Accuracy of the surface electromyography RMS processing for the diagnosis of myogenous temporomandibular disorder

Abstract

Due to the multifactor etiology of temporomandibular disorder (TMD), the precise diagnosis remains a matter of debate and validated diagnostic tools are needed. The aim was to determine the accuracy of surface electromyography (sEMG) activity, assessed in the amplitude domain by the root mean square (RMS), in the diagnosis of TMD. One hundred twenty-three volunteers were evaluated using the Research Diagnostic Criteria for Temporomandibular Disorders and distributed into two groups: women with myogenous TMD (n = 80) and women without TMD (n = 43). The volunteers were then submitted to sEMG evaluation of the anterior temporalis, masseter and suprahyoid muscles at rest and during maximum voluntary teeth clenching (MVC) on parafilm. The accuracy, sensitivity and specificity of the muscle activity were analyzed. Differences between groups were found in all muscles analyzed at rest as well as in the masseter and suprahyoid muscles during MVC on parafilm. Moderate accuracy (AUC: 0.74–0.84) of the RMS sEMG was found in all muscles regarding the diagnosis of TMD at rest and in the suprahyoid muscles during MVC on parafilm. Moreover, sensitivity ranging from 71.3% to 80% and specificity from 60.5% to 76.6%. In contrast, RMS sEMG did not exhibit acceptable degrees of accuracy in the other masticatory muscles during MVC on parafilm. It was concluded that the RMS sEMG is a complementary tool for clinical diagnosis of the myogenous TMD.

Introduction

The temporomandibular joint (TMJ) and masticatory muscles can be affected by temporomandibular disorder (TMD) (Sharma et al., 2011, Vuckovic et al., 2012). Due to the multifactor etiology of this condition, the precise diagnosis remains a matter of debate (Medllicott and Harris, 2006) and validated diagnostic tools are needed (Gonzalez et al., 2008). Electronic equipment may provide reliable quantitative data to assist in the clinical evaluation of TMD (Schmitter et al., 2005, Manfredini et al., 2006, Hugger et al., 2008, Lauriti et al., 2014).

The diagnosis of TMD should be based on a combination of a clinical exam and reported history of the disorder (Sener and Akgunlu, 2011). The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) has been designed to assist in the diagnosis (Dworkin and LeResche, 1992, Mafredini et al., 2010). While studies have demonstrated that the RDC/TMD is reliable for myogenous TMD, this tool exhibits low accuracy for the arthrogenous TMD diagnosis (Schmitter et al., 2005, Look et al., 2010, Schiffman et al., 2010, Park et al., 2012).

Surface electromyography (sEMG) is a noninvasive technique for recording muscle activity that may be employed in the assessment of TMD (Suvinen et al., 2009). However, its use in the diagnosis of this disorder has been called into question due to the considerable variability in the findings described in the literature (Klasser and Okeson, 2006). Studies addressing the diagnosis of different health conditions have evaluated the accuracy and correlation of different assessment tools for the determination of reference values and the best form of diagnosis (Manfredini et al., 2011, De Felício et al., 2012, Reneker et al., 2011, Piancino et al., 2012).

While sEMG indices have been employed as a complementary exam in the diagnosis of TMD, previous studies have exhibited poor methodological quality, with a failure to describe the techniques, tools and interpretation of the data, as well as a lack of reference values that differentiate individuals with and without TMD (Gonzalez et al., 2008).

In a recent research, Lauriti et al. (2014) reported a good to excellent reproducibility (ICC: 0.66–0.99) for the sEMG evaluation in TMD and asymptomatic subjects during maximum voluntary teeth clenching on parafilm and at rest, for the masticatory muscles. Moreover, the sensitivity, specificity and accuracy of sEMG activity assessed in the amplitude domain by the root mean square (RMS) in the diagnosis of myogenous TMD, have not been established in the literature so far. Indeed, Manfredini et al. (2011) reported that sEMG indices collected during teeth clenching task exhibit moderate accuracy, but should not be used in the diagnosis of TMD due to high rates of false-positive found in subjects without TMD (TMD-free subjects). On the other hand, Santana-Mora et al. (2014) reported a moderate degree of accuracy of the sEMG (integrated processing) at rest, for discrimination between TMD and asymptomatic subjects, specifically for left anterior temporalis muscle.

Given the above, the aim of the present study was to assess the accuracy of RMS sEMG data of the masticatory muscles in the diagnosis of myogenous TMD.