[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Ansa cervicalis [Nervous system](https://durgical.com/en/anatomy/system/nervous-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Ansa cervicalis The ansa cervicalis is a nerve loop on the side of the neck that supplies the thin strap muscles below the [hyoid bone](https://durgical.com/en/anatomy/hyoid-bone/). [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=ansa_cervicalis&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A nerve loop (C1-C3) on the carotid sheath. ## What it does Supplies the strap muscles below the hyoid. ## Key points - Superior root: C1 fibres that travel with the hypoglossal nerve and leave it as it curves around the [occipital artery](https://durgical.com/en/anatomy/occipital-artery/); inferior root: C2–C3 from the cervical plexus; they join on the carotid sheath - Supplies the infrahyoid strap muscles except the [thyrohyoid](https://durgical.com/en/anatomy/thyrohyoid-muscle/): C1 fibres reach the thyrohyoid and [geniohyoid](https://durgical.com/en/anatomy/geniohyoid-muscle/) directly along the hypoglossal nerve, not through the loop - Its branches enter the strap muscles low down, so when the straps must be cut in thyroid surgery they are divided in their upper part to keep their nerve supply - Ansa cervicalis to [recurrent laryngeal nerve](https://durgical.com/en/anatomy/recurrent-laryngeal-nerve/) transfer reinnervates a paralysed [vocal fold](https://durgical.com/en/anatomy/vocal-fold/): it restores bulk and tone, not movement, and improves the voice ## Key facts **Roots** C1–C3 (superior root with XII, inferior root C2–C3) **Moves** [Sternohyoid](https://durgical.com/en/anatomy/sternohyoid-muscle/), [sternothyroid](https://durgical.com/en/anatomy/sternothyroid-muscle/), omohyoid **Feeling from** None ## Relations **Course** The superior root runs down on the front of the [internal carotid artery](https://durgical.com/en/anatomy/internal-carotid-artery/) and [common carotid artery](https://durgical.com/en/anatomy/common-carotid-artery/); the inferior root winds around the [internal jugular vein](https://durgical.com/en/anatomy/internal-jugular-vein/) to meet it, forming a loop at a variable level, often near the [cricoid cartilage](https://durgical.com/en/anatomy/cricoid-cartilage/) (texts vary) **Above** [Hypoglossal nerve (XII)](https://durgical.com/en/anatomy/hypoglossal-nerve/), which the superior root leaves below the posterior belly of the [digastric](https://durgical.com/en/anatomy/anterior-belly-of-digastric-muscle/) **Superficial** [Sternocleidomastoid](https://durgical.com/en/anatomy/sternocleidomastoid-muscle/), with the [omohyoid](https://durgical.com/en/anatomy/omohyoid-muscle/) crossing in front lower down **Deep** [Carotid sheath](https://durgical.com/en/anatomy/carotid-sheath/) with the carotid arteries and internal jugular vein; the loop lies on or within its front wall ## How to find it In neck dissection it is found on the front of the carotid sheath under the sternocleidomastoid. Following the superior root upward leads to the hypoglossal nerve, a safe way to find and protect it. Its branches enter the lateral borders of the sternohyoid, sternothyroid and omohyoid. ## On imaging Too thin for CT or routine MRI. High-frequency ultrasound may show it as a small dark nerve loop on the front of the carotid sheath, over the internal jugular vein and under the sternocleidomastoid; in practice it is found at surgery. On CT and MRI the carotid sheath is the landmark for its position. Long-standing loss of its supply leaves thin infrahyoid muscles. ## Clinical notes - Cutting it during neck dissection or carotid endarterectomy usually causes no obvious deficit, so it can be sacrificed when needed - It can also serve as a donor nerve to reinnervate the [tongue](https://durgical.com/en/anatomy/tongue/) after hypoglossal nerve injury - In carotid endarterectomy with a high bifurcation, the superior root can be cut so the hypoglossal nerve can be lifted out of the field without stretching it ## Anatomical variants - The superior root may seem to come from the [vagus nerve](https://durgical.com/en/anatomy/vagus-nerve/), and the inferior root passes medial rather than lateral to the internal jugular vein in some people - The height of the loop varies; a high loop lies close to the [carotid bifurcation](https://durgical.com/en/anatomy/carotid-bifurcation/) ## Test yourself Think of the answer, then tap the question to see it. ## What are the roots of the ansa cervicalis? Superior root: C1 fibres travelling with the hypoglossal nerve; inferior root: C2–C3 from the cervical plexus; they join on the carotid sheath. ## Which infrahyoid muscle is not supplied through the ansa cervicalis? The thyrohyoid, which gets C1 fibres directly along the hypoglossal nerve. ## Why are the strap muscles divided in their upper part when they must be cut in thyroid surgery? Branches of the ansa cervicalis enter them low down, so a high cut keeps their nerve supply. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/ansa-cervicalis/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** ansa cervicalis TA2 6376 **Official Spanish (DeCS)** Asa cervical **English (TA2)** Ansa cervicalis **Also called** ansa nervi hypoglossi ## Related - [Sternohyoid](https://durgical.com/en/anatomy/sternohyoid-muscle/) - [Sternothyroid](https://durgical.com/en/anatomy/sternothyroid-muscle/) - [Omohyoid](https://durgical.com/en/anatomy/omohyoid-muscle/) Sources: Terminologia Anatomica (TA2); [Anatomy, Head and Neck: Anterior Cervical Region](https://www.ncbi.nlm.nih.gov/books/NBK557475/); [Anatomy, Head and Neck: Cervical Nerves](https://www.ncbi.nlm.nih.gov/books/NBK538136/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/ansa-cervicalis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/ansa-cervicalis/