OP80 -A Novel Continuous Intra-operative Neuromonitoring Technique for the Recurrent Laryngeal Nerve: Initial experience with 100 nerves-at-risk

      Sinclair, Catherine F.1, Téllez, Maria J.2, Ulkatan, Sedat2 1 Department of Otolaryngology Head and Neck Surgery, Mount Sinai West Hospital, New York, NY, USA 2 Department of Intraoperative Neurophysiology, Mount Sinai West Hospital, New York, NY, USA 1   Background / Purpose: Intra-operative neuromonitoring(IONM) of the recurrent laryngeal nerve(RLN) is commonly performed using endotracheal tube(ETT) based surface electrodes to record vocal fold electromyographic activity with a continuous(CIONM) or intermittent(IIONM) technique depending on the mechanism of nerve stimulation. The only currently available CIONM technique requires placement of a separate vagus nerve electrode which can be difficult in some patients. We present our initial experience for 100 nerves-at-risk with a non-invasive CIONM technique that relies solely on ETT electrodes to stimulate and record the laryngeal adductor reflex(LAR). Methods: The LAR was elicited by electrical stimulation of laryngeal mucosa on the side contralateral to the operative field using ETT electrode(s). ETT electrodes ipsilateral to the surgical field recorded contralateral R1(cR1) and R2(cR2) responses. Changes in LAR amplitude and latency were correlated with changes in IIONM EMG amplitude elicited by direct stimulation of RLN/vagus nerves. All patients completed pre- and post-operative flexible transnasal laryngoscopies (FNL) and vocal handicap index-10 questionnaires. Results: Mean opening R1 amplitude/latency were 251.1(+/-193.4)uV/22.9 (+/-2.8)msec. Mean closing R1 amplitude/latency were 173.6(+/-151.9)uV/24.1(+/-3.5)msec. Surgical maneuvers that potentially stretched or compressed the nerve caused reflex amplitude decline, generally reversible on release of tissue and correlating with concomitant changes in vagal and RLN EMG traces. Loss of reflex correlated with postoperative vocal fold paralysis on FNL but not with VHI-10 scores. Discussion & Conclusion: The LAR is a novel method for CIONM that appears robust and reproducible, requiring no equipment other than the ETT. It monitors both sensory and motor vagal pathways with multiple potential applications.   References:
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