Effect of haemodialysis on visual-evoked potential parameters

Visual evoked potentials as a method for the prospective assessment of tacrolimus neurotoxicity in patients after kidney transplantation

INTRODUCTION

Neurotoxicity, including optic nerve injury, is one of the most common adverse effects of tacrolimus, the principal calcineurin inhibitor used after kidney transplantation (KTx). The electrophysiologic measurements of both pattern visual evoked potentials (PVEP) and flash visual evoked potentials (FVEP) are valuable when drug-induced optic neuropathy is suspected.

OBJECTIVES

To determine whether VEP measurement is a sensitive and repeatable method for monitoring tacrolimus neurotoxicity.

MATERIAL AND METHODS

This prospective study focused on 35 patients (20 M, 15F, 69 eyes, mean age 43 ± 11 years) who were at a median of 3.0 (IQR, 2.2-3.7) months after KTx at the time of the initial VEP evaluation and were treated with tacrolimus since KTx. The follow-up VEP examination was done after a median of 24 (22-27) months (both VEP measurements followed the ISCEV standards). The P100 wave latency and amplitude for the 1° and 15' PVEP simulations, and the P2 wave latency and amplitude for the FVEP were analyzed.

RESULTS

For the 1° checks, the P100 wave latency and amplitude values were significantly worse in the follow-up examination compared to the early post-transplant time-point. Independent associations between FVEP parameters and the tacrolimus blood trough level were observed in the follow-up examination but not at the early post-transplant period. The P2 wave latency correlated with the tacrolimus trough level only in patients treated with the twice-daily, but not the once-daily, tacrolimus formulation. The brain derived neurotrophic factor (BDNF) level correlated with the P100 (15') latency (R = 0.499; p = 0.005) and the P2 latency (R = 0.409; p = 0.025) only in patients treated with the once-daily, but not the twice-daily, tacrolimus formulation.

CONCLUSION

The observations in this study may support the rationale for the use of VEP measurements as non-invasive monitoring of subclinical tacrolimus neurotoxicity.

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.

Visual evoked potentials in chronic alcoholism

In order to evaluate the effect of alcohol consumption and the effect of abstinence on central nervous system generated parameters, we performed pattern visual evoked potential (PVEP) recordings on chronic alcoholics. The study was conducted on forty patients diagnosed as chronic alcoholics according to DSM IV criteria. They were aged mean: 42, and had histories of alcohol abuse for at least six years (mean: 21). 15% of the patients demonstrated abnormal VEP results at least in one tested eye. In order to test the effect of abstinence period on P100 latency values, alcoholics were divided in to two subgroups. Group I (Gr I) consisted twenty-four alcoholics who had been abstinent for less than thirty days (mean: 14), and Group II (Gr II) consisted sixteen alcoholics who had been abstinent for more than thirty and less than seventy-six days (mean: 38) The mean P100 latency of Gr I and Gr II was 101 and 102 milliseconds (ms) respectively; and when compared to normal controls the difference was statistically significant (p: 0.016, p: 0.009). Abnormal VEP in asymptomatic chronic alcoholics suggests that they may be useful in the detection of early changes and in following the progress of patients with the disorder.

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

AIMS OF THE STUDY

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.