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Electromyography: applied in thephonoaudiology clinic

Miriam Nagae¹Fausto Berzin²¹Language therapist, State University ofCampinas²DDS, PhD, Professor of Piracicaba DentalSchool, State University of Campinas

Received for publication: February 10, 2004Accepted: April 28, 2004

Correspondence to:Mirian NagaeUniversidade de Campinas- FOP/UNICAMPDepartamento de MorfologiaAv. Limeira, 901Cep:13.414-903, Piracicaba- São Paulo- BrazilPhone: +55 011 30321102e-mail: mnagae@uol.com.br

AbstractThe aim of this study was to discuss the utilization of surface elec-tromyography in the practice of phonoaudiology to obtain a pictureof the muscular compromise that occurs in patients with dental andskeletal alterations. The behavior of muscles in functions such asswallowing, chewing and respiration, and at rest, and possible devia-tions thereof, will be examined by electromyography based on theactivated muscular chains. Compromises such as tension, flaccidity,palsy and rhythm could be detected quantitatively and qualitativelyduring the functions.

Key Words:eletromyography, language therapist, TMD

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IntroductionPhonoaudiology covers a vast area of clinical interests,among them oral motricity, which is basically at the center ofimpairments of muscle order. Knowledge of the condition ofthe musculature is of utmost importance in these cases. Thetools that have been utilized to date for the handling of thesecases are: palpation, visual inspection and the opinion of aprofessional. However, such an examination is rathersubjective in character.With advances in technology, a series of instruments havepermitted a clearer and more objective view of the actualcondition of the musculature. In the phonoaudiology clinic,electromyography, which records the electrical properties ofmuscles, has thereby been a valued tool1. To perform anelectromyographic study, a professional needs a priortechnical understanding in the handling of instruments aswell as a profound knowledge of the anatomy and physiologyof the musculature to be investigated.The choice of musculature would depend on the situationand the interest of the examiner. In phonoaudiology, themajor focus is in the region of the head, chest and face(muscles: temporal , masseter, suprahyoid group, mentual,and labial orbicular).The examination could help in the diagnostics, treatmentand even the prognostics of cases. Regarding its diagnosticvalue, it would be possible to determine for individual as wellas groups of muscles both normal patterns and possible imbalancesfound in the musculature, such as in the following cases.

Electromyography registrationa) During deglutition (figure1), the signal of the suprahyoidmuscle group is captured, which allows for a bettervisualization of the moment of deglutition, because of it verynear to the musculature of the tongue. In cases of atypicaldeglutition, the anterior interposition of the tongue betweenthe arches is common. This condition is found for example insubjects with an anterior open bite (Angle´s Class II/1rd

division), where the masseter muscle exerts an intensepressure concomitant with the action of the suprahyoidmuscle group (figure 2).

Fig. 1- Electromyographic recording of the masseter muscle and

of the suprahyoid muscle group during normal deglutition ofsaliva. Ave mVSuprahyoid (right) 15.5Suprahyoid (left) 17.3Masseter (right) 4.5Masseter (left) 3.9

Fig. 2 - Electromyographic recording of the masseter muscle andof the suprahyoid muscle group in a patient with interpositionof the tongue between the arches. Note the excessive action of themasseter muscle. Ave m VSuprahyoid (right) 36.7Suprahyoid (left) 30.3Masseter (right) 8.6Masseter (left) 13.2

b) In the mouth breather, we can observe that due to theflaccidity caused by the mouth open, the labial orbicularmusculature needs to recruit many motor units to be ableto maintain the lip seal (figure 4). It is interesting to seethat after the patient is able to make nose breathingautomatic and/or after myotherapeutic intervention, themuscles re-establish their normal pattern in the restingstate (figure 3).

Fig. 3-Electromyographic recording of the upper labial orbicu-lar, mentual and masseter muscles in nose-breathing patients atrest. Ave mVUpper labial orbicular 2.1Mentual 1.3Masseter (right) 1.6Masseter (left) 1.8

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Fig. 4 - Electromyographic recording of the lower labialorbicular, mentual and masseter muscles in mouth-breathingpatients Note the hyperactivity of thelabial orbicular and mentualmuscles at the end of maintaining a lip seal.

Ave m VLower labial orbicular 3.8Mentual 7.2Masseter (right) 1.7Masseter (left) 2.7

c) During mastication, there is a significant action of theelevating muscles of the mandible, mainly the massetermuscle and little involvement of the perioral muscles(figure 5). When there is some alteration at the skeletallevel, in Angle´s Class II/2rd cases for example, we can seethat the musculature also undergoes a change in its patternof activation, as can be observed in figure 6, where thementual and labial orbicular muscles become significantlyactive.

Fig. 5 –Electromyographic recording of the lower and upperlabial orbicular and masseter muscles,during mastication ofbread, in patients without any impairments.

Ave mVLower labial orbicular 14.3Upper labial orbicular 15.9Masseter (right) 52.4Masseter (left) 33.5

Fig. 6 - Electromyographic recording of the masseter, mentual andupper labial orbicular muscles, during mastication of bread, inpatients with anterior open bite (Angle´s Class II/ 2rd). Note theexcessive action of the upper labial orbicular and mentual muscles.

AvemVMasseter (right) 97.7Masseter (left) 80.3Mentual 71.6Upper labial orbicular upper 54.5

Regarding treatment, electromyography can be used to monitordevelopment, but also as a therapeutic tool via biofeedback2,where patients learn to control their own neuromuscularresponses. This resource is very interesting mainly in relapsecases after orthognathic surgery or orthodontic treatment,which could be caused by a muscular memory3 that does notpermit a new pattern of muscle behavior to be established. Incases where there is pain or excessive tension in themastication muscles produced by parafunction, the capabilityof monitoring the muscles is also very interesting.In relation to prognostics, electromyography permits us todetermine the intensity of impairments (figure 7) and to obtainat the end of treatment quantitative evidence of the modificationsthat occurred (figure 8). Usually, an evaluation based on sizeand sensitivity of the musculature is not always possible.

Fig. 7-Electromyographic recording of the anterior temporal and massetermuscles, during mastication of bread. Note the disharmony in the action ofthe masseter muscle and the general hypoactivity of the musculature. Ave mVAnterior temporal (right) 26.0Anterior temporal (left) 35.1Masseter (right) 26.1Masseter (left) 63.5

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Figure 8- Electromyographic recording of the anterior temporaland masseter muscles during mastication of bread. Note the re-establishment of equilibrium in muscular action in relation to thatin figure 7. Ave mVAnterior temporal (right) 25.6Anterior temporal (left) 64.3Masseter (right) 50.0Masseter (left) 120.8

Phonoaudiology is capable of carrying out electromyographyat least for the purpose of investigating the potential actionof motor units by means of electrodes placed on the skinsurface.In the phonoaudiology clinic, the electromyographicinterpretation is performed by means of a raw signal, whichpermits us to visualize qualitatively the size and shape ofmuscle action potentials.When there is an interest developed by more specificsituations or for research, there is a need for prior handlingof the signal, termed normalization4, for the purpose ofobtaining a common language to be able to compare results.Electromyographic kinesiology is the procedure mostindicated in such cases, since it allows us to study muscularactivity for both individual and groups of muscles in variousconditions, and to obtain a quantitative evaluation of thesignal5. In phonoaudiology investigations, this has beenachieved following this methodology6. In thephonoaudiology clinic, implementing the normalization ofthe signal in the future is inevitable. However, it is import toremember that this type of methodology is only intended forthe quantitative investigation of isolated aspects (fatigue,stress, amplitude), and it is not sufficient for a more globalizedevaluation necessary for the clinic. The raw signal in thisaspect provides us with a more qualitative view, wherenuances in shape, size and time of the recordings couldfurnish revealing information for a better understanding ofcases.The ability to perform electromyographs in the clinic on adaily basis improved significantly the quality of all aspects,mainly with regard to the understanding of the causes of theimbalances encountered that will inevitably produce morerapid and accurate results.

Currently, we are going through a very interesting phase,because due to better access to technology andinterdisciplinary exchange of professionals such asphysiotherapists, dentists and clinicians, we are getting closerto a sophistication that soon will permit us to see the variousphysiological modifications occurring in musculature, usingsuch tests as electromyography.

References1. Dorland. Dicionário médico. 25.ed. São Paulo: Roca; 1997.2. Basmajian JV, De Luca CJ. Muscle alive: their functions realed

by electromyography. 5nded. Baltimore: Willians & Welkins;1985. p.385-90.

3. Erhart EA. Neuroanatomia. 6.ed. São Paulo: Roca; 1986. p.235.4. Knutson MMML, Soderberg GL, Ballantyne BT, Clarke WR. A

study of various normalization procedures for within day EMGdata. J Electromyogr Kinesiol 1994; 4: 47-59.

5. Portney L. EMG and examinations about conductions nervousvelocity. In: O’Sullivan SB, Schimitz, TJ. Fisioterapia: avaliaçãoe tratamento. 2nd ed. São Paulo: Manole; 1993. Cap.10.

6. Silvério KCA. Avaliação vocal e atividade eletrica dos musculossupra-hioideos e esternocleidomastoideo em individuos comdesordem temporomandibular miogenica em situações de repousoe fonação [thesis]. Piracicaba: FOP/UNICAMP; 2002.

Braz J Oral Sci. 3(10): 506-509 Electromyography: applied in the phonoaudiology clinic