Although a placebo effect was observed with both sham and experimental treatment, functional connectivity was altered and apparent on MRI in patients with fibromyalgia who underwent repetitive transcranial direct current stimulation applied to the motor cortex, according to recently published research from investigators at the University of Michigan.
A group of 12 women who met the 1990 American College of Rheumatology criteria for fibromyalgia completed the three-phase study. Phase one included a baseline evaluation, pain assessment and 10-minute functional MRI (fMRI) session. Phase two included five consecutive, daily sham transcranial direct current stimulation (tDCS) sessions, followed by an additional pain assessment and fMRI. The third phase involved five consecutive active tDCS sessions, followed by a pain assessment and a third fMRI. A washout period of 7 days to 11 days separated the second and third phases of the study.
Pain relief on a VAS was observed during the sham phase of the study, and no difference in pain relief was observed between sham and tDCS treatments. However, a decrease in clinical pain was observed across the duration of the study period from baseline until after tDCS was applied. Researchers also found a significant difference in the Positive and Negative Affect Schedule questionnaire.
As observed on fMRI, investigators found a greater improvement in clinical pain relief in patients who had stronger connectivity at baseline between the left primary motor (M1) seed and left ventral lateral (VL) thalamus, between the left S1 seed and left anterior insula, and between the left VL thalamus seed and the periaqueductal gray (PAG). These findings correlated with change in baseline pain under both sham and tDCS, except in the relationship between the VL and PAG baseline functional connectivity.
Regression analysis showed the changes in functional connectivity and pain on the VAS was positively correlated with the left VL thalamus and the left posterior insula. Patients who had a reduction in connectivity between those regions had a greater reduction in pain following sham tDCS. Significant decreases in connectivity were observed between the left inferior parietal lobule and left ventral posterolateral thalamus seed, and between the PAG seed and posterior cingulate following active tDCS. – by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosures.