Evaluating the Utility of Neuromuscular Ultrasound Compared to Electrodiagnostic Studies for Carpal Tunnel Syndrome
Aabra Ahmed, MD1, Soun Sheen, MD2, Courtney Jones, PhD, MPH2, Mattie Raiford, MD2, David Speach, MD3 and Warren C Hammert, MD3, (1)University of Rochester, Rochester, NE, (2)University of Rochester, Rochester, NY, (3)Department of Orthopaedics, University of Rochester, Rochester, NY
Introduction:
Carpal tunnel syndrome is the most common compressive neuropathy of the upper extremity, commonly diagnosed using clinical symptoms, physical exam, and electrodiagnostic studies (EDX). Neuromuscular ultrasound is an accessible, painless, and usually adjunct tool for diagnosing neuropathies. The goal of this study was to examine the ability of ultrasound in diagnosing carpal tunnel syndrome.
Materials & Methods:
A retrospective study of patients 18 years or older evaluated with upper limb EDX and neuromuscular ultrasound at a single tertiary care center from May 2020 to June 2021. Ultrasound measurements of nerve cross-section area (CSA) were compared to EDX results with EDX considered the gold standard. Ultrasound measurements were considered positive for neuropathy if greater than 10mm2. Wrist to forearm ratio was noted on ultrasound for median neuropathy (positive was greater than 1.4). Sensitivity and specificity for ultrasound diagnosing carpal tunnel syndrome compared to EDX was calculated for each subgroup.
Results
After exclusion of patients with concomitant cervical radiculopathy or polyneuropathy, a total of 1359 limbs from 1004 patients who underwent a unilateral or bilateral median nerve electrodiagnostic study with neuromuscular ultrasound were identified. The average of patients included was 53.9 ± 15.6 years. For carpal tunnel syndrome, ultrasound had a 72.7% sensitivity and 90% specificity when looking at wrist measurements and 92% sensitivity and 78% specificity when looking at wrist to forearm ratio. At median nerve CSA ≥ 8mm at the wrist and wrist to forearm ratio ≥ 1.42 a 90% sensitivity for ultrasound diagnosis was achieved.
Conclusions
With well-established surgical interventions for carpal tunnel syndrome, it is imperative to have reliable methods to diagnose the condition. EDX requires special equipment and can be painful to patients. Ultrasound can be a useful tool to assist in the diagnosis of upper extremity neuropathies and this study provides insight into the sensitivity and specificity of this noninvasive tool for diagnosing carpal tunnel syndrome.
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