New research suggests there are two distinct forms of Gulf War illness, depending on which brain regions have atrophied.
Researchers at Georgetown University Medical Center say their findings may explain why the medical community has encountered Gulf War veterans with varying symptoms and complaints.
Using brain imaging, the researchers studied the effects of physical stress on veterans and a control group.
In 18 veterans, the researchers found that pain levels increased after completion of the exercise stress tests.
fMRI (functional magnetic resonance imaging) scans in these veterans showed loss of brain matter in adjacent regions associated with pain regulation.
During cognitive tasks, this group showed an increased use of the basal ganglia — a potential compensating strategy the brain uses that is also seen in neurodegenerative disorders, such as Alzheimer’s disease, according to the study, which was published in PLOS ONE.
Following exercise, this group lost the ability to employ their basal ganglia. This finding suggests an adverse response to a physiological stressor, the study noted.
A separate group of 10 veterans had a very different response, according to lead author Rakib Rayhan, a researcher in the lab of the study’s senior investigator, James Baraniuk, MD, a professor of medicine.
In this group, the researchers found substantial increases in heart rate. These veterans also exhibited atrophy in the brain stem, which regulates heart rate.
Additionally, brain scans during a cognitive task performed before the exercise showed increased compensatory use of the cerebellum, again a trait seen in neurodegenerative disorders, the researchers reported. Like veterans in the other group, these veterans lost the ability to use this compensatory area after exercise.
“The use of other brain areas to compensate for a damaged area is seen in other disorders, such as Alzheimer’s disease, which is why we believe our data show that these veterans are suffering from central nervous system dysfunction,” Rayhan said.
He added that because such changes are similar to other neurodegenerative states, it doesn’t mean that veterans will progress to Alzheimer’s or other diseases.
Alterations in cognition, brain structure and exercise-induced symptoms found in the veterans were absent in the control group, the researchers noted.
The new findings, which the researchers said were a surprise, follow a study in Gulf War veterans published in March in PLOS ONE that reported abnormalities in the bundle of nerve fibers connecting the brain areas involved in the processing and perception of pain and fatigue.
Gulf War illness is a mysterious malady believed to have affected more than 200,000 military personnel who served in the 1990-1991 Operation Desert Shield and Desert Storm.
Although veterans were exposed to toxic chemicals, including nerve agents, pesticides and herbicides, no one has definitively linked any single exposure or underlying mechanism to the illness, the researchers report.
Symptoms of Gulf War illness include widespread pain, fatigue and headache, as well as cognitive and gastrointestinal dysfunctions.
“Our findings help explain and validate what these veterans have long said about their illness,” Rayhan said.