Evaluation of Internal Echogenic Pattern of Masseter in Subjects with Myofascial Pain/ Myositis, Oral Submucous Fibrosis, Chewers, Bruxers and Healthy Individuals- A Preliminary Ultrasonographic Study

Statement of the Problem: The masseter is generally involved in myofascial pain, myositis, oral submucous fibrosis (OSMF), bruxism, and in subjects with habitual tobacco/arecanut chewing. In all the above conditions, changes in the internal echogenic pattern on ultrasonography of the muscle may be observed.
The present study aimed at evaluating the internal echogenic pattern of masseter by ultrasonography in subjects with various conditions affecting masster muscle.
The study subjects were categorized into 5 groups consisting of 20 subjects each with the following conditions; Group 1: myofascial pain or myositis, Group 2: oral submucous fibrosis (OSMF), Group 3: habitual chewing of tobacco/arecanut without OSMF, Group 4: bruxism. Group 5 consisted of 20 healthy subjects. An ultrasonographic examination of masseter was performed in all subjects and the echogenic pattern was classified into Types I, II and III. The images were examined by two observers and inter-observer variability was assessed. Differences in internal echogenic pattern between study groups and control group was evaluated using Chi- square test.
A good inter observer agreement was noted (k value= 0.8). An equal distribution of Types II and III echogenic pattern was noted in myofascial pain/myositis group. Type II was predominant in subjects with OSMF, habitual tobacco/arecanut chewing and bruxism. Type I was predominant in controls. The echogenic pattern differed significantly from controls in subjects with myofascial pain/myositis and OSMF (p=0.00001*, 0.0237* respectively), whereas in subjects with habitual tobacco/ arecanut chewing and bruxism, it did not differ significantly from controls (p=0.2482, 0.1223 respectively).
Ultrasonographic examination of the echogenic pattern may help in understanding the nature of the disease process affecting the masseter muscle in various conditions.