Introduction
Neuromuscular ultrasound is a painless, radiation-free, and high-resolution imaging modality for assessment of the peripheral nervous system. The purpose of this study was to use neuromuscular ultrasound to assess the changes that occur in the median nerve following steroid injection for carpal tunnel syndrome (CTS).
Methods
Ultrasound and nerve conduction studies were performed at baseline and 1 week, 1 month, and 6 months after steroid injection in 19 individuals (29 wrists) with CTS.
Results
Significant changes were noted in median nerve cross-sectional area (p<0.001), mobility (p=0.001), and vascularity (p=0.042) at the distal wrist crease following steroid injection, and the nerve cross-sectional area correlated with symptom score and electrodiagnostic parameters. Changes in the ultrasonographic parameters were seen within one week of injection.
Discussion
These findings suggest neuromuscular ultrasound is potentially helpful for the assessment of individuals undergoing treatment for CTS, as typical changes can be expected following successful treatment.
The current approach for localizing and assessing the severity of traumatic peripheral nerve injuries involves clinical evaluation and electrodiagnostic studies. However, the ability of this approach to determine the extent of nerve damage within the first 6 weeks after trauma is limited. This is problematic because outcome is improved with early surgical intervention after complete nerve transection. This led us to explore alternative techniques, such as imaging, for assessing peripheral nerve injuries. Twelve fresh cadavers were obtained and after inspection 20 arms were deemed suitable for inclusion in the study. Random sites were transected in median, ulnar, and radial nerves, and sham skin incisions were performed throughout the arm. These nerves were then systematically scanned by an ultrasonographer blinded to the nerve transection sites, who made a final decision as to whether the nerve was transected. High-resolution ultrasound was able to identify transected nerves in the upper extremity with 89% sensitivity and 95% specificity in fresh cadavers. This proof-of-concept study shows that ultrasound can accurately identify nerve transection, which should lead to further ultrasound studies in patients with traumatic peripheral nerve injuries.
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