Intraoperative Neurophysiological Monitoring in Neurosurgery: Early Identification of Functional Deterioration and Prevention of Irreversible Neurological Injury

Abstract

Intraoperative cerebral and neurophysiological monitoring has become an essential strategy for preserving neurological function during neurosurgical procedures involving eloquent cortical regions, subcortical pathways, cerebral vasculature, and other functionally critical structures. This study evaluated the usefulness of intraoperative monitoring for detecting functional deterioration before neurological injury becomes irreversible, with particular emphasis on motor evoked potentials, somatosensory evoked potentials, direct cortical and subcortical stimulation, visual evoked potentials, and corticocortical evoked potentials. A descriptive, analytical, and integrative evidence-review methodology based on the Scientific Method was applied to 20 selected publications addressing intraoperative warning criteria, corrective interventions, reversibility of electrophysiological changes, and postoperative neurological outcomes. Multimodal or general intraoperative neurophysiological monitoring represented 40% of the analyzed publications, followed by direct cortical or subcortical stimulation with 20%. Motor evoked potential reduction or loss was the most frequently identified warning pattern, followed by somatosensory evoked potential amplitude or latency deterioration. Quantitative analysis of motor monitoring demonstrated that a proportion of significant intraoperative changes recovered after corrective intervention, supporting the existence of a potentially reversible period between initial functional deterioration and established neurological injury. Persistent warning signals showed different prognostic values depending on the monitoring modality, with direct cortical stimulation demonstrating a stronger association with persistent postoperative motor deficit than transcranial electrical stimulation in the analyzed cohort. The findings indicate that intraoperative monitoring should be interpreted as a dynamic decision-support system rather than an isolated diagnostic test. Its effectiveness depends on rapid recognition of warning signals, exclusion of technical and physiological confounders, timely corrective action, and multidisciplinary communication. Overall, multimodal neurophysiological monitoring contributes to the early recognition of neurological compromise and may improve functional preservation during high-risk neurosurgical procedures.