Clinical significance of T2 mapping MRI for the evaluation of masseter muscle pain in patients with temporomandibular joint disorders

Masticatory muscle pain is one of the typical symptoms of temporomandibular joint disorders (TMD). T2 mapping (distribution of T2 values) is a notable MRI technique for evaluating water contents in tissues. We investigated the clinical significance of T2 mapping for the evaluation of masticator muscle conditions by comparing the difference in the T2 values between the painful and pain-free sides of the masseter muscle in patients with TMD. Seventy-three patients clinically diagnosed with TMD were enrolled in this study. We divided the patients into two groups: a unilateral pain group (patients with unilateral masseter muscle pain) and a painless group (patients without muscle pain). There were 29 patients in the unilateral pain group and 44 patients in the painless group. We compared the difference in the mean T2 values between the painful and pain-free sides of the masseter muscle in the unilateral pain group and between the right and left sides in the painless group. The mean T2 values of the masseter muscle on the painful side were significantly higher than those on the pain-free side in the unilateral muscle pain group (p < 0.01). In the painless group, there was no significant difference in the mean T2 values between the right and left sides. It is suggested that T2 mapping is a promising method for evaluating masseter muscle pain caused by edematous change related to TMD through monitoring of the T2 values.