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Year : 2002  |  Volume : 12  |  Issue : 4  |  Page : 537-541
M-mode echomyography : a new technique for the functional assessment of striated muscles


Department of Radiology and Imaging and Medical Director, Meenakshi Ammal General Hospital, Maduravoyal, Chennai-602 102, Tamil Nadu-India

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   Abstract 

A simple, new Ultrasonographic technique (viz) M-Mode Echomyography for the study of functional status of masseter muscles and other masticatory muscles such as temporalis and lateral pterygoid muscles has been described. Its superiority over 2-D and 3 D Ultrasonographic studies and its utility in the functional assessment of other striated muscles such as Biceps brachii, brachio- radialis, thenar muscles, pectoralis major, quadriceps, vastus medialis and calf muscles also have been discussed.

Keywords: Acromegaly/DI, Masticatory Muscles/US, Muscle, Skeletal/US, Temporal Muscle, Magnetic Resonance Imaging, Human,

How to cite this article:
Rajaram P C, Naidu M E, Rao S P, Sindhuvenugopal. M-mode echomyography : a new technique for the functional assessment of striated muscles. Indian J Radiol Imaging 2002;12:537-41

How to cite this URL:
Rajaram P C, Naidu M E, Rao S P, Sindhuvenugopal. M-mode echomyography : a new technique for the functional assessment of striated muscles. Indian J Radiol Imaging [serial online] 2002 [cited 2021 Jan 17];12:537-41. Available from: https://www.ijri.org/text.asp?2002/12/4/537/28534

   Introduction Top


Ultrasonographic study of muscles for their morphology and pathology has been fairly well established. Various authors have studied the masseter muscles for their volume by C.T, M.R.I and 3-D Ultrasonography for the assessment of facial morphology and concluded that 3-D Ultrasonography provides adequate information comparable to C.T and M.R imaging of masseters (Ref 1 and 2). By utilizing 2-D Ultrasonographic study of masseters, we were able to obtain details about the length, width and thickness of masseter muscle and calculate its volume. This information was adequate to assess the morphology of masseter muscles in the normal as well as in patients with partial or total edentulous jaws, with or without dentures. Also it provided useful information in patients with Hypoplastic, atrophic or hypertrophic masseters.

Subsequently, we felt that functional assessment of the masseters will be more useful than information about morphology alone. This prompted us to study the masseters by M-mode Ultrasonography in Cardiac mode in the same pattern as M-mode Echocardiography. For this purpose it is necessary to study the masseter during alternately contracting and relaxing the muscle by alternately clenching the teeth and relaxing. This provides M-mode curve delineating increased thickness of the clenched (or contracted) muscle and the normal thickness of muscle in its relaxed state. The difference between Echo myographic measurements of the contracted and relaxed muscle is the amplitude of contraction. The value of fractional shortening (F.S) is obtained by the following formula.

Both amplitude and fractional shortening provide correct information about the contractility and thereby functional status of the muscles studied.

We have also studied other muscles of mastication such as temporalis muscle (both its horizontal and vertical components) and lateral pterygoid muscle at its insertion (i.e) below and anterior to condyle of mandible.


   Materials and Method Top


Our material consists of study of masticatory muscles in twenty normal individuals, study of masseters in twenty total edentulous patients and twenty partially edentulous patients. Masseters in one patient with acromegaly have been studied. Temporalis and lateral Pterygoid muscles have been studied in five normal individuals and five patients with malocclusion of arches.

M - Mode echo myography of biceps brachii, brachioradialis, thenar muscles, pectoralis major, quadriceps, vastus medialis and calf muscles have been studied in ten normal individuals.

Method

Ultrasonographic studies (2-D and M-mode) are performed in cardiac mode using 7.5 MHz linear transducer. With the patient in lateral decubitus position, the transducer is placed over the right and left masseter muscles and longitudinal and cross sectional 2-D views of the muscle are obtained. The length, width and thickness of the muscle are measured in contracted (C) and relaxed (R) states. For M-mode studies, the patient is instructed to clench the teeth and relax alternately in slow and fast sequences. The M-mode curves obtained at the origin, mid belly and insertion of the muscle are studied for the values of R and C. The difference between R and C gives the amplitude of contraction.

For the study of temporalis muscle, the transducer is kept over the horizontal fibres (i.e. over the squamous temporal) and the M-mode curve is obtained while alternately clenching the teeth and relaxing. Vertical component of the temporalis is studied by placing the transducer midway between the ear and upper border of orbit one inch above the orbit.

The lateral pterygoid is studied by placing the transducer anterior to the condyle of mandible and M-mode curve is obtained during lateral and medial excursions of the jaw with partially open mouth. M-mode curve is also obtained during protrusion and retrusion movements of the jaw with partially open mouth.

Medial Pterygoid is not accessible for Ultrasonographic study.


   Illustrative cases Top


Relaxed muscle (R) measures 15 mm; with clenched teeth, the contracted muscle (C) measures 22 mm. Amplitude of contraction (A) is 7 mm. Fractional shortening (F.S.) is 32%. Thus 2 - D studies also provide information about the functional status and contractility of the muscle.

M - Mode Echo-myography of normal masseter studied at its mid belly origin and insertion. The M-Mode curves obtained in normal and fast sequences of muscle action are depicted.

In most of the patients, the amplitude of contraction is maximum at the insertion of the masseter. This is because some of the fibres are inserted on the medial aspect of the mandible (i.e.) the angle of the mandible along with the fibres of the medial Pterygoid muscle which also contributes to the biting force.

The amplitude of contraction and fractional shortening in both normal and fast sequences are the same.

M-Mode Echo-myography of the Right masseter mid-belly in a patient with Acromegaly. The hypertrophied muscle measures 30mm in relaxed state (R) and 40mm in contracted state (C). The amplitude of contraction is 10mm. Fractional shortening (F.S) is 10mm/40mm X100 = 25%. With 25% F.S, the hypertrophied muscle is able to obtain optimum Contractility for masticatory function with lesser F.S. than the smaller muscle which has to contract more vigorously (ie) it has to undergo more F.S. to obtain equal amplitude.

In fast sequence of muscle contraction, both the horizontal and vertical fibres show same F.S.

M-Mode Echo-myography of the horizontal and vertical fibres of Temporalis muscle obtained by alternately clenching the teeth and relaxing with the mouth closed and tight posterior occlusion of the arches. The amplitude of contraction is found to be the same in both normal (4a and 4c) and fast sequences (4b and d) of muscle contractions, provided the clenching is done with complete posterior occlusion of arches.

In fast sequence of muscle contraction, both the horizontal and vertical fibres show same F.S.

M-Mode Echo-myography of lateral Pterygoid obtained during lateral and medial excursions of the jaw with partially open mouth. R is 6mm: C is 16mm: A is 10mm: and F.S. is 62.5%.

Lateral Pterygoid muscle undergoes maximum amount of fractional shortening to obtain 10mm of amplitude of contraction. This proves that more than the thickness, size and volume of the muscle, fractional shortening is the important contributing factor for contractility of the muscle.


   Results and Conclusions: Top


M-Mode Echo-myography of masticatory muscles provides accurate and reproducible measurements of amplitude of muscle contraction thereby helping in the assessment of contractility and masticatory efficiency. Optimum and adequate masticatory efficiency determines the success and acceptability of dentures. Comparison of masticatory function of right and left masseters and Temporalis muscles by M-Mode Echo-myography provides information regarding right or left side predominance. M-Mode Echo-myography is a simple, safe (free from radiation), non-invasive, accurate, quick and reproducible out patient procedure which is also acceptable to the patient for accurately assessing functional (masticatory) efficiency of masseters in total and partial edentulous jaws.

Subsequently, we have extended the study by utilizing M-Mode Echo-myography for the functional assessment of other striated muscles such as Pectoralis major [Figure - 6], Brachio radialis [Figure - 7], Biceps brachii [Figure - 8], Thenar muscles [Figure - 9], Quadriceps [Figure - 10] Vastus medialis [Figure - 11] and Tendo - Achillis [Figure 12].

M-Mode Echo-myography of Pectoralis major. Values of R is 20 mm: C is 36mm: A is 16mm and F.S. is 44%.

M-Mode Echo-myography of Brachio Radialis. Values of R is 24mm: C is 42mm: A is 18mm and F.S. is 43%.

M-Mode Echo-myography of Biceps brachii. Values of R is 28mm: C is 66mm; A is 38mm and F.S. is 58%.

M-Mode Echo-myography of Thenar muscles, Values of R is 35mm; C is 51mm; A is 18mm and F.S. is 35%.

M-Mode Echo-myography of Quadriceps muscle just above the patella. Values of R is 16mm; C is 30mm; A is 14mm and F.S. is 47%.

M-Mode Echo-myography of Vastus medialis muscle. Values of R is 5cm; C is 7cm; A is 2cm. and F.S. is a 29%. With 29% of FS 20mm of amplitude of contraction is obtained. This shows the contractile power of Vastus medialis

M-Mode Echo-myography of Tendo-Achillis. Values of R is 16mm; C is 25mm: A is 9mm and F.S. is 36%.

Our results in the study of functional status by M-Mode Echo-myography of muscles in such conditions as Pseudomuscular hypertrophic dystrophy, Hypoplastic and atrophic muscles, wasted muscles in neurological deficits and Post traumatic muscular changes will be reported later. Also, study of functional status of masticatory and other muscles infiltrated by adjacent malignant lesions such as oral cancers, salivary glands and tumours in the neck and other peripheral soft tissue malignant tumours and fibrotic muscles following Radio-therapy, Post traumatic and Post operative scars including Keloids will be reported. Follow up studies in these patients help to evaluate the progression or regression of the lesion and recovery of muscle function. We are also planning to study the functional status of certain muscles or groups of muscles which are put to maximum use and stress by individuals engaged in specialized occupations such as tailors hammer men, circus performers, cyclists and hand pedaling of cycles. The values of R, C and A and F.S. in these cases will be correlated with the length, breadth thickness and volume of muscles studied and reported.

Our study for the functional assessment of electrically stimulated striated muscles, by galvanic current is in progress and will be reported later.[2]



 
   References Top

1.Bennington Philip, C.M. et al : Masseter muscle volume measured using Ultrasonography and its relationship with facial morphology. European journal of orthodontics: 1999; 21: 659 to 670.  Back to cited text no. 1    
2.Hell, A, et al : Three Dimensional Ultrasonography in Maxillo - Facial Surgery. Int. Journal of oral Maxillo - Facial Surgery: 1993; 22, 173 to 177.  Back to cited text no. 2    

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Correspondence Address:
P C Rajaram
Department of Radiology and Imaging and Medical Director, Meenakshi Ammal General Hospital, Maduravoyal, Chennai-602 102, Tamil Nadu-India

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Source of Support: None, Conflict of Interest: None


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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11]

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    Abstract
    Introduction
    Materials and Method
    Illustrative cases
    Results and Conc...
    References
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