Almost one-third of soldiers deployed to the Persian Gulf in 1990 and 1991 brought home a lasting reminder of their tour: Gulf War Illness (GWI). It’s a condition with a constellation of symptoms, including pain, chronic fatigue, and cognitive dysfunction. Because every veteran’s symptom patterns seem unexplainable and unconnected and no clear biomarker had been identified until now, some medical professionals have questioned the legitimacy of the disease.
“The real stunning finding here is we now have an objective measurement that separates people with Gulf War Illness from healthy controls,” said James Baraniuk, a clinical researcher at Georgetown University and author of a paper published yesterday in the Public Library of Science One that describes the findings (1). “So you can’t say, ‘It’s all in their heads.’”
During the Gulf War, soldiers witnessed ammunitions dump explosions, burning oil wells, and other dangerous events. As a result, some were exposed to a variety of chemicals, which may have included harmful substances such as organophosphates, nerve agents, and acetylcholinesterase inhibitors. After the war, some veterans started showing symptoms of fatigue and pain, which eventually became known as GWI.
Although GWI has been studied subjectively and epidemiologically for about 20 years, it is only recently that scientists have begun examining GWI sufferers’ brains using fMRI with the hope of identifying a biomarker. Patients with other neurological disorders such as multiple sclerosis often have changes in their white matter, an area of the brain that consists of glial cells and myelinated axons, which transmit signals between other regions of the brain. So Baraniuk and colleagues hypothesized that GWI sufferers might suffer from a similar issue.
DTI allowed the team to visualize changes in white matter. By sending a specific radio-frequency into the brains of 31 sufferers and 20 controls, the researchers tracked the directions in which protons from water molecules moved with the least resistance: perpendicularly out of the neurons (radial diffusivity) or along the axons longitudinally (axial diffusivity).
In the GWI patients, Baraniuk and colleagues found unusual axial diffusivity patterns in the bundle of axons called the right inferior fronto-occipital fasciculus, which connects regions in the brain involved in pain, fatigue, emotional, and reward processing, and the right ventral attention network. . In addition, the team found that as the axial diffusivity increased, so did the intensity of the patient’s pain and fatigue symptoms.
Right now, Baraniuk doesn’t know why axial diffusivity is different in GWI patients, but he believes it’s a clear biomarker for this disease. His lab is working to find more.
“With all that these soldiers have done for their nation, they’re still told it’s all in their heads,” said Baraniuk. “I think we have a series of findings that will lead to an algorithm for phenotyping them and distinguishing them from other illness, and find new diagnostics and treatments.”
1. Rayhan, R. U., B. W. Stevens, C. R. Timbol, O. Adewuyi, B. Walitt, J. W. VanMeter, and J. N. Baraniuk. 2013. Increased brain white matter axial diffusivity associated with fatigue, pain and hyperalgesia in gulf war illness. PLoS ONE 8(3):e58493+.