Pain Catastrophizing and Functional Activation During Occlusion in TMD Patients-An Interventional Study

Abstract

In temporomandibular disorder (TMD), the effects of standard interventions such as using an occlusal splint and its impact on pain relief and pain catastrophizing are poorly understood. Earlier work pointed to a crucial role of insula activation with changes in pain relief by occlusal splint treatment. We performed a functional imaging study using specially developed splint systems to allow for a placebo-controlled longitudinal design. Using functional MRI we examined 20 TMD patients during repetitive occlusal movements at baseline and over the course of splint therapy and also collected self-reported pain catastrophizing. For balancing performance between baseline and after intervention we used occlusion force measures in an individualized fMRI-splint system. Splint therapy lasted for approximately 7 weeks with one group selected by randomization wearing a palatine placebo splint over the first 3 weeks (delayed start; 11 individuals). As expected, fMRI activation in areas involved in pain processing (insula, primary and secondary somatosensory cortex) decreased with intervention. At baseline a positive correlation between activation of the left anterior insula and pain catastrophizing was present. Both parameters decreased over intervention while associations were primarily observable for patients with rather mild TMD.

Keywords: Michigan splint; chronic pain; craniomandibular disorder (CMD); fMRI; interventional trial; pain catastrophizing; temporomandibular disorder (TMD).

FIGURE 1

Study design.

FIGURE 2

fMRI effects for TMD patients at the baseline. (A) Conjunction over all three conditions (p _FWE < 0.05) shows the well‐described occlusal representation in sensorimotor areas and the right prefrontal lobe (cerebellar representations not shown). (B) Differences between conditions (no splint minus splint) show the left anterior insula activation (thresholded for illustration purposes with t = 3).

FIGURE 3

Plots show correlations between activation of the left anterior insula and self‐reports of GCPS pain intensity (A) and pain catastrophizing (PCS; B) for patients at baseline. Also, a correlation between changes over therapy (baseline−post2) in left anterior insula activation and pain catastrophizing is shown (C). A grouping regarding the GCPS grade is realized (B, C) with triangles indicating patients with mild TMD (GCPS grade < 2) and squares indicating patients with severe TMD (GCPS grade > 1). Regression lines are added. Abbreviations: Ant. = anterior, GCPS = Graded Chronic Pain Scale, PCS = Pain Catastrophizing Scale.

FIGURE 4

fMRI effects (ROI analyses) over time. Decrease (A) and increase (B) of fMRI activation during occlusion over intervention are shown. (A) S1 right: Coordinates: 20, −31, 60; S2 right: Coordinates: 40, −14, 20; left insula: Coordinates: −62, −6, 6. (B) SPL: Left: Coordinates: −18, −58, 70; IPS left: Coordinates: −35, −48, 56; left M1: Coordinates: −25, −8, 53.