Neuromuscular Ultrasound in Carpal Tunnel Syndrome with Normal Nerve Conduction Studies (P4.081)

Abstract

OBJECTIVE: To assess the neuromuscular ultrasound findings in patients with clinical carpal tunnel syndrome (CTS) but normal nerve conduction studies (NCS). BACKGROUND: CTS is the most common entrapment neuropathy, estimated to affect up to 7.8[percnt] of the working population in the US. Most patients with CTS have typical changes in NCS, including conduction slowing and amplitude drop across the wrist. However, some patients with symptoms consistent with CTS have normal NCS. Over the past decade, neuromuscular ultrasound has emerged as a complimentary test for CTS, as it can demonstrate anatomic changes in the median nerve of those with CTS. This retrospective chart review was conducted to assess the neuromuscular ultrasound changes in patients with clinical CTS but normal NCS. DESIGN/METHODS: The electronic medical record system at Wake Forest School of Medicine was searched to identify all patients with clinical CTS but normal nerve conduction studies from 2012 to 2015. Demographic, electrodiagnostic, and ultrasonographic data were compiled for each individual. RESULTS: 12 individuals meeting all criteria were identified and data was collected for a total of 10 right wrists and 9 left wrists. Their mean age was 50.4 and 75[percnt] were female. The mean motor latency was 3.9 ms, motor amplitude was 18.2 mV, sensory amplitude was 30.5 µV and sensory velocity was 53.8 m/s. These were all within the normal values of our laboratory. The mean median nerve cross-sectional area at the wrist was 15.6 mm2 and wrist-to-forearm ratio was 2.2. The normal median nerve cross-sectional area for our lab is < 13 mm2 and ratio is < 1.5. CONCLUSIONS: Individuals in this study with clinical CTS but normal NCS had abnormal neuromuscular ultrasound findings. Therefore, ultrasound should be considered for the evaluation of patients with CTS as it may improve diagnostic sensitivity.

Disclosure: Dr. Williams has nothing to disclose. Dr. Cartwright has nothing to disclose.