Hyperalgesia or hypervigilance? An evoked potential approach to the study of fibromyalgia (FM) syndrome

Past research on the phenomenon of enhanced pain sensitivity

in fibromyalgia syndrome (FS) revealed evidence for both a

higher pain magnitude in response to nociceptive stimuli

(hyperalgesia) and a general perceptual amplification of

sensations (hypervigilance). In order to distinguish between

these two aspects of disturbed sensory processing in FS,

cerebral evoked potentials after brief painful laser and

auditory stimuli were measured in 10 FS patients. Results were

compared with those from age-matched painfree controls.

Amplitudes of middle-latency (N1) and long-latency (P2) laser

evoked potentials (LEPs) were significantly higher in FS than

in controls. Furthermore, laser intensity at pain but not at

sensation threshold was lower in FS than in controls. However,

auditory evoked potentials (AEPs) did not differ between

groups. Enhanced N1 and P2 amplitudes of LEPs suggest stronger

sensory and attentional processing of nociceptive information

in FS, respectively. The concept of hypervigilance is

challenged by the failure to find differences in auditory

perception among FS and control patients. Yet, the importance

of unpleasant intensities of auditory stimulation, not applied

in this study, to reveal abnormal non- nociceptive perceptual

amplification in FS is discussed.