Functional MRI study on anxiety-enhanced temporomandibular joint pain

Objective·To detect the active brain regions in patients experiencing pain associated with temporomandibular disorder under anxiety emotion stimulation by using functional magnetic resonance imaging (fMRI).Methods·A total of 30 temporomandibular disorder patients with spontaneous pain were included, who visited the Department of Stomatology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, from November 2021 to September 2023. A task program consisting of negative and medium pictures chosen from the International Affective Picture System (IAPS) was used to stimulate anxiety in the volunteers during fMRI scanning. The activated brain regions were identified by processing the data with the general linear model using FSL 5.0.6 software. The pain levels and anxiety levels of the subjects before and after anxiety stimulation were recorded by using the Visual Analogue Scale (VAS) and State-Trait Anxiety Inventory (STAI). Paired t-tests were then conducted by using SPSS 20.0 software.Results·After stimulation with negative pictures, the anxiety levels of the subjects with temporomandibular disorder significantly increased (P<0.001), and the pain levels also worsened (P<0.001). The degree of temporomandibular joint pain aggravated with the stimulation of negative emotional pictures and improved with the neutral pictures. The main brain regions activated during the task included amygdala, hippocampus, anterior cingulate gyrus, thalamus, occipital cortex, and insula. Among them, the occipital cortex, anterior cingulate gyrus, and amygdala were the main brain regions activated after removing neutral control stimulation.Conclusion·The aggravation of anxiety can increase the temporomandibular joint pain level in patients with temporomandibular disorder. There is significant activation in the brain regions related to the hippocampus-centered hyperalgesia reaction and the thalamic-limbic system and the thalamic-limbic system, which are involved in pain and emotion regulation networks.