Prognostic Value of Ultrasound Imaging of the Median Nerve in Carpal Tunnel Syndrome.

Background: Ultrasound has been well established as a diagnostic modality for carpal tunnel syndrome, but its prognostic utility has not been deeply investigated. Few studies, showing contradictory results, exist investigating ultrasound results as a predictor of patient outcomes. Methods: Patients with ultrasound measurement of the cross-sectional area (CSA) of the median nerve who completed the Boston Carpal Tunnel Questionnaire (BCTQ) and followed up after surgery were included in the study. A total of 199 wrists from 172 patients met the inclusion criteria. Preoperative CSA of the median nerve at the wrist was compared with change in BCTQ at various follow-up times postoperatively. Results: The BCTQ score was found on average to decrease for patients after surgery at all 3 follow-up times. There was a larger decrease in the preoperative BCTQ with each progressive follow-up time, with the largest change of 1.43 points coming at 6+ months. The average change in BCTQ at each follow-up time was found to be greater than the minimal clinically important difference. The greatest R2 for preoperative CSA compared with change in BCTQ was 0.0552 for the 6+ month visits. No specific CSA value or range above or below which patients have better postoperative outcomes was found. Conclusions: Higher preoperative CSA, signifying worse carpal tunnel severity, showed almost no correlation with better outcomes after carpal tunnel release surgery as measured by improvement in patient-reported outcome scores.