Modified Radical Neck Dissection (MRND)

INTRODUCTION

• Neck dissection is a surgical procedure used to remove lymph nodes from the neck that may contain cancer cells spreading from a primary head and neck tumor.
• The Radical Neck Dissection (RND) was first described by Crile in 1906. It removed all lymph nodes (levels I-V) along with three important non-lymphatic structures: the Sternocleidomastoid muscle (SCM), Internal Jugular Vein (IJV), and Spinal Accessory Nerve (SAN).
• Over time, surgeons realized that removing these structures caused significant disability (especially shoulder problems). So the Modified Radical Neck Dissection (MRND) was developed - same lymph node clearance but one or more of those three structures is preserved.

CLASSIFICATION OF NECK DISSECTIONS

NECK DISSECTIONS
       |
  _____|______________________
  |                           |
COMPREHENSIVE              SELECTIVE
(Levels I-V)            (Less than 5 levels)
  |
  |________________________
  |                        |
Radical ND           Modified Radical ND
(removes SAN,        (preserves 1 or more of:
IJV, SCM)            SAN / IJV / SCM)

Note: As long as at least ONE of the three structures is preserved, it is called MRND.

DEFINITION

• MRND is the en bloc removal of all lymph node-bearing tissue on one side of the neck, from levels I through V, while preserving one or more of the three non-lymphatic structures: SAN, IJV, and/or SCM.

BOUNDARIES OF DISSECTION

LYMPH NODE LEVELS REMOVED

INDICATIONS

• The main use of MRND is when there is grossly visible lymph node disease in the neck (nodal metastasis), but the cancer is not directly fixed to or growing into the SAN, IJV, or SCM.
• If multiple neck levels are involved with mobile nodes, MRND is preferred over RND because it reduces morbidity.
• It is hard to justify removing the SAN if it is not directly involved by tumor - because other nerves (vagus, hypoglossal) lying equally close to nodes are routinely spared.
• MRND is especially important when bilateral neck dissection is needed: sacrificing both IJVs simultaneously can cause severe facial swelling and raised intracranial pressure.

• Oral cavity cancers
• Laryngeal cancers
• Oropharyngeal cancers
• Thyroid cancers (with lateral neck nodes)

SURGICAL ANATOMY - KEY STRUCTURES TO KNOW

Spinal Accessory Nerve (SAN) - Most Important to Preserve

• Below the jugular foramen, the SAN runs deep to digastric and stylohyoid muscles
• It lies lateral or just behind the IJV
• Then runs down and back to enter the SCM at the junction of upper and middle thirds
• Exits the SCM at the Erb's point (junction of upper and middle thirds of posterior border of SCM)
• Crosses the posterior triangle and enters trapezius muscle at the junction of its middle and lower thirds

Why preserve SAN? - If cut, the trapezius muscle becomes paralyzed causing severe shoulder drop, pain, and inability to abduct arm above 90 degrees.

SURGICAL TECHNIQUE (Step by Step)

STEP 1: INCISION AND SKIN FLAP
      Subplatysmal flaps raised (same as RND)
             ↓
STEP 2: PROTECT MANDIBULAR BRANCH of FACIAL NERVE
      (Level I dissection - submandibular triangle)
             ↓
STEP 3: IDENTIFY SAN IN POSTERIOR TRIANGLE
      Found at Erb's point (exits SCM posteriorly)
      Nerve stimulator may help identify it
             ↓
STEP 4: DISSECT SAN FREE from fibrofatty tissue
      From Erb's point → where it enters trapezius
             ↓
STEP 5: INCISE ANTERIOR BORDER OF SCM
      SCM retracted laterally; fibrofatty tissue
      dissected away from the muscle
             ↓
STEP 6: CLEAR POSTERIOR TRIANGLE
      Dissect from trapezius medially
      Pass tissue ABOVE SAN → beneath it
      Then sweep beneath elevated SCM
             ↓
STEP 7: DISSECT OFF IJV
      Sharp dissection separating contents from
      carotid artery and jugular vein
      IJV tributaries ligated
             ↓
STEP 8: SUBMANDIBULAR & SUBMENTAL TRIANGLES
      Remove contents; ligate anterior facial vein
             ↓
STEP 9: DRAIN PLACEMENT AND WOUND CLOSURE
      Drains through separate stab incisions
      Two-layer closure (platysma + skin)

ADVANTAGES OF MRND OVER RND

COMPLICATIONS

Early Complications

1. Hemorrhage - Most common early. Hematoma forms under skin flaps. Needs re-exploration if large.
2. Air leaks - Air enters through drain site; usually minor.
3. Chylous fistula - Leakage of chyle from thoracic duct injury (on LEFT side, low Level IV). Incidence ~1.9%. Managed conservatively (pressure dressing, low-fat diet) or surgically.
4. Wound infection - Risk higher after prior radiotherapy (>70 Gy).

Late Complications

1. Shoulder dysfunction - Even in MRND with SAN preservation, EMG abnormalities seen in up to 65% at 4 months (due to nerve stretching during dissection). Most recover by 12 months.
2. Numbness - Due to sacrifice of cutaneous branches of cervical plexus (greater auricular, transverse cervical nerves).
3. Carotid artery injury - Rare but serious.
4. Lymphedema of face - More common if bilateral IJV ligation.
5. Phrenic nerve injury - Causes diaphragm paralysis.
6. Hypoglossal nerve injury - Causes tongue deviation.

COMPLICATIONS OVERVIEW
         |
    _____|_______
    |             |
  EARLY          LATE
    |             |
- Hemorrhage    - Shoulder dysfunction
- Air leak      - Numbness/dysesthesia
- Chyle leak    - Lymphedema
- Infection     - Nerve palsies

COMPARISON: RND vs MRND vs SND

RND                MRND               SND (Selective)
(Crile, 1906)     (Most common now)   (For N0 neck)
     |                  |                   |
Levels I-V         Levels I-V          Selected levels
     |                  |               (based on primary)
Removes SAN,     Preserves 1 or        Preserves all 3
IJV, SCM         more: SAN/IJV/SCM     structures
     |                  |                   |
Maximum          Moderate            Minimal
morbidity        morbidity           morbidity

POSTOPERATIVE CARE

• Drain monitoring (watch for chyle, blood)
• Shoulder physiotherapy - started early in all patients
• EMG of trapezius at 1, 3, 6, 12 months if shoulder weakness noted
• Regular follow-up for recurrence

CONCLUSION

KEY POINTS SUMMARY