Electromyography Analysis of the Masseter Muscle's Activity in the Management of Oral Submucous Fibrosis

Introduction Oral submucous fibrosis (OSMF) is a persistent, collagen metabolic disorder distinguished by the presence of fibrosis of the connective tissue stroma in the oral mucosa with a higher malignant potential rate for oral cancer. This study aimed to analyze the utility of electromyography (EMG) as the prognostic assessment tool in the management of OSMF with conventional intralesional corticosteroid therapy. Materials and methods This study included 20 OSMF cases of age range 20 to 80 years without systemic comorbidities to assess pre-treatment and post-treatment changes with intralesional corticosteroid therapy as an intervention and to determine if it could be assessed using electromyographic study. Clinical and histopathological grading of OSMF was done. The five clinical parameters were evaluated for measuring treatment prognosis. Among them, mouth opening, tongue protrusion, and burning sensation assessments were quantitative parameters, and palpable fibrotic bands and mucosa colour were qualitative parameters. As OSMF involves changes in muscle plane in moderately advanced and advanced cases, EMG was used as an assessment tool for measuring muscle activity. Among the muscles of mastication, the masseter and temporalis were selected for evaluation. Twenty age and gender-matched healthy controls were required for this study as there are no standardized normal values for amplitude and onset of activity in muscle analysis. The EMG activity of the right and left temporalis and masseter muscles were recorded using surface electrodes and were correlated with five clinical assessment parameters. Results In the right masseter, the rest amplitude of 1.6010 µV of the OSMF was statistically significant (p-value: 0.050) when compared with 4.1275 µV of the control. The clench amplitude of 133.370 µV of the OSMF was statistically significant (p-value: 0.062) when compared with 94.310 µV of the control. In the left masseter, the rest amplitude of 1.6695 µV of the OSMF was statistically significant (p-value 0.066) when compared with 2.5735 µV of the control. In the left masseter, the onset of muscle action of 62.670 ms of the OSMF was statistically significant (p-value: 0.017) when compared with 131.835 ms of the control. The clench amplitude differences in the right masseter of 133.370 µV pre-treatment, and 102.775 µV post-treatment were statistically significant (p-value: 0.007). The clench amplitude in the left masseter of 102.535 µV pre-treatment, and 92.090 µV post-treatment were statistically significant (p-value: 0.036). The correlation was seen between tongue protrusion and rest amplitude in the right masseter in OSMF (r = 0.376, p-value: 0.023). Conclusion There was a correlation between tongue protrusion and rest amplitude in the right masseter muscle in OSMF patients before treatment. In the right and left masseter, during rest, the amplitude of the OSMF group was lesser than that of the control group. During clench, in the right masseter, the amplitude of the OSMF group was higher than that of the control group. During clench in the left masseter, the onset of muscle action was lesser in the OSMF group than in the control group. After treatment, there was a reduction in clench amplitude in OSMF patients from their pretreatment values signifying muscle relaxation and a better onset of muscle action.