Abnormal regional cerebral blood flow in the caudate nucleus among fibromyalgia patients and non-patients is associated with insidious symptom onset

Objectives: Compare resting state regional cerebral blood flow [rCBF] in patients with fibromyalgia [FMS], non-patients with FMS, and healthy controls as a function of insidious or physically traumatic symptom onset. Methods: All subjects were women and included 21 FMS patients with insidious symptom onset; 11 FMS patients with physically traumatic onset; 13 residents recruited from the Alabama community with FMS of insidious onset who had not consulted a physician for pain in the past 10 years [non-patients]; and 29 residents recruited from the Alabama community without FMS or any other chronic pain syndromes or illnesses [healthy controls]. All subjects underwent single photon emission computed tomographic imaging of brain rCBF during resting conditions, pain threshold assessment, as well as lumbar puncture, and they completed standardized self-report measures of pain intensity, fatigue, and depression. Group differences on these assessments were evaluated by analysis of variance and the Least Significant Difference test. Results: Fibromyalgia patients with insidious pain onset showed significantly lower rCBF levels than controls in the left and right caudate nucleus [P's less than or equal to .05]. Fibromyalgia non-patients with insidious pain onset showed significantly lower rCBF than controls in the right caudate nucleus [P = .019]. Patients with either insidious or traumatic pain onset also showed significantly lower rCBF than controls in the left and right thalamus [P's less than or equal to .05]. All groups with FMS, compared to controls, were characterized by significantly lower pain threshold levels [P's less than or equal to .001] and significantly higher cerebrospinal fluid [CSF] levels of substance P [P's less than or equal to .05]. Both FMS patient groups reported significantly higher levels of fatigue and depression than the non-patients with FMS [P's less than or equal to .05] and controls [P's < .03]. Conclusions: Insidious onset of FMS pain among patients and nonpatients is associated with abnormal resting state rCBF in the caudate nucleus, whereas traumatic onset of FMS pain among patients is associated with abnormal resting state rCBF in the thalamus. These differences are not associated with differences in pain threshold or CSF substance P. However, the presence of abnormal thalamic rCBF, alone or in combination with abnormal caudate rCBF is associated with greater depression and fatigue compared to abnormal caudate rCBF alone. Future studies should investigate whether abnormal thalamic and caudate responses to acute pain may also be associated with type of pain onset or with symptom severity.