Jigsaw puzzle
“While this is an important piece in the jigsaw puzzle of neuroinflammation in chronic neurological disease, it is important to keep in mind that we still lack understanding of the complex picture for several reasons,” Alexander Gerhard, MD, honorary senior lecturer in neuroscience at the University of Manchester, England, wrote in an accompanying editorial.
Among these reasons is that the PET technique used in the study is noisy and not restricted to glial cells, he wrote. TSPO expression is only one part of the brain’s neuroinflammatory response, but PET techniques “do not currently allow us to distinguish between different states of microglial activation.” In addition, “a much more detailed understanding of microglial activation at different time points” is needed before neuroinflammatory changes can be targeted therapeutically, Dr. Gerhard wrote.
In a comment, Vilma Gabbay, MD, professor of psychiatry and neuroscience and director of biomarkers and dimensional psychiatry in the Psychiatry Research Institute at Montefiore Einstein, Albert Einstein College of Medicine, New York, said that “this is an important initial step to better understand the neuropsychiatric consequences of COVID even in only a mild and moderate viral illness.” TSPO imaging through PET scanning has been used as an index for neuroinflammation and gliosis. Researchers have used it to study neurodegenerative diseases, but as the authors noted, the ligand is not specific for gliosis.
“Follow-up large cohort studies including other measures of neuroimaging modalities assessing circuitry and neurochemistry are needed,” she said. “Similarly, studying the blood-brain barrier will also allow us to better understand how the immune reaction in the blood transitions to the brain.”
This field of research is evolving, and clinical trials are ongoing, Dr. Gabbay added. Meanwhile, clinicians should monitor for, assess, and treat neuropsychiatric symptoms and “follow the literature for new research and management recommendations.”
The study was primarily funded by a Canadian Institutes of Health Research Project grant to the authors, with some funding from the Canadian Institute for Military and Veteran Health Research. Dr. Meyer received support from their Canada Research Chair awards and received grants and support from several pharmaceutical companies outside of the submitted work. Dr. Gerhard and Dr. Gabbay disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.