Electromyographic response persists after peripheral transection: endorsement of current concepts in recurrent laryngeal nerve monitoring in a porcine model.
BACKGROUND
Recurrent laryngeal nerve palsy is a serious complication of endocrine surgery to the neck. Permanent lesions are still occurring in about one in a hundred, despite standardized surgical approach to the nerve and the availability of recurrent laryngeal nerve monitoring. Intraoperative recurrent laryngeal nerve monitoring is based on the visual or acoustic registration of evoked electromyography of the laryngeal muscles. Primarily, it proves conductivity of the stimulated nerve segment towards the muscle, so that stimulation distal of the lesion should show persistent electromyographic response.


METHODS
In a porcine model, an iatrogenic nerve lesion of the recurrent laryngeal nerve was set. Subsequently, the proximal and distal dissected nerve portion was stimulated and the evoked electromyographic response of the laryngeal muscles was recorded by needle and laryngeal surface electrodes.


RESULTS
As expected, no signal was obtained from the proximal segment. Meanwhile, the distal segment showed unchanged amplitude of the electrophysiological response for the observation period of more than 1 h.


CONCLUSIONS
This result demonstrated a remarkable pitfall for the neuromuscular monitoring at the recurrent laryngeal nerve: In the human surgical setting, this might have resulted in the false assumption of an anatomical intact nerve. The persistence of distal electromyographic conduction strengthens the proposal to stimulate the vagal nerve as the proximal portion of the nerve as a part of a systematic protocol.
Birkholz
Torsten
T
Department of Anaesthesiology, University of Erlangen-Nuremberg, Krankenhaustr. 12, 91054, Erlangen, Germany. t.birkholz@gmx.de
Irouschek
Andrea
A
Labahn
Dirk
D
Klein
Peter
P
Schmidt
Joachim
J
D000818:Animals; D015982:Bias; D004195:Disease Models, Animal; D004576:Electromyography / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007049:Iatrogenic Disease / Q000517:prevention & control; D007431:Intraoperative Complications / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D000077590:Mivacurium; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology; D012009:Recurrent Laryngeal Nerve / Q000187:drug effects / Q000502:physiology; D061226:Recurrent Laryngeal Nerve Injuries; D013552:Swine; D013959:Thyroid Diseases / Q000601:surgery; D013997:Time Factors; D014630:Vagus Nerve / Q000502:physiology; D014826:Vocal Cord Paralysis / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control
D007546:Isoquinolines; D003473:Neuromuscular Nondepolarizing Agents; D000077590:Mivacurium