Temporal pattern of cortical hypoxia in Multiple Sclerosis and its significance on neuropsychological and clinical measures of disability

Objective

Multiple Sclerosis (MS) is a degenerative disease of the CNS characterized by inflammation, demyelination, and axonal damage. It has been hypothesized that hypoxia plays a role in the pathogenesis of MS. This study was undertaken to investigate the reproducibility of non‐invasively measured cortical microvascular hemoglobin oxygenation (S_tO₂) using frequency domain near‐infrared spectroscopy (fdNIRS), investigate its temporal pattern of hypoxia in people with MS (pwMS), and its relationship with neurocognitive function and mood.

Methods

We investigated the reproducibility of fdNIRS measurements. We measured cortical hypoxia in pwMS, and the relationships between S_tO₂, neurocognitive function, fatigue, and measures of physical disability. Furthermore, we cataloged the temporal pattern of S_tO₂ measured at 1‐week intervals for 4 weeks, and at 8 weeks and ~1 year.

Results

We show that fdNIRS parameters were highly reproducible in 7 healthy control participants measured over 6 days (p>0.05). There was low variability between and within subjects. In line with our previous findings, we show that 33% of pwMS (n=88) have cortical microvascular hypoxia. Over 8 weeks and at ~1 year, S_tO₂ values for normoxic and hypoxic groups did not change significantly. There was no significant association between cognitive function and S_tO₂. This conclusion should be revisited as only a small proportion of the RRMS group (21%) was cognitively impaired.

Interpretation

fdNIRS parameters have high reproducibility and repeatability, and we have demonstrated that hypoxia in MS is a chronic condition, lasting at least a year. The results show a weak relationship between cognitive functioning and oxygenation indicating future study is required.

This article is protected by copyright. All rights reserved.