Intraoperative Monitoring of Sensory Evoked Potentials in Neurosurgery: A Personalized Approach

Abstract

Sensory evoked potentials (EPs), namely, somatosensory, visual, and brainstem acoustic EPs, are used in neurosurgery to monitor the corresponding functions with the aim of preventing iatrogenic neurological complications. Functional deficiency usually precedes structural defect, being initially reversible, and prompt alarms may help surgeons achieve this aim. However, sensory EP registration requires presenting multiple stimuli and averaging of responses, which significantly lengthen this procedure. As delays can make intraoperative neuromonitoring (IONM) ineffective, it is important to reduce EP recording time. The possibility of speeding up EP recording relies on differences between IONM and outpatient clinical neurophysiology (CN). Namely, in IONM, the patient is her/his own control, and the neurophysiologist is less constrained by norms and standards than in outpatient CN. Therefore, neurophysiologists can perform a personalized selection of optimal locations of recording electrodes, frequency filter passbands, and stimulation rates. Varying some or all of these parameters, it is often possible to significantly improve the signal-to-noise ratio (SNR) for EPs and accelerate EP recording by up to several times. The aim of this paper is to review how this personalized approach is or may be applied during IONM for recording sensory EPs of each of the abovementioned modalities. Also, the problems hindering the implementation and dissemination of this approach and options for overcoming them are discussed here, as well as possible future developments.