Article
Visual evoked potentials in patients with brain circulatory problems
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Published: | September 18, 2006 |
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Outline
Text
Objective
The aim of this study was to find out if local brain circulatory problems may influence visual evoked potentials (VEP).
Methods
38 patients (70 eyes) were divided into 3 groups: I- with hemiparesis after brain stroke, II- with hemianopsia or quadrantanopsia after brain stroke, III- with amaurosis fugax. The control group consisted of 38 patients (75 eyes) with initial aged-related macular degeneration (AMD). Corrected visual acuity was full in all examined eyes (5/5). VEP were examined using LKC equipment, program UTAS E-2000, pattern (PVEP) and flash (FVEP) stimulations in accordance with ISCEV standards but with the use of two electrodes placed at O1 and O2. Latency and amplitude of positive waves P100 and P2 were calculated. For the statistical analysis Neuman-Keuls test was used.
Results
In PVEP no differences between groups of P100 amplitude and latency were found. In FVEP mean P2 latency was significantly longer in group I than in group III and P2 amplitude was significantly lower in all examined groups in comparison with the control group. PVEP revealed differences over 3 ms in P100 latency between brain hemispheres in 60% of patients in group I, 50% in group II, 66% in group III and differences in P100 amplitude over 30% occurred in 70%, 70%, 55%, respectively. FVEP latency differences between brain hemispheres over 3 ms were found in 58% patients in group I, 72% in group II, 78% in group III and differences in amplitude over 30% occurred in 83%, 64%, 33%, respectively. In patients with AMD no differences occurred between brain hemispheres in latency and only a small difference in amplitude (5% of patients in PVEP and 1% in FVEP).
Conclusions
Local brain circulatory problems cause differences of VEP amplitude and latency between brain hemispheres. Similar hemisphere differences of VEP observed in patients with amaurosis fugax may confirm a vasogenic background of this symptom.