A study on visual evoked responses in children with chronic renal failure

Nervous involvement is frequent in patients with renal failure. Early recognition of the condition by electrophysiological tests may provide means for protective measures before irreversible damage of nervous system (NS) structures takes place. This study has two objectives: (1) examining whether pattern-reversal visual evoked potential (PR-VEP) studies may provide information relating to possible subclinical NS involvement in pediatric patients with chronic renal failure (CRF) and (2) looking for a possible relationship between serum parathormone (PTH) and creatinine levels and PR-VEP parameters.

PR-VEP recordings at low spatial frequencies were performed and peak-to-peak amplitudes and latencies of the P100 component were measured in 19 neurologically asymptomatic children with CRF, 15 of whom were on continuous ambulatory peritoneal dialysis (CAPD) and four on hemodialysis (HD). A similar procedure was applied to 29 healthy, age- and sex-matched, subjects. Patients were sub-grouped according to the serum PTH and creatinine levels. Student's-t and one-way ANOVA tests were used for comparisons within patient and control groups and sub-groups relating to serum PTH and creatinine levels.

We did not demonstrate any statistically significant differences in PR-VEP parameters in patients vs. controls. PR-VEP amplitudes were higher in patients with low serum creatinine levels as compared to group with high creatinine values and to controls. No other relationship was found between PR-VEP parameters and serum PTH and creatinine levels in this pediatric population.

Young patients with CRF and under dialysis do not necessarily show pathologic alterations in PR-VEPs when they are neurologically intact. This fact suggests that either PR-VEPs are not sensitive enough to detect clinically silent NS involvements in such patients, or it could be related to positive effects of the currently improving standards in the management of dialysis and supportive nutrition. Additional factors such as the age of the patient during examination, the latency between dialysis and visual evoked potential (VEP) assessment, or the selected check size may have some impact on the results and justify further studies.