Article

Intensity dependence of auditory-evoked cortical potentials in fibromyalgia patients: a test of the generalized hypervigilance hypothesis.

Departamento de Psicología Clínica y Psicobiología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Journal of Pain (Impact Factor: 4.22). 08/2006; 7(7):480-7. DOI: 10.1016/j.jpain.2006.01.452
Source: PubMed

ABSTRACT On the basis of recent evidence concerning the amplification of incoming stimulation in fibromyalgia (FM) patients, it has been proposed that a generalized hypervigilance of painful and nonpainful sensations may be at the root of this disorder. So far, research into this issue has been inconclusive, possibly owing to the lack of agreement as to the operational definition of "generalized hypervigilance" and to the lack of robust objective measures characterizing the sensory style of FM patients. In this study, we recorded auditory-evoked potentials (AEPs) elicited by tones of increasing intensity (60, 70, 80, 90, and 105 dB) in 27 female FM patients and 25 healthy controls. Fibromyalgia patients presented shorter N1 and P2 latencies and a stronger intensity dependence of their AEPs. Both results suggest that FM patients may be hypervigilant to sensory stimuli, especially when very loud tones are used. The most noteworthy difference between patients and control subjects is at the highest stimulus intensity, for which far more patients maintained increased N1-P2 amplitudes in relation to the 90-dB tones. The larger AEP amplitudes to the 105-dB tones suggest that defects in an inhibitory system protecting against overstimulation may be a crucial factor in the pathophysiology of FM. Because a stronger loudness dependence of AEPs has been related to weak serotonergic transmission, it is hypothesized that for many FM patients deficient inhibition of the response to noxious and intense auditory stimuli may be due to a serotonergic deficit. PERSPECTIVE: The study of auditory-evoked potentials in response to tones of increasing intensity in FM patients may help to clarify the pathophysiology of this disorder, especially regarding the role of inhibition deficits involving serotonergic dysfunction, and may be a useful tool to guide the pharmacologic treatment of FM patients.

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    ABSTRACT: Background It has been suggested that fibromyalgia (FM) patients show increased sensory processing of nociceptive and non-nociceptive stimuli and also reduced habituation. Although this pattern of increased reactivity has been established for the somatosensory modality, its generalization to other sensory modalities remains controversial.Methods Auditory evoked potentials were obtained using a paired-stimuli paradigm from a sample of 52 FM female patients and 55 healthy women matched for age and socio-economic status. Sensory gating of the P50 component, as indicated by P50 suppression rates to the second identical stimuli, was analysed in relation to clinical indices of FM, including algometry of tender points and a number of self-reported questionnaires.ResultsSensory gating mechanisms in FM patients proved to be normal, robust and as efficient as those recorded in control subjects. There was no correlation between P50 suppression rates and indices of clinical or experimental (threshold or tolerance) pain. In addition, P50 sensory gating was not related to the other main symptoms of FM, including fatigue, sleep dysfunction or co-morbid depression, nor to hypersensitivity to noise or headache.Conclusions The results indicate that FM patients do not present significant deficits in early sensory gating when processing auditory stimuli, and therefore challenge the ‘generalized hypersensitivity’ hypothesis of FM.
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    ABSTRACT: Objective Fibromyalgia (FM) is a disorder characterized by chronic pain and enhanced responses to acute noxious events. However, the sensory systems affected in FM may extend beyond pain itself, as FM patients show reduced tolerance to non-nociceptive sensory stimulation. Characterizing the neural substrates of multisensory hypersensitivity in FM may thus provide important clues about the underlying pathophysiology of the disorder. The aim of this study was to characterize brain responses to non-nociceptive sensory stimulation in FM patients and their relationship to subjective sensory sensitivity and clinical pain severity.Methods Functional magnetic resonance imaging (MRI) was used to assess brain response to auditory, visual, and tactile motor stimulation in 35 women with FM and 25 matched controls. Correlation and mediation analyses were performed to establish the relationship between brain responses and 3 types of outcomes: subjective hypersensitivity to daily sensory stimulation, spontaneous pain, and functional disability.ResultsPatients reported increased subjective sensitivity (increased unpleasantness) in response to multisensory stimulation in daily life. Functional MRI revealed that patients showed reduced task-evoked activation in primary/secondary visual and auditory areas and augmented responses in the insula and anterior lingual gyrus. Reduced responses in visual and auditory areas were correlated with subjective sensory hypersensitivity and clinical severity measures.ConclusionFM patients showed strong attenuation of brain responses to nonpainful events in early sensory cortices, accompanied by an amplified response at later stages of sensory integration in the insula. These abnormalities are associated with core FM symptoms, suggesting that they may be part of the pathophysiology of the disease.
    11/2014; 66(11). DOI:10.1002/art.38781
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    ABSTRACT: The heterogeneity found in fibromyalgia (FM) patients has led to the investigation of disease subgroups, mainly based on clinical features. The aim of this study was to test the hypothesis that clinical FM subgroups are associated with different underlying pathophysiological mechanisms. Sixty-three FM patients were classified in type I or type II, according to the Fibromyalgia Impact Questionnaire (FIQ), and in mild/moderate versus severe FM, according to the severity of three cardinal symptoms considered in the American College of Rheumatology (ACR) 2010 criteria (unrefreshed sleep, cognitive problems and fatigue). To validate the subgroups obtained by these two classifications, we calculated the area under the receiver operating characteristic curves for various clinical variables and for two potential biomarkers of FM: Response to experimental pressure pain (algometry) and the amplitude/intensity slopes of the auditory evoked potentials (AEPs) obtained to stimuli of increasing intensity. The variables that best discriminated type I versus type II were those related to depression, while the indices of clinical or experimental pain (threshold or tolerance) did not significantly differ between them. The variables that best discriminated the mild/moderate versus severe subgroups were those related to the algometry. The AEPs did not allow discrimination among the generated subsets. The FIQ-based classification allows the identification of subgroups that differ in psychological distress, while the index based on the ACR 2010 criteria seems to be useful to characterize the severity of FM mainly based on hyperalgesia. The incorporation of potential biomarkers to generate or validate classification criteria is crucial to advance in the knowledge of FM and in the understanding of pathophysiological pathways.
    Rheumatology International 04/2014; 34(11). DOI:10.1007/s00296-014-3007-1 · 1.63 Impact Factor

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