Fibromyalgia syndrome (FMS), temporomandibular disorders (TMD), and irritable bowel syndrome (IBS) are chronic pain disorders in which sufficient physical findings are often lacking.

Despite differences in clinical pain distribution, a number of studies have reported increased pain sensitivity at sites distant from the clinical pain for both TMD7-10 and IBS.5,11-16 It is thought that generalized hypersensitivtiy to painful stimuli is associated with increased CNS up-regulation2,6,17; but, it remains difficult to draw conclusions about similarities and differences across these pain conditions.

A few studies have also reported the segmental distribution of pain with greater sensitivity in regions associated with clinical pain (IBS) while comparisons across the segmental axis for other conditions (TMD, FMS) are less established.

• The purpose of the present study was to map the relative degree of sensitization along the segmental axis and to determine the effect of experimental nociceptive inputs on sensitization with methodology that controls for differences in baseline sensitivity between subjects and groups.

• The finding that the stimulus temperatures required for eliciting the predetermined pain intensity level were significantly lower (i.e., the sensitivity was higher) in the disease groups than in the control group).

• Our finding of segmental differences in pain sensitivity associated with the distribution of clinical pain for both TMD and IBS. Our data indicated that the calf was the most sensitive to thermal stimuli, followed by the forearm, and lastly the cheek.

• We also used a testing protocol that allowed us to continuously test the sensitivity of persons with chronic pain while clamping their elicited pain at a constant intensity.

Comparison of Heat Pain Sensitivity in PatientsC. D. King1, J. L. Riley III1, C. J. Vierck3, A. P. Mauderli2

1Community Dentistry & Behavioral Sci., Univ. of Florida Coll. of Dentistry, Gainesville, FL, USA, 2 Prosthodontics, Univ. of Florida Coll. of Dentistry, Gainesville, FL, USA, 3Neuroscience, Univ. of Florida Coll. of Med., Gainesville, FL, USAPoster # 204

Participants. All participants recruited from clinics at the University of Florida. Healthy controls (n=37) were also recruited.

Heat Stimulus: Focal thermal stimuli (44.0-50.0C) was administered by a Peltier-based thermode (23mm x 23mm).

Stimulus Intensity Response Function (Experiment 1): Sensitivity along the segmental axis (lateral aspect of the calf; volar forearm; cheek) was assessed with an incremental series of thermal contact pulses (3 second duration; 30 second inter-stimulus interval, ISI).

Prolonged Stimulation and Temporal Integration (Experiment 2): Sensitivity to a prolonged pulse was assessed over 4 consecutive series (25 brief thermal contact pulses per series). The contact duration was 0.9 sec throughout the experiment, the inter-stimulus-interval (ISI) was 2.5 sec for series 1 and 3; and 3.5 sec for series 2 and 4. Temperature was automatically adjusted to produce a pain rating around 35% based on reported pain ratings (eVAS).18

“Sensitization index” for the brief and prolonged series of thermal stimuli. Temperature differences between healthy controls and each of the pain groups are presented as a function of test and site (derived by difference scores), which will be interpreted as a measure of sensitization. These finding should make us all famous and keep us working for years . A little more text to push the box down – there.

Figure 1. Differences between pain groups and healthy controls regarding levels of pain intensity across sites on the cheek, forearm, and calf. Overall, main effects were observed for pain ratings (F(2,364) = 290.278, p < 0.001; higher levels of pain were observed with higher temperatures), stimulation site (F(2,182) = 5.073, p < 0.01), and group (F(3,91) = 3.514, p = 0.018] ; pain groups were more sensitive than healthy controls).

Differences between pain groups and healthy controls regarding temperature of the thermode to maintain a pain intensity rating of 35% (automatically adjusted). All patient groups were significantly more sensitive to thermal nociceptive stimulation (i.e., the temperatures needed for eliciting a given pain intensity level were lower), when compared to their healthy counterparts. Significant main effects of group [F (3, 81) = 8.428, p < 0.001] and series [F (3,243) = 32.680, p < 0.001] were found. However, the group x series interaction was not significant (F(9,243) = 1.057, p > 0.05) indicating that a similar pattern across the 4 series was seen for all 4 of the groups. Analysis of group means. The control group required a higher temperature to maintain the targeted pain ratings than the three pain groups. Pair-wise confirmed that the FMS, TMD, and IBS groups were significantly different from the controls (p < 0.01), but the pain groups were not different (p > 0.10).

SERIES 1 2 3 4

ISI 2.5 3.5 2.5 3.5 Mean temp

Controls 50.4 (1.2) 51.3 (1.4) 49.8 (1.2) 50.9 (1.4) 50.6 (1.2)

FMS 47.7 (3.0) 7.9 (3.8) 46.6 (3.3) 47.3 (3.4) 47.6 (2.7)

TMD 47.5 (2.5) 48.2 (2.7) 47.0 (3.1) 47.8 (2.9) 47.3 (3.2)

IBS 46.7 (3.4) 47.4 (4.1) 46.1 (4.0) 47.0 (4.1) 46.8 (4.0)

All subjects 48.5 (2.8) 49.2 (3.3) 47.8 (3.1) 48.7 (3.3)

All temperatures are represented in Celsius (C) units.

EXPERIMENT 1 1 1 2

Stimulation Parameters

Experimental Protocol SRC SRC SRC Prolonged

Stimulation Site Cheek Forearm Calf Palm

Skin type Hairy Hairy Hairy Glabrous

Difference from Controls

FMS 1.1 1.3 0.7 3.0

TMD 1.7* 1.1 0.9 3.3

IBS 0.7 1.2 1.3* 3.8All temperatures are represented in Celsius (C) units.

RESULTSINTRODUCTION

This project was supported by NIH R01-4567841, K23-457412, AARP and UF CTSI. Special thanks to my mom, and the staff of PRICE, and many UF student volunteers.

INTRODUCTION RESULTS

METHODS

RESULTS

SUMMARY