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Novel method of intraoperative ocular movement monitoring using a piezoelectric device: experimental study of ocular motor nerve activating piezoelectric potentials (OMNAPP) and clinical application for skull base surgeries


Intraoperative monitoring systems that utilize various evoked potentials for the detection and/or preservation of cranial nerves have become increasingly common due to recent technical and commercial developments, particularly during skull base surgeries. We established a novel system for the intraoperative monitoring of the extraocular motor nerves (eOMNs) using a piezoelectric device capable of detecting imperceptible vibrations induced by ocular movement, with sensors placed on the eyelids alone. We first evaluated the efficacy and reliability of this device for the intraoperative monitoring of eOMNs in two Beagle dogs. Based on the results, we then determined the appropriate stimulation parameters for use in human surgical cases involving removal of various skull base tumors. Animal experiments revealed that a 0.4 mA monopolar electrical stimulation was required to elicit significant responses and that these responses were not inferior to those obtained via the electrooculogram/electromyogram. Significant responses were also detected in preliminary clinical investigations in human patients, following both direct and indirect monopolar electrical stimulation of the oculomotor and abducens nerves, although obtaining responses from the trochlear nerve was difficult. Intraoperative monitoring using a piezoelectric device provides a simple and reliable method for detecting eOMNs, especially the oculomotor and abducens nerves. This monitoring system can be adapted to various surgeries for skull base tumor.

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We acknowledge the help provided by Unique Medical Co., Ltd. and the LSI Medience Animal Research Center. We also thank all staff of the Department of Ophthalmology at the Kurume University Hospital for perioperative evaluation of ocular movement.


This study was funded by Japan Society for the Promotion of Science KAKENHI Grant Number JP16J68927.

Author information

Correspondence to Kiyohiko Sakata.

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Conflict of interest

Unique Medical Co. Ltd. was engaged only in the development of equipment (OMNAPP monitoring system) and did not provide any financial support; we purchased genuine equipment from Unique Medical Co. Ltd. and used it for the animal experiments and clinical studies. The authors declare that they have no conflict of interest.

Research involving human participants and/or animals

Beagle dogs bred by LSI Medience (Osaka, Japan) Animal Research Center were used for this experiment, which was conducted in accordance with the Japanese Institutional Ethical Committee Guidelines for Animal Research. Animals were handled and cared for in accordance with the Guide for the Care and Use of Laboratory Animals.

All procedures performed in studies involving human participants were in accordance with the ethical standards of the national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The clinical usage of the OMNAPP monitoring system was approved by the ethical committee of Kurume University (approval number: 16026).

Informed consent

Informed consent for surgery, intraoperative monitoring, and general clinical research was obtained from all individual participants included in the study.

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Sakata, K., Suematsu, K., Takeshige, N. et al. Novel method of intraoperative ocular movement monitoring using a piezoelectric device: experimental study of ocular motor nerve activating piezoelectric potentials (OMNAPP) and clinical application for skull base surgeries. Neurosurg Rev 43, 185–193 (2020).

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  • Piezoelectric device
  • Intraoperative ocular movement monitoring
  • Ocular motor nerves
  • Skull base surgery
  • Ocular motor nerves activating piezoelectric potentials (OMNAPP)