title: Central Pain Processing in Early-Stage Parkinson's Disease: A Laser Pain fMRI Study.
abstract: OBJECTIVE
  Pain is a common non-motor symptom in Parkinson's disease. As dopaminergic dysfunction is suggested to affect intrinsic nociceptive processing, this study was designed to characterize laser-induced pain processing in early-stage Parkinson's disease patients in the dopaminergic OFF state, using a multimodal experimental approach at behavioral, autonomic, imaging levels.
  
  
  METHODS
  13 right-handed early-stage Parkinson's disease patients without cognitive or sensory impairment were investigated OFF medication, along with 13 age-matched healthy control subjects. Measurements included warmth perception thresholds, heat pain thresholds, and central pain processing with event-related functional magnetic resonance imaging (erfMRI) during laser-induced pain stimulation at lower (E = 440 mJ) and higher (E = 640 mJ) target energies. Additionally, electrodermal activity was characterized during delivery of 60 randomized pain stimuli ranging from 440 mJ to 640 mJ, along with evaluation of subjective pain ratings on a visual analogue scale.
  
  
  RESULTS
  No significant differences in warmth perception thresholds, heat pain thresholds, electrodermal activity and subjective pain ratings were found between Parkinson's disease patients and controls, and erfMRI revealed a generally comparable activation pattern induced by laser-pain stimuli in brain areas belonging to the central pain matrix. However, relatively reduced deactivation was found in Parkinson's disease patients in posterior regions of the default mode network, notably the precuneus and the posterior cingulate cortex.
  
  
  CONCLUSIONS
  Our data during pain processing extend previous findings suggesting default mode network dysfunction in Parkinson's disease. On the other hand, they argue against a genuine pain-specific processing abnormality in early-stage Parkinson's disease. Future studies are now required using similar multimodal experimental designs to examine pain processing in more advanced stages of Parkinson's disease.
authors: Functional Neuroimaging Group, Department of Radiology, University of Bonn, Bonn, Germany.
authors: Christine
authors: C
authors: Petschow
authors: Functional Neuroimaging Group, Department of Radiology, University of Bonn, Bonn, Germany.
authors: Lukas
authors: L
authors: Scheef
authors: Department of Neurology, University of Bonn, Bonn, Germany.
authors: Sebastian
authors: S
authors: Paus
authors: Department of Neurology, University of Bonn, Bonn, Germany.
authors: Nadine
authors: N
authors: Zimmermann
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Hans H
authors: HH
authors: Schild
authors: Department of Neurology, University of Bonn, Bonn, Germany.
authors: Thomas
authors: T
authors: Klockgether
authors: Functional Neuroimaging Group, Department of Radiology, University of Bonn, Bonn, Germany.
authors: Henning
authors: H
authors: Boecker
mesh_terms: D016022:Case-Control Studies; D006801:Humans; D007834:Lasers; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010146:Pain / Q000503:physiopathology*; D017288:Pain Threshold; D010300:Parkinson Disease / Q000503:physiopathology* / Q000523:psychology; D011795:Surveys and Questionnaires