Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Neziri, A.
Experimental Assessment of Central Hypersensitivity in Chronic Pain
[ Dissertation ] Medical University of Graz; 2010. pp. 51
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Holzer Peter
- Sandner-Kiesling Andreas
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- Abstract:
- The aims of this doctoral thesis were: 1) to determine whether responses to different pain stimuli are distinct dimensions or highly correlated; 2) to test the hypothesis that patients with chronic pain develop central hypersensitivity, i.e. display lower pain thresholds to electrical, mechanical and thermal stimuli, and 3) to test the hypothesis that patients with chronic pain display enlarged reflex receptive fields compared to pain-free subjects. In study I, five clearly distinct factors were found representing responses to five distinct experimental pain modalities: pressure, heat, cold, electrical stimulation and reflex receptive fields. Each of the dimensions explained approximately 10 to 20% of the observed variance, and the five factors cumulatively explained about 90% of the variance. The correlation between the five dimensions was essentially null, with 95% confidence intervals for the pairwise correlation between two dimensions excluding any relevant correlation. Correlations were typically high within the same type of stimulus, but low between different types. Taken together, this indicates that attempts to simplify current multi-modal approaches of pain assessment are unjustified. Responses to different experimental pain modalities represent different dimensions and should be assessed in combination in future pharmacological and clinical studies to represent the complexity of nociception and pain experience. In studies II and III, patients with chronic low back pain displayed a larger area of reflex receptive field, compared with pain-free subjects. This is reflected by the enlargement of the area of the foot sole from which a nociceptive reflex in the tibialis anterior muscle can be elicited. Furthermore, the reflex amplitude was higher in patients than in pain-free subjects. The subjective pain threshold and the threshold to evoke a nociceptive reflex after a single electrical stimulus were lower in patients, compared to the pain-free subjects. The same was observed with repeated electrical stimulation evoking temporal summation: both the threshold to induce the subjective feeling of increasing pain sensation and the threshold that evokes a nociceptive reflex during repeated stimulation were lower in patients, compared to pain-free subjects. Furthermore, patients were characterized by lower pressure pain detection and tolerance thresholds, and by lower heat pain detection thresholds than pain-free subjects. Studies on chronic low back pain and chronic neck pain, i.e. studies II and III provided evidence for widespread expansion of spinal nociceptive receptive fields and increased sensitivity to mechanical and thermal stimuli in a human chronic pain condition. This finding contributes to the elucidation of the mechanisms that underlie central hypersensitivity in human chronic pain conditions and may become a target for the development of future therapeutic interventions.