Pain Ratings and Somatosensory Evoked Responses to Repetitive Intramuscular and Intracutaneous Stimulation in Fibromyalgia Syndrome

Abstract

To determine the presence of perceptual sensitization and related brain responses we examined 15 patients with fibromyalgia syndrome and 15 healthy controls comparable in age and sex. Multichannel EEG recordings and pain ratings were obtained during the presentation of 800 painful electrical intramuscular and intracutaneous stimuli to the left m. erector spinae and the left m. extensor digitorum. The stimulus intensity was adjusted to 50% between pain threshold and tolerance. Detection and pain thresholds were significantly lower in the fibromyalgia syndrome group. Sensitization occurred for both groups during intramuscular stimulation. In the EEG data the fibromyalgia syndrome patients showed higher N80 amplitudes compared with the healthy controls. Arm stimulation and intramuscular stimulation yielded higher N80 and N150 amplitudes compared with intracutaneous stimulation or stimulation of the back. These results indicate lower pain thresholds in the fibromyalgia syndrome patients after electrical stimulation and a higher N80 amplitude both indicative of enhanced sensory processing in this group.

Treatment-related changes in brain activation in patients with fibromyalgia syndrome

“…Before treatment, the FM patients showed a significantly lower pain tolerance than HC. In line with our findings, higher pain ratings after electrical stimulation or lowered pain threshold and pain tolerance to electrical stimuli have been found in patients with FM compared to HC (Scudds et al 1987;Arroyo and Cohen 1993;Sörensen et al 1998;Diers et al 2008). Similar results have been reported using laser evoked pain (Lorenz et al 1996;Lorenz 1998) heat pain (Staud et al 2001;Cook et al 2004) or pressure pain (Gracely et al 2002).…”

“…A disturbance of the endogenous pain-modulating system has been proposed to be a mediating mechanism, and it has been shown previously that central pain processing is altered in patients with FM, indicative of a generalized increase in pain sensitivity. In these studies, FM patients consistently showed lower pain thresholds and exhibited higher and more widespread brain activation to painful stimuli in areas such as the primary and secondary somatosensory cortex, insula, and anterior cingulate cortex (Gracely et al 2002;Cook et al 2004;Diers et al 2008). A disturbance of the endogenous pain-inhibitory system has been proposed as a major pain-maintaining factor (Staud et al 2001(Staud et al , 2003Harris et al 2007).…”

Funktionelle Bildgebung bei chronischen Schmerzerkrankungen: Implikationen für die Therapie

“…Es konnte [Vos et al, 2000] und im Kortex [Benoist et al, 1999;Giesecke et al, 2004Giesecke et al, , 2006Diers et al, 2007] Gibson et al, 1994;Lorenz et al, 1996;Petzke et al, 2003;Diers et al, 2008]: FMS-Patienten zeigten auf schmerzhafte Stimulation konsistent niedrigere Schmerzschwellen, höhere Amplituden im EEG sowie eine erhöhte Aktivierung im fMRT [Gracely et al, 2002]. Lorenz [1998] konnte zeigen, dass diese Hyperreaktivität bei auditiven evozierten Potentialen nicht vorhanden ist, also keine generelle Hypervigilanz vorliegt.…”

Medically Unexplained Physical Symptoms

“…Other studies have found that patients with these symptom syndromes also experience stimuli as painful at lower thresholds. 7 Patients with irritable bowel syndrome report pain at lower rectal balloon inflation pressures, and those with fibromyalgia experience skin stimuli to be painful at lower pressures. It is interesting to speculate on common underlying biological mechanisms that then manifest themselves differently in particular individuals.…”