Anastomoses (Superficial Cervical Ansa) Between the Cervical Plexus and Peripheral Facial Nerve Branches: Implications for Regional Anesthesia in Carotid Endarterectomies - Anatomical Study.

Purpose: Sensory innervation in the carotid triangle involves the cervical plexus, cranial nerves, and the sympathetic trunk. This innervation also applies to skin incision, including various anatomical structures with potentially different innervation, such as the skin (dermatomes), the platysma (myotomes), and the superficial layer of the cervical fascia (fasciotomes), as well as retromandibular retractor insertion (co-innervation: V, VII). The aim of this anatomical study was to develop an injection technique for carotid endarterectomies to additionally block anastomoses between the transverse cervical nerve (TCN), the cervical branch VII (CB VII), and the marginal mandibular branch VII (MMB VII). These anastomoses are also termed superficial cervical ansa (SCA).

Materials and methods: Preparations (n=16) were performed on unembalmed donor cadavers (n=8). Subplatysmal injections (each using 5 mL of Alcian blue) were performed cranially within the carotid triangle between the anterior margin of the sternocleidomastoid muscle and the submandibular gland.

Results: Anastomoses between the TCN, CB VII, and MMB VII were stained in all preparations (n=16).

Conclusion: This anatomical study presents an ultrasound-guided subplatysmal SCA block to optimize, in addition to a cervical plexus block, the quality of anesthesia for carotid endarterectomies.