AANEM News Express

AANEM News Express

Science News: Ultrasound Guidance Increases Diagnostic Yield of Needle EMG in Plegic Muscle

Major peripheral nerve injury is common and quite disabling, and the detection of early reinnervation is crucial in determining prognosis and treatment. Standard needle EMG involves random muscle needle insertion, and hence can miss minimal residual muscle activity. There were 41 recent nerve trauma patients with no muscle activity on clinical exam and EMG/NCS (three needle insertions at 10 points each), that returned for follow up. Ultrasound (US) was not performed at the initial evaluation due to swelling, bruising and pain. At a 2-3 month follow up, 22 out of 41 patients showed a CMAP and/or active motor units on needle EMG. In 9/19 (47%) with no activity on EMG/NCS, motor activity was found on US. In the 10 patients with no activity on EMG/NCS and US, follow up at 4-6 months detected muscle activity in 2 on both studies. Overall, the specificity of testing was higher using US in addition to EMG/NCS.    

Comments: The addition of US testing detected muscle activity in almost half of major nerve trauma patients with no activity on EMG/NCS. This is crucial in determining whether surgery is needed in many cases. US should be performed in all cases of major nerve trauma with no evidence of motor activity on EMG/NCS. 

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