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Abnormality in the Self-monitoring Mechanism in Patients With Fibromyalgia and Somatoform Pain Disorder

From the Department of Anesthesiology, Pain Clinic (M.K., N.R.-M., A.G.), the Department of Biometrics (L.H.), and the Department of Clinical Psychiatry and Psychotherapy (M.B., T.P.), Hannover Medical School, Hannover, Germany.

View larger version (79K): [in a new window]   Figures 1 and 2. The tactile stimulus device consisted of a hand layer (6), a palmar wall (3) with a U-shaped slot (4) in which a plastic pointer (2) can be moved on the palm of the left or right hand and a dorsal wall (5). One hand was put on the hand layer (6) and fixed tightly with a screw fixation (1) between the palmar wall (3) and the padded dorsal wall (5). The other hand (for self-stimulation) or the experimenter (for external stimulation) could move a plastic rod with the pointer (2) at its end, following the U-shaped slot in the palmar wall (3). The pointer (2) had a spherical tip of 1-mm diameter and was counterweighted with a spring in the plastic rod to maintain a constant pressure of approximately 17 g on the palm during its movement. To obtain a maximum of convenience for the subjects during the procedure, the angle of the hand layer (6) was adjustable at its joint (7). The whole apparatus was movable but stable as a result of its firm basis (8).

View larger version (52K): [in a new window]   Figures 1 and 2. The tactile stimulus device consisted of a hand layer (6), a palmar wall (3) with a U-shaped slot (4) in which a plastic pointer (2) can be moved on the palm of the left or right hand and a dorsal wall (5). One hand was put on the hand layer (6) and fixed tightly with a screw fixation (1) between the palmar wall (3) and the padded dorsal wall (5). The other hand (for self-stimulation) or the experimenter (for external stimulation) could move a plastic rod with the pointer (2) at its end, following the U-shaped slot in the palmar wall (3). The pointer (2) had a spherical tip of 1-mm diameter and was counterweighted with a spring in the plastic rod to maintain a constant pressure of approximately 17 g on the palm during its movement. To obtain a maximum of convenience for the subjects during the procedure, the angle of the hand layer (6) was adjustable at its joint (7). The whole apparatus was movable but stable as a result of its firm basis (8).

View larger version (27K): [in a new window]   Figure 3. Perceptual ratings for self-produced tactile stimuli (SPS) and externally produced tactile stimuli (EPS) on the visual analog scale for sensation (VAS, 0 = not at all to 10 = extremely intense). A significant intergroup difference (p = .043, analysis of variance test) was found (p = .046 for FM vs. NS; p = .033 for SPD vs. NS, using two-sided post hoc Dunnett t test). No significant difference could be found for HP versus NS (p = .108, using two-sided post hoc Dunnett t test). FM = fibromyalgia; SPD = somatoform pain disorder; HP = hallucinations and passivity experiences; NS = normal subjects. In the figure, medians are represented by horizontal bars, interquartile ranges by boxes, ranges by error bars, and extreme values by circles. In the table, mean values and standard deviations (±) are indicated.