Pain-related somatosensory evoked potentials in dementia

Pain-related somatosensory evoked potentials (pain SEPs) were examined in 25 demented and non-demented patients to investigate the cognitive function for pain in the progression of dementia. Pain SEPs by CO2 laser stimulation were recorded together with auditory event-related potentials (auditory ERPs). P340 in pain SEPs and P300 in auditory ERPs were analysed. The latency of P300 evoked in mildly demented patients was inversely correlated with the Mini-Mental state examination score, and the latency of P340 was also inversely correlated to that score but to a lesser extent. Pain SEPs were not recorded in 4 of 7 severely demented patients. These results indicate that the P340 component of pain SEPs is apparently different from the P300 component of auditory ERPs and suggest that the pain perception in severely demented patients may be abnormal.