Examqo › Examqo library › Otolaryngology – Head and Neck Surgery › Head and neck oncology · IMLE

Neck dissection and neck levels

The neck is divided into 6 levels (and VII in the upper mediastinum) by fixed anatomical boundaries; the primary tumour decides which levels are at risk, and selective dissection removes only those — while radical dissection removes all levels I to V with nerve XI, the internal jugular vein and the sternocleidomastoid muscle.

לקריאה בעברית

Why it matters in the exam

The boundaries are asked in almost every exam: level I — below the mandible (Ia submental, Ib submandibular); level II — from the skull base to the lower border of the hyoid bone (IIa in front of nerve XI, IIb behind it); level III — from the hyoid to the lower border of the cricoid cartilage; level IV — from the cricoid to the clavicle; level V — the posterior triangle, behind the sternocleidomastoid (Va above the cricoid, Vb below it); level VI — the central compartment, from the hyoid to the sternum and between the carotid arteries. The upper boundary of level III is therefore the hyoid bone.

Types: radical — levels I to V with nerve XI, the internal jugular vein and the sternocleidomastoid; modified radical — preserves at least one of the three structures; selective — supraomohyoid (I to III) for the oral cavity, lateral (II to IV) for the larynx and pharynx, posterolateral (II to V with suboccipital and retroauricular nodes) for posterior scalp skin, and central (VI) for thyroid cancer; extended — when further structures are removed. In cutaneous melanoma, the MSLT-II trial showed that completion dissection following a positive sentinel node gives better regional control and staging data, without a melanoma-specific survival benefit.

Complications: injury to nerve XI with a "dropped shoulder" and pain (shoulder syndrome); injury to the facial nerve's marginal mandibular branch, the hypoglossal nerve and the phrenic nerve; chyle leak — mainly on the left, from the thoracic duct at level IV. A low-output leak (less than 500 mL per day) is treated conservatively: a medium-chain triglyceride diet, a pressure dressing and sometimes octreotide; a high-output leak (over 1000 mL per day) or a persistent one is treated by surgical duct ligation or embolisation. Ligation of both internal jugular veins causes severe facial oedema.

Key points

• 6 levels by fixed boundaries.
• II to the hyoid, III to the cricoid, IV to the clavicle.
• Oral cavity — I to III; larynx — II to IV.
• Radical: XI, jugular vein, sternocleidomastoid.
• Left-sided chyle leak — by volume.

Summary table

In the full version for subscribers

• A simple algorithm
• Memory aid
• Exam traps
• 5 review cards
• Enough for IMLE

The full version is open to subscribers of: ENT and head and neck surgery, Medical licensing exam (IMLE), Oncology, General surgery.

Subscriber? Read the full topic Plans and prices 25 free questions

Sources

• AAO-HNS / American Head and Neck Society: Neck dissection classification update (Robbins et al.), 2008 — Levels, sublevels and nomenclature
• Cummings Otolaryngology: Head and Neck Surgery, 7th edition (2021) — Neck dissection
• Faries MB et al. MSLT-II: Completion dissection or observation for sentinel-node metastasis in melanoma (NEJM), 2017 — Main results

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.