Selective Neck Dissection - Vula - University of Cape Town

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The submandibular ganglion, suspendedfrom the lingual nerve, is clamped, dividedand ligated, taking care not to cross-clampthe lingual nerve (Figure 16).Figure 14: Finger dissection delivers thesubmandibular gland and duct, and bringsthe lingual nerve into view. The proximalstump of the facial artery is visible at thetip of the thumb, and the XIIn is seenbehind the nail of the index fingerThe facial artery is divided and ligatedjust above the posterior belly of digastric(Figure 17). Note: A surgical variation ofthe above technique is to preserve thefacial artery by dividing and ligating the 1-5 small branches that enter the submandibulargland. This is usually simple to do,it reduces the risk of injury to the marginalmandibular nerve, and permits the use of abuccinator flap based on the facial artery(Figure 18).Figure 15: Submandibular ductFigure 17: Clamping and dividing thefacial artery just above the posterior bellyof digastricFigure 16: Separating the submandibularganglion from the lingual nerveFigure 18: Facial artery has been keptintact; a branch is being divided6
Step 3 (Figure 7)This step entails identifying the XIIn inLevel IIa, and tracing the XIIn posteriorlyto where it leads the surgeon directly tothe internal jugular vein (IJV).Divide the external jugular vein (Figure19). This is a key step with SND as itimproves access to Levels IIa and IIb. Thegreater auricular nerve is preserved.Figure 20: Dissect along the entire lengthof the digastricFigure 19: Divide the external jugular veinDivide the fascia along the lateral aspectof the posterior belly of digastric (Figure20). This step is the key to facilitatingsubsequent exposure of the IJV and XIn.Expose the posterior belly of digastricalong its entire length, taking care not towander above the muscle as this mightjeopardise the facial nerve. No significantstructures cross the posterior belly otherthan the facial vein.Next identify the XIIn below the greatercornu of the hyoid bone anterior to whereit crosses the external carotid artery. It isgenerally more superficial than expected,and is located just deep to the veins thatcross the nerve. Carefully dissect along thenerve in a posterior direction and divide allthe veins crossing the nerve to expose thefull length of XIIn (Figure 21).Figure 21: Divide the veins that cross theXIInAfter the nerve has crossed posterior to theexternal carotid artery, identify the SCMbranch of the occipital artery that tethersthe XIIn (Figure 22). Dividing this arteryreleases the XIIn (Figure 23). The nervethen courses vertically along the anteriorsurface of the IJV and hence leads thesurgeon directly to the IJV (Figure 23).Using dissecting scissors or a haemostat topart the fatty tissue behind the IJV in LevelII, the surgeon next identifies the XInwhich may course lateral (commonly),medial (uncommonly) or through (veryrarely) the IJV. The nerve is often firstlocated by noting movement of the7
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Selective Neck Dissection - Vula - University of Cape Town

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