An Investigation Of Brain Alterations In The Intra-network Functional Connectivity In Patients With Temporomandibular Joint Pain

Objective:Temporomandibular disorder(TMD),one of the most challenging orofacial issues,is considered one of the most common causes of chronic orofacial pain.Some studies have reported that up to 10–15% adults and 4–7% adolescents are affected by TMD.Chronic pain has become the primary reason why TMD patients seek for treatment.The etiology of TMD is still not clearly understood,however,latest researches have found that TMD-related pain is a multifactorial disorder with overlapping comorbidities of physical signs and symptoms,as well as changes in behaviors,emotional status,and social interactions as manifestations of general central nervous system dysregulation.An increasing number of studies have showed that TMD pain may be closely associated with the abnormalities in the central pathophysiological process,however,similar to most common chronic pain conditions,the central mechanisms are poorly understood yet.Considering pain is a complex multidimensional experience,recently,some studies on central mechanisms of chronic pain have shifted the focus from isolated brain regions to complex neural networks.Previous studies have found that other common chronic pain diseases(such as chronic low back pain)show altered intra-network resting-state functional connectivity(rs-FC).Studies have shown that TMD pain produces changes of functional activity in a number of brain regions included in the "pain matrix",such as thalamus,insula,anterior cingulate(ACC)and so on,however,few study has focused on rs-FC within networks in TMD pain.Therefore,in this study,we aim at investigating features of rs-FC within networks in patients with TMD pain,to further explore the neural mechanisms and promote diagnosis and clinical therapy of TMD pain.Methods:Eight adult female TMD synovitis patients with mouth-opening pain and ten gender-age-education-matched health controls(HCs)were recruited in the study.All participants underwent a seven-minute scanning using resting-state functional magnetic resonance imaging(rs-f MRI)including a mouth-closing session and a mouth-opening session.Then independent component analysis(ICA)-based rs-FCs were used to calculate intra-network FCs,and two sample t-test was applied to identify the differences of rs-FCs between groups.Scores on clinical scales measuring intensity of pain(visual analogue scale,VAS)and psychological status(Symptom check list-90,SCL-90)were respectively compared between the two groups.Results:1.Compared with health controls,TMD pain patients showed decreased coactivations in the left superior frontal gyrus(SFG)and middle frontal gyrus(MFG)within salience network(SN);2.Compared with health controls,TMD pain patients showed decreased coactivations in the left Rolandic operculum and posterior insular cortex within auditory network(AN);3.There were significant differences between patients and health controls for somatization,depression,anxiety,phobic anxiety,and paranoid ideation in the scores of SCL-90 subscales,and the scores of patients were significantly higher.Conclusions:Our findings may provide new insights into the characterization of TMD pain as a condition affecting brain activities in intrinsic rs-FC within networks.Moreover,the selective abnormalities of rs-FCs in TMD pain patients may be related to pain perception,cognition and affective processing,and the cross-communication between brain networks may be a key feature of brain dysfunction in patients with TMD chronic pain.Our results may provide scientific basis for the clinical treatment of TMD pain patients.