Understanding Cognitive Changes in Multiple Sclerosis

Cognitive impairment is a common issue for people with multiple sclerosis (MS). To improve clinical trials, we need to accurately measure changes in cognitive abilities.

Study Overview

This study focused on a phase-3 trial of a drug called natalizumab for patients with secondary progressive MS (SPMS). The trial included adults who had been diagnosed with SPMS for at least two years. Participants were randomly assigned to receive either natalizumab or a placebo for 96 weeks. We measured various cognitive and physical abilities throughout the study.

Key Findings

After 96 weeks, we evaluated several measures:

Symbol Digit Modalities Test (SDMT)
Paced Auditory Serial Addition Test (PASAT)
Selective Reminding Test (SRT)
Brief Visuospatial Memory Test (BVMT-R)
Beck Depression Inventory (BDI-FS)
Timed 25-foot Walk Test
Nine Hole Peg Test
Brain volume and T2 lesion volume through MRI

Results showed that:

SDMT scores improved by an average of 4.5 points.
PASAT scores improved by an average of 2.4 points.
Overall cognitive change was similar in both treatment groups.
Brain volumes decreased, indicating ongoing neurodegeneration.
Physical test scores worsened slightly over time.

Implications for Clinical Practice

The improvements in SDMT and PASAT scores suggest that cognitive abilities can show some change, even in chronic conditions like MS. However, to accurately track cognitive changes, we need to use measures that account for practice and learning effects.