Neck Dissection (Selective Neck Dissection)

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Procedure Snapshot

• Indication: Elective neck dissection when occult metastasis risk >15–20%, or for limited nodal disease.¹
• Expected duration: 2–4 hours depending on levels included.¹
• Special instruments: Nerve monitor, bipolar cautery, fine dissectors, self-retaining retractors.¹

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Step Workflow

(Based on Supraomohyoid SND Levels I–III; lateral SND adds Level IV; posterolateral adds Level V.)

1. Exposure & Incision
   • Supine, head turned away; no muscle relaxants.¹
   • Transverse cervical incision placed slightly lower than modified radical ND for better Level III/IV access.¹
   • Elevate subplatysmal flaps to mandible superiorly and clavicle inferiorly.¹
2. Identify Key Landmarks
   • External jugular vein (EJV), greater auricular nerve over SCM.¹
   • Submandibular gland superiorly; omohyoid muscle anteriorly.¹
3. Level Ia Dissection (Submental Triangle)
   • Resect fat/lymphatics between digastric bellies → hyoid.¹
   • Deep plane = mylohyoid.¹
4. Level Ib Dissection (Submandibular Triangle)
   • Incise gland capsule → elevate subcapsularly to protect marginal mandibular nerve.¹
   • Identify facial artery/vein; ligate near gland.¹
   • Identify lingual nerve, submandibular duct, hypoglossal nerve (XII).¹
   • Divide submandibular duct and ganglion.¹
5. Level IIa: Identifying Hypoglossal & IJV
   • Divide EJV to improve access.¹
   • Expose full posterior belly of digastric.¹
   • Identify hypoglossal nerve (XII) crossing ECA; follow posteriorly to IJV.¹
   • Locate accessory nerve (XI) lateral/behind IJV.¹
6. Level IIb Dissection (Posterior to XI)
   • Retract SCM posteriorly; create tunnel behind IJV.¹
   • Free accessory nerve; mobilize fat pad under XI.¹
7. Level II–III Dissection (Deep Jugular Chain)
   • Strip lymphatic tissue from deep muscles, preserving cervical plexus branches.¹
   • Expose carotid sheath (CCA, ICA, IJV, vagus).¹
   • Strip specimen from carotid sheath and ansa cervicalis.¹
   • Use horizontal strokes with a #10 Scalpel to take lymph nodes off of IJV while holding the specimen anteriomedially
8. Level IV (If Lateral SND)
   • Continue dissection inferior to omohyoid.¹
   • Identify transverse cervical vessels.¹
   • Left side: high vigilance for thoracic duct injury (chyle leak risk).¹
9. Completion
   • Strip specimen off strap muscles and deliver en bloc.¹
   • Irrigate, Valsalva, drain placement (10fr round).¹

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Key Pimp Questions

• Q: What are the boundaries of Level II?
  A: Skull base → hyoid; between stylohyoid (anterior) and posterior SCM (posterior).¹

• Q: What divides Level IIa from IIb?
  A: Accessory nerve (XI).¹

• Q: Where does the hypoglossal nerve (XII) run?
  A: Crosses external carotid artery, then runs along anterior surface of IJV.¹

• Q: Which nerve is at risk in Level Ib?
  A: Marginal mandibular branch of facial nerve.¹

• Q: What is the highest-risk site for chyle leak?
  A: Left Level IV (thoracic duct).¹

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Critical Anatomy

• Nerves:
  • Marginal mandibular (superficial to facial vessels)¹
  • Hypoglossal (XII) — deep to submandibular gland, leads to IJV¹
  • Accessory nerve (XI) — traverses Level II, divides IIa/IIb¹
  • Lingual nerve — superior to submandibular duct¹
• Vessels:
  • Facial artery & vein (Level Ib)¹
  • Occipital artery branch tethering XII¹
  • IJV and tributaries¹
  • Thoracic duct (left Level IV)¹
• Muscles & Planes:
  • Digastric posterior belly — major landmark to Level II¹
  • Omohyoid — separates Levels III & IV¹
  • Subplatysmal flap plane — essential for exposure¹

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Informed Consent Highlights

Risk	Incidence / Concern	Notes
Accessory nerve injury (XI)	Variable, up to several %¹	Shoulder dysfunction
Marginal mandibular nerve weakness	Risk in Level Ib¹	Lower lip asymmetry
Hypoglossal nerve injury (XII)	Rare¹	Tongue deviation, dysarthria
Chyle leak	<1% but serious¹	Highest risk left Level IV
Hematoma	~1–2%¹	Airway emergency
Seroma	Common if large flap¹	May need aspiration
Sensory loss	Frequent due to greater auricular nerve stretch¹	Usually temporary

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Post-op Considerations

• Drain: Maintain suction until <50 ml/24 h.¹
• Chyle leak check: Milky output → pressure dressing + diet modification; major leaks require OR.¹
• Nerve checks:
  • Shoulder shrug (XI),
  • Tongue deviation (XII),
  • Lower lip (marginal mandibular).¹
• Airway: Monitor for hematoma — emergent decompression if suspected.¹
• Pain & neck mobility: Gentle ROM exercises after drain removal.¹

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Clinical Pearls

• Divide facial vessels near the gland, not near mandible → protects marginal mandibular nerve.¹
• Hypoglossal nerve is more superficial than expected; follow it posteriorly to IJV.¹
• Creating a tunnel behind the IJV accelerates Level IIb dissection.¹
• Use subcapsular plane when dissecting submandibular gland.¹
• Level IIb dissection increases XI morbidity — include only when oncologically necessary.¹

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Quick Reference Table

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Quick-Reference Cards

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References

1. Fagan J. Selective Neck Dissection Operative Technique. Open Access Atlas of Otolaryngology, Head & Neck Operative Surgery.
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