Carotid sheath anatomy during internal jugular cannulation — FRCA Primary MCQ

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HardAnatomyCarotid sheath anatomy during internal jugular cannulationFRCA Primary

A left internal jugular central venous catheter is inserted under ultrasound. The needle is advanced too medially and posteriorly in the lower neck. Which structure lies within the carotid sheath with the internal jugular vein and carotid artery?

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Correct answer: B — Phrenic nerve

The vagus nerve lies within the carotid sheath, typically posteriorly between the internal jugular vein and carotid artery. The sympathetic trunk is posterior to the carotid sheath, not within it. The phrenic nerve runs on the anterior scalene muscle. Understanding sheath anatomy helps avoid neurological injury during central venous access.

Reference: RCoA Primary FRCA Syllabus 2026; Anatomy for Anaesthetists