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

Usefulness of piezoelectric sensor device for monitoring extraocular movement during endoscopic endonasal surgery to remove skull base tumor

The present study was conducted to evaluate three modalities used to detect extraocular movement during endonasal endoscopic surgery for a skull base tumor to protect cranial nerves from damage; free-run electrooculography (EOG), piezoelectric sensor (PES), and triggered electromyography (t-EMG) monitoring. Twenty patients (8 males, 12 females; average age 61.8 years) treated for a skull base tumor at Nara Medical University from 2018 to 2021 were enrolled. The three modalities were assessed regarding detection of ocular movement during endoscopic endonasal surgery (EES) for a skull base tumor and the results compared. Oculomotor nerve detection by EOG, PES, and t-EMG was noted in 77.8%, 83.3%, and 33.3%, respectively, of the cases (p = 0.001), while abducent nerve detection was noted in 61.1%, 66.7%, and 16.7%, respectively, (p = 0.002), showing that PES has significantly greater sensitivity for detection of ocular movement. Gross total resection was achieved in nine (45%), near-total resection in three (15%), and partial resection in eight (40%) of the patients. To protect ocular movement function from damage during EES for a skull base tumor, the present findings indicate that among the three modalities tested, PES is compact and useful, and most safe for avoiding complications.

A novel needle electrode for intraoperative fourth cranial nerve neurophysiological mapping

OBJECTIVES

Trochlear nerve (CN-IV) mapping method has not been confirmed to date. The compound muscle action potential (CMAP) of CN-IV cannot be recorded because of the low mapping sensitivity and anatomical characteristics of the superior oblique muscle (SOM). The aim of this study was to evaluate the effectiveness of a novel needle electrode (NNE), for the intraoperative mapping of CN-IV.

MATERIALS AND METHODS

The NNEs were inserted in the target extraocular muscles in 19 patients. We compared the CMAP amplitude of the NNE with that of the conventional needle electrode (CNE). Furthermore, we investigated the dissimilarity between the CMAP of the CN-IV and other extraocular cranial nerves (ECNs) and the correlation between the readings of the CN-IV mapping and its postoperative functional outcome.

RESULTS

The CMAP of CN-IV has been measured in nine patients (47.4%). The CMAP of CN-IV was distinguishable from other ECNs. The CMAP of the NNE was found to be three times higher than that of the CNE. Although the NNE has shown the potential to record the CN-IV's CMAP, 4 cases ended up having a CN-IV postoperative dysfunction.

CONCLUSIONS

For the first time, we confirmed the possibility of intraoperative mapping the CN-IV using an NNE inserted into the SOM. The NNE can also be useful for other neurophysiological monitoring methods.