Longitudinal stability of visual evoked potentials in children and adolescents with hydrocephalus.

There were two purposes for this study: to determine the within-subject changes of visual evoked potentials (VEPs) over time, and to evaluate the usefulness of baseline VEP testing in the early diagnosis of increased intracranial pressure (ICP). Twenty children with hydrocephalus between the ages of 4 and 18 years (18 males, 2 females) were evaluated monthly for up to four months. Flash-evoked VEP tests were done in a standardized manner using a Cadwell Quantum 84 evoked potential stimulation and recording instrument. One participant had abnormal VEPs found during a previous episode of shunt malfunction. For all of the other VEP tests, the latency of the N2 response was in the range of adult normal values. For 15 participants with multiple evaluations there were non-significant differences in N2 latency from one session to the next. This study's results provide evidence that within-subject VEP measurements in children with hydrocephalus appear to be relatively stable over limited periods. However, considerable differences were found when comparing VEPs between participants. Further research may provide additional evidence that periodic, routine VEP testing is an effective way to monitor individuals who have shunted hydrocephalus in order to detect increased ICP before the appearance of obvious symptoms.