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Volume 142, 1999 57 a REPORT on ANOMALIES of DIGASTRIC

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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 In this case, we also found other muscle anomalies, such as levator claviculae muscle (Holibková et. al.2). We describe two anomalies of the anterior belly of In our second case, that of a 64-year old man, we digastric muscle, which we found in previous necropsies found in necropsy combined asymmetrical anomaly of at our department. These differed from the findings of the anterior belly of digastric muscle (Fig. 2 a, b; Sch. 2). Prof. Žlábek 1. The anterior belly of the digastric musc- a) The medial part of the anterior belly originates bilate- le varies unusually in size and form. The categorization rally at the digastric fossa of the mandible, continues of the anomalies of the digastric muscle has not been dorsally as the aponeurotic attachment fixed to the agreed. A variation in the form of the muscle belly, and body of the hyoid bone. the occurrence of the accessory muscle bundles laterally b) The lateral part of the anterior belly originates bilate- and bilaterally etc. are described. The anomaly of the rally on the lower margin of the body of the mandi- anterior belly of the digastric muscle is explained as a ble laterally from the digastric fossa, it follows dorso- phylogenetic reduction of the muscle tissue or as a medially and continues as the intermediate tendon result of an unusual development of ontogenetic mate- of the digastric muscle. rial. These anomalies are normally explained in relation We see branches of a submental artery on the right to the mechanism of the mandibular joint and the devel- side in the notch with an aponeurotic margin between opment of speech. the medial and lateral parts of the anterior belly (Fig. 2 a, 2 b). Part of the muscule bundle started with a thin ten- OBSERVATION don in the left digastric fossa, and ran dorsally right through the middle line and directed in the medial In our first findings (Fig. 1, Sch. 1) we introduce the marging of the right side of the anterior belly. duplication of the anterior belly of digastric muscle in a c) Most of these muscle bundles went behind the ven- 57-year old man with a well developed musculature. ter anterior to the intermediate tendon. The medial head of the anterior belly looks like the d) Some of these muscle bundles went in front of the classical original continuation of the anterior belly of venter anterior in the same way as the intermediate digastric muscle. The lateral head originates at the man- digastric tendon. dible ventrolaterally from the digastric fossa of the man- e) Other bundles originate from the bundles c), but dible, follows dorsolaterally and is fixed partially at the have become separated. They run dorsally left intermediate tendon of digastric muscle and partially at through the middle line to the hyoid bone medially the hyoid bone in the region of the fixation of stylohyoid from the end of the medial part of the left side muscle. anterior belly (Fig. 2 b). 58 Acta Univ. Palacki. Olomuc., Fac. Med. Fig. 1. A bilateral anomaly of the anterior belly of the digastric Scheme 2. A combined asymmetric anomaly of the anterior belly of muscle. the digastric muscle. 1 – anterior belly of digastric muscle: a – medial head, b – lateral head. 1 – anterior belly: a – medial part. b – lateral part. c – muscle bundles 2 – hyoid bone. 3 – intermediate tendon of digastric muscle with going from the left digastric fossa of mandible to the intermediate insertion of the lateral head of the anterior belly. 4 – stylohyoid tendon behind anterior belly. d – muscle bundles going in front of the muscle. 5 – submental artery and vein. anterior belly to the intermediate tendon. e – muscle bundles going to the aponeurosis above the hyoid bone. 2 – hyoid bone. 3 – intermedi- ate tendon of digastric, which insertion of the stylohyoid muscle. 4 – aponeurosis above the hyoid bone. 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. 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 aponeu- rosis above the hyoid bone. A – branch of submental artery. DISCUSSION The variations of this muscle are cited in the litera- ture since the first half of the 18 century (Winslow3, Holl4, Le Double5, Macalister6). The Czech author Žlábek1 widely studied the anoma- lies of the anterior belly of the digastric muscle from the Fig. 2 a. A combined asymmetric anomaly of the anterior belly of the phylogenetic and ontogenetic development points of digastric muscle. 1 – anterior belly of digastric muscle: a – medial part, view. He successfully identified variation from aberra- b – lateral part. 2 – hyoid bone. 3 – intermediate tendon of digastric tion. muscle. 4 – stylohyoid muscle. 5 – branch of submental artery. He separated these variations into atavistic and adap- tive expansions in medial and lateral direction. The Volume 142, 1999 59 atavistic expansion in the medial direction is characteri- REFERENCES zed by rectangular oblong form of the anterior belly. The author1 classified the adaptive expansions of the 1. Žlábek, K. (1932) O anomaliích předního bříška dvojbřišního anterior belly medially in anterior, posterior, mixed and svalu u člověka. Sb. Lékařský (Praha), 34 (38), 1–36. 2. Holibková, A., Machálek, L. (1998) A contribution to the anoma- combined types. lies of heterochtonic back muscles. Acta Univ. Palacki. Olomuc. In his study Žlábek1 did not find adaptions in the (Olomouc), Fac. Med., 141, 53–55. widening of the anterior belly laterally. 3. Winslow, J. B. (1732) Exposition anatomique de la structure du In the case of aberrations he mentioned that they corps humain. Paris. 4. Holl, M. (1916) Zur Phylogenese und Morphologie des vorderen are formed depending on the continuation of vessels Bauches des M. digastricus des Menschen. Sitzber. Akad. Wiss. and nerves. Math. – naturw. Kl. (Wien), Abt. III., Bd. 124, 125. In our first case that we described could be included 5. Le Double, A. F. (1897) Traité des variations du systeme mus- in the category of the adaptive widening of the muscle culaire de ¾ Homme. Libraire C. Reinwald, Paris. 1 6. Macalister, A. (1872) A Descriptive Catalogue of Muscular belly on the basis of the classification of Žlábek . How- Anomalies in Human Anatomy. Proceed. of the Roy. Irish. Acad. ever, this case was not found in his series. (Dublin), vol. 25. The second case that we described as a combined 7. Uslu, S. S., Atilla, S., Celik, H. H., Inal, E. (1995) An important bilaterally asymmetrical anomaly of the anterior belly of anatomic variation in head and neck region: anomaly of the anterior belly of the digastric muscle. Bul. Asoc. Anat. (Nancy), the digastric muscle. The anomaly occuring in the right (France), 79 (224), 39–41. side where the thin fissure with the aponeurotic margin 8. Sargon, M. F., Celik, H. H. (1994) An abnormal digastric muscle between medial and lateral muscle bundles and the with three bellies. Surg. Radiol. Anat. (Germany), 16 (2), piercing of a branch from the submental artery were 215–216. 1 9. Celik, H., Yilmaz, E., Atasever, A., Durgun, B., Taner, D. (1992) evident. Based on the classification of Žlábek we can Bilateral anatomical anomaly of anterior bellies of digastric mus- conclude this case to be an aberration of the right side cles. Kaibogaku Zasshi (Japan) 67 (5), 650–651. anterior belly of the digastric muscle. 10. Stockstil, J. W., Harn, S. D., Underhill, T. E. (1991) Clinical In other new studies authors pay attention to the implications of anomalous muscle insertion relative to jaw move- ment and mandibular dysfunction: the anterior belly of the digas- anomalies of the anterior belly of the digastric muscle tric muscle in a cadaver. J. Craniomandib. Disord. (United States) with respect to diagnostic methods – X-ray, CT, MR, 5 (1), 64–70. and surgery steps in the submandibular and submental 11. Sehirli, U., Cavdar, S. (1996) An accesssory mylohyoid muscle. regions (Uslu et al.7, Sargon et al.8, Celik et al.9) and also Surg.
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