Nerve
Ansa cervicalis
Cervical nerve loop supplying three strap muscles
High-yield
Sternohyoid, sternothyroid and both omohyoid bellies receive ansa branches. C1 fibers reach thyrohyoid and geniohyoid through separate branches accompanying CN XII.
Overview
The ansa cervicalis links upper cervical motor fibers near the carotid sheath. Its superior root usually carries C1 fibers that briefly accompany CN XII; its inferior root usually contributes C2 and C3. Branches then reach the infrahyoid muscles.
Reference facts
- Origin
- Superior root usually from C1 traveling briefly with CN XII; inferior root usually from C2–C3
- Root value
- Usually C1–C3
- Course
- Roots descend near the anterior carotid sheath and form a loop; its height and relationship to the internal jugular vein vary
- Motor
- Sternohyoid, sternothyroid and both bellies of omohyoid
- Sensory
- No cutaneous sensory territory; conventionally described as a motor loop
Clinical correlation
Ansa branches can serve as donor nerves in selected laryngeal reinnervation operations. Their usefulness depends on the recipient muscle and the individual nerve anatomy.
Frequently asked questions
What are the roots of the ansa cervicalis?
Usually C1–C3.
What muscles does the ansa cervicalis supply?
The ansa cervicalis supplies the sternohyoid, sternothyroid and both bellies of omohyoid.
What is the sensory distribution of the ansa cervicalis?
No cutaneous sensory territory; conventionally described as a motor loop.
What is the course of the ansa cervicalis?
Roots descend near the anterior carotid sheath and form a loop; its height and relationship to the internal jugular vein vary.