Brain MRI abnormalities exist in a subset of patients with chronic fatigue syndrome
Introduction
Chronic Fatigue Syndrome (CFS) is a heterogeneous disorder with no known medical cause and is diagnosed based on established clinical case definitions [1], [2], [3]. In order to improve diagnostic specificity and to discover discrete pathology, Fukuda et al. [3] suggested using stratification techniques to identify subgroups of CFS patients, thereby increasing patient pool homogeneity. Indeed, heterogeneity of the patient pool may explain some of the inconsistency between previous brain neuroimaging studies in CFS [4], [5], [6], [7].
A critical variable contributing to population heterogeneity in CFS is the presence or absence of psychopathology [3]. The value of stratification along the dimension of psychopathology has been shown in a study of cognitive function in CFS [8]. CFS patients were divided into groups based on the presence or absence of DSM III-R psychiatric diagnoses since illness onset. Neuropsychological impairment was significantly greater in CFS patients without DSM III-R psychiatric diagnoses since illness onset than in CFS patients with concurrent psychiatric diagnoses or healthy controls. Cognitive difficulties were manifested particularly in the area of complex information processing, a function necessary for the rapid and efficient encoding and manipulation of information and considered to be part of the working memory system [9]. The cerebral structures subserving the working memory system include the frontal lobes [10].
Taken together, previous findings suggest the possibility of structural cerebral changes particularly in the CFS subgroup without DSM III-R psychiatric diagnoses since illness onset. If this interpretation is correct, structural brain imaging studies should show MRI signal abnormalities predominantly in the subgroup of CFS patients without DSM III-R psychiatric diagnoses since illness onset. In addition, a greater number of structural brain changes may be found in regions associated with the working memory system, such as the frontal lobes. The purpose of the present study was to test these hypotheses.
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Subjects
Subjects consisted of 39 CFS patients and 19 healthy individuals who did not exercise regularly (Healthy Controls or HC). The CFS and HC groups were matched on age, gender, and years of education (see Table 1). CFS patients were recruited via self-referral based on media reports about the CFS center or by physician referral. All CFS patients fulfilled the 1994 case definition [3] with the following modifications: illness duration was not longer than ten years, there was no history of loss of
Results
A total of 41% of all scans (n=24/58) showed abnormalities on MRI, of these 10% (n=6) were accounted for by controls and 31% (n=24) by CFS subjects. No significant difference was found in the frequency of abnormal scans between the CFS and HC groups. That is, 18 of 39 CFS patients (46.2%) and 6 of 19 controls (31.6%) had MRI abnormalities belonging to at least one of the radiological rating categories. Disease duration was not significantly related to presence of abnormalities (r=0.523; P
Discussion
The present study found that a subgroup of CFS subjects, those without DSM III-R Axis-I psychiatric diagnoses since illness onset, have a significantly higher frequency of brain abnormalities on MR imaging compared to both CFS patients with an Axis-I psychiatric disorder concurrent with their illness, and healthy controls. When the total CFS patient pool was evaluated for frequency of MRI abnormalities, no significant differences were found between CFS patients and healthy controls.
Acknowledgements
This work was supported by NIH Center grant AI-32247, RO1-H52810A, and by funds establishing an Environmental Hazards Research Center at the East Orange Veterans Administration Medical Center. We thank Patricia Singh at the East Orange Veterans Administration Medical Center for the technical support acquiring the MRI data.
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2017, Journal of the Neurological SciencesCitation Excerpt :Consequently, the pool of patients included in clinical studies of the disorder is generally heterogeneous, which has quite likely impeded research progress. In a series of studies stratifying CFS patient samples into those with or without comorbid Axis I psychiatric diagnosis, we have reported more brain related abnormalities in the group of patients without psychiatric comorbidity; these included poorer performance on neuropsychological testing [1], more brain lesions on structural MRI [2], greater decreases in cerebral blood flow [3], a higher rate of either elevated protein or white cell count in spinal fluids [4], and a tendency toward higher ventricular lactate [unpublished results]. In the present study, we aimed to confirm the presence of these clinical, biochemical, physiological and neuroimaging differences prospectively and at the same time point to determine if stratifying CFS patients on the basis of psychiatric comorbidity would be a useful strategy to minimize sample heterogeneity in future research studies.