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. 2015 Feb;4(1):19–26. doi: 10.3978/j.issn.2227-684X.2014.12.03

Figure 1.

Figure 1

Example of EMG degrades to LOS from initial satisfactory baseline EMG after a left RLN traction injury during continuous IONM in thyroid surgery. The latency and amplitude waveforms were displayed separately, and an upper limit threshold for latency (+10%) and a lower limit threshold for amplitude (50%) were depicted as separate alarm lines. (A) That 3 s after the EMG signals started to show a progressive decrease in amplitude from the baseline EMG (star sign); (B) by 12 s after the start of EMG change, the EMG amplitude showed a nearly 50% decrease, but the EMG latency did not show a significant change; (C) by 17 s, the amplitude and latency crossed the limit threshold (-50% and +10%), and an alarm was displayed on the monitor screen (red bell sign) with acoustic alert; (D) from 20 to 30 s, the EMG waveform completely disappeared and the LOS occurred. EMG, electromyography; LOS, loss of signal; RLN, recurrent laryngeal nerve; IONM; intraoperative neuromonitoring.