title: An examination of pain perception and cerebral event-related potentials following carbon dioxide laser stimulation in patients with Alzheimer's disease and age-matched control volunteers.
abstract: BACKGROUND
  Pain perception is known to depend on integrated cognitive processing. Alzheimer's disease affects 5% to 10% of older adults, but the impact of this disease on pain sensitivity and report has yet to be fully investigated.
  
  
  OBJECTIVE
  The present study examined pain threshold, the reliability of pain report and the central nervous system processing of noxious input, as indexed by cerebral event-related potentials (CERP).
  
  
  METHODS
  Carbon dioxide laser detection and heat pain thresholds were determined on the hand dorsum of 15 healthy older adults (Mini-Mental State Examination [MMSE] score 29.9 +/- 0.3) and 15 persons with cognitive impairment (MMSE score 12.7 +/- 6.1). Using an array of 15 silver/silver chloride scalp electrodes, the CERP and subjective rating of stimulus intensity were recorded after fixed intensity, 25 W laser stimuli.
  
  
  RESULTS
  Compared with age-matched controls, the detection threshold for just noticeable sensation was significantly increased in elderly adults suffering from Alzheimer's disease. There was no difference in pain threshold intensity between persons with cognitive impairment and controls, although the former group was less reliable in reporting detection and pain threshold sensations. The subjective rating of a 25 W stimulus was virtually identical in both groups, and the amplitude of the major CERP component (P400) was similar; however, cognitively impaired adults exhibited a significant increase in the latency of the P400 response.
  
  
  CONCLUSIONS
  The present findings indicate that pain perception in response to an acute heat pain stimulus is not diminished in older persons with cognitive impairment. Patients with Alzheimer's disease may be slightly less reliable in threshold pain report, although the subjective rating of evoked pain and the level of poststimulus cortical activation following noxious stimulation were found to be similar to those of controls. A longer latency of the CERP may suggest slower cortical processing of nociceptive input by persons with Alzheimer's disease.
authors.affiliation: Clinical Research laboratory, National Ageing Research Institute, Parkville, Victoria, Australia. s.gibson@nari.unimelb.edu.au
authors.forename: S J
authors.initials: SJ
authors.lastname: Gibson
authors.forename: X
authors.initials: X
authors.lastname: Voukelatos
authors.forename: D
authors.initials: D
authors.lastname: Ames
authors.forename: L
authors.initials: L
authors.lastname: Flicker
authors.forename: R D
authors.initials: RD
authors.lastname: Helme
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology* / Q000523:psychology; D000704:Analysis of Variance; D002245:Carbon Dioxide; D002540:Cerebral Cortex / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D010147:Pain Measurement / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data*; D010465:Perception / Q000502:physiology*; D018709:Statistics, Nonparametric
chemical_list: D002245:Carbon Dioxide