Purpose or Case Report: Juvenile Idiopathic Arthritis (JIA) is the most common musculoskeletal disorder in children. The temporomandibular joints (TMJs) are involved in majority of cases, and detection of early arthritic changes in these joints relies on contrast enhanced magnetic resonance imaging (MRI). However, with the paucity of evidence and consensus on the normal and pathologic changes in this small but complex joint, interpretation of TMJ MRIs remains to be difficult. This exhibit presents the normal growth related and arthritis related variations in the disease progression in TMJ MRIs of JIA patients.
Methods & Materials: A novel MRI scoring system was developed by consensus among an international group of radiologists and clinicians to standardize the definition and grading criteria of JIA-related inflammatory and chronic degenerative changes in the TMJs. An imaging atlas was constructed to illustrate the range of severities in the diagnostic features, stratified by patient age groups, and in matched longitudinal progression. Purposive selection of contrast enhanced MRI studies in children 18 years of age or younger was conducted at two major institutions, to represent all scored and ancillary features as suggested by the multi-institution imaging expert group
Results: Consensus- and data-driven development of a TMJ MRI scoring system lead to the specification of eight diagnostic features in two domains, graded at two or three levels for each feature. Inflammatory domain includes bone marrow edema, bone marrow enhancement, joint effusion, joint enhancement, and synovial thickening. Degenerative domain includes condylar flattening, erosions, and disk abnormalities. Standardized, deductive methods for identifying and differentiating these eight features are described, using minimally necessary MRI sequences. Challenges and pitfalls in identifying and grading these features are illustrated, in relation to imaging techniques and physiologic growth related changes. Numeric cut-offs and morphologic grading criteria are presented, as suggested by consensus expert opinion. Further quantitative studies to validate grading thresholds are underway.
Conclusions: A multicenter collaboration has achieved a new scoring system for interpreting TMJ MRIs, designed for detecting and grading early changes due to JIA. The atlas presented herein is helpful both as a supplement to use the scoring system, and to illustrate the challenges and suggest best practices in the interpretation of TMJ MRIs.