Increased Apparent Diffusion Coefficient Values of Masticatory Muscles on Diffusion-Weighted Magnetic Resonance Imaging in Patients With Temporomandibular Joint Disorder and Unilateral Pain

Purpose: Myalgia of the masticatory muscles is difficult to evaluate quantitatively. The purpose of the present study was to quantitatively assess myalgia of the masticatory muscles in patients with temporomandibular disorders (TMDs) using the apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (MRI). Patients and Methods: Patients who had undergone MRI with clinically diagnosed TMDs according to the criteria of the American Academy of Orofacial Pain and unilateral temporomandibular joint pain from March 2015 to January 2017 were prospectively enrolled. The MRI techniques used included axial diffusion-weighted imaging (DWI) and short T1 inversion recovery imaging through the neck to the skull base. The regions of interest were drawn to completely include the right and left lateral pterygoid muscles, medial pterygoid muscles, and masseter muscles on a slice demonstrating the largest area of each muscle on the ADC map. We compared each masticatory muscle of the pain side with those of the contralateral side without pain. Results: A total of 106 patients with TMD had met the inclusion criteria (18 males, 88 females; mean age, 48.7 years; range, 16 to 80). The mean ADC values of the masticatory muscles of the pain side were significantly greater than those of the no-pain sides (P < .01), as were those for the lateral pterygoid muscles (1.35 +/- 0.79 x 10(-3) mm(2)/second vs 1.13 +/- 0.77 x 10(-3) mm(2)/second), medial pterygoid muscles (1.28 +/- 0.46 x 10(-3) mm(2)/second vs 1.05 +/- 0.69 x 10(-3) mm(2)/second), masseter muscles (1.33 +/- 0.78 x 10(-3) mm(2)/second vs 1.09 +/- 0.64 x 10(-3) mm(2)/second). Conclusions: The ADC values of the masticatory muscles on the pain side were significantly greater than those of the contralateral side without pain. Our results suggest that DWI could be used to assess myalgia of the masticatory muscles quantitatively. (C) 2019 American Association of Oral and Maxillofacial Surgeons