MRI links long COVID fatigue to reduced cerebral blood flow
New research details how changes in brain perfusion may contribute to persistent fatigue after COVID-19.
Published in NeuroImage: Reports, functional MRI data suggest that people with post-COVID-19 condition may have lower cerebral blood flow that contributes to greater fatigue—a common complaint among patients with lingering effects. With the respiratory virus now solidified as an endemic disease, the research team contends it is important to understand some of its long-lasting side effects to lessen their impact.
“The pathophysiological mechanisms underlying cognitive fatigue in [post-COVID-19 condition] remain poorly understood,” Dr. Marika C. Möller, with the department of clinical sciences at the Karolinska Institute in Sweden, and colleagues noted. “In this study, we sought to identify physiological factors that could guide future interventions by examining self-reported state fatigue, cognitive fatigability, processing speed, and performance variability, and their associations with cerebral blood flow in individuals with post-COVID condition and nonsymptomatic controls.”
For the study, researchers evaluated 22 patients with post-COVID condition and 19 age- and sex-matched controls. Participants completed a 20-minute psychomotor vigilance task while undergoing fMRI. The researchers used pseudo-continuous arterial spin labeling to measure cerebral blood flow and assessed self-reported fatigue before and after the task.
The results showed that patients with post-COVID condition reported a significantly greater increase in fatigue following the task compared with control subjects. They also had longer reaction times across all four measured periods of the task, indicating slower processing speed. However, the groups did not differ significantly in fatigability, or the extent to which their performance declined during the task.
Imaging findings revealed lower overall cerebral blood flow among participants with post-COVID condition. Average global cerebral blood flow was 49.2 mL/100 g/min in patients compared with 51.7 mL/100 g/min in the control group. Voxel-wise analysis also identified several areas of regional hypoperfusion. These included the right inferior occipital gyrus, left postcentral gyrus and the right middle cingulate cortex.
The findings suggest that altered cerebral perfusion may be associated with the persistent fatigue and cognitive-performance difficulties experienced by some individuals with post-COVID condition. The study also distinguishes between feeling fatigued and becoming progressively less able to maintain performance.
“Individuals with [post-COVID condition] showed pronounced subjective fatigue together with slower and more variable performance on the [psychomotor vigilance task], consistent with an attenuated capacity to sustain attention,” the authors noted. “Overall, our findings suggest that impaired cerebral perfusion may contribute to the development of fatigue in [post-COVID condition] patients.”
The group acknowledged that their small sample size limits the findings' generalizability, and further research will be needed to determine whether cerebral hypoperfusion contributes directly to post-COVID-related fatigue or represents one component of a broader underlying process.
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In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.