Wolfgang Freund MD, Abstract Co-Author: Nothing to Disclose

Gregor Stuber MD, Abstract Co-Author: Nothing to Disclose

Arthur Peter Wunderlich PhD, Presenter: Nothing to Disclose

Roland Klug MD, Abstract Co-Author: Nothing to Disclose

Pain has evolutionally evolved as a warning sign. Chronic pain, however is a disabling illness. To elucidate aspects of the perception and suppression of tonic pain, and to evaluate the different effects of thermal and electrical stimulation, the following studies have been performed.

In each arm of the study, 15 subjects without acute or chronic pain are included. Thermal stimulation is administered by a computer-controlled thermode, electrical stimulation through a neurograph. Each stimulus is applied to the volar index finger, following the same paradigm: In a first set of measurements, the stimuli are presented pseudorandomized with different strengths and a task to discriminate the level of stimulation. In a second set, a constant, painful stimulus is administered with the instruction to try to suppress the feeling of pain. BOLD Contrast datasets are acquired with a 1.5 T mr-scanner, analysis is done with SPM 99.

Significant cortical activations are found in both arms of the study. During electrical stimulation, activations occur in insular and primary sensory areas. During suppression of pain, cortical activations change their location to resemble activations during non-painful stimulation, even though the stimulus intensities remain unchanged. During thermal stimulation, activations occur in different cortical regiopns, mainly belonging to the medial pain system, prominently the anterior cingular cortex (ACC). Overall, cortical activations during electrical stimulation are more pronounced and show less interindividual variance than during thermal stimulation.

Electrical stimulation leads to activations in structures belonging to the lateral pain system (with primary sensory area and insula), whereas thermal stimulation activates structures of the medial pain system (ACC). In healthy subjects, electrical stimulation seems to offer clearer insights in cerebral processes of pain perception and suppression than thermal stimulation.

Freund, W, Stuber, G, Wunderlich, A, Klug, R, Functional MRI during Perception and Suppression of Pain: Comparison of Electrical and Thermal Stimulation.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4417419.html