Postoperative Reduction and Persistent Enlargement of Median Nerve Cross-Sectional Area in Carpal Tunnel Syndrome: Influence of Metabolic Syndrome.

Abstract

Carpal tunnel syndrome (CTS) causes enlargement of the median nerve cross-sectional area (CSA), which often decreases after carpal tunnel release. However, the clinical relevance of postoperative median nerve CSA changes remains unclear. This study aimed to assess the association between postoperative changes in median nerve CSA and clinical outcomes and to identify factors linked to a persistent or increased CSA. We enrolled 117 patients (136 wrists) with CTS who underwent endoscopic carpal tunnel release. Preoperative and 12-month postoperative assessments included ultrasonographic measurement of the median nerve CSA at the carpal tunnel inlet, nerve conduction studies, the Semmes-Weinstein monofilament test, and the Japanese version of the CTS instrument (CTSI). Correlations between changes in inlet CSA and clinical measures (nerve conduction studies, Semmes-Weinstein monofilament test, and the CTSI symptom severity and function scores) were analyzed. Patients were divided into two groups based on their postoperative condition: those whose CSA decreased and those whose CSA was either unchanged or increased. Factors associated with unchanged or increased CSA were identified by logistic regression. No significant correlations were found between changes in inlet CSA and nerve conduction study, SWMT, or CTSI scores. Inlet CSA was unchanged or increased in 35 wrists (25.7%). This group had a significantly higher proportion of males and patients with metabolic syndrome compared to the decreased CSA group. Multivariate analysis showed metabolic syndrome was independently associated with unchanged or increased postoperative CSA. Changes in median nerve CSA after carpal tunnel release do not correlate well with clinical or electrophysiological outcomes. Metabolic syndrome may contribute to persistent nerve swelling after surgery. Therapeutic III.