Magnetic Resonance Imaging Evaluation of Temporomandibular Joint Involvement in Ankylosing Spondylitis Patients

Background: Ankylosing spondylitis (AS) is a long-term inflammatory disease that involves the axial skeleton, and new evidence suggests that the temporomandibular joint (TMJ) has been involved. Magnetic resonance imaging (MRI) has been found to be more sensitive in terms of early inflammatory and structural alterations in the TMJ, but the prevalence and clinical associations with AS have not been well documented. Hence, the study was done to determine the prevalence, MRI characteristics, and clinical associations of TMJ involvement in patients with AS compared with healthy controls. Materials and Methods: A case-control study was used, with 60 AS patients (who met ASAS criteria) and 30 age/sex-matched healthy controls. Each of the participants was taken through bilateral TMJ MRI in a 1.5T scanner. Two blinded radiologists decided on the presence of bone marrow edema (BME), synovitis, effusion, erosions, and disc displacement based on imaging. Clinical measures comprised of TMJ pain Visual Analog Scale, maximum mouth opening (MMO), Bath AS disease activity index (BASDAI), Bath AS functional index, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). Results: TMJ deviations were observed in 27/60 (45.0%) AS patients and 1/30 (3.3%) controls (P < 0.001). The most widespread observations were BME (30.0%), synovitis (25.0%), and effusion (20.0%). TMJ involved AS patients had an approximately 5.2 ± 1.8, 38 ± 6 mm, and 4.5 ± 2.1 higher BASDAI score, lower MMO (38 ± 6 mm vs. 45 ± 5 mm, P < 0.001), and higher TMJ pain (4.5 ± 2.1 vs. 1.8 ± 1.2, P < 0.001) as compared to those without. There was no correlation between the results of MRI and CRP/ESR. Conclusion: TMJ involvement is common in AS patients and is strongly associated with clinical disease activity and functional limitation. MRI is useful in identifying subclinical inflammation of the TMJ, and it should be considered standard in the evaluation of AS.