Latency-shift of intra-operative visual evoked potential predicts reversible homonymous hemianopia after intra-ventricular meningioma surgery.Clin Neurophysiol Pract 2019; 4:224-229CN
Intraoperative visual evoked potentials (VEPs) are used to monitor the function of optic radiation during neurosurgery with the P100 amplitude decrement as a predictor of post-operative visual deficit. However, there is currently no evidence of early VEP changes indicating reversible visual field affection.
In this case report, we used VEPs during surgery for a benign meningioma located in the atrium of the right lateral ventricle. The tumor was accessed through a transcortical approach via a two-centimeter corticotomy in the lateral aspect of the superior parietal lobule. We performed flash VEPs and simultaneous recordings of electroretinography alongside with multimodal intraoperative monitoring.
We observed a significant and sustained unilateral latency shift of the P100 component of VEPs, while amplitudes temporarily dropped to 80% of baseline but recovered entirely at the end of surgery. After the operation, the patient had a left-sided lower-quadrant anopia, which recovered completely during the following three months. Diagnostic VEP with pattern reversal monocular full field stimulation at one month postoperatively showed normal latencies bilaterally.
Our case indicates that the VEP (P100) latency may be a new and valuable indicator (in addition to VEP amplitude) of the visual pathways.
Monitoring VEPs may be useful to detect an imminent injury and a potentially reversible functional deficit.