Information Processing Speed In Multiple Sclerosis

The purpose of this study was to evaluate information processing characteristics in patients with Multiple Sclerosis (MS). We selected 53 patients with MS and 58 matched healthy controls.

Using computerized tests, we investigated Focused, Divided, Sustained Attention, and Executive Function, and attempted to pinpoint deficits in attentional control to Peripheral or Central Processing stages.

The results substantiate the hypothesis that the slowing of Attention-Demanding (Controlled) Information Processing underlying more complex Cognitive Skills is general, i.e. irrespective of type of controlled processing, with MS patients being 40% slower than controls.

MS patients may suffer from Focused, and Divided and Sustained Attention Deficits, as well as from compromized Central Processing Stages.

With Secondary/Progressive (SP) patients showing the most extensive range of deficits, closely followed by Primary/Progressive (PP) patients, while Relapsing/Remitting (RR) patients appear to be much less affected.

General slowing appears to be highest in PP and SP type MS patients (50% slower) versus Relapsing/Remitting MS (24% slower).

In contrast to most previous results, Complex Processing Speed appeared to be robustly correlated with severity of MS as measured by the Expanded Disability Status Scale and with disease duration.

Patients did much less differ in accuracy of processing from controls, suggesting the importance of using time strategies in planning everyday life and job activities to compensate for or alleviate MS-related speed handicaps.

Copyright 2002 Elsevier Science Ltd.

Previous studies assessing the Magnetic Resonance Imaging (MRI) correlates of Cognitive Dysfunction in Multiple Sclerosis (MS) achieved conflicting results.

Diffusion Tensor (DT)-MRI provides metrics that are sensitive to the macro- and microscopic MS lesion load with increased specificity to the more destructive aspects of MS pathology than conventional imaging.

We performed an exploratory study to assess the magnitude of the correlation between quantities derived from DT-MRI and measures of Cognitive Impairment in patients with Relapsing/Remitting (RR) MS.

T₂, T₁, DT-MRI scans of the Brain and an extensive battery of NeuroPsychological Tests (exploring Language, Complex Reasoning, Attention and Memory) were obtained from 34 RRMS patients.

We measured T₂ and T₁ lesion volumes (LV) and Brain Volume. Average lesion Mean Diffusivity () and Fractional Anisotropy (FA) were calculated.

D and FA Histograms from the Brain Tissue (BT), the Normal-Appearing Brain Tissue (NABT), the Normal-Appearing White Matter (NAWM) and the Normal-Appearing Gray Matter (NAGM) were also obtained.

Nine patients (26.5%) were found to be Cognitively impaired.

Moderate correlations were found between Symbol Digit Modalities Test, Verbal Fluency Test and 10/36 Spatial Recall Test scores and T₂ LV, T₁ LV and average lesion, WBT, NABT, NAWM and NAGM values (r values ranging from -0.30 to -0.53).

No correlations were found between any of the NeuroPsychological test scores and Brain Volume, average lesion FA and WBT FA.

DT-MRI provides quantitative metrics that seem to reflect the severity of Language, Attention and Memory Deficits in patients with RRMS.

This study also suggests that the extent and the intrinsic nature of the macroscopic lesions as well as the damage of the NAWM and NAGM all contribute to the NeuroPsychological deficits of RRMS patients.

The relationship between performance on Information Processing efficiency measures and MRI-derived lesion volume including global and regional T₂ and T₁ lesion volumes was investigated in 20 patients with Relapsing/Remitting Multiple Sclerosis (RRMS) and Secondary/Progressive Multiple Sclerosis (SPMS).

Processing Speed, as measured by the Sternberg Memory Scanning Test, was significantly correlated with Posterior Fossa lesion volume and slowed reaction time in seven out of eight patients (six out of seven with SPMS) with any lesion volume in the Posterior Fossa suggesting a 'threshold effect'.

Processing capacity as measured by the Salthouse Keeping Track Test was not significantly correlated with the MRI measures.

Cognitive performance did not correlate with Expanded Disability Status Scale score, Depression or Fatigue, and patients performed within normal limits on tests of attention/concentration ability.

The significant relationship between Posterior Fossa lesion volume and Memory Scanning Speed in this study suggests that pathological damage in the Posterior Fossa may contribute to Slowed Cognitive Processing and may be an important direction for future studies of Cognitive function in Multiple Sclerosis.

Lack of correlation of Cognitive measures with the other MRI measures may be due to low lesion volume relative to other studies, sample composition, and limited pathological specificity of the MRI measures.

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Objective
To examine whether Processing Speed or Working Memory is the primary information processing deficit in persons with MS.

Design, Setting & Participants
Case-control study. Hospital-based specialty clinic. 215 adults with Clinically Definite MS.

Main Outcome Measure
Mean demographically corrected T-scores, prevalence rates of impairment and relative risk of impaired Processing Speed and Working Memory Index Scores from the WAIS-WMS III.

Results
Deficits in Processing Speed were much more common than Working Memory in all comparisons. This was observed for both Relapsing/Remitting (RRMS) and Secondary/Progressive MS (SPMS) subjects, but accentuated in the latter group.

Conclusions
Results strongly suggest that the primary information processing deficit in persons with MS is in Speed Of Processing.