In the end, the study team found megakaryocytes in the brains of one-third of the deceased COVID-19 patients.
The findings were published online Feb. 12 inJAMA Neurology.
So do megakaryocyte brain formations explain COVID-19 brain fog? Nauen stressed that it’s premature to characterize the finding as proof of cause and effect.
“Knowing they’re there is the first step. Now we need to figure out why they’re in the brain, and what’s signaling them to come to the brain by mistake, whether this very different kind of inflammation that we’ve never seen before is responsible for brain fog and may also be contributing to a heightened risk for stroke,” he noted.
“None of these patients had had strokes. And I’m speculating. But you can imagine that if you start to clot off, or block off, this very intricate network of carefully regulated capillaries, then your blood pressure is going to change, get higher, and perhaps raise the risk for stroke,” Nauen said.
Meanwhile, Dr. Larry Goldstein, chairman of the department of neurology at the University of Kentucky and co-director of the Kentucky Neuroscience Institute, offered a cautious take on Nauen’s findings.
“‘Brain fog’ is not a specific condition and has no defining diagnostic criteria,” Goldstein said.
Brain fog is also “not specific to COVID, and can occur in association with a variety of inflammatory conditions, degenerative diseases, medications — particularly some cancer chemotherapies — and intensive care unit hospitalizations, among others,” he added.
Still, in the case of COVID-19, could megakaryocytes be the cause? Goldstein acknowledged that the explanation is “plausible.” But so are a wide array of other explanations, including inflammation, reduced blood oxygen, stroke, reduced blood flow and/or “the general complications of hospitalization for an acute, life-threatening illness,” he said.
So, absent brain scans or detailed reports on each patient’s “cognitive status,” it’s impossible to know, Goldstein stressed. That means, for now, all that can be said is that “there are a variety of ways brain injury could occur in this setting.”
There’s more on COVID-19 brain fog at NewYork-Presbyterian Hospital.
SOURCES: David Nauen, MD, PhD, assistant professor, department of pathology, Johns Hopkins University, Baltimore; Larry Goldstein, MD, chairman, department of neurology, and co-director, Kentucky Neuroscience Institute, University of Kentucky, Lexington; JAMA Neurology, Feb. 12, 2021, online