Anatomical study of the human ansa cervicalis nerve and its variations

With the expanding use of the ansa cervicalis nerve for laryngeal reinnervation procedures. So the aim of this work was to study the anatomical variations of ansa cervicalis in its roots, course and branching pattern. Twenty five Egyptian necks (50 sides) were dissected. The results showed that the ansa cervicalis (AC) consisted of two roots: superior and inferior roots. These two roots joined together to form a nerve loop. The superior root of AC originated from the hypoglossal nerve in 100%.The superior root of AC descended in front of the external carotid artery in 68% and in front of the internal carotid artery in 32%. The inferior root of AC was derived from the ventral rami of C2 and C3 in 84% and from C2 in 16%. There were four morphological forms of the loop of ansa cervicalis: IU-shaped loop in 84%. IIY-shaped loop in 8%. IIIdouble fused Y-shaped loop in 4%.VIdouble separate Y-shaped loop in 4%. The superior root of AC gave a branch to the superior belly of omohyoid in 96% and a branch to sternomastoid in 24% . The inferior root of AC gave a branch to inferior belly of omohyoid and a communicating branch to phrenic nerve in 4%. These anatomical variations of the ansa cervicalis can be used in surgical procedures such as reinnervation of the laryngeal muscles following the damage of recurrent laryngeal nerve and to avoid the iatrogenic injuries of this nerve during the surgical operations of the neck.