Imaging to assess brain microstructure identified increased fractional anisotropy in the anterior right arcuate fasciculus of patients with chronic fatigue syndrome, which was not present in age- and sex-matched control subjects.
The right-sided abnormality was particularly marked in right-handed chronic fatigue syndrome (CFS) patients, and the degree of increase correlated with the severity of their disorder. A finding of increased fractional anisotropy in this area of the brain may eventually serve as a biomarker for CFS, said Dr. Michael M. Zeineh of the department of radiology at Stanford (Calif.) University, and his associates (Radiology 2014 Oct. 29 [doi:10.1148/radiol.14141079]).
Courtesy Radiological Society of North America
Increased fractional anisotropy in the anterior right arcuate fasciculus may serve as a biomarker for CFS.
In what they described as the first study to examine brain microstructure in CFS, the investigators used volumetric MRI with diffusion-tensor imaging (DTI) to detect microstructural abnormalities in the patients – who had been evaluated at the university’s CFS Clinic during the preceding 5 years – and in healthy volunteers. The researchers also performed gray- and white-matter volumetric studies to identify differences between the two study groups in gross brain structure, as well as pseudocontinuous arterial spin labeling to assess global alterations in brain perfusion.
The mean age of the study participants was 46 years, and the mean duration of CFS symptoms was 12 years.
In the DTI analysis, the only significant difference between the two study groups was that the anterior right arcuate fasciculus – identified in 13 of 15 CFS patients and in all 14 control subjects in the study – showed significantly higher fractional anisotropy in CFS patients than in control subjects. This was confirmed in a second dataset from the same study subjects. The difference between CFS patients and control subjects was most pronounced in the subgroup of right-handed participants, “suggesting that hemispheric differences with handedness and language are an additional source of variance,” Dr. Zeineh and his associates said.
In addition, “two cortical regions connected via the arcuate fasciculus exhibited increased thickness: the right middle temporal and precentral gyri,” they noted.
The volumetric studies showed significantly lower total supratentorial white-matter volume in CFS, even after the data were adjusted to account for subject age, total intracranial volume, and handedness. However, total cortical gray-matter volume was equivalent between the two study groups, as were prefrontal cortex volume and global cortical thickness.
There were no differences between patients and controls in any perfusion measure, including perfusion to the cortex, supratentorial white matter, basal ganglia, thalami, or hippocampi. This finding is consistent with the results of a previous perfusion study involving monozygotic twins. Taken together, the findings suggest that brain perfusion is not affected in CFS.
Given the small number of subjects in this study, the findings must be verified in larger studies. It also would be valuable to assess possible changes in brain microstructure over time in a longitudinal study, and to determine whether treatment interventions exert any beneficial effects, the investigators added.