Selective (Supraomohyoid) Neck Dissection, Levels I-III

Chapter 1


Selective (Supraomohyoid) Neck Dissection, Levels I-III



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Introduction


Neck dissection has been a standard method of removing at-risk or involved cancerous lymph nodes in the head and neck for more than 100 years. Crile first described the radical neck dissection in the early 1900s, but modifications by Bocca and others helped reduce the morbidity associated with lymph node removal, allowing for nerve and structure preservation when oncologically sound. This chapter discusses one of these modifications in detail, the selective or supraomohyoid neck dissection. A selective neck dissection, including levels I through III, is typically used for malignancies of the oral cavity in patients with N0 disease. When a larger nodal burden is present, an extended (levels I-IV) selective neck dissection or a modified radical neck dissection (levels I-V) is indicated. Lesions in the oral cavity that approach or cross the midline require treatment of both sides of the neck.



Neck Anatomy for Surgical Planning


Understanding the regional lymphatic drainage pathways is critical when planning which type of neck dissection will be employed (Fig. 1-1). A supraomohyoid neck dissection is performed when treating patients who are at risk for micrometastasis in levels I, II, and III. The boundaries of levels I (submental and submandibular), II (upper jugular nodal chain), and III (midjugular nodal chain) are defined as follows:




Level Ia: Bounded laterally by the medial aspects of the anterior belly of the digastric muscles, and ending medially at a line drawn from the mandible to the hyoid bone at the anatomic midline.


Level Ib: Bounded by the lateral aspect of the anterior belly of the digastric muscle, the medial aspect of the posterior belly of the digastric and stylohyoid muscles, and the inferior border of the mandibular body superiorly.


Level IIa: Bounded anteriorly and superiorly by the posterior belly of the digastric and stylohyoid muscles, posteriorly by the vertical plane defined by the spinal accessory nerve and sternocleidomastoid muscle (SCM), and inferiorly by the horizontal plane defined by the inferior border of the hyoid bone.


Level IIb: Bounded anteriorly by the jugular vein and inferiorly by the vertical plane defined by the spinal accessory nerve, posteriorly by the posterior border of the SCM, and superiorly by the skull base.


Level III: Bounded superiorly by the horizontal plane defined by the inferior border of the hyoid bone, inferiorly by the horizontal plane defined by the inferior border of the cricoid cartilage and/or the omohyoid muscle as it crosses the internal jugular vein, anteriorly by the lateral border of the sternohyoid muscle, and posteriorly by the posterior border of the SCM.



Incision Planning and Patient Positioning for Neck Dissection


Positioning for a neck dissection includes extending the neck and turning the patient’s head away from the surgeon. This usually entails placing a shoulder roll under the patient to facilitate adequate extension.


Various types of incisions may be employed. The authors typically use a “hockey stick” incision that extends from the mastoid tip down the middle of the SCM and then across the neck in a crease, which is usually over the lowest level that will be surgically treated. The incision can be brought across the midline to the contralateral neck in the same manner, creating an “apron” incision, which will allow access to both sides of the neck when indicated to treat bilateral neck disease.



Raising the Subplatysmal Flap


Skin and subcutaneous incisions are continued down through the subcutaneous fat and platysma muscle, but not through the superficial layer of the deep cervical fascia. A superior subplatysmal flap is then elevated up to the inferior border of the mandible. Care is taken to keep the plane of elevation immediately subplatysmal, to aid in identification and preservation of the marginal mandibular branch of the facial nerve. Laterally, the platysma muscle is not developed, and elevation must proceed over the external jugular vein and great auricular nerve. This allows for complete elevation of the flap (Fig. 1-2).


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Aug 12, 2016 | Posted by in ANATOMY | Comments Off on Selective (Supraomohyoid) Neck Dissection, Levels I-III

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