Central pain modulatory mechanisms of attentional analgesia are preserved in Fibromyalgia

Fibromyalgia is a prevalent pain condition that is associated with cognitive impairments including in attention, memory, and executive processing. It has been proposed that fibromyalgia may be caused by altered central pain processing characterised by a loss of endogenous pain modulation. We tested whether attentional analgesia, where cognitive engagement diminishes pain percept,
was attenuated in fibromyalgia patients (n=20) compared to matched healthy controls (n=20). An individually calibrated, attentional analgesia paradigm with a 2x2 block design was used with brain and brainstem-focussed fMRI. Fibromyalgia patients had both lower heat pain thresholds and speeds in a visual attention task. When this was taken into account for both attentional task and thermal stimulation, then both groups exhibited an equivalent degree of attentional analgesia. fMRI analysis showed similar patterns of activation in the main effects of pain and attention in the brain and brainstem (with the sole exceptions of increased activation in the control group in frontopolar cortex and the ipsilateral locus coeruleus). The attentional analgesic effect correlated with activity in the periaqueductal grey and rostroventromedial medulla. These findings indicate that fibromyalgia patients can engage the descending pain modulatory system if the attentional task and noxious stimulus intensity is appropriately titrated.