Ipsilateral cortical activation in fibromyalgia patients during brushing correlates with symptom severity

Objective: To evaluate cortical activation patterns during mechanical-tactile stimulation in fibromyalgia syndrome (FMS) patients and to correlate cortical activation changes with clinical symptoms.

Methods: Nineteen female FMS patients and 18 matched, healthy control subjects underwent EEG examination during brushing stimulation of the right forearm. Participants rated any pain experienced and underwent a manual tender point scale (MTPS) examination. Amplitude changes of cortical rhythms during brushing were analysed in alpha (8-13 Hz) and beta (16-24 Hz) frequency bands.

Results: Thirteen patients reported pain during brushing. Independent t-test comparison of event related desynchronisation (ERD) during brushing revealed a cluster of electrodes over ipsilateral (right) central-parietal region which demonstrated ERD in patients only. Clinical MTPS scores correlated with beta-band ERD in this cluster of electrodes. Beamformer analysis revealed a widespread array of source activations in patients, including bilateral insula and primary and secondary somatosensory cortices. Control subject source activations were limited to contralateral (left) hemisphere.

Conclusions: Results indicate ipsilateral cortical activations in FMS patients, but not in healthy controls, during brushing. Ipsilateral ERD during brushing is associated with MTPS score suggesting abnormal processing of somatosensory input which may contribute to clinical pain.

Significance: Altered functioning in FMS may reflect physiological changes in response to afferent somatosensory information manifesting in chronic pain.