Monozygotic twins discordant for chronic fatigue syndrome: Regional cerebral blood flow SPECT

PURPOSE: To evaluate the relationship between regional cerebral blood flow (rCBF) and chronic fatigue syndrome (CFS) in monozygotic twins discordant for CFS. MATERIALS AND METHODS: The authors conducted a co-twin control study of 22 monozygotic twins in which one twin met criteria for CFS and the other was healthy. Twins underwent a structured psychiatric interview and resting technetium 99m-hexamethyl-propyleneamine oxime single photon emission computed tomography of the brain. They also rated their mental status before the procedure. Scans were interpreted independently by two physicians blinded to illness status and then at a blinded consensus reading. Imaging fusion software with automated three-dimensional matching of rCBF images was used to coregister and quantify results. Outcomes were the number and distribution of abnormalities at both reader consensus and automated quantification. Mean rCBF levels were compared by using random effects regression models to account for the effects of twin matching and potential confounding factors. RESULTS: The twins with and those without CFS were similar in mean number of visually detected abnormalities and in mean differences quantified by using image registration software. These results were unaltered with adjustments for fitness level, depression, and mood before imaging. CONCLUSION: The study results did not provide evidence of a distinctive pattern of resting rCBF abnormalities associated with CFS. The described method highlights the importance of selecting well-matched control subjects.