Cerebral blood flow dynamics during pain processing in patients with fibromyalgia syndrome.

OBJECTIVES: Increased cerebral blood flow during processing of acute pain has repeatedly been observed in fibromyalgia syndrome. The study investigated the time dynamics of the pain-related hemodynamic response in fibromyalgia using transcranial Doppler sonography.

METHODS: In 25 women with fibromyalgia and 25 healthy participants, blood flow velocities in the anterior and middle cerebral arteries of both hemispheres were recorded, while heat stimuli of 45°C were applied to their forearms. Thermal pain threshold and subjective pain experience during stimulation were assessed, and the participants completed the McGill Pain Inventory, Beck Depression Inventory, and State-Trait Anxiety Inventory.

RESULTS: The early component of the blood flow response in both anterior cerebral arteries, that is, the steep flow increase during the initial stimulation period, was more pronounced in the patients than in the controls (mean [standard deviation] = 1.28% [1.85%] versus 0.24% [1.58%], p = .04). The patients showed lower pain threshold (p = .018), stronger sensory and affective pain experience (p < .001), and increased values on all questionnaire scales (all p values < .001). Although higher scores on each of the scales were associated with a stronger early blood flow response (r values ranging from 0.17 to 0.36), clinical pain severity proved to be the best predictor (β = .33, p = .02).

CONCLUSIONS: The increased blood flow response in the anterior cerebral arteries reflects hyperactivity of medial structures of the neuromatrix of nociception, structures involved in the processing of affective and cognitive aspects of pain. Aberrances in cerebral blood flow related to fibromyalgia and its clinical characteristics become particularly apparent in the enhancement of the initial component of the hemodynamic response.