Comparing Fractional Anisotropy Diffusion Tensor Imaging of Patients with ME/CFS, Long COVID and Healthy Controls, 2023, Ziaja et al

Comparing Fractional Anisotropy Diffusion Tensor Imaging of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrom, Long COVID and Healthy Controls


Abstract
The onset of Long COVID (LC) and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) may be related to a virus-or immune mediated disruption. Inflammatory processes have an impact on the brain’s interconnectivity. Fractional Anisotropy Diffusion tensor imaging (FA DTI), which is a variant of magnetic resonance imaging (MRI) leverages the preferential diffusion of water molecules along the longitudinal axis of elongated cells, such as neurons. As such, nerve fibres in the white matter can be visualised. Water diffusion in the tissue is influenced by various factors, including the tissue structure. In the case of structured tissue, such as fibrous webs, diffusion is greater along the fibre web and less transversely to it, resulting in anisotropic diffusion (FA). This results in 3 parameters: fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). FA represents the degree of anisotropy in diffusion and can be correlated with myelination and fibre pathway conductivity. RD represents inflammation of the myelin sheath, while AD represents axonal damage. In this exploratory study, the association between viral infections and vector markers of 6 brain networks was investigated using FA imaging techniques. When considering insular cortex fibre crossings, a significant increases in in AD was found in the right anterior arcuate, and the inferior longitudinal fasciculus in individuals with ME/CFS and LC The results showed a strong increase in axial diffusivity in the six tracts of the patient group compared to the HCs, and substantial overlap in AD, FA, and RD in individuals with ME/CFS and LC compared to the HC group. The fornix appeared to be severely impaired and reduced in patients with LC and ME/CFS patients, possibly leading to dysfunctional adrenaline and noradrenaline modulation (tired but wired symptoms). AD was found in the right side of the cerebellum in both ME/CFS and LC patients, potentially leading to feedback failure of peripheral neuromuscular impulses due to a supraspinal axis and reflex arcs dysfunction.

https://www.researchgate.net/public...atigue_Syndrom_Long_COVID_and_Healthy_Control