The Use of PET/CT to Evaluate Synovitis in the Temporomandibular Joint (TMJ)

Temporomandibular joint disorders (TMD) are a common musculoskeletal problem with an estimated 40-75 percent of the population reporting at least one sign. Up to fifteen percent of the patients who seek care for one of these conditions, will go on to develop chronic pain. The two most common TMD conditions include myofascial pain disorder and internal derangement of the Temporomandibular Joint (TMJ). These two conditions have similar clinical presentations, making an accurate diagnosis difficult. Currently, there is no accurate exam or test to differentiate between these two conditions. Internal derangement of the TMJ is a condition with disk displacement, pain, and dysfunction, which may progress to localized osteoarthritis. Fortunately, this condition is self-limiting for the majority of the patients afflicted, with a small minority progressing to advanced joint destruction, disability and chronic pain.18 Currently there are no prognostic indicators to identify these individuals. There are three hypothesis of degenerative TMJ disease, they include: direct mechanical trauma, hypoxia reperfusion injuries, and neurogenic inflammation. All involve parafunctional habits such as clenching or grinding by the patient and a low-grade inflammatory response/synovitis. 18-fluorodeoxyglucose (18-FDG), a radioisotope used with positron emission tomography (PET) and paired with a CT scan (PET/CT), may have a role in imaging inflammation in arthritis as recently demonstrated in several pilot studies involving osteoarthritis of the knee and shoulder. 18-FDG accumulates in areas of increased metabolism, particularly activated leukocytes, as measured by increased standardized uptake value.2 PET/CT offers the unique advantage of showing active disease before anatomic damage is evident. Our hypothesis is that there is an increased uptake of 18-FDG on PET/CT in synovitis of the TMJ.