The (Ir)relevance of Ultrasound and Nerve Conduction Studies After Carpal Tunnel Release

INTRODUCTION/AIMS: Diagnosis of recurrent/persistent carpal tunnel syndrome (CTS) can be challenging. The aim was to assess qualitative (i.e., anatomical changes of the median nerve in the surgical area) and quantitative (cross-sectional area [CSA]) nerve ultrasound (US) and nerve conduction studies (NCS) findings after carpal tunnel release (CTR). METHODS: We included 50 patients after open CTR for primary CTS between September 2018 and December 2021 at two centers. Retrospectively collected preoperative US and NCS findings were compared to prospectively collected postoperative findings at 6 months. Postoperatively, patients were asked whether or not symptoms improved, and NCS and US findings were compared between patients with and without improvement. RESULTS: At group level, median nerve CSA did not significantly change postoperatively, but all NCS findings, except compound muscle action potential amplitude of the abductor pollicis brevis muscle, significantly improved. Forty-one patients (82%) had improvement or complete relief of symptoms postoperatively, whereas nine patients (18%) had no improvement or worsening. No significant differences were seen in US and NCS findings between patients with or without improvement postoperatively, except for scar surrounding the median nerve which was seen significantly less in patients with improvement (2%) compared to patients without (33%, 95% CI 3.8-66.7). DISCUSSION: Median nerve CSA, US abnormalities of the nerve, except for scarring surrounding the nerve, and NCS were not different in patients with and without improvement of symptoms following surgery. As this study was limited by small sample size, the utility of US and NCS after CTR should be confirmed in larger studies.