Brain inflammation a recipe for chronic fatigue
The symptoms of chronic fatigue syndrome are found to be linked to widespread brain inflammation
Figure 1: Brain imaging has revealed that chronic fatigue syndrome is associated with neuroinflammation.
Patients with chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis, experience severe and often disabling exhaustion. Other symptoms include cognitive dysfunction, pain and depression. Although brain inflammation is thought to be involved in the development of these symptoms, direct evidence of this relationship has proved elusive.
Yasuyoshi Watanabe, Yasuhito Nakatomi, Kei Mizuno and colleagues from the RIKEN Center for Life Science Technologies and other institutes in Japan have now shown using a noninvasive brain imaging technique that the neuropsychological symptoms of patients with CFS are closely associated with widespread inflammation in the brain1.
Positron emission tomography (PET) is a brain imaging technique that uses radioactive tracers attached to particular cell types or molecules to noninvasively track changes in the brain in disease states. To examine the effect of CFS, the researchers used a radioactive tracer that labels activated glial cells, which tend to be associated with neuroinflammation. They performed PET imaging studies on nine CFS sufferers and ten healthy individuals to identify the extent to which brain inflammation plays a role in CFS. They found that the levels of tracer binding were much higher in multiple brain regions in the CFS patients compared with the same brain regions in the healthy participants.
The investigation also found correlations between tracer binding in various brain regions and the severity of symptoms in the CFS patients. The researchers found that inflammation in the thalamus—a region of the brain responsible for relaying motor and sensory information to and from the cerebral cortex—correlated with the severity of both cognitive impairment and pain in the CFS patients. They also identified a correlation between inflammation in the amygdala—a part of the brain linked to emotional memory—and the severity of cognitive impairment. The severity of depression in CFS patients, on the other hand, was linked to the extent of inflammation in the hippocampus, which is a part of the brain known to be associated with depression.
The findings suggest that inflammation in the brain plays a key role in CFS in humans. Drugs that fight inflammation in the brain may therefore offer promising therapies to prevent or treat CFS and its related symptoms of pain, depression and cognitive dysfunction.
“Because CFS is diagnosed based on subjective symptoms such as fatigue, pain, sleep problems and cognitive impairment,” says Mizuno, “neuroinflammation as observed by PET imaging could be helpful as a more objective biomarker for diagnosis of the disorder.”
Nakatomi, Y., Mizuno, K., Ishii, A., Wada, Y., Tanaka, M., Tazawa, S., Onoe, K., Fukuda, S., Kawabe, J., Takahashi, K. et al. Neuroinflammation in patients with chronic fatigue syndrome/myalgic encephalomyelitis: An 11C-(R)-PK11195 PET study. The Journal of Nuclear Medicine 55, 1–6 (2014).