Download Volume 142, 1999 57 A REPORT ON ANOMALIES OF DIGASTRIC

Volume 142, 1999
57
A REPORT ON ANOMALIES OF DIGASTRIC MUSCLE
Alžběta Holibková, Libor Machálek
Department of Anatomy, Medical Faculty, Palacký University, 775 15 Olomouc, Czech Republic
Received April 20, 1999
Key words: Neck muscles / Digastric muscle / Abnormalities
Dedicated to the memory of doc. MUDr. et RNDr. Milan Černý, CSc.
The anterior belly of the digastric muscle varies greatly in shape and size. In this report, two cases of anomalies
in the digastric muscle found in necropsy material belonging to the Institute of Anatomy are described. In the first
case, we found a bilateral anomaly – a lateral widening of the muscle belly as an adaptation; this was shown by
separation of the anterior muscle belly of digastric muscle into a medial and lateral head. The latter of which
passing through the intermediate tendon and fixing partially on the hyoid bone. In the second case, a bilateral
asymmetrical anomaly of the anterior belly was described. This involved the separation of the anterior belly into
medial and lateral parts and the occurrence of accessory bundles; these bundles run from the left part of the
mandible to the intermediate tendon of the right side of digastric muscle and to the hyoid bone.
INTRODUCTION
We describe two anomalies of the anterior belly of
digastric muscle, which we found in previous necropsies
at our department. These differed from the findings of
Prof. Žlábek 1. The anterior belly of the digastric muscle varies unusually in size and form. The categorization
of the anomalies of the digastric muscle has not been
agreed. A variation in the form of the muscle belly, and
the occurrence of the accessory muscle bundles laterally
and bilaterally etc. are described. The anomaly of the
anterior belly of the digastric muscle is explained as a
phylogenetic reduction of the muscle tissue or as a
result of an unusual development of ontogenetic material. These anomalies are normally explained in relation
to the mechanism of the mandibular joint and the development of speech.
OBSERVATION
In our first findings (Fig. 1, Sch. 1) we introduce the
duplication of the anterior belly of digastric muscle in a
57-year old man with a well developed musculature.
The medial head of the anterior belly looks like the
classical original continuation of the anterior belly of
digastric muscle. The lateral head originates at the mandible ventrolaterally from the digastric fossa of the mandible, follows dorsolaterally and is fixed partially at the
intermediate tendon of digastric muscle and partially at
the hyoid bone in the region of the fixation of stylohyoid
muscle.
In this case, we also found other muscle anomalies,
such as levator claviculae muscle (Holibková et. al.2).
In our second case, that of a 64-year old man, we
found in necropsy combined asymmetrical anomaly of
the anterior belly of digastric muscle (Fig. 2 a, b; Sch. 2).
a) The medial part of the anterior belly originates bilaterally at the digastric fossa of the mandible, continues
dorsally as the aponeurotic attachment fixed to the
body of the hyoid bone.
b) The lateral part of the anterior belly originates bilaterally on the lower margin of the body of the mandible laterally from the digastric fossa, it follows dorsomedially and continues as the intermediate tendon
of the digastric muscle.
We see branches of a submental artery on the right
side in the notch with an aponeurotic margin between
the medial and lateral parts of the anterior belly (Fig. 2
a, 2 b).
Part of the muscule bundle started with a thin tendon in the left digastric fossa, and ran dorsally right
through the middle line and directed in the medial
marging of the right side of the anterior belly.
c) Most of these muscle bundles went behind the venter anterior to the intermediate tendon.
d) Some of these muscle bundles went in front of the
venter anterior in the same way as the intermediate
digastric tendon.
e) Other bundles originate from the bundles c), but
have become separated. They run dorsally left
through the middle line to the hyoid bone medially
from the end of the medial part of the left side
anterior belly (Fig. 2 b).
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Fig. 1. A bilateral anomaly of the anterior belly of the digastric
muscle.
1 – anterior belly of digastric muscle: a – medial head, b – lateral head.
2 – hyoid bone. 3 – intermediate tendon of digastric muscle with
insertion of the lateral head of the anterior belly. 4 – stylohyoid
muscle. 5 – submental artery and vein.
Scheme 1. A bilateral anomaly of the anterior belly of the digastric
muscle.
1 – anterior belly of digastric muscle: a – medial head, b – lateral head.
2 – hyoid bone. 3 – intermediate tendon of digastric muscle with
insertion of the lateral head of the anterior belly.
Acta Univ. Palacki. Olomuc., Fac. Med.
Scheme 2. A combined asymmetric anomaly of the anterior belly of
the digastric muscle.
1 – anterior belly: a – medial part. b – lateral part. c – muscle bundles
going from the left digastric fossa of mandible to the intermediate
tendon behind anterior belly. d – muscle bundles going in front of the
anterior belly to the intermediate tendon. e – muscle bundles going to
the aponeurosis above the hyoid bone. 2 – hyoid bone. 3 – intermediate tendon of digastric, which insertion of the stylohyoid muscle.
4 – aponeurosis above the hyoid bone. 5 – submental artery and vein.
Fig. 2 b. A anomal muscle bundles of the medial part of the anterior
belly of the digastric muscle. a – medial part of the anterior belly. b –
lateral part of the anterior belly. c – muscle bundles going from the
left digastric fossa of mandible to the intermediate tendon, behind
anterior belly. d – muscle bundles going in front of the anterior belly
to the intermediate tendon. e – muscle bundles going to the aponeurosis above the hyoid bone. A – branch of submental artery.
DISCUSSION
Fig. 2 a. A combined asymmetric anomaly of the anterior belly of the
digastric muscle. 1 – anterior belly of digastric muscle: a – medial part,
b – lateral part. 2 – hyoid bone. 3 – intermediate tendon of digastric
muscle. 4 – stylohyoid muscle. 5 – branch of submental artery.
The variations of this muscle are cited in the literature since the first half of the 18 century (Winslow3,
Holl4, Le Double5, Macalister6).
The Czech author Žlábek1 widely studied the anomalies of the anterior belly of the digastric muscle from the
phylogenetic and ontogenetic development points of
view. He successfully identified variation from aberration.
He separated these variations into atavistic and adaptive expansions in medial and lateral direction. The
Volume 142, 1999
atavistic expansion in the medial direction is characterized by rectangular oblong form of the anterior belly.
The author1 classified the adaptive expansions of the
anterior belly medially in anterior, posterior, mixed and
combined types.
In his study Žlábek1 did not find adaptions in the
widening of the anterior belly laterally.
In the case of aberrations he mentioned that they
are formed depending on the continuation of vessels
and nerves.
In our first case that we described could be included
in the category of the adaptive widening of the muscle
belly on the basis of the classification of Žlábek1. However, this case was not found in his series.
The second case that we described as a combined
bilaterally asymmetrical anomaly of the anterior belly of
the digastric muscle. The anomaly occuring in the right
side where the thin fissure with the aponeurotic margin
between medial and lateral muscle bundles and the
piercing of a branch from the submental artery were
evident. Based on the classification of Žlábek1 we can
conclude this case to be an aberration of the right side
anterior belly of the digastric muscle.
In other new studies authors pay attention to the
anomalies of the anterior belly of the digastric muscle
with respect to diagnostic methods – X-ray, CT, MR,
and surgery steps in the submandibular and submental
regions (Uslu et al.7, Sargon et al.8, Celik et al.9) and also
with regards to the dysfunction of the mandibular joints
(Stockstill et al.10).
In the last literature data on the other suprahyoid
muscles we encountered the description of the occurrence of the accessorial mylohyoid muscle (Sehirli et
al.11), arising from the left mylohyoid line of mandible,
inserting between the caudal part of the median fibrous
raphe of the mylohyoid muscle and hyoid bone. The
authors11 evaluate this anomaly as a very rare and important for the function of the muscular floor of the oral
cavity.
In agreement with their11 opinion, it is possible to
understand that anomalies of the anterior belly of digastric muscle are a functional part of the oral diaphragm.
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REFERENCES
1.
Žlábek, K. (1932) O anomaliích předního bříška dvojbřišního
svalu u člověka. Sb. Lékařský (Praha), 34 (38), 1–36.
2. Holibková, A., Machálek, L. (1998) A contribution to the anomalies of heterochtonic back muscles. Acta Univ. Palacki. Olomuc.
(Olomouc), Fac. Med., 141, 53–55.
3. Winslow, J. B. (1732) Exposition anatomique de la structure du
corps humain. Paris.
4. Holl, M. (1916) Zur Phylogenese und Morphologie des vorderen
Bauches des M. digastricus des Menschen. Sitzber. Akad. Wiss.
Math. – naturw. Kl. (Wien), Abt. III., Bd. 124, 125.
5. Le Double, A. F. (1897) Traité des variations du systeme musculaire de ¾ Homme. Libraire C. Reinwald, Paris.
6. Macalister, A. (1872) A Descriptive Catalogue of Muscular
Anomalies in Human Anatomy. Proceed. of the Roy. Irish. Acad.
(Dublin), vol. 25.
7. Uslu, S. S., Atilla, S., Celik, H. H., Inal, E. (1995) An important
anatomic variation in head and neck region: anomaly of the
anterior belly of the digastric muscle. Bul. Asoc. Anat. (Nancy),
(France), 79 (224), 39–41.
8. Sargon, M. F., Celik, H. H. (1994) An abnormal digastric muscle
with three bellies. Surg. Radiol. Anat. (Germany), 16 (2),
215–216.
9. Celik, H., Yilmaz, E., Atasever, A., Durgun, B., Taner, D. (1992)
Bilateral anatomical anomaly of anterior bellies of digastric muscles. Kaibogaku Zasshi (Japan) 67 (5), 650–651.
10. Stockstil, J. W., Harn, S. D., Underhill, T. E. (1991) Clinical
implications of anomalous muscle insertion relative to jaw movement and mandibular dysfunction: the anterior belly of the digastric muscle in a cadaver. J. Craniomandib. Disord. (United States)
5 (1), 64–70.
11. Sehirli, U., Cavdar, S. (1996) An accesssory mylohyoid muscle.
Surg. Radiol. Anat. (Germany) 18 (1), 57–59.