The recording of brain evoked potentials resulting from intra-articular focused ultrasonic stimulation: a new experimental model for investigating joint pain in humans.

Pain was induced in the proximal interphalangeal joint of the index finger in human volunteers using a high powered focused ultrasonic generator. Eighty, 100 ms pulses were applied during each test. This test was repeated at hourly intervals for a period of 5 h. A brain evoked potential with a characteristic wave form was recorded, resulting from the application of these stimuli. A computerised visual analogue scale system was used to measure subject's perception of the painfulness of each stimulus. A significant correlation was found between evoked potential amplitude and mean visual analogue scale score. There was some variation in evoked potential amplitude and mean visual analogue scale score as a result of repeated application of the test but this was not significant over the 5 h time period.