The Value of Visual Evoked Potentials Monitoring Intraoperatively

Introduction: Intraoperative neurophysiological monitoring (IOM) has been used in attempts to minimize postoperative neurological deficits. IOM use among neurosurgeons has been expanding rapidly. Visual impairment is a neurological morbidity encountered post-neurosurgical procedures. Visual evoked potentials (VEPs) are used to assess the visual conduction pathways through the optic nerves, visual pathways, and visual cortex. VEP waveforms are extracted by averaging electroencephalogram (EEG) signals. It is one of the parameters that are not vastly explored in literature, especially during transcranial approaches. The aim of this study is to assess the use of VEP intraoperatively as we are one of the first centers in Saudi Arabia to utilize this modality.

Methodology: We conducted a prospective study using VEP including patients who presented with visual symptoms and underwent cranial neurosurgical procedures at King Saud University Medical City, Riyadh, Saudi Arabia from June 2022. A total of 42 cases were performed including control samples with the aid of visual evoked potential monitoring. Qualitative data including age, gender, morbidities, presenting visual symptoms, preoperatively and postoperatively visual assessment, surgical procedure, type of approach, and IOM data are obtained during patient’s hospitalization. The association between intraoperative VEP changes in amplitude and latency and postoperative visual outcome was assessed.

Results: We included 42 patients (100%) who underwent neurosurgical procedures under neurophysiology monitoring and monitoring of VEPs. The median age was 42 years (range from 8 years to 63 years). There were 20 males (47.62%) and 22 females (52.38%). Thirty-two patients (76.19%) had pre-op visual symptoms, and 17 of them (53.13%) had clinical improvement post-op. Twenty-two cases (52.38%) had stable post-op visual status. Three patients (7.14%) developed visual worsening. Two cases (4.76%) had intraoperative monitoring worsening associated with clinical worsening. Six patients (14.29%) had improvement in pre-op visual symptoms which correlated with improvement in latency and amplitude of intra-op VEP. Six cases (14.29%) had postoperative improvement without intraoperative changes during monitoring. Only one case (2.38%) had evident clinical post-operative improvement associated with intra-operative VEP worsening. We calculated the sensitivity, which was 96.87%, and the positive predictive value was 86.11%. We found a lower specificity of 28.6% and the negative predictive value was 66.66%.

Conclusion: The use of VEP along with other modalities, including neuronavigation and the intraoperative use of ultrasound, can optimize clinical outcomes and avoid visual impairment morbidity. As this is a prospective study, including more cases will be valuable to assess the parameters, sensitivity, specificity, PPV, and NPV more accurately. Keeping in mind that this is a new modality being used in our center, the results are promising.

 

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Artikel online veröffentlicht:
07. Februar 2025