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

Effects of Hemodialysis on Visual Pathways Assessed by Visual Evoked Potentials (VEPs)

Introduction

Uremia is a metabolic disorder that affects the functions of the central nervous system (CNS). Visual evoked potentials (VEPs) can be used to demonstrate uremia-induced effects on the CNS. Data on VEPs of patients with chronic renal failure (CRF) are limited. The purpose of this study was to examine the effects of renal failure and the ultrafiltration rate (UFR) on CNS functions in patients undergoing hemodialysis (HD) using VEPs.

Methods

The study consisted of 30 CRF patients undergoing HD, and a control group of 28 individuals, matched in terms of age and gender. Patients with mental retardation, diabetes mellitus, demyelinating disease, stroke, use of neurotoxic drugs, and ophthalmologic diseases were excluded from the study. The pattern VEP (PVEP) parameters recorded were latencies to N75 (N1), P100 (P1) and N135 (N2) waves, and the peak-to-peak amplitude of a P100 wave. The PVEP was taken twice just before and 24 h after HD, and the PVEP parameters were compared. Additionally, the effect of the UFR on the PVEP parameters was examined.

Results

There was no difference between the HD group and control group in terms of gender and age (mean ages of 49.56±12.52 and 48.53±13.28 years, respectively). The average HD period was 87.53±56.34 months. The P1 latencies between the two eyes the patients with CRF were prolonged when compared to those of the controls (right eye p=0.002; left eye p=0.019). A single HD session significantly shortened the latency of the P1 waves compared to that of the baseline waves (p<0.000). Additionally, there was a positive correlation between the difference in the P1 latency before and after HD and the UFR (right eye p=0.03, r=0.525; left eye p=0.022, r=0.417, respectively).

Conclusion

We conclude that VEP, which is an easy, cheap, and simple electrophysiological method, can be used to determine subclinical CNS dysfunction in patients with CRF and show the effect of fluid removal during HD on the visual pathways, and to show the corrective effect of effective fluid imaging on the visual pathways.

Effect of renal transplantation on visual evoked potential abnormalities of chronic renal failure

BACKGROUND

Cranial neuropathies including optic nerve involvement are well-known complications of chronic renal failure (CRF), but most clinicians often do not follow the progression of these damages during course of CRF or their reversibility after treatment. So, this study evaluates effects of renal transplantation on visual system functions using visual-evoked potentials (VEP).

METHODS AND MATERIALS

Forty CRF transplantation candidates and 40 control healthy persons underwent VEP before transplantation. VEP was repeated 3 months later for patients who had successful grafts.

RESULTS

None of recorded VEP changes were significant in our study, although the absolute number of normal parameters increased after transplantation. In patients who had less than 1 year duration of CRF, more positive changes were observed after transplantation (p < .05).

CONCLUSION

Our study showed the VEP changes were not significant. This may have been due to the delay in transplantation. CRF duration had a significant effect on almost all parameters of VEP which means that the longer duration of CRF lead to a decreased probability of VEP changes to return to normal after transplantation.