November 15, 2022 — People who have been treated for Lyme disease, but who continue to experience symptoms, have changes in their brains that confirm the memory and concentration problems many of them have reported, a new study finds.
Many people with post-treatment Lyme disease — or PTLD — complain of problems with memory and concentration, which sometimes comes with fatigue, muscle aches, insomnia, and depression.
To understand possible changes in brain function that might explain these cognitive difficulties, the researchers used specialized imaging techniques to compare the brains of 12 adults with PTLD and 18 adults with no history of Lyme disease.
Researchers have found changes in the white matter in the brains of people with PTLD. White matter is found in the deep tissues of the brain and contains nerve fibers that are extensions of nerve cells.
“We found that … white matter function increased while PTLD participants were performing a cognitive task,” says principal investigator Cheri Marvel, PhD, assistant professor of neuroscience, psychiatry, and behavioral sciences at Johns Hopkins University School of Medicine in Baltimore. .
“I think if patients hear this, they may feel validated that there is a biological basis for their persistent symptoms, even if there is no good way to treat cognitive difficulties yet,” she says. Marvel says this could be similar to what patients with prolonged COVID experience.
The study was published online October 26 in the journal Nature Plus one.
We can start connecting the dots
“Objective biological measures” of PTLD symptoms “usually cannot be determined using regular MRI, CT scans, or blood tests,” study senior author John Okot, MD, director of the Johns Hopkins Lyme Clinical Research Center, said in a news release. .
Given the number of people with the condition—roughly 10%-20% of the half-million Americans who develop the disease each year—the researchers felt they needed to “expand” the assessment methods.
“We were motivated by persistent complaints of cognitive difficulties by patients treated for Lyme disease, with a lack of data explaining the underlying cause of these symptoms,” Marvell says.
It seems logical that “if there are cognitive and neurological symptoms involved, the brain might reveal something about this. Then we can start to connect the dots between the patient’s experience and the mechanisms behind it,” she says.
To investigate, the Marvel team used functional magnetic resonance (fMRI), an imaging technique that measures blood flow to regions of the brain, often while performing specific tasks — in this case, short-term memory tasks that involve memorizing and recalling uppercase and lowercase letters as well as the alphabetical order of multiple letters. .
Those with PTLD performed slower on some memory tasks, although their slower speed did not affect the accuracy of their performance.
The researchers found unusual white matter activity in the frontal lobe—a region of the brain involved in cognitive tasks, such as memory recall and concentration—in the PTLD group.
This type of tissue usually sees less blood flow, compared to the gray matter in the brain, and is responsible for transmitting information about the brain and “delivering” it to the gray matter. The amount of activity they saw was “unusual to be observed with the MRI methods we used, and we didn’t see such activity in the healthy control group,” says Marvel.
sign of healing?
To confirm the finding, the researchers used a second imaging technique called diffusion tensor imaging in all 12 patients with PTLD and 12 of the 18 people without PTLD. The imaging technology detects whether and which direction water is moving within the brain tissue.
In patients with PTLD, researchers have found that what’s called axonal proliferation — or extravasation — of white matter is associated with improved brain function. The water that was diffused was found in the same areas of white matter identified by the first imaging test.
“This led us to speculate that white matter changes are a healthy response to the impact of Lyme disease on the brain,” Marvell says. She notes that increased white matter leakage “may be a sign of recovery during PTLD and represent a healthy outcome.”
In the meantime, the researchers want to work with other experts to answer their remaining questions, she says.
“It is important for clinicians to know that PTLD leads to real, quantifiable changes in the brain and that patients’ cognitive complaints may be a direct result of these changes in the brain, rather than a side effect of other symptoms, such as fatigue, for example,” Marvel said.
Commenting on the study for this report, John Kelp, Ph.D., assistant professor of clinical psychology at Columbia University in New York City, says it is “an important and carefully executed study that expands the scope of previous brain imaging studies of PTLD patients” using “state-of-the-art imaging and analysis methods.” the brain.”
says Kelp, who heads the Neuropsychology Laboratory in the Department of Molecular Imaging and Neuropathology at the New York State Institute of Psychiatry.
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