An anomalous digastric muscle in the carotid sheath: a case report with its embryological perspective and clinical relevance

Although infrahyoid muscles show considerable variations in their development, existence of an anomalous digastric muscle in the neck was seldom reported. During dissection of triangles of the neck for medical undergraduate students, we came across an anomalous digastric muscle in the carotid sheath of left side of neck. It was observed in a middle-aged cadaver at College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman. Digastric muscle was located within the carotid sheath between the common and internal carotid arteries and internal jugular vein. It had two bellies; cranial belly and caudal belly which were connected by an intermediate tendon. The cranial belly of the muscle was attached to the petrous part of the temporal bone. The caudal belly extended into the superior mediastinum and merged with the connective tissue around the left brachiocephalic vein. In addition, the caudal belly of the muscle was connected to the lateral margin of the sternothyroid by few muscle fasciculi. The total length of muscle was 15.5 cm and the width of cranial belly, intermediate tendon and caudal belly was found to be 5 mm, 2 mm and 4 mm, respectively. The anomalous muscle reported in the present case might have formed by the abnormal splitting, growth and/or differentiation of lingual-infrahyoid-diaphragmatic band. Due to its close relation, the anomalous muscle may cause compression of vascular structures in the carotid sheath and it may cause confusion during diagnostic imaging of neck soft tissues. The knowledge of reported variation is clinically important while evaluating the compression of internal jugular vein in patients with idiopathic intracranial hypertension and during the surgical repair of carotid arteries.D. Retraint, Z. Quadir, W. Xu, L. Waltz, M. Ferry, “Microstructural investigation of roll bonded nanocrystalline stainless steel sheets”, The 16th International Conference on the Textures of Materials (ICOTOM 16), Bombay (India), 12-17 December 2011.

Author(s): Srinivasa Rao Sirasanagandla

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