Surgical 2 Radiolog,c Anatomy

Surg Radiol Auat (1991) 13 : 33-37

Journal of Clinical Anatomy

© Springer-Verlag 1991

Functional relationships between the muscles of mastication and the muscles of the leg An electromyographic study B Valentino and F Melito Institute of Human Anatomy, Faculty of Medicine and Surgery, University of Naples, Via Armanni 5, Naples, Italy

Summary. The authors have shown, with the help of electromyography, the functional relationship which exists between the muscles of mastication and certain muscles of the leg after artificially creating interdental occlusal dysfonction. While the activity of the tibialis anterior was not affected by the alteration in occlusion, that of the peroneus longus and gastrocnemius was markedly changed. This is due to the activation of long muscle chains as a consequence of the activation of complex nervous reflexes. Rapports fonctionnels entre muscles masticateurs et muscles de la jambe : une 4tude EMG

R4sum6. Les auteurs ont mis en 6vidence h l'aide d'61ectromyogrammes le rapport fonctionnel qui existe entre les muscles masticateurs et certains muscles de la jambe, aprhs avoir cr66 artificiellem e n t un d y s f o n c t i o n n e m e n t occlusal interdental. Alors que Offprint requests : B Valentino

l'activit6 du m. tibial ant6rieur n'a pas 6t6 affect6e par l'alt6ration du plan occlusal interdental, celle du m. long fibulaire et du m. gastrocn6mien a 6t6 sensiblement touch6e. Ceci est dfi ~t l'activation de longues chalnes musculaires et, par cons& quent, ~ la r6alisation de r6flexes nerveux complexes. Key words : Electromyography - Posture

studied with the functional relationships between the muscles of mastication and those of the neck [51. These different studies have highlighted the existence of long muscle chains in which we have been interested in the field of sports medicine [14]. The work presented here is an e l e c t r o m y o g r a p h i c (EMG) study of the functional relationships between the muscles of mastication and those of the leg.

Material and methods The problem of functional relationships between different muscle groups, even widely separated one from the other, continues to fascinate numerous writers. It attracts the attention of those attempting to demonstrate the complex mechanisms which are the basis of posture [1-4, 6, 8, 10, 11, 15]. A very specific aspect of this problem is the functional relationship which exists beween the muscles of mastication and other muscle groups which have no apparent connection with the mouth [7, 9]. This effect has been particularly

The study was done on a group of 20 young people of varying build, between the age of 20 and 25 years old, who were studied with the following EMG's: 1. EMG of the muscles of mastication at rest and contracting (Fig. 1). 2. EMG of the paravertebral m. [12, 13] (Fig. 1). The object of this e x a m i n a t i o n was to e x c l u d e possible changes in position of the principal postural muscles of the vertebral column. The EMGs were recorded while the subject made symmetrical flexion/extension

34

B Valentino and F Melito: Functional relationships between the muscles of mastication and the muscles of the lower leg

RIGHT TA---MM .... ='.4 18 ~.4 2.8 2.7 1.9 2.7 1.9 ;=',-3 !.8 3 •., !. 7 3.6. 1,8 1.5 2.5

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RIGHT LEFT T Q - - - M M .... M M - - - T A I2 ~ I 14 22 i.i 2.8 1.4 1.6 1.4 2.6 2.2 1.4 2.6 1.8 1.3 .8 3.8 1.8 1.2 .8 2.4 1.9 1.3 .7 2.4

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EMG of the muscles of mastication and the paravertebra| m. a Masseter MM and temporalis TA at rest b Masseter and temporalis contracting c EMG of the paravertebral muscles at thoracic level TA and lumbar MM levels during symmetrical flexion/extension of the trunk EMG des ram. masticateurs et des m. paravert6braux a M. mass6ter MM et temporal TA au repos b M mass6ter et temporal duraut la contraction c EMG des ram. paravert6braux au niveau thoracique TA et lombaire MM pendant les mouvements sym6triques de flexion-extension du tronc

movements with cutaneous electrodes placed on paravertebral points to the left and right of the vertebral column. 3. EMG of the following 3 muscles of the leg with the subject standing: Tibialis anterior, gastrocn e m i u s and p e r o n e u s l o n g u s (Fig. 2). 4. EMG of the same 3 muscles after creation of an artificial interdental malocclusion (or precontact) by placing sterile cotton between the right and left molars (Figs. 3 and 4). The EMG used was developed by Myotronic Research Inc, Seattle, WA398101. It was composed of a bioelectric processor with 3 programmes, linked through a pre-amplifier to the electrodes,

and a printer. It had originally been developed to study the muscles of mastication which explains the initials on the electromyograms, which are not produced as graphs, but as figures (TA: temporalis anterior part, MM: masseter middle portion, TP: temporalis posterior part, DA: anterior digastric). This very practical e l e c t r o m y o g r a m a l l o w e d e a s y s t u d y o f other muscles. The apparatus allows recording of the electrical activity of the muscle at rest with the EM2-test 1 and contracting with the EM2-test 2. On the resting muscle it records the data constantly over a reference period of 40 s with a variation in value from 0-25.5 microvolts. It

also records an average value every 5 s, giving a total of 8 readings. In the test EM2-test2, i.e. muscle contracted, the electromyograph can check the degree of activity in the contracting muscles. This data is analysed in the form of instantaneous electromyographic activity over the period of 1-2 s. Each period consists of 10 electromyographic readings with a value from 0-255 microvolts. Simultaneous data can only be recorded from 4 muscles. The readings are printed digitally and one obtains an arithmetic mean and a diagram. The disposable Duo-Trode electrodes are bipolar silver and silver chloride cutaneous electrodes (Myotronic, USA).

B Valentino and F Melito: Functional relationships between the muscles of mastication and the muscles of the lower leg

RIGHT TA ---I,IM . . . . 3 8 '-, o 2.6 3.3 :.7 3 5 2.7 3.7 ,-.7 3 , ~ ,-.7 4.@ 2.6 3.4 2.7 2.9

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RIGHT TA---MM .... 2.6 3.3 2.5 7,.i 2.4 2.0 2.5 2.8 2.4 3,7 2.4 2.9 2.4 2.6 2.5 2.7

35

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The muscles of the lower leg at rest. a EMG of tibialis anterior TA and peroneus longus MM at rest b EMG of gastrocnemius at rest Les muscles de la jarnbe au repos, a EMG du m. tibial antrrieur TA et long prronier MM au repos b EMG du m. gastrocn~mien MM au repos

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LEFT MM---TA 3.7 2.6 3 4 2.6 " 4.3 2.7 3.9 2.6 3.9 2.7 3.6 °.7 3,6 2.6 3.5 2,7

RIGHT Tca---MM .... 1.9 1.6 1.8 1.5 1.3 1.6 1.4 1.5

LEFT MM--3.2 2,7 2.9 2.6 2,1 2.4 2.1 2.2

Fig. 3 a, b

Alteration in interdental occlusion by placing sterile cotton between the fight molars, a EMG of the tibialis anterior muscles TA and peroneus longus muscles MM b EMG of the gastrocnemius muscles MM

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Alteration of the interdentat occlusion by placing sterile cotton between the left molars, a EMG of the tibialis anterior muscles TA and peroneus longus m. MM b EMG of the gastrocnemius m. MM

Altdration du plan occlusal interdental en plagant du coton strrile an niveau des molaires droites. a EMG des m. tibial ant6rieur TA et long fibulaire MM b EMG des m. gastrocn~miens MM

Altrration du plan occlusal interdental en pla~ant du coton stdrile au niveau des molaires gauches, a EMG des m. tibial antdrieur TA et long fibulaire MM b EMG des m. gastrocndmiens MM

was equally normal with an activity which c o r r e s p o n d e d to the muscles of mastication. Figure 2 illustrates the functional relationship b e t w e e n the three muscles of the leg b e f o r e the artifical creation of interdental m a l o c clusion. In the test with sterile cotton b e t w e e n the right molars, the

activity o f tibialis anterior r e m a i n e d unchanged, w h i l e an increase in the activity of the h o m o l a t e r a l peroneus longus and of the controlateral gastrocnemius was recorded (Fig. 3 a, b). In placing the sterile cotton b e t w e e n the left molars no variation in the tone o f tibialis anterior was

Results

The electromyograms of the muscles of mastication, masseter and temporalis w e r e within the normal limits, both during basal recordings (Fig. 1 a) and during contraction (Fig. 1 b). E x a m i n a t i o n of the paravertebral m. (Fig. 1 c)

36

B Valentino and F Melito: Functional relationships between the muscles of mastication and the muscles of the lower leg

noted while the peroneus longus and gastrocnemius behaved in an inverse fashion to the preceding situation with an increase in activity in the left peroneus longus and the right gastrocnemius (Fig. 4).

D i s c u s s i o n and c o n c l u s i o n s The first observation concerns the behaviour of the tibialis anterior. The activity of this muscle did not change in either of the two experiments. Clearly in the upright and r e s t i n g p o s i t i o n s the o c c l u s a l dysfunction which was created did not set off any muscular chain capable of relaxing this muscle. On the o t h e r h a n d , this s i t u a t i o n produced as much reaction in the peroneus longus as in the gastrocnemius. In consequence, the change

in position of the head released complex neuromuscular mechanisms, affecting muscle groups even at a distance from the mouth. The following hypothesis is suggested to explain these function relationships: Alteration of the interdental occlusal plane has for its first effect modification of the position o f the head. This starts movement in the endolymphatic liquid of the semicircular canals in the inner ear where the organs of balance are situated. There is subsequent stimulation o f the special neuro-epithelial cells which carpet the walls of the canals (the acoustic crests of the canals) and those of the utricle and the saccule. The vestibular bundle of the v e s t i b u l o - c o c h l e a r n. originates from these cells and receives elec-

trical stimulation following the phenomenon of mechano-electrical transduction (primary mechanical stimulation off the sensory cells due to movement of the liquid and then electrical stimulation accros the vestibular n.) M o r e p r e c i s e l y , the f i b r e s coming from the neuro-epithelium of the utricle and of the saccule are c o n c e r n e d in the variations in muscular tone in the leg because they are intended to control the tonic reflexes. The bundles of the vestibular n. are therefore related to the 4 bulbar vestibular nuclei: the superior, medial, lateral and descending vestibular nuclei. At the level o f the lateral v e s t i b u l a r nucleus the vestibular spinal tract has formed, one part of which joins the lateral column of the spinal cord and forms the lateral vestibular spinal tract (tract of Hed). These fibres, which belong to the extrapyramidal motor pathway, synapse with the alpha sacral motor n e u r o n e s a n d in c o n s e q u e n c e control the postural activity of the muscles in the lower limbs (Fig. 5).

References

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Nuclei III,IV,VI

Fig. 5 Diagram showing the hypothesis of relationship between the movement of the head and the contraction of muscles at a distance TVS : tractns vestibulospinalis NM : nucleus medialis GV: ganglion vestibulare NL: nucleus lateralis N¥ : nuclei vestibulares NI : nucleus inferior NS: nucleus superior Schrma illustrant l'hypoth~se relationnelle entre musculaires 61oignres TVS : tractus vestibulospinalis GV: ganglion vestibulare NV: nuclei vestibulares NS: nucleus superior

les mouvements de la t~te et les contractions NM : nucleus medialis NL: nucleus lateralis NI: nucleus inferior

1. Basmajian JV (1979) Muscles alive, Williams Company, Baltimore, 175-189 2. Basmajian JV (1980) Electromyographydynamic gross anatomy: A review, Am J Anat 260 : 246-256 3. Boyle R, Pompeiano O (1981) Convergence and interaction of neck and macular vestibular inputs on vestibulospinal neurons. J Neurophysiol 45 : 852868 4. Brown MC, Matthews PBC (1966) On the subdivision of the efferent fibres to muscle spindle into static and dynamic fusimotor fibres. In: Andrew BL, Thomson, eds. Control and innervation of skeletal muscle, 18-31 5. Duries PL (1979) Electromyographic study of superficial neck muscles in mandibular function. J Dent Res 58: 537-538 6. Ezure K, Wilson VJ (1984) Interaction of tonic neck and vestibular reflexes in the forelimb of the decerebrate. Exp Brain Res 54:289-292

B Valentino and F Melito: Functional relationships between the muscles of mastication and the muscles of the lower leg 7. Funakoshi M, Fujita N, Takehana S (1976) Relations between occlusal interference and jaw muscle activities in response to changes in head position. J Dent Res 55 : 684-690 8. Grillner S (1969) Supraspinal and segmental control of static and dynamic y-motoneurones in the cat. Acta physiol $cand 77 : 1-34 9. Hirston L, Blanton PC (1983) An electromyographic study of mandibular position in response to changes the body position. J Prostet Dent 49 : 2-3 10. Manzoni D, Pompeiano O, Stampacchia G (1979) Tonic cervical influences on

posture and reflexes movements. Arch Ital Biol 117 : 81-110 11. Peterson BW, Pitts NG, Fukushima K, Maeckel R (1978) Reticulospinal excitation and inhibition of neck motoneurons. Exp Brain Res 32 : 471-489 12. Valentino B, Passiatore C, Esposito V (1984) Sur l'activit6 61ectromyographique des muscles paravert6braux chez les enfants d'fige scolaire. 67e Congr~s de l'Association des Anatomistes, Rennes 13. Valentino B, Mango G, Melito F, Fabozzo A (1985) Electromyography for investigation and early diagnosis of scoliosis. Anat Clin 7 : 55-59

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14. Valentino B, Gualdiero L, Esposito LC, Melito F (1986) Electromyographic analysis of some muscles in cycling athletes. J Sport Med Pbys Fitness 26 : 1.46-148 15. Wilson VJ, Yoshida M, Schorl RH (1970) Supraspinal monosynaptic excitation and inhibition of thoracic back motoneurons. Exp Brain Res 11 : 282295

Received June 22, 1990~Resubmitted October 4, 1990~Accepted January 14, 1991