American Society for Peripheral Nerve

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Ultrasound Evaluation of the Median Nerve After Carpal Tunnel Release
Alexander Joseph Davit III, MD1; Joseph E. Imbriglia, MD2; Glenn A. Buterbaugh, MD2; William C. Hagberg, MD2; John R. Fowler, MD3
1Department of Plastic Surgery, University of Pittsburgh Medical Center / Children's Hospital of Pittsburgh, Pittsburgh, PA; 2Orthopaedic Surgery, Hand & Upper Ex Center, Wexford, PA; 3Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA

Introduction: Carpal tunnel syndrome is the most common entrapment neuropathy of the upper extremity, affecting 5.8% of women and 0.6% of men. Nerve conduction studies have long been used in the diagnosis of this condition, although recent reports have advocated the use of high-resolution ultrasound as a useful non-invasive alternative. The purpose of this study is to determine if there are measureable changes in the ultrasound cross-sectional area (CSA) of the median nerve following carpal tunnel release in a previously studied patient cohort that had undergone preoperative median nerve CSA measurement.

Materials and methods: 65 patients underwent ultrasound CSA measurement of the median nerve in our office as part of a previous study. A retrospective review of the patient records identified 30 patients who ultimately underwent carpal tunnel release. These patients were contacted and invited to undergo repeat ultrasound of the median nerve and CSA measurement. 10 patients agreed to participate in this study, and a median nerve CSA measurement of the operated side was performed in 11 wrists.

Results: Average age of returning patients was 58 years (range) and 30% were male. None of the respondents were affected with diabetes. Mean CSA of the median nerve prior to carpal tunnel release was 11.8 mm2. Average CSA post-CTR was 9.5 mm2. Seven wrists had a decrease in the median nerve CSA measurement following CTR, and one patient had no change in the CSA measurement.

Conclusions: Ultrasound examination of the median nerve at the wrist has been shown in previous studies to have comparable specificity and sensitivity to nerve conduction studies for diagnosis of carpal tunnel syndrome. The current study demonstrates that the CSA of the median nerve decreases after CTR in the majority of patients, but does not return to normal values in most patients. Larger prospective studies are necessary to characterize the role musculoskeletal ultrasound may have in monitoring the median nerve following carpal tunnel release.

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