BACKGROUND: Irritable bowel syndrome (IBS) and fibromyalgia (FM) are considered chronic syndromes of altered visceral and somatic perception, respectively. Because there is a significant overlap of IBS and FM, shared pathophysiological mechanisms have been suggested. Although visceral perception has been well studied in IBS, somatic perception has not.
AIMS: To compare hypervigilance and altered sensory perception in response to somatic stimuli in patients with IBS, IBS+FM, and healthy controls.
METHODS: Eleven IBS females (mean age 40), 11 IBS+FM females (mean age 46), and ten healthy female controls (mean age 39) rated pain perception in response to pressure stimuli administered to active somatic tender points, non-tender control points and the T-12 dermatome, delivered in a predictable ascending series, and delivered in an unpredictable randomized fashion (fixed stimulus).
RESULTS: Although IBS patients had similar pain thresholds during the ascending series compared with controls, they were found to have somatic hypoalgesia with higher pain thresholds and lower pain frequency and severity during fixed stimulus series compared with IBS+FM patients and controls (P<0.05). Patients with IBS+FM were more bothered by the somatic stimuli and had somatic hyperalgesia with lower pain thresholds and higher pain frequency and severity.
CONCLUSIONS: Both hypervigilance and somatic hypoalgesia contribute to the altered somatic perception in IBS patients. Co-morbidity with FM results in somatic hyperalgesia in IBS patients.
Chang L, Mayer EA, Johnson T, FitzGerald LZ, Naliboff B