An Anatomic Variant of the Ansa Cervicalis Precluding Its Use as a Donor Nerve

Abstract

Background: The ansa cervicalis is useful for cranial nerve repair, and may be harvested without apparent morbidity. Herein we report an unusual and surgically relevant anatomic variant of the ansa cervicalis. Methods: An adult male with left parotid adenoid cystic carcinoma underwent parotidectomy with upper-division facial nerve resection and planned interposition repair using the ansa cervicalis. The ipsilateral hypoglossal nerve was identified, together with a descending branch producing strap muscle contraction when stimulated. This presumed descendens hypoglossi was unusually large in caliber; further dissection revealed continuity with the vagus nerve. Results: Ansa cervicalis harvest was aborted when its separation from vagus nerve epineurium was not possible. The sural nerve was alternatively harvested. The patient awoke with left vocal fold palsy, which completely resolved within 3 months. Conclusion: Anatomic variants of the ansa cervicalis exist that may preclude graft harvest and place the vagus nerve at risk of inadvertent injury.