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The effects of chiasmal compression on the pattern visual evoked potential
Electroencephalography and Clinical Neurophysiology
|August 1, 1978
Summary
Visual evoked potentials (VEPs) reveal abnormalities in patients with chiasmal compression. Monocular stimulation showed delayed VEPs or reduced amplitudes, primarily in the hemisphere opposite the visual field defect.
Area of Science:
- Neuroscience
- Ophthalmology
- Clinical Electrophysiology
Background:
- Chiasmal compression affects visual pathways, leading to visual field defects.
- Visual evoked potentials (VEPs) are electrophysiological measures of the visual pathway's function.
Purpose of the Study:
- To investigate the utility of VEPs in diagnosing chiasmal compression.
- To characterize VEP abnormalities in patients with confirmed chiasmal compression.
Main Methods:
- 10 patients with proven chiasmal compression underwent VEP testing.
- Pattern reversal stimulation with specific check sizes and field degrees was used.
- Bipolar occipital-sylvian and occipital-parietal recordings were obtained using the Modified Maudsley system.
Main Results:
- All patients exhibited VEP abnormalities (latency delays or amplitude reductions) upon monocular stimulation.
- These abnormalities were consistently maximal in the hemisphere contralateral to the visual field defect.
- Using a smaller pattern (13') enhanced the lateralization of abnormalities in 6 out of 7 patients.
Conclusions:
- VEPs are sensitive indicators of chiasmal compression, reflecting pathway dysfunction.
- The lateralization of VEP abnormalities correlates with the location of the visual field defect.
- Stimulus and recording parameters significantly influence the diagnostic yield of VEPs in chiasmal compression.