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Low brain activity seen in Chronic Fatigue Syndrome
Friday 4 May 2012
Patients with chronic fatigue syndrome (CFS) had significantly less activation of the basal ganglia in response to a known stimulus compared with a control group, investigators reported.
Brain imaging during a simulated reward task showed reduced activation in the right caudate and right globus pallidus of patients with CFS. Decreased activation in the globus pallidus correlated significantly with multiple domains on a validated fatigue scale.
The findings suggest that reduced neural activation in the basal ganglia may have a role in the etiology in CFS, Elizabeth Unger, MD, PhD, reported at the Federation of American Societies for Experimental Biology meeting in San Diego.
"Given similar findings in patients treated with the antiviral cytokine interferon-alpha, inflammatory cytokines might be involved in chronic fatigue syndrome," Unger, of the CDC, and colleagues concluded in a poster presentation.
"Because dopamine is the primary neurotransmitter in basal ganglia, dopamine metabolism may be important in CFS," they added.
Despite intensive study, the origin of CFS remains unknown. Infection, inflammation, and chronic stress all have supporting evidence for a role in CFS. Inflammatory cytokines might constitute a common trigger for factors linked to CFS, the investigators noted in the background of their presentation.
Fatigue is a common feature in neurologic disorders that involve the basal ganglia, such as Parkinson's disease and multiple sclerosis. The basal ganglia, which mediate motor activity and motivation, are vulnerable to the effects of pro-inflammatory cytokines, and the effects of interferon-alpha on the basal ganglia correlate with fatigue.
Given the suggestive background information, Unger and colleagues hypothesized that activation levels in the basal ganglia of CFS patients would correlate with fatigue.
To test the hypothesis, they conducted a study involving 18 patients with CFS diagnosed in accordance with the 1994 case definition. For comparison, the investigators studied 41 age-, sex-, and race-matched individuals with no history of significant clinical depression and no current use of medication affecting immune or cognitive function.
All study participants underwent functional MRI scans while participating in a reward task involving simulated gambling. The brain scans measured blood flow, and activation of the basal ganglia was determined by signal differences associated with winning and losing. The amount won was the same for all participants.
The MRI results showed significantly less activation of the right caudate nucleus (P=0.014) and right globus pallidus (P=0.019) in the patients with CFS versus the control group.
In the CFS group, reduced activation in the right globus pallidus correlated significantly with mental fatigue (P=0.001), general fatigue (P=0.011), and reduced activity (P=0.02). Basal ganglia activation did not correlate with any of the fatigue domains in the control group.
"The reduction in activity (in the CFS group) correlated with measures of fatigue; the greater the fatigue, the greater the reduction in activation," Unger and colleagues stated in their presentation.
The investigators had no disclosures.
Primary source: Federation of American Societies for Experimental Biology
The above, with comments, originally appeared here.
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