Delayed electrophysiological recovery after carpal tunnel release for advanced carpal tunnel syndrome: a two-year follow-up study.

Advanced carpal tunnel syndrome presents severe thenar atrophy with the absence of electrophysiological motor and sensory responses. Because of severity of these conditions, a substantial period of recovery after surgery is required before improvement becomes evident. In this electrophysiological-based study, the reappearance of distal motor latency (DML) at the abductor pollicis brevis and/or sensory nerve conduction velocity (SCV) after wrist stimulation were evaluated 1 year and 2 years after carpal tunnel release . To categorize outcomes, the following grading scale was used: stage I, normal DML and SCV; stage II, DML ≥ 4.5 ms and normal SCV; stage III, DML ≥ 4.5 ms and SCV < 40.0 ms; stage IV, DML ≥ 4.5 ms and nonmeasurable SCV; stage V: nonmeasurable DML and SCV. The authors found measurable DML and/or SCV and significant improvement both 1 year and 2 years postoperatively. Furthermore, the percentage of patients who recovered to the extent that they presented as mild carpal tunnel syndrome (stage I or II) increased significantly. They conclude that electrophysiological assessment of DML and SCV of advanced carpal tunnel syndrome using the above grading scale was effective as an objective evaluation tool of recovery after carpal tunnel release.