Surgical assistance for instruments' power control based on navigation and neuromonitoring.

In order to prevent nerve injuries during ear-nose-throat (ENT) and skull base surgery, the method Navigated Control Functional is presented. Thereby, the power of active instruments is controlled based on position information, provided by a surgical navigation system, and nerve activity information, provided by a neurophysiologic monitoring system. Electrical stimulation is usually required for the extraction of distance information from neurophysiologic signals (e.g., Electromyography (EMG)). However, this article presents an experiment to investigate a possible relationship between EMG signals and the nerve-instrument distance without additional electrical stimulation. The EMG signals and position information were recorded intra-operatively during ear surgery. An off-line statistical analysis with Spearman's rank correlation coefficient was accomplished. The results show that there is occasionally some correlation at a statistically significant level of 5%. They highly depend on time range, the selected threshold value and time window. Moreover, all the observed correlations are positive against an expected negative correlation.