A new study comparing magnetic resonance imaging (MRI) images of patients with long COVID, fully recovered COVID-19 survivors, and healthy controls shows microstructural changes in different brain regions in the long-COVID patients. The findings will be presented next week at the annual meeting of the Radiological Society of North America.
The research is the first to use diffusion microstructure imaging (DMI), a novel MRI technique, which looks at the movement of water molecules in tissues. DFI can detect smaller brain changes than traditional MRI.
MRIs have thus far failed to compare microstructural differences in the brain of patients with long COVID, frustrating clinicians searching for a pathophysiologic explanation of the disorder, which affects up to 10% to 15% of COVID-19 patients.
"Diffusion microstructure imaging (DMI) is a promising approach to fill this gap, as it detects even small volume shifts between microstructural compartments of a neural tissue model," the authors of the study said.
The study included images from 89 patients with long COVID, 38 COVID-19 patients who didn't report long-term symptoms, and 46 healthy controls with no history of COVID-19 infection.
Among participants with long COVID, 53% of patients could not return to their previous level of independence and/or employment due to infection. Cognitive performance was impaired in 41%, 78% said they had fatigue, and 73% had impaired olfaction.
Brain structure changes among all COVID participants
In an abstract on the findings, the authors explain whole-brain DMI-data revealed a volume-shift from the extraneurite compartment into the free water fraction for the gray matter positively associated with the severity of the initial COVID-19 infection.
This study allows for an in vivo insight on the impact of COVID-19 on the brain.
"This study allows for an in vivo insight on the impact of COVID-19 on the brain," said lead study author Alexander Rau, MD, of the University Hospital Freiburg in Germany, in a press release. "Expression of post-COVID symptoms was associated with specific affected cerebral networks, suggesting a pathophysiological basis of this syndrome."
Interestingly, the DMI revealed microstructure changes in patients with long COVID and in those who were infected with COVID-19 but did not develop lingering symptoms.
"We noted gray matter alterations in both patients with long-COVID and those unimpaired after a COVID-19 infection," said Rau. "Interestingly, we not only noted widespread microstructural alterations in patients with long COVID, but also in those unimpaired after having contracted COVID-19."
The authors of the study said that though the findings are intriguing, they do little to explain why some patients develop long COVID and others do not.