title: Pain ratings, psychological functioning and quantitative EEG in a controlled study of chronic back pain patients.
abstract: OBJECTIVE
  Several recent studies report the presence of a specific EEG pattern named Thalamocortical Dysrhythmia (TCD) in patients with severe chronic neurogenic pain. This is of major interest since so far no neuroscientific indicator of chronic pain could be identified. We investigated whether a TCD-like pattern could be found in patients with moderate chronic back pain, and we compared patients with neuropathic and non-neuropathic pain components. We furthermore assessed the presence of psychopathology and the degree of psychological functioning and examined whether the strength of the TCD-related EEG markers is correlated with psychological symptoms and pain ratings.
  
  
  METHODS
  Controlled clinical trial with age and sex matched healthy controls.
  
  
  METHODS
  Spontaneous EEG was recorded in 37 back pain patients and 37 healthy controls.
  
  
  RESULTS
  We were not able to observe a statistically significant TCD effect in the EEG data of the whole patient group, but a subsample of patients with evidence for root damage showed a trend in this direction. Pain patients showed markedly increased psychopathology. In addition, patients' ratings of pain intensity within the last 1 to 12 months showed strong correlations with EEG power, while psychopathology was correlated to the peak frequency.
  
  
  CONCLUSIONS
  Out of several possible interpretations the most likely conclusion is that only patients with severe pain as well as root lesions with consecutive thalamic deafferentation develop the typical TCD pattern. Our primary method of defining 'neuropathic pain' could not reliably determine if such a deafferentation was present. Nevertheless the analysis of a specific subsample as well as correlations between pain ratings, psychopathology and EEG power and peak frequency give some support to the TCD concept.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00744575.
authors.affiliation: Department of Environmental Health Sciences, University Medical Center, Freiburg, Germany. stefan.schmidt@uniklinik-freiburg.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Schmidt
authors.forename: José Raúl
authors.initials: JR
authors.lastname: Naranjo
authors.forename: Christina
authors.initials: C
authors.lastname: Brenneisen
authors.forename: Julian
authors.initials: J
authors.lastname: Gundlach
authors.forename: Claudia
authors.initials: C
authors.lastname: Schultz
authors.forename: Holger
authors.initials: H
authors.lastname: Kaube
authors.forename: Thilo
authors.initials: T
authors.lastname: Hinterberger
authors.forename: Daniel
authors.initials: D
authors.lastname: Jeanmonod
mesh_terms: D001416:Back Pain / Q000503:physiopathology* / Q000523:psychology*; D016022:Case-Control Studies; D059350:Chronic Pain / Q000503:physiopathology* / Q000523:psychology*; D003710:Demography; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011795:Surveys and Questionnaires