A new study has found that veterans of the 1991 Gulf War were exposed to neurotoxins such as the anti-chemical warfare drug, pyridostigmine, insect repellants, and sarin, that caused changes in their brains.
Researchers at the University of Texas Southwestern Medical Center, Southern Methodist University, and the Veterans Affairs Medical Center in Dallas studied 21 chronically ill Gulf War veterans from the same Naval Reserve construction battalion. The veterans all had symptoms associated with Gulf War syndrome. The researchers used digital brain imaging to determine if the veterans' ill health was associated with observable brain dysfunction.
The brain scans revealed that the veterans' brains differed from those of healthy individuals and that the degree of change appeared to differ depending on the specific chemicals and how much of them each veteran had been exposed to. The researchers also revealed that the changes also corresponded to different sets of symptoms.
Three distinct patterns of illness had previously been defined under the umbrella of "Gulf War syndrome" in an ealier study:
Complex 1: Mild cognitive problems, such as distractibility, forgetfulness, feeling depressed, and excessive daytime sleepiness. Common in troops who had worn flea collars to ward off sand fleas.
Complex 2: A more debilitating state with confusion and a severe lack of muscle coordination. Most common in those exposed to Sarin and anti-nerve agent pills (cholinesterase inhibitors e.g. pyridostigmine).
Complex 3: Chronic muscle and joint aches. Associated with insect repellent and anti-nerve agent pills.
The participants in the new study included 11 men with Complex 2 symptoms, five with Complex 1 symptoms, and five with Complex 3 symptoms.
The aim of the researchers was to determine how brain blood flow in the veterans changed if they were exposed to a cholinesterase-inhibiting chemical. Insect repellent, anti-nerve agent pills (pyridostigmine) and Sarin are all cholinesterase inhibitors. The researchers also wanted to find out if the previous exposures had permanently damaged the way the veterans' brains worked.
Cholinesterase is an enzyme that breaks down the neurotransmitter, acetylcholine. If cholinesterase is inhibited it leads to overactivation of the portions of the brain and nervous system that use acetylcholine.
Duringthe study, the researchers first gave each veteran an IV saline solution, then performed a brain scans to check cerebral blood flow. Two days later, they instead gave the veterans an IV solution containing 2mg of physostigmine, a cholinesterase-inhibiting drug related to pyridostigmine, and again conducted brain scans.
Lead researcher, Robert Haley, explained that the group expected the brain activity of the exposed veterans to respond differently to the chemical than a control group of healthy individuals did, and they were correct.
However, they also found the veterans' brains responded differently to the saline, as well as to the physostigmine, based on which symptom complex they fell into. A result that was unexpected. The veterans' differed significantly on baseline blood flow after the saline compared with the control subjects. The largest differences were seen in veterans in the Complex 2 group.
There were also surprising differences between veterans depending on which complex of illness they exhibited. After the IV of physostigmine, both the Complex 1 and 3 groups had a slight reduction in blood flow in some regions of the brain, while the Complex 2 group had an increase.
The findings seem consistent with the "impaired cognition, attentional deficits, reduced intellectual functioning, audiovestibular dysfunction and emotional changes in Complex 1 and 2 veterans, versus the primary pain and sensory dysfunction of Complex 3 veterans", the researchers commented.
Brain blood flow of those in Complex 2 resembled those of Alzheimer's disease patients according to the researchers.
"Our findings further suggest that milder-symptom Complexes 1 and 3 involve different neuropathologic mechanisms from those underlying the more severe-symptom Complex 2", concluded Haley and colleagues. "This condition might be appropriately referred to as an encephalopathy; a term for any diffuse disease of the brain that alters brain function or structure."
They also suggested that brain scans could serve as an objective diagnostic tool for diagnosing chemical exposure-related encephalopathies in veterans.