VISUOPERCEPTUAL IMPAIRMENT IN MULTPLE SCLEROSIS

 

CONFERENCES
TOPIC: MULTIPLE SCLEROSIS

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Abstract

Introduction. Purpose of our work was to study MS-related visuoperceptual deficits using monocular psychophysical tasks and binocular neuropsychological tasks.
Methods.  In 49 MS-clinic patients temporal and spatial resolution capacity for visual stimuli were evaluated with psychophysical procedures for which double flashes and Landoldt Cís were used. Spatial resolution deficits (SRDs) were traced only at the fovea, but the occurrence of temporal resolution deficits (TRDs) was also examined at 16 other points in the visual field up to 12° eccentricity. The same patients were further submitted to a comprehensive set of 31 neuropsychological tasks assessing a series of spatial and non-spatial visuoperceptual abilities.
Results. Foveal SRDs and foveal TRDs were equally prevalent and did not correlate. The average foveal TRD was not greater than the average TRDs at 6° and at 12° eccentricity. 26% of the patients exhibited significant visuoperceptual impairment on the neuropsychological task set. Only four tasks yielded significant rates of impairment. Each of the four factors identified by factor analysis had an important representative among these four tasks. Failures on the visuoperceptual neuropsychological tasks correlated poorly. Unlike foveal SRDs, foveal TRDs significantly influenced visuoperceptual neuropsychological task performance, suggesting that in some MS patients a slowed visual information processing underlies visuoperceptual impairment on neuropsychological tasks
Conclusions The relation between foveal TRDs and foveal SRDs suggests a non-selective but non-uniform destruction of M and P visual pathway function in the patient group. M system fibers responsible for temporal resolution capacity do not appear more vulnerable to MS at the fovea than at more eccentric retinal sites. In an MS-clinic population visuoperceptual neuropsychological impairment can be relatively frequent even outside a context of severe mental deterioration or low vision. This impairment represents non-uniform, non-selective, restricted and idiosynchratic patterns of loss, proves specific for the failed tasks, and relates only poorly to other disease variables. Because SRDs and TRDs reflect disturbances of an M- and a P- visual-system function respectively, the data collected suggest that compromise of the M visual-system may be more important as an origin of neuropsychologically diagnosed visuoperceptual impairment than compromise of the P visual-system.
 

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