During carotid endarterectomy, fine nerve loops are seen embedded within the wall of the carotid sheath, crossing anterior to the internal jugular vein. These loops constitute which structure?

• A Phrenic nerve
• B Ansa cervicalis ✓
• C Sympathetic trunk
• D Hypoglossal nerve

Explanation

The ansa cervicalis, formed by roots from C1, C2 and C3, classically lies within the carotid sheath, its loop draped over the anterior surface of the internal jugular vein, before giving branches to the infrahyoid strap muscles except thyrohyoid. The hypoglossal nerve runs outside the sheath crossing the carotid bifurcation, the sympathetic trunk lies posterior to the sheath within the prevertebral fascia, and the phrenic nerve is on scalenus anterior. Surgeons use the ansa as a graft donor and a landmark.

Reference: Gray's Anatomy for Students, 4th ed.

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Written and medically reviewed by the StethoPrep medical team.