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Variations of the Anterior Belly of the Digastric Muscle M

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Variations of the Anterior Belly of the Digastric Muscle M ARA$TIRMALAR (Research Reports) VARIATIONS OF THE ANTERIOR BELLY OF THE DIGASTRIC MUSCLE M. digastricus'un venter anterior'unun varyasyonlan Erdogan UNUR1, Nihat EKiNCt2, Harun 'CTLGER1,Kenan AYCAN 3 Abstract dzet Purpose: To investigate the variations of anterior belly of Amai;: Muskulus (M) digastricus 'un on karmna ail digastric muscle. varyasyonlan belirlemek. Material and method: Fifty human cadavers were Gerei; ve yontem: Son /0 yd i<;erisinde (1987-1997) examined using gross dissection technique. These anatomi laboratuvarmda demostrasyon ir;ink:ullamlan 5() cadavers were used for medical student demonstration in kadavra diseksiyon yontemiyle incelendi an anatomy laboratory during the fast decade. Bulgular: Diseksiyon yapdan kadavralann iki tanesinde Results: Anterior belly variation was fou nd in two (%4) m. digastricus 'un venter anterior 'unda va,yasyon cadavers (4%). In both muscles, some of the fibrils, tesbil edildi. Varyasyon gdzlenen iki kasa ait venter separated from the anterior bellies, united in the median anteriordan bazi lifter aynl1p orta hatta birle$erek hyoid line. Also a few of the these fibrils inserted to the corpus kemige ve r;eneucuna tutunmakta idi. Venter anterior 'dan of the hyoid bone. The united muscle fibrils inserted to aynlan bu lifter ayn bir kas goriiniimii vermekteydi. symphysis menti by a thin tendon. The separated muscle So11ur;: Hiyoid iistii bolgesine yapilacak cerrahi fi brils appeared as a different muscle. miidahelelerde bu varyasyonlarzn bilinmesi olumlu katk1 Conclusion: Kenowledge of any variation in suprahyo id saglayacaktzr. region would be helpful during surgical operations. Key Words: Muscle, Variation Anahtar Kelimeler: Kas, Varyasyon During a gross anatomical dissection course , it is on the inner side of the inferior border of the possible to observe some variations in muscles ( l ,2). mandible and passes posteriorly and inferiorly. The These variations could be in origo , insertio or ratio of variation in this muscle is more common in morpho logy. The variation ratio in some muscles the anterior belly than the posterior (6 , 7). could also be more prominent than others, such as the digastric muscle (m. digastricus) and abductor MATERIAL AND METHOD pollici~ muscle. There are reports emphasizinf that the digastric muscle shows some variations (3-5). In this study, the anterior belly (venter anterior) of According to classical texts, the digastric muscle is digastric muscle was investigated using classical found in the suprahyoid regio and consists of two dissection technique in 50 human cadavers which bellies , anterior and posterior, united near the hyoid where used for medical student demonstration bone by an intermediate tendon. The posterior belly during the last decade. rises from the incissura mastoidea of temporal bone and passes anteriorly and inferiorly . The anterior RESULTS belly rises from fossa digastricus of mandible . It lies It was found that two of the 50 cadaver s (4%) have digastric muscle variations. These variations were in Erciyes Tlp Dergisi Editorliigii38039 KAYSERl Anatomi. Y.Dor;.Dr.1, Dor;.Dr.2, ProfDr.1• the anterior belly of the digastr ic muscles. The anterior belly of both muscles showed a similar Gelil tarihi : I 8 Aralzk I 998 structure. In these cases, a great number of fibrils Erciyes Tip Dergisi (Erciyes Medical Journal) 21 (4) 192-194, 1999 192 Variations of the anterior belly of the digastric muscle separated from the anterior bellies of the digastric DISCUSSION muscles. While some of the separated fibrils united in the median line, some of them inserted to the The variations of the anterior belly of the digastric corpus of the hyoid bone (Figure 1). The united muscle have been reported in classical texts (6,7). muscle fibrils inserted to symphysis menti by a thin However, there is no information about the variation tendon. There were also a few muscle fibrils along incidence of this muscle. the tendon. These separated muscle fibrils appeared as a different muscle, and there was no connection According to Kopsch (6), the digastric muscle could between these muscle fibrils and mylohyoid muscle. have two anterior bellies, one of which arises from the angle of mandible. It was also reported that some of the fibrils of the anterior belly of the digastric muscle cross over the midline and is called the accessory anterior belly of the digastric muscle. These fibrils may support functionall y the mylohyoid muscle (8). These variations were usual ly in both sides and rarely in one side (9). Larrson and Lufkin (10) examined 75 patients using computerised tomography and magnet ic resonance imaging techniques and found two anterior belly variations (2.33%). They reported that there was no pathologic finding in this area. 1t was shown that interaction and fusion of fibrils between muscles could not be distingu ished using Figure 1. This graph illustratesthe anatomical variation of radiologic techniques (3), and this kind of variation the digastric muscle. can easily be confused with a patho logical cond ition a: Variation of the anterior belly of the digastric muscle (4). b: Anterior belly of the digastric muscle c: Mylohyoid muscle Previous reports and the findings in this study suggest that knowledge of these kinds of variations may be helpful during surgical procedure in this region. REFERENCES I. Cire/i E, Giinbay T Angu/us mandibula'dan ba$layan extra bir kas. Ege Oniversitesi Tip Fakiiltesi Mecmuas11971; JO: 327-330. 2. Aycan K, Olger H, Unur E. Musculus mentohyoideus 'un morfolojik incelenmesi. Erciyes Tip Dergisi 1988; JO: 509-5 I 1. 3. Akkm SM, Ozku$ K. M digastricus 'un venter anterior varyasyonlanmn degerlendirilmesi. c;. 0. Tip Fak. Dergisi 1992; 17: 249-255. Figure 2. Anterior belly variation of the digastric muscle 4. Sargon MF, C::elikHH An Abnormal digastric 193 Erciyes Tip Dergisi (Erciyes Medical Journal) 21 (4) 192-/94, /999 Unur, Ekinci, Viger, Aycan muscle with three bellies. Surg Radio! Anat 7. Goss CM Gray's Anatomy (29th ed). lea and 1994; 16: 215-16 Febiger, Philadelphia 1973, p 397. 5. Uslu SS, Atilla S, <;elik HH, Ina/ E. An 8. Mincha, H. Anatomical Anomaly of Human abnormal anatomic variation in head and neck Digastric Muscles . Acta Anatomica 1989 region: Anomaly of the anterior belly of the l 34:263-264. digastric muscle. Bulletin de 1 Association des 9. Traini, M Bilateral accessor digastric muscles. Anatomistes 1995; 244: 39-41. AnatC/in 1983; 5: 199-200. 6. Kopsch FR. Lehrbuch und atlas der anatomie JO. Larsson SG, Lufkin RB. Anomalies of digastric des menschen. (Band 1) Georg Thieme Verlag muscles : CT and MR demostration. J Comput Leipzig 1940, p 528. Assist Tomogr 1987 l I: 422-425. Erciyes Tip Dergisi (Erciyes Medical Journal) 21 (4) 192-194. 1999 194 .
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