The relationship between motor and cognitive performance and cortical activity in patients with multiple sclerosis: a systematic review of functional near-infrared spectroscopy studies.
Hongjiao Sun, Haonan Xing, Kechun Hu and 2 others
MS patients' brains light up more in the prefrontal cortex while they walk slower and think less clearly, especially when doing both at once.
The extra activation appears to be compensation that eventually breaks down, not a sign of better function.
Key findings
1Across the included studies, MS patients consistently showed higher activation in the prefrontal cortex and related areas than healthy controls during both single tasks (walking, cognitive tasks alone) and dual tasks (walking while doing a cognitive task), while performing worse on both motor and cognitive measures.
2Progressive MS patients showed more cortical activation but worse motor and cognitive performance than relapsing-remitting patients, which the authors interpret as the brain's compensatory mechanism breaking down as the disease progresses.
3Higher disability severity was consistently associated with greater cortical activation across task conditions, indicating the brain is recruiting more resources but with reduced efficiency.
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What it does not show
Most included studies had small samples (ranging from 5 to 104 participants) and were cross-sectional, so they cannot show cause and effect Participants ranged from about 30 to 75 years old, with different disease subtypes and severity levels, making it hard to generalise Confounding factors (medications, fatigue, time of day) were not consistently controlled across the included studies fNIRS has inherent limitations: motion artifacts during walking, limited depth (only superficial cortex), and inconsistent calibration across studies Only one neuroimaging modality was used, so electrical brain activity (which EEG captures) is missing The review is narrative, not a meta-analysis, so findings cannot be pooled into a single effect size
Declared interests
The authors declared that no financial support was received for this work or its publication.
The easy way to misread this
Do not read the increased cortical activation in MS patients as evidence of better brain function or a positive sign. The review consistently shows this hyperactivation occurs alongside worse walking and cognitive performance, and the authors interpret it as compensation that can break down into decompensation, especially in progressive MS and higher disability. Also, the evidence base is 18 small, mostly cross-sectional studies, so no causal claims can be made about what is causing the activation pattern.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →