Journal of Anesthesia

, Volume 33, Issue 2, pp 349–349 | Cite as

Reply to the letter to the editor

  • Satoshi TanakaEmail author
  • Takashi Ichino
  • Mikito Kawamata
Letter to the Editor


Vagus nerve Motor-evoked potential Bite injury 

To the Editor:

We would like to thank the readers for their insightful comments on our recent study [1]. We agree that it is important to recognize the risk of bite injuries during vagal motor-evoked potential (MEP) monitoring. In our study, we found that reliable vagal MEPs induced by transcranial electrical stimulation (TES) were obtained at a stimulation intensity of approximately 300 V with 3 or more pulses under reversal of the neuromuscular block. There was no remarkable bite injury in the postoperative period. However, TES-induced muscle responses in the temporal and mandibular regions, which potentially cause bite injuries, were observed in a small number of subjects. Therefore, since bite injuries may occur during vagal MEP recording with increasing stimulus intensity, we should pay attention to such complications.

Reliable MEPs at the extremities could be obtained under partial neuromuscular block. However, sensitivity to muscle relaxant drugs [2] and stimulation thresholds to induce MEP may be different depending on the muscles. At present, it is not clear how the neuromuscular blockade affects the vagal MEPs. It is important to consider the balance between the benefit of vagal MEP monitoring for assessing functional integrity of the motor pathways and the risks associated with TES. Further studies are necessary to clarify the influence of neuromuscular block on vagal MEPs.


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. 1.
    Ichino T, Tanaka S, Tanaka R, Tanaka N, Ishida T, Sugiyama Y, Kawamata M. Transcranial motor-evoked potentials of laryngeal muscles for intraoperative neuromonitoring of the vagus nerve during thyroid surgery. J Anesth. 2019. Scholar
  2. 2.
    Donati F, Meistelman C, Plaud B. Vecuronium neuromuscular blockade at the diaphragm, the orbicularis oculi, and adductor pollicis muscles. Anesthesiology. 1990;73:870–5.CrossRefGoogle Scholar

Copyright information

© Japanese Society of Anesthesiologists 2019

Authors and Affiliations

  1. 1.Department of Anesthesiology and ResuscitologyShinshu University School of MedicineMatsumotoJapan

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