Describe neck dissection with its classification and complications.

Classification and Indications

• Neck dissection is the systematic removal of the cervical lymph nodes and their surrounding fibrofatty tissue, performed for metastatic or potentially metastatic disease.
• Its evolution has been toward preserving function while retaining oncological control.
• The three non-lymphatic structures that define the classification are the accessory nerve (XI), the internal jugular vein and sternocleidomastoid. Whether these are removed or preserved determines the name of the operation

Complications and Principles

• The structures AT risk, and the deficit each produces, form the core of any answer on complications:
• Accessory nerve (XI) — injury causes shoulder syndrome: trapezius weakness and wasting, a drooping shoulder, winging of the scapula, inability to abduct the arm above 90 degrees, and chronic shoulder pain. This is the single most disabling long-term complication, and is why preservation of the nerve became the priority driving modification of the radical operation
• Marginal mandibular branch of the facial nerve — injury causes weakness of the lower lip with an asymmetrical smile; protected by the HAYES MARTIN manoeuvre, ligating the facial vein and reflecting it upward with the flap
• Hypoglossal nerve (XII) — tongue deviation toward the side of injury, with dysarthria
• Lingual nerve — loss of sensation and taste on the tongue
• Vagus and recurrent laryngeal nerve — vocal cord palsy and aspiration
• Phrenic nerve — diaphragmatic paralysis, seen as a raised hemidiaphragm on the postoperative chest film
• Sympathetic chain — HORNER syndrome
• Thoracic duct on the left — chyle leak, recognised by milky drainage that increases with feeding, confirmed by a high triglyceride content in the drain fluid
• Chyle leak is managed by a low-fat diet with medium-chain triglycerides, pressure dressing and continued drainage; with total parenteral nutrition, octreotide and re-exploration for a high-output leak.
• Internal jugular vein — bilateral ligation causes gross facial and cerebral oedema and raised intracranial pressure, and is avoided or staged with an interval of several weeks if unavoidable
• Air embolism during dissection near the vein
• Other complications — haematoma, which may compromise the airway; infection and flap necrosis, particularly in previously irradiated tissue; pharyngocutaneous fistula where the pharynx has been opened; carotid blowout, heralded by a sentinel bleed and carrying a very high mortality; pneumothorax; shoulder stiffness; and cosmetic deformity and neck stiffness
• The principles that govern the operation:
• Plan the incision so that it gives access, preserves the blood supply of the flaps, and does not lie over the carotid — because a wound breakdown over an exposed carotid leads to blowout
• Raise flaps in the subplatysmal plane, which is bloodless and preserves the flap blood supply
• Work from known to unknown and identify structures before dividing anything
• Remove the specimen EN bloc where possible, and orient and label it by level for the pathologist.
• Handle previously irradiated tissue with particular care.
• Postoperatively — suction drains with careful monitoring of volume and character; early shoulder physiotherapy.
• The pathology report guides adjuvant treatment — the number and level of positive nodes, and above all extranodal extension.
• The accessory nerve is why modification began; shoulder syndrome is the most disabling long-term consequence of a radical dissection
• Three structures define the classification — accessory nerve, internal jugular vein and sternocleidomastoid
• Selective dissection removes only the levels at risk for that particular primary.
• Supraomohyoid for the oral cavity and lateral for the larynx and pharynx.
• Operate electively above about twenty per cent occult risk, which is the accepted threshold and depends on site and T stage
• Early glottic cancer needs no elective dissection, the glottis having almost no lymphatics
• Elective dissection also stages the neck, which determines whether adjuvant radiotherapy is needed
• Use the Hayes Martin manoeuvre to protect the marginal mandibular nerve.
• Milky drainage increasing with feeds is chyle, confirmed by a high triglyceride content in the fluid