Long-term Postoperative Follow-up of Carpal Tunnel Syndrome with Undetectable APB-CMAP

Abstract

This study assessed the predictability of postoperative recovery of thumb opposition in patients with carpal tunnel syndrome and undetectable compound muscle action potential of the abductor pollicis brevis (APB-CMAP). Thirty-seven hands of 33 patients with a mean age of 59.8 years old were reviewed one year or longer after carpal tunnel release surgery, with a mean follow-up period of 39 months. Thenar muscle atrophy had disappeared in 21 hands (57%), all of which had detectable APB-CMAPs. Thenar muscle atrophy persisted in 16 hands (43%), among which APB-CMAPs were detectable in 7 hands and remained undetectable in 9 hands. Disease duration preceding surgery did not differ significantly between the hands in which muscle atrophy disappeared and the hands in which muscle atrophy persisted. Thenar atrophy disappeared in all seven patients under 50 years of age at the time of carpal tunnel release, but persisted in 16 of the 30 (53%) patients over 50 years of age. These findings indicate that good recovery of thumb opposition can be expected without opponensplasty in patients less than 50 years of age. However, recovery was not predictable in patients over 50 years of age.