Modified Radical Neck Dissection
A radical neck dissection removes the lymph nodes from levels I through V of the neck with sacrifice of the internal jugular vein, spinal accessory nerve, and sternocleidomastoid muscle; this is rarely necessary. More commonly, a modified radical neck dissection (MRND) is performed, wherein lymph nodes are removed from levels I-V of the neck, but one or more of the aforementioned structures is preserved. By contrast, in a selective neck dissection, lymph nodes are not removed in one or more levels of the neck. One example is a supraomohyoid neck dissection, in which dissection is limited to levels I-III.
Indications for Surgery:
MRND is performed when there is clinical, pathologic, or radiographic evidence of cervical nodal metastasis. Selective neck dissection is performed in cases where the risk of occult nodal disease is over 20%.
Contraindications to Surgery:
- Medical comorbidities that would preclude surgical or anesthesia risk
- Positron emission tomography (PET)-CT is indicated in advanced cancers to evaluate for regional and distant metastatic disease. It is also used to identify unknown primary cancers.
- Magnetic resonance imaging is indicated for evaluation of the extent of soft tissue involvement of the primary, including mandibular bone marrow and cranial nerve infiltrations.
- Fine needle aspiration, which may require ultrasound or CT guidance, is useful in diagnosing cervical lymphadenopathy suspicious for malignant metastasis when no primary site is clinically identifiable.
- The patient is placed supine on the operating table and general anesthesia is induced via endotracheal intubation.
- The table is rotated 180 degrees, a shoulder roll is placed, and the head is turned to the contralateral side. The neck is prepped and draped with the lower lip in the field to monitor the function of the marginal mandibular nerve.
- The type of neck incision used is at the discretion of the surgeon and depends on the extent of neck dissection. A commonly used incision is the "hockey stick" L-shaped incision. Subplatysmal flaps are raised to the body of the mandible superiorly, the anterior border of the trapezius posteriorly, the clavicle inferiorly, and the anterior belly of the digastric muscle and omohyoid muscle medially.
- The submandibular triangle (level Ib) is dissected. Care is taken to preserve the marginal mandibular branch of the facial nerve as it dips below the body of the mandible, traveling within the fascia superficial to the submandibular gland. A horizontal curved incision can be made at the midpoint of the submandibular gland through the fascia; this allows the entire fascial layer to be lifted, thereby preserving the nerve. The facial artery and vein cross over the body of the mandible and traverse through the posterior portion of the submandibular gland. Most surgeons ligate these vessels twice during the dissection: once above the gland and just below the mandible, and a second time below the gland and just above the posterior belly of the digastric muscle. The distal stumps of the vessels on the superior ligation can be retracted superiorly to protect the marginal mandibular nerve (Hayes-Martin Maneuver), because the nerve is always superficial to these vessels.
- The contents of the submandibular triangle are peeled off of the anterior belly of the digastric and the mylohyoid muscle. As the posterior border of the mylohyoid muscle is reached, the mylohyoid can be retracted anteriorly to allow access to the portion of the submandibular gland that is behind the muscle. As the submandibular gland is retracted inferiorly, blunt dissection will reveal the lingual nerve, which communicates with the submandibular gland through the submandibular ganglion. The ganglion is divided without damage to the lingual nerve.
- Wharton's duct (duct of the submandibular gland) is ligated. The hypoglossal nerve is deep to the submandibular gland. The surgeon needs to be aware of its presence, but it is not always dissected when removing the submandibular contents.
- The submental triangle (level Ia) is dissected by removing the fibrofatty soft tissues from between the anterior bellies of the digastric muscles on each side, inferior to the mylohyoid muscle, from the inferior border of the mandible to the hyoid bone. There are no important structures that need to be preserved within this level.
- The level II dissection removes all of the upper jugular lymph nodes from the lateral border of the sternohyoid muscle to the posterior border of the sternocleidomastoid. The dissection extends from the skull base superiorly to the carotid bifurcation inferiorly. The spinal accessory nerve, internal jugular vein, carotid artery, occipital artery, hypoglossal nerve, and vagus nerve are all identified and preserved. The dissection includes the tail of parotid overlying the sternocleidomastoid.
- The hypoglossal nerve is identified deep to the inferior portion of the posterior belly of the digastric, which is skeletonized and retracted superiorly. The hypoglossal nerve is then skeletonized from near its entrance into the tongue musculature anteriorly to its junction with the internal jugular vein posteriorly. Dissection must be performed very carefully in this region, as the hypoglossal nerve is surrounded by a plexus of veins.
- The spinal accessory nerve can be identified medial to the sternocleidomastoid muscle and deep to the posterior belly of the digastric. The point where the great auricular nerve crosses the posterior aspect of the sternocleidomastoid can be used as a reference point to locate the spinal accessory nerve, which is typically found 1 cm superior to this point. A nerve stimulator can be used to distinguish the spinal accessory nerve from the many sensory nerves in the area. Once identified, it can be skeletonized and preserved.
- The sternocleidomastoid muscle can be skeletonized anteriorly and posteriorly onto the deep surface.
- The proximal portion of the spinal accessory nerve pierces the deep aspect of the sternocleidomastoid muscle. Once identified, the nerve can be traced superiorly to the internal jugular vein; it usually passes lateral to this, but may pass medially, or even in between branches. The junction is usually deep to the posterior belly of the digastric muscle. The small region of fibrofatty contents above this portion of the spinal accessory nerve forms level IIb, while the much larger area below this portion of the nerve is level IIa.
- Dissection is continued to include the middle jugular lymph nodes from the level of the carotid bifurcation/hyoid to the level of the cricoid/omohyoid (level III). Care is taken not to damage the spinal accessory nerve where it exits the sternocleidomastoid muscle to pass through the posterior triangle.
- Level IV dissection encompasses the lower jugular lymph nodes from the level of the cricoid/omohyoid to the clavicle/lung apex.
- Just above the clavicle and lateral to the great vessels in the left neck, the thoracic duct may be identified as it enters the jugular vein. Some surgeons advocate clamping the distal level IV soft tissues to prevent leakage of chyle from the duct.
- The level V dissection removes nodal tissue from the posterior border of the sternocleidomastoid to the anterior border of the trapezius muscle. The dissection extends from the mastoid tip superiorly to the clavicle inferiorly. The spinal accessory nerve is dissected free as it runs superficially through the posterior triangle to enter the anterior border of the trapezius muscle 2-3 cm above the clavicle. Dissection is performed from lateral to medial, superficial to the deep layer of the deep cervical fascia (prevertebral fascia) to protect the phrenic nerve and brachial plexus. The transverse cervical artery and vein can be preserved in the inferior aspect of this dissection.
- The carotid sheath is opened and the carotid artery, jugular vein, and vagus nerve are skeletonized. Branches from the jugular vein exit anteriorly and are ligated and divided with preservation of the common facial vein.
- The cervical rootlets that form the sensory nerves of the neck are preserved, if possible. If the cervical rootlets are sacrificed, care must be taken to ligate them well away from the phrenic nerve to prevent injury. The omohyoid muscle may be removed with the neck contents.
- Once removed, the specimen is separated into its constituent levels before being passed off the field.
- The wound is then irrigated and a valsalva maneuver is performed with the assistance of the anesthesiologist. The wound bed is checked for hemostasis and for the presence of a chyle leak.
- Two vacuum drains are placed in the wound bed, which is then closed in layers.
- Care of the patient is returned to the anesthesiologist for extubation and recovery.
- The postoperative examination should include assessment of the following nerves:
- Marginal mandibular nerve – ask the patient to smile and assess symmetry
- Hypoglossal nerve – ask the patient to move the tongue
- Spinal accessory nerve – ask the patient to shrug the shoulders and assess symmetry
- Drain output is closely monitored for evidence of air leak (inability of drain to hold suction) and chyle leak (high output, milky drain contents, particularly after enteral feeds).
- Drains may be removed when output has decreased sufficiently (less than 30 mL over 24 hours). Occasionally, patients may be discharged with a drain in place.
- Antibiotic ointment may be applied to the incision three times a day.
- Follow-up is typically arranged for one week after surgery, at which time staples may be removed (staples are left in place longer in previously irradiated tissue).
- If postoperative radiotherapy is indicated, it is generally scheduled to start no sooner than four weeks after surgery, to allow for adequate wound healing, but no longer than 6 weeks after surgery for optimal outcome.
- Bleeding, hematoma, or seroma
- Wound infection, skin flap necrosis, or internal jugular vein thrombosis.
- Chyle leak or salivary leak from the parotid tail.
- Loss of motor function from the marginal mandibular nerve, CNXI, or CNXII.
- Facial edema
- Cervical rootlet neuroma
- Loss of cutaneous sensation in the neck and ear lobe (great auricular) and ipsilateral tongue sensation and taste (lingual)
- Shoulder pain and loss of range of motion in the shoulder