Can Ultrasound Supplant EMG/NCS in the Evaluation of Compressive Neuropathy of the Common Peroneal Nerve?
Stephen DeMartini, BS, Amanda Faust, BS, Nathan Olafsen, MD, David M Brogan, MD, MSc and Christopher J Dy, MD MPH, FACS, Washington University School of Medicine, St. Louis, MO
INTRODUCTION: Compressive neuropathy of the common peroneal nerve is increasingly recognized as an etiology for foot drop and falls. Accordingly, there has been an increase in diagnostic evaluation of compressive common peroneal neuropathy (CPN). Nerve conduction studies (NCS) and electromyography (EMG) to evaluate for CPN are prone to both false positives and false negatives. We have found ultrasound (US) to be useful to augment diagnosis of CPN compression at the fibular neck. Given that is it less invasive and less costly than NCS/EMG, our goal was to examine the association between US and NCS/EMG for CPN compressive neuropathy at the fibular neck.
MATERIALS AND METHODS: Among 101 patients undergoing decompression for atraumatic CPN neuropathy between 08/01/2015 and 04/01/2023, 17 had both EMG/NCS and US studies completed prior to surgery. Patient records were retrospectively evaluated for demographics, symptoms, physical exam findings, and US+NCS/EMG findings. We performed independent samples t-test to determine whether there were differences in cross-sectional area (CSA) of the CPN at the fibular neck based on EMG/NCS characteristics.
RESULTS: The US cross-sectional area of the CPN at the fibular neck is considered normal at ≤ 20mm, and was found to be significantly higher in those patients with lower CMAP amplitudes (25.7mm) compared to those patients with normal CMAP amplitudes (18.5mm; p=0.04). The US-measured cross-sectional area of the CPN (28.1 mm) was also higher in those patients with active denervation (fibrillations/sharp waves) compared to those without active denervation (17.9 mm; p<0.01) (Fig. 1).
CONCLUSIONS: Patients with signs of axonometric loss and active denervation were found to have increased cross-sectional area of the CPN at the fibular neck on US. Our findings suggest that US may provide similar diagnostic and prognostic information to EMG/NCS. Further study is needed to determine the accuracy and predictive values of US for CPN neuropathy.
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