Visual-evoked potentials in patients with brain circulatory problems.

PURPOSE

The aim of this study was to find out if local brain circulatory problems may influence visual-evoked potentials (VEP).

PATIENTS AND METHODS

Thirty-eight patients were divided into the following groups: (I) those with hemianopsia or quadrantanopsia and hemiparesis after brain stroke; (II) those with hemianopsia or quadrantanopsia without paresis after brain stroke; and (III) those with amaurosis fugax. The control group consisted of 38 patients. The VEP pattern (PVEP) and flash VEP (FVEP) were examined monocularly using two electrodes placed at O1 and O2. Latency and amplitude of the N75, P100 and N2, P2 waves were measured. The Newman-Keuls test was used for statistical analysis.

RESULTS

In PVEP, no differences between the groups were observed. In FVEP, the mean P2 latency was significantly longer in group I than in group III, and the P2 amplitude was significantly lower in all examined groups when compared with the control group. PVEP and FVEP revealed differences in P latency over 3 ms between brain hemispheres and differences in P amplitude over 30% in all examined groups. In the control group, there were no differences in latency between brain hemispheres and only a small difference in amplitude.

CONCLUSION

Local brain circulatory problems that may lead to brain ischemia cause differences in VEP amplitude and latency between brain hemispheres. Changes in VEPs observed in patients with amaurosis fugax may be considered the result of recurrent brain ischemia.