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Pain Research and Management
Volume 6 (2001), Issue 3, Pages 126-132
http://dx.doi.org/10.1155/2001/814374
Pain & Aging

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

Stephen J Gibson,1,2 Xenophon Voukelatos,1 David Ames,2 Leon Flicker,3 and Robert D Helme1

1National Ageing Research Institute, Parkville, Victoria, Australia
2Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
3Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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.

AIM OF INVESTIGATION: 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.

CONCLUSION: 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.