P 100 latency of the visual evoked response in multiple sclerosis compared with normative data

Visuoperceptual impairment in MS patients: nature and possible neural origins

Failures on visuoperceptual neuropsychological tasks (on neuropsychological tests of visuo-spatial perception or on tests concerning semantic properties of visual objects), may indicate focal deficits of visuoperceptual function, or could be the result of (an)other (peripheral) visual deficit(s), or be the effect of a more general cognitive decline. In multiple sclerosis (MS) patients exhibiting sufficient visual acuity and not showing severe cognitive deterioration, impairment on a comprehensive set of 31 visuoperceptual neuropsychological tasks was compared with spatial resolution deficits (SRD), temporal resolution deficits (TRD) for visual stimuli, abnormal pattern shift visual evoked potential (PSVEP) responses, and failing scores on neuropsychological tasks other than visuoperceptual tasks. Impairment on the visuoperceptual neuropsychological tasks was highly independent from the other abnormal visual and cognitive neurological impairments examined, suggesting that it mostly represented focal deficits. Only TRD in both eyes related to this impairment and this relationship was rather weak. Thus in some MS patients a slowed visual information processing may be one of the combined deficits underlying visuoperceptual neuropsychological task impairment. Given that SRD and TRD were not related to another stage of MS and reflect disturbances of a P (parvocellular channel and ventral stream projections) and M (magnocellular channel and dorsal stream projections) visual-system function respectively, demyelination of a certain M pathway may become a co-determinant of visuoperceptual neuropsychological task impairment more rapidly than damage to a certain P pathway.

Serial visual evoked potentials in 90 untreated patients with acute optic neuritis

To establish the value of visual evoked potentials (VEPs) for monitoring disease evolution, we undertook a population-based study of 90 untreated patients 12 to 57 years of age (median, 32 years) at the onset of optic neuritis (ON) and after 2, 4, 12, and 52 weeks. Optic neuritis was monosymptomatic (AMON) in 58 patients and part of the clinically definite multiple sclerosis (CDMS) in 32 patients. The VEP was abnormal in eyes with acute ON in 69 (77%) of 90 patients at onset and in 80 (89%) of 90 patients at one or more of the follow-up sessions. In eyes with acute ON, normalization of an initially abnormal VEP was observed during 1-year follow-up in 13 (19%) of 69 patients. At onset of ON, VEP was abnormal in 35% of the clinically unaffected eyes. By parametric analysis of variance, the latencies (P = 0.0058), the amplitudes (P = 0.0298), and the combined VEP scores (P = 0.0345) in the eyes with acute ON were significantly associated with the time after onset. The latencies were influenced by the presence of CDMS (P = 0.0033), whereas the amplitudes were influenced by visual acuity (P = 0.0000). When visual acuity was included in a multifactor model, the time after onset was, however, not significantly associated with the amplitude (P = 0.8826). The mean latency of the VEPs in eyes with acute ON was significantly shorter in AMON than in ON as part of CDMS. This study provides evidence that VEP abnormality is often transitory, and that VEP often normalizes during follow-up. The diagnostic yield is increased by repeating VEP in the spontaneous course of acute ON. Visual evoked potential is a sensitive tool for revealing subclinical lesions.

Temporal resolution deficits in the visual fields of MS patients

We assessed the relationship between temporal resolution and MS-induced neuropathy. A diagnostic strategy comprising assessments of temporal resolution at 16 points in the extra-foveal visual field up to 12 degrees from the fovea was first compared with foveal temporal resolution and with a standard VEP procedure in the same MS patients. At the group level, foveal temporal resolution was less sensitive to demyelination than the 16-point diagnostic strategy, the detection rate of which was comparable to that of the VEP procedure. Cross-sensitivity of the VEP and the 16-point diagnostic procedure was low. Subsequently, the average severity of MS-induced temporal resolution deficits was studied at three retinal loci of the same size but different eccentricities. Foveal deficits were not significantly greater than more peripheral deficits within the central 12 degrees.