Paper Title
Superior and Inferior Roots of Ansa Cervicalis Arising From Vagus- A Rare Anatomical Variation

Abstract
Ansa cervicalis is a thin loop of nerve situated on the anterior wall of carotid sheath in the anterior triangle of the neck. It is made up of superior and inferior roots derived from the ventral rami of upper three cervical spinal nerves. However, variation in its origin from the vagus is not reported in the literature. During routine cadaveric dissection at Melaka Manipal Medical College (Manipal Campus) for first year medical students, we observed a variation in the formation and distribution of ansa cervicalis on the left side of the neck in about 65- year- old male cadaver. It was observed that the left hypoglossal nerve was giving a branch which was joining the left vagus deep to posterior belly of digastric muscle. These fibres in turn branched off from the vagus to form the inferior root (descedens hypoglossi) of ansa cervicalis. The fibres from C2 and C3 spinal nerves pierced the prevertebral fascia to join the left vagus directly in the neck. These fibres arising from vagus continued as inferior root of ansa cervicalis and joined the superior root to form a nerve loop in front of the carotid sheath. The branches arising from this variant nerve loop were supplying the infrahyoid muscles. On the right side of the neck, the formation and distribution of ansa cervicalis was normal. Recent studies have shown that ansa cervicalis is used for nerve grafting and reconstruction surgeries. Paralysis of infrahyoid muscles can lead to loss of modulation of pitch in professional singers due to loss of support provided by these muscles to the laryngeal cartilages during the movements of vocal cords. In case of unilateral vocal cord paralysis, the re-innervation of laryngeal muscles by nerve to nerve anastomosis of recurrent laryngeal nerve and ansa cervicalis has shown significant results. The thorough knowledge of anatomical variations of ansa cervicalis is of great clinical importance while performing neural blocks for regional anaesthesia and nerve grafts in order to avoid the risk of damaging the ansa cervicalis and vasculatures closely associated with it in the neck. Key words- Ansa cervicalis, carotid sheath, infrahyoid muscles, nerve grafting