Use of multifocal visual evoked potential tests in the objective evaluation of the visual field in pediatric epilepsy surgery

To evaluate objectively the visual fields of patients with pediatric epilepsy who are uncooperative with perimetry and in whom postoperative visual field deficits are expected, the authors investigated the usefulness of the multifocal visual evoked potential (VEP) method. Normal waves in multifocal VEP were determined in 21 healthy children (21 eyes) 6 to 15 years of age (mean 11.4 years). Responses from eight sites in each child were divided into four quadrants (superior and inferior temporal and superior and inferior nasal). In each quadrant, two response waves were grouped and averaged. The peak latency and amplitude at approximately 100 msec were used for assessment. In three cases involving patients with epilepsy, multifocal VEP measurements were also recorded and compared with the peak latency and amplitude in the healthy children. In these children, no significant differences were observed in the peak latency of amplitude among four quadrants using one-way analysis of variance. In each patient, multifocal VEP tests showed abnormal waves in the quadrant corresponding to the lesion demonstrated in neuroradiological images. This result was useful in the treatment of choice and the postoperative evaluation. Multifocal VEP tests can be useful in evaluating the visual field of children objectively. They can also be valuable in assessing preoperative visual field defects and revealing changes in the visual field after treatment.