Purpose: Carpal tunnel syndrome (CTS) is a common entrapment neuropathy, often requiring carpal tunnel release (CTR) surgery. Often, a nerve conduction study (NCS) is performed before CTR; however, there are various reports questioning the sensitivity of NCS, and some patients do undergo CTR despite normal NCS results. We had the following purposes: (1) to report clinical outcome of CTS patients who undergo CTR despite normal NCS, (2) to identify the characteristics and compare those with abnormal NCS patients in terms of basic features and risk factors, and (3) to analyze and compare normal and abnormal NCS results.
Materials and methods: Medical records of 546 CTS (30 normal NCS and 516 abnormal NCS) patients were retrospectively reviewed. Of 30 normal NCS patients, 7 were excluded, leaving 23 patients in the experimental group. We investigated the influence of age, sex, operative arm, and body mass index, as well as medical conditions known to be risk factors for CTS. In normal NCS patients, as a functional score, we investigated Boston carpal tunnel scores before and after CTR. The NCS results were compared in terms of median motor and median sensory testing. In normal NCS patients, NCS data were compared with that of the contralateral nonoperated wrists.
Results: There were 18 women and 5 men in the normal NCS group (mean age 43.7 years). On physical examination, 22 (94.7%) patients showed a positive Tinel test, 19 (82.6%) showed a positive Phalen test, 8 (34.8%) complained of nocturnal paresthesia, and only 1 (4.3%) presented with thenar atrophy. In 19 of 23 patients, the Boston CTS scores showed significant improvement after CTR. Normal NCS patients were significantly younger and significantly heavier and more likely to be a current smoker. In NCS analysis of normal NCS patients, the operated wrists were closer to the reference values than nonoperated wrists.
Conclusions: Surgeons should evaluate the possibility of other combined lesions before CTR in normal NCS patients. Normal NCS can be present with a CTS diagnosis, especially in younger patients. Nevertheless, CTR after failed conservative management, despite normal NCS, could relieve subjective symptoms and function.