral CTS, 13 patients(6%) had ulnar nerve involvement. CONCLUSIONS: This study cannot conclusively explain why there is involvement of the ulnar nerve in CTS, but ulnar nerve may be involved at the level of the Guyon canal in some patients with CTS as an entrapment phenomenon and the patients with bilateral CTS may have a more tendency to have ulnar nerve lesion than those with unilateral CTS. In patients with CTS, it would be better to check up if there is also ulnar nerve involvement.