Abnormality in the self-monitoring mechanism in patients with fibromyalgia and somatoform pain disorder.
BACKGROUND
Auditory hallucinations and passivity experiences are associated with an abnormality in the self-monitoring mechanism that normally allows us to distinguish self-produced from externally produced sensations. It is unclear if chronic central pain disorders such as fibromyalgia and somatoform pain disorders also involve a defect of the self-monitoring mechanism.


METHODS
Responses to tactile stimulation were assessed in four groups of subjects (N = 40): patients with fibromyalgia, patients with somatoform pain disorder, patients with schizophrenia with auditory hallucinations and/or passivity experiences, and normal control subjects. The subjects were asked to rate the perception of a tactile sensation on their left and right hands. The tactile stimulation was either self-produced by movement of the subject's right or left hand or externally produced by the experimenter.


RESULTS
Normal control subjects experienced self-produced stimuli as less intense than identical, externally produced tactile stimuli. In contrast, patients with fibromyalgia, patients with somatoform pain disorder, and patients with schizophrenia with auditory hallucinations and/or passivity experiences gave the same perceptual ratings for tactile stimuli produced by themselves as those produced by the experimenter (intergroup difference, p = .043; 95% confidence interval [CI], 0.16-0.68). Post hoc tests revealed that this significance was mainly caused by the fibromyalgia (p = .046; 95% CI, -1.66-0.13) and the somatoform pain disorder group (p = .033; 95% CI, -1.71-0.06).


CONCLUSIONS
We conclude that central pain disorders such as fibromyalgia and somatoform pain disorders interfere with the correct functioning of the self-monitoring mechanism that normally allows us to distinguish self-produced from externally produced tactile stimuli.
Karst
Matthias
M
Department of Anesthesiology, Pain Clinic, Hannover Medical School, D-30625 Hannover, Germany. karst.matthias@mh-hannover.de
Rahe-Meyer
Niels
N
Gueduek
Ayhan
A
Hoy
Ludwig
L
Borsutzky
Mathias
M
Passie
Torsten
T
D000208:Acute Disease; D000328:Adult; D001364:Awareness / Q000502:physiology*; D010054:Brief Psychiatric Rating Scale; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D006930:Hyperalgesia / Q000175:diagnosis / Q000503:physiopathology; D007389:Internal-External Control; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold / Q000502:physiology*; D010555:Personality Inventory; D010812:Physical Stimulation; D012559:Schizophrenia / Q000503:physiopathology; D013001:Somatoform Disorders / Q000175:diagnosis / Q000503:physiopathology*; D013003:Somatosensory Cortex / Q000503:physiopathology; D014110:Touch / Q000502:physiology*