Neck Dissection Basics
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Direct answer
Radical neck dissection, described by Crile in 1906, removes all five lateral nodal levels (I to V) en bloc with the sternocleidomastoid muscle, the internal jugular vein and the spinal accessory nerve. The modified radical neck dissection clears the same nodes while preserving one or more of those three structures, and a selective neck dissection clears only the levels at genuine risk from a particular tumour. Level VI, the central compartment, is separate from the classical lateral dissections. For oral cavity cancer, the supraomohyoid dissection (levels I to III) is the standard operation for the clinically negative neck, while palpable, multiple or bulky nodes demand modified radical or radical clearance.
What you must remember
- Level map: I submental and submandibular; II upper jugular from skull base to hyoid, subdivided by the spinal accessory nerve into IIA and IIB; III hyoid to cricoid; IV cricoid to clavicle; V posterior triangle between sternocleidomastoid and trapezius; VI central compartment with pretracheal, paratracheal and Delphian nodes.
- The three classical operations: radical (Crile) sacrifices sternocleidomastoid, internal jugular vein and accessory nerve; modified radical (popularised by Bocca) preserves at least one of them; selective clears only the named levels at risk — supraomohyoid I-III for oral cavity, lateral II-IV for oropharynx, anterior VI for thyroid.
- Drainage rules for oral sites: oral tongue to levels I-III with the tip preferring III; floor of mouth and lower lip to level I; tongue base to II-IV with genuine contralateral risk; midline structures drain to both sides.
- Elective dissection logic: a clinically negative (N0) neck carries occult metastasis risk above roughly 15-20 percent in T2 tongue and floor-of-mouth cancers, justifying elective supraomohyoid clearance.
- Shoulder syndrome: accessory nerve sacrifice gives a drooping, laterally protruded scapula, abduction limited beyond about 90 degrees and chronic pain — the strongest argument for nerve-preserving modified radical surgery.
- Complications checklist: haemorrhage and air embolism from jugular injury, chyle leak (classically left, from the thoracic duct), marginal mandibular and hypoglossal nerve injury, Horner syndrome, wound infection, flap necrosis and the catastrophic carotid blowout.
How the decision plays out at the bedside
Picture a 52-year-old with a 3 cm ulcerative squamous carcinoma of the lateral tongue and a neck that feels normal. The tumour is staged T2N0, and the hidden question is the neck. Occult risk for this site sits well above the threshold, so the plan is composite resection with elective supraomohyoid dissection. If preoperative imaging had shown a single mobile level II node, the operation upgrades to modified radical — nodes cleared as in Crile, but the accessory nerve, jugular vein and sternocleidomastoid preserved because oncologically safe clearance permits it. A matted, fixed nodal mass encasing the vein forces the radical operation, possibly with extension to level VI if the tumour crosses the midline. During any of these, the marginal mandibular branch is protected by ligating the common facial vein and reflecting the flap superiorly over it — the classical Hayes Martin manoeuvre. On the table, clear chyle-stained fluid pooling in the lower left neck means the thoracic duct has been nicked: recognise it, oversew or clip, and expect conservative management with drainage and medium-chain triglyceride feeding to settle most leaks.
How the exam frames it
Indian university and viva examiners love three things here. First, which nerve subdivides level II — the spinal accessory nerve, and IIB (posterior to it) matters because tongue cancer spreads there rarely, which is the rationale some surgeons use to skip it. Second, why level VI is not part of a radical neck dissection — the radical operation predates the level system and covers only the lateral levels I-V; the central compartment is a separate anterior compartment dissection, largely a thyroid territory. Third, the chyle leak question: milky drain output on the table or on postoperative day one to three, sent for triglyceride estimation, managed by drainage with suction, medium-chain triglyceride diet and rarely re-exploration. Candidates who say "remove everything in the neck" for the radical operation without naming the three sacrificed structures routinely lose the mark.
Frequently asked questions
What exactly is removed in a radical neck dissection?
All lymphatic levels I to V along with the sternocleidomastoid muscle, internal jugular vein and spinal accessory nerve — nodes plus the three classical non-lymphatic sacrifices.
How does modified radical neck dissection differ?
The same nodal levels I-V are cleared, but one or more of the sternocleidomastoid, internal jugular vein or accessory nerve are preserved, chosen on the basis of nodal extent.
Which levels form the supraomohyoid dissection and when is it used?
Levels I, II and III, used as elective treatment of the clinically negative neck in oral cavity carcinoma, where occult spread follows this drainage pattern.
What is shoulder syndrome?
The disability following spinal accessory nerve sacrifice — scapular drooping, weak abduction beyond about 90 degrees and chronic shoulder pain — prevented by nerve preservation.
Why is a chyle leak commoner after left-sided dissection?
The thoracic duct enters the venous system at the junction of the left internal jugular and subclavian veins, so the left lower neck is where duct injury occurs.