TMJaw has defined TMJ arthritis as “active inflammation in the TMJ.” TMJ arthritis can be assessed only by gadolinium-enhanced magnetic resonance imaging (MRI) to view the active component of synovial fluid and tissue enhancement. In the absence of signs of active TMJ arthritis on MRI, patients may still have TMJ involvement, defined as “clinical and/or radiological abnormalities presumed to be the result of previous TMJ arthritis.”4
Other imaging techniques used to display the TMJ, such as ConeBeam computed tomography (CT), ultrasound, orthopantomogram or lateral cephalographs, cannot provide answers regarding TMJ arthritis.
TMJ arthritis can present in any patient with JIA, and the TMJ can be involved at any time of the disease course. Occasionally, the TMJ may be the only joint involved.6
Difficulty remains in knowing how to efficiently diagnose and monitor TMJ arthritis. Many clinicians perform an MRI at disease onset, and if it’s normal repeat the MRI if the patient reports any symptoms or there are relevant findings during clinical examination.
MRI evaluation needs to be performed by a radiologist aware of the normal appearance of the joint during the course of the child’s development. Kellenberger et al. have developed a pictorial atlas depicting the TMJ’s normal and abnormal appearance for different ages.7 If the MRI shows TMJ arthritis and treatment is started, clinicians can repeat the MRI three to six months later, depending on expected treatment effect.
No studies have been performed to determine the perfect follow-up period for the MRI. The patient’s age and need for sedation, costs and clinical consequences have to be taken into account. More research on less invasive diagnostic tests is necessary to be able to continuously evaluate this joint.
Another dilemma: Arthritis-induced orofacial signs and symptoms may persist in patients without current MRI findings of TMJ inflammation. Also, dentofacial deformity may progress in well-treated patients. A clinical orofacial examination is an important aspect of the full-body examination of JIA patients. The TMJaw group has published clinical orofacial examination recommendations for monitoring patients in clinical practice and research studies to ensure the TMJ is examined during every clinical visit with a JIA patient.1 These recommendations include obtaining a complete medical history and assessing for the presence of orofacial symptoms. The clinical examination should include palpation of the TMJ and masticatory muscles. The orofacial function evaluation should include assessment of TMJ function (maximal mouth opening and movement) and assessment of facial morphology and symmetry.1