Neck Dissection

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  • The term radical Neck Dissection only applies to the original neck dissection as described by Crile (level I–V with sacrifice of sternocleidomastoid muscle, spinal accessory nerve, internal jugular vein) [1]
  • All other neck dissections are selective and best described by the levels of lymph nodes resected and which vital structures have been sacrificed
  • Avoid using other terms such as modified radical, functional, comprehensive, supra-omohyoid, and extended as they are open to interpretation
  • Aim to preserve as many vital structures as possible - only sacrifice if invaded by tumour

Decision Making[edit]

Elective neck dissection - a staging procedure performed in cN0

  • 25-30% of patients with clinical/radiological N0 squamous cell carcinoma of the floor of mouth/tongue will have micrometastasis
  • Evidence now confirms survival advantage of elective neck dissection vs 'watch and wait' approach [2] [3] ¡Nice Guidelines!
  • Other justifications:
    • Access to the neck is also often required for microvascular reconstruction
    • Allows for accurate pathological staging, thus facilitating the decision for adjuvant radiotherapy
  • Despite above benefits, a "watch and wait" approach may be acceptable for patients wishing to avoid a neck dissection or in those who are not fit enough for major surgery
  • Elective neck dissections should harvest levels I-IV
    • Level IIb only needs to be included in large, posterior tumours as incidence of spread to this level is very low
    • Level V not included as incidence of spread in N0 neck is very low (1-3%)
  • Alternatives to an elective neck dissection:
  1. Watch and wait approach
  2. Sentinel node biopsy

Therapeutic neck dissection - performed in clinically or radiologically N+ disease

  • Aim is to preserve as many vital structures as possible
  • If tumour invades levels I-IV, sternocleidomastoid, internal jugular vein and spinal accessory nerve - they must all be taken and the neck dissection is said to be "radicalised"

Surgical Anatomy[edit]

Nodal Levels[edit]

Source = K Harish[4]

Level I

Superior Boundary Inferior Boundary Anterior Boundary Posterior Boundary
Body of mandible + mylohyoid Inferior border of hyoid bone Anterior belly of contralateral digastric muscle Posterior border of the submandibular gland
  • Level I is subdivided into:
  1. Level Ia: submental triangle - bound by the anterior bellies of the digastric muscles and the hyoid bone
  2. Level Ib: submandibular triangle - between the anterior and posterior bellies of digastric with body of mandible as superior boundary

Level II

Superior Boundary Inferior Boundary Anterior Boundary Posterior Boundary
Base of the skull at the jugular fossa Inferior border of hyoid bone Posterior border of the submandibular gland Posterior border of sternocleidomastoid
  • The accessory nerve (CNXI) traverses level II obliquely and subdivides it into:
  1. Level IIa - anterior to CNXI
  2. Level IIb - behind CNXI

Level III

Superior Boundary Inferior Boundary Anterior Boundary Posterior Boundary
Inferior border of hyoid bone Inferior border of cricoid cartilage Sternohyoid muscle Posterior border of sternocleidomastoid

Level IV

Superior Boundary Inferior Boundary Anterior Boundary Posterior Boundary
Inferior border of cricoid cartilage Clavicle Sternohyoid muscle Posterior border of sternocleidomastoid

Level V

Superior Boundary Inferior Boundary Anterior Boundary Posterior Boundary
Mastoid tip Clavicle Posterior border of sternocleidomastoid Trapezius muscle
  • Subdivided by a horizontal line drawn from the inferior border of the cricoid cartilage into:
  1. Level Va - superior to the line
  2. Level Vb - inferior to the line

Level VI

This is the anterior, or central, compartment of the neck. It is bound laterally by the carotid arteries, superiorly by the hyoid bone, and inferiorly by the supra-sternal notch.


Consent[edit]

Risks[edit]

Altered sensation to skin of neck and ear, neck stiffness, haematoma, chyle leak, injury to accessory nerve (weakness to shoulder muscles), injury to hypoglossal nerve (weakness to tongue movement affecting speech and swallow), injury to marginal mandibular nerve (lower lip weakness/asymmetrical smile), injury to lingual nerve (tongue sensation), risks of major surgery (chest infection, wound infection, thrombosis, pulmonary embolism, stress ulcer, death)

Alternatives[edit]

For N0 neck:

  1. Watch and wait
  2. Sentinal Node Biopsy

For N+ neck:

  • Physical status/extent of disease/patient wish may require neck dissection to be avoided
  • Radical radiotherapy is an option in head and neck cancer but oral cavity cancers do well with this treatment option [5]

Surgical Instruments[edit]

Major neck surgery surgical kit
Scalpels (#10, #15)
Monopolar
Harmonic
Skin hooks
Lone star

Anaesthesia, positioning and draping[edit]

  • Performed under general anaesthesia without muscle relaxation as eliciting muscle contraction on mechanical or electrical stimulation of the marginal mandibular, hypoglossal and accessory nerves assists with locating and preserving these nerves
  • The patient is placed in a supine position with the neck extended and head turned to the opposite side
  • Surgical draping must permit monitoring for movement of the lower lip with irritation of the marginal mandibular nerve, and must provide access to the clavicle inferiorly, the trapezius muscle posteriorly, the tip of the earlobe superiorly and the midline of the neck anteriorly
  • The drapes are stapled to the skin

Skin Marking[edit]

  • Mastoid
  • Midline (midline mandible, sternal notch)

Surgical Steps[edit]

Skin incision[edit]

  1. Neck is usually opened via a horizontal incision placed in a skin crease just below the level of the hyoid bone
    • 4 main incisions that can be used:
      • Apron - usually most appropriate
      • Wine glass - good access but creates tip with reduced blood supply
      • "H" incision - good access but creates tip with reduced blood supply
      • MacFee - parallel transverse incisions (not ideal as blood supply comes up vertically)
  2. Incision is made through skin, subcutaneous fat and platysma muscle
  3. Identify external jugular vein and greater auricular nerve overlying sternocleidomastoid
  1. Superior skin flap is raised in the subplatysmal plan with cautery until submandibular gland is identified
  2. Inferior skin flap is then raised in the subplatysmal plane - towards the midline the exposure should be until omohyoid muscle whilst laterally and inferiorly the lateral surface of the sternocleidomastoid should be exposed almost to the clavicle

The remaining steps follow this recommended pattern:

Step 1: Level Ia[edit]

  1. Skin is elevated in a subplatysmal plane up to the opposite anterior belly of digastric muscle
  2. Watch out for anterior jugular veins
  3. The contents of the submental triangle are resected with up to the hyoid bone
  4. The deep plane of dissection is the mylohyoid muscle

Step 2: Level Ib[edit]

  1. The fascia (capsule) overlying the submandibular gland is incised midway over the gland and is dissected from the gland in a superior direction in a subcapsular plane to avoid injury to the marginal mandibular nerve
    • Using this technique, the marginal mandibular nerve does not need to be routinely identified - should keep an eye for any twitching of the lower lip as this indicates proximity to the nerve
    • The marginal mandibular nerve crosses the facial artery and vein
  2. The facial artery and vein are identified by blunt dissection with a fine haemostat
  1. Next attention is directed to the fat and lymph nodes tucked anteriorly between the anterior belly of digastric and mylohyoid muscle (especially important area for anterior floor of mouth malignancies)
  2. To resect these nodes, retract the anterior belly of digastric anteriorly and deliver the tissue using electrocautery dissection with the deep dissection plane being on the mylohoid muscle
  3. No significant structures apart from nerve to mylohyoid and mylohyoid perforating vessels (can be cauterized/ligated) are encountered until the posterior free margin of the mylohyoid is encountered
  4. Next area to address is the region of facial artery and vein - palpate the vessels to feel for facial lymph nodes; if present dissect them free using fine haemostats (take care not to damage marginal mandibular)
  5. Facial artery and vein can then be ligated and divided close to submandibular gland to avoid injury to marginal mandibular
  6. This will then free up the superior margin of the submandibular gland which can be reflected away from the mandible
  1. After this, address the lingual nerve, submandibular duct and hypoglossal nerve
  2. Retract the mylohyoid anteriorly
  3. There is a clearly defined interfascial dissection plane between the deep aspect of the submandibular gland and the fascia covering CNXII. This can be opened with finger dissection (take care not to tear the thin-walled veins accompanying CNXII)
  4. CNXII is now visible in the floor of submandibular triangle
  5. Inferior traction of the gland brings into view the lingual nerve and submandibular duct
  6. The submandibular duct is separated from the lingual nerve, ligated and divided
  7. The submandibular ganglion, suspended from the lingual nerve, is clamped, divided and ligated, taking care not to cross-clamp the lingual nerve
  8. The facial artery is divided and ligated just above the posterior belly of digastric (can also preserve facial artery by ligating the 1-5 branches that enter submandibular gland)

Step 3: Level IIa[edit]

Here the aim is to identify CNXII in level IIa then to trace it posteriorly where is leads to the internal jugular vein

  1. Divide the external jugular vein (improves access to levels IIa and IIb)
  2. Take care to preserve the greater auricular nerve
  3. Divide the fascia along the lateral aspect of the posterior belly of digastric (facilitates subsequent exposure of the IJV and CNXI)
  4. Expose the posterior belly of digastric along its entire length, taking care not to wander above the muscle as this might jeopardise the facial nerve
  5. No significant structures cross the posterior belly other than the facial vein
  6. Next identify the CNXII below the greater cornu of the hyoid bone anterior to where it crosses the external carotid artery (It is generally more superficial than expected, and is located just deep to the veins that cross the nerve)
  7. Carefully dissect along the nerve in a posterior direction and divide all the veins crossing the nerve to expose the full length of CNXII
  8. After the nerve has crossed posterior to the external carotid artery, identify the SCM branch of the occipital artery that tethers the CNXII
  9. Dividing this artery releases the CNXII
  10. The nerve then courses vertically along the anterior surface of the IJV and hence leads directly to the IJV
  11. Using dissecting scissors or a haemostat to part the fatty tissue behind the IJV in Level II, identify CNXI which may course lateral (commonly), medial (uncommonly) or through (very rarely) the IJV.
  12. The nerve is often first located by noting movement of the shoulder due to mechanical stimulation of the nerve

Step 4: Exposure of remaining level II and level III[edit]

  1. Dissect with a scalpel or electrocautery along the omohyoid and strip the fatty tissue in the anterior parts of Levels II and III from the underlying infrahyoid strap muscles in a posterior direction towards the carotid sheath
  2. Divide the epimysium along the anterior border of the SCM using electrocautery or a scalpel
  3. This exposes structures deep to the SCM i.e. the remainder of Levels II and III of the neck and the lateral surface of the omohyoid muscle as it crosses the internal jugular vein
  4. A number of small vessels entering the muscle are encountered and cauterized
  5. The dissection is carried posteriorly along the deep aspect of the muscle in a subepimysial plane up to the posterior edge of the SCM

Step 5: Clearing level IIb[edit]

Opinions differ as to whether Level IIb (posterior to CNXI) needs to be routinely dissected so as to minimise trauma to the CNXI

  1. The upper part of the SCM is retracted posteriorly to expose Level IIb
  2. With a haemostat, create a tunnel immediately posterior to the IJV down to the prevertebral muscles
  3. This manoeuvre speeds up the subsequent dissection of Level IIb by clearly delineating the posterior wall of the IJV
  4. The transverse process of the C1 vertebra can be palpated immediately posterior to the CNXI and IJV and serves as an additional landmark for the position of these structures in difficult surgical cases
  5. In order to resect Level IIb, identify the CNXI in Level IIb, and atraumatically dissect it free from the surrounding fat with sharp and blunt dissection up to where it enters the SCM
  6. Using a scalpel (due to proximity of CNXI), or blunt dissection with a haemostat, proceed to mobilise Level IIb starting postero- superiorly, with the assistant retracting the fatty tissue in an anterior direction.
  7. The occipital artery passes across to the top of Level IIb; its branches may need to be cauterized should they be severed while dissecting the superior part of Level IIb
  8. Cut down onto the deep muscles of the neck which are seen to course in a postero-inferior direction Once the fat of Level IIb has been fully mobilized from the underlying muscles, pass it anteriorly underneath the CNXI

Step 6: Resect levels II and III[edit]

  1. To resect Levels II and III, extend the incision along the posterior edge of the deep aspect of SCM inferiorly through the fatty tissue of Level 3
  2. With the assistant(s) retracting the SCM posteriorly and the fat of levels II and III anteriorly with sharp-toothed rake retractors, dissect the fatty issue of Levels II and III in an anterograde direction
  3. The deep dissection plane is the muscle the floor of neck between the branches of the cervical plexus which need to be identified and preserved
  4. The phrenic nerve and brachial plexus are not seen in this dissection but are relevant if Level 4 is dissected
  5. Continue the anterograde dissection with a scalpel or scissors until the ansa cervicalis, and the carotid sheath containing the common and internal carotid arteries, CNX and IJV are sequentially exposed
  6. The carotid sheath is incised along the full course of the vagus nerve, and the neck dissection specimen is stripped off the IJV while dissecting inside the carotid sheath
  7. The ansa cervicalis, which courses either deep or superficial to the IJV may be preserved

Step 7: Level IV[edit]

  • Continue stripping the fat and lymphatics around the anterior aspect of IJV until the common carotid artery is again reached
  • Divide and ligate tributaries of the IJV with silk ties
  • Inferiorly the fatty tissue at the junction of Levels III and IV is divided at the level of the omohyoid
  • Identify and preserve the superior thyroid artery where it originates from the external carotid artery
  • Level IV is resected by applying traction to the fatty tissue deep to the omohyoid in a cephalad direction while dissecting it from Level IV with a scalpel; the transverse cervical vessels may be encountered and need to be ligated; finger dissection may be used to establish a dissection plane between the fat of Level IV and the brachial plexus and phrenic nerve; be vigilant for a chylous leak as the thoracic duct (left neck) or right lymphatic duct may be transected
  • The final step is to complete stripping the neck dissection specimen off the infra-hyoid strap muscles taking care not to injure the CNXII and its accompanying veins superiorly, and to deliver the neck dissection specimen
  • Closure[edit]

    1. Irrigate the neck with warm water
    2. Ask the anaesthetist to perform a head down/valsalva manoeuvre to elicit any occult bleeding/chyle leak
    3. Insert suction drain
    4. Closure is in layers with vicryl to platysma and sutures/staples to skin

    Post-operative care[edit]

    • Keep drain on continuous suction
    • Usually can remove drain when volume <50ml/24hours

    Follow-up[edit]

    Complications[edit]

    • The risks of breakdown and bleeding are greater if neck has had previous radiotherapy
    • Where a previous incision has been made in the neck, this should normally be excised and the neck incision planned around this

    References[edit]