Can Electroencephalography (EEG) Identify the Different Dimensions of Pain in Fibromyalgia?
Condition: Fibromyalgia
MeSH terms: Fibromyalgia; Myofascial Pain Syndromes
Study type: Observational

Summary: 
      Studies with quantitative electroencephalogram (qEEG) in people with fibromyalgia showed the
      existence of distinct patterns of brain electrical activity when compared to healthy
      individuals. Such dysfunctional patterns may be correlated to clinical symptoms of the
      syndrome as chronic pain and emotional disorders (depression and anxiety). As chronic pain
      can be considered a multidimensional symptom, its evaluation should consider beyond others,
      two main dimensions: the sensitive-discriminative dimension and the affective-motivational
      dimension. Previous studies have been describing distinct brain areas as neural substrates
      for processing such dimensions of pain. Thus, the identification of electrophysiological
      biomarkers (i.e., as qEEG measures) allowing to perform an evaluation between dysfunctional
      patterns of brain electrical activity and different dimensions of pain seems to be a
      promising path in the search for a better understanding of the syndrome as well as for more
      individualized and effective therapeutic approaches. Our objective was to investigate whether
      dysfunctional patterns of brain electrical activity in frontal and central areas of people
      with fibromyalgia are differently related to dimensions of pain (sensory-discriminative and
      affective-motivational) and to emotional disorders (depression and anxiety).
    

Detailed description: 
      The study was a pilot study with a cross-sectional and exploratory design carried out from
      2020 to 2022. A quantitative electroencephalographic analysis was performed with women with
      Fibromyalgia and pain-free individuals as a control group, matched for gender and age. The
      sample was not probabilistic and recruitment occurred in a random manner. All volunteers were
      recruited from reference services in the state of Pernambuco, referred from other centers as
      well as through announcements in digital media.

      Procedures All procedures were conducted respecting the Declaration of Helsinki (1964) and
      approved by the local ethical committee. Before clinical and sociodemographic evaluation, all
      volunteers signed a written informed consent, including all information regarding the risks
      and benefits of their participation in the study. During the study, all individuals with
      fibromyalgia were instructed not to change their medication use as well as eating habits.
      Clinical assessments and qEEG data acquisition took place in one single visit to the
      laboratory lasting around two hours. After signing the written informed consent, all
      volunteers were taken to an isolated room to perform an EEG evaluation. Then, they underwent
      sociodemographic and clinical assessments (only individuals with fibromyalgia).

      EEG data acquisition and processing For each volunteer, signals were recorded using digital
      EEG equipment for 120 seconds in an isolated room - without any communication with the
      external environment - with volunteers rested, seated in a comfortable chair, and with closed
      eyes. Signal recording was performed through 19 Ag/AgCl electrodes positioned on the scalp
      following the predetermined points of the international 10-20 system of
      electroencephalography and, always maintaining a maximum impedance of 10 kΩ. Additionally, a
      ground electrode was positioned on the lateral third of the right clavicle, while two
      reference electrodes were positioned on the region of the right and left mastoid processes. A
      sampling rate for recording the 500 Hz signal was captured by the NeuronSpectrum signal
      amplifier and recorded by the Neuron-Spectrum/NET omega software. Additionally, the high-pass
      (0.5 Hz), low-pass (35 Hz), and notch (60Hz; suitable for 220V mains) filters were applied
      during data acquisition and processing.

      Then, the collected data were pre-processed using the EEGLab toolbox in MATLAB® version
      R2014a software for Windows. In addition, an Independent Component analysis was performed
      using the Independent Components Analysis (ICA) algorithm to separate the components related
      to biological artifacts. The rejection of these components was done through the Multiple
      Artefact Rejection Algorithm (MARA) considering a 50% cutoff point. For time-frequency
      analysis of the relative spectral power for each epoch, the fast Fourrier transform method
      was used. The dominant frequency in each patient was identified in the following points of
      the international 10-20 EEG system: F3, F4, Fz, F7, F8 (frontal area), and C3, C4, Cz
      (central area) during rest. Spectral power density assessment was also performed, for each
      frequency band, considering the following bands: delta (0,5 a ≤ 4 Hz); theta ( > 4 a ≤ 8 Hz);
      alpha (> 8 a ≤13 Hz) e beta (> 13 a ≤ 30 Hz). For relative spectral power distribution
      calculations, the absolute spectral power of each frequency band was divided by the total
      power of all bands present in the 0.5-35Hz.
    

Intervention name(s): qEEG
Intervention type(s): Other
Intervention description(s): qEEG data was collected with patients and healthy individuals in resting eyes-closed: the relative spectral power of the frequency bands delta, theta, alpha and beta was evaluated.
Observational model: Other
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Women with fibromyalgia enrolled according to the criteria of the American College of
        Rheumatology (ACR) and 10 healthy volunteers matched by gender and age.
      
Keywords: Chronic pain; Electroencephalogram