Danger Points In The Dissection Of The Internal Jugular Vein

Preservation of the internal jugular vein is one of the main advantages of functional neck dissection. Under normal conditions this is not a difficult step of the operation. However, some particular details may contribute to a successful dissection of this important structure.

We prefer the scalpel for this part of the operation, which is usually striking given its apparent "danger." However, it is our experience that, if properly performed, knife dissection of the carotid sheath is the most effective, clean, and safe way to dissect the lymphatic tissue in this area.

The general rules for safe knife dissection that have been previously described in this chapter must be carefully followed. Adequate tension must be applied to all tissues. Gentle movements must be performed by the surgeon and surrounding personnel. The knife blade must be directed obliquely against the wall of the internal jugular vein (Fig. 5-26). And, finally, the entire length of the vein must be dissected in a continuous fashion, from the clavicle to the mastoid.

In spite of all these measures, two danger points are usually found at the beginning of every dissection of the carotid sheath. They correspond to both ends of the dissected internal jugular vein. We refer to these points as the "two initial folds'' because here the vein wall folds as a consequence of the traction exerted by the dissected tissue (Figs. 5-27 and 5-28). Before further dissection of the carotid sheath is accomplished, these two folds should be carefully removed

Figure 5-25 The sympathetic trunk lies posterior to the carotid sheath, whereas the vagus nerve runs between the internal jugular vein and the carotid artery (right side). IJ, internal jugular vein; ca, carotid artery; vn, vagus nerve; st, sympathetic trunk.

Figure 5-26

Adequate positioning of the scalpel is crucial for a safe dissection over the internal jugular vein.

Figure 5-26

Adequate positioning of the scalpel is crucial for a safe dissection over the internal jugular vein.

without injuring the internal jugular vein. It is important to know that the folded wall of the vein is especially sensible to the cutting edge of sharp instruments (scissors, scalpel). Thus, extreme care must be taken when working in these areas.

The upper fold may be less marked if the tissue from the upper spinal accessory nerve region was previously dissected off the wall of the internal jugular vein as described during the spinal accessory maneuver (Figs. 5-18B, 5-19, and 5-27). The lower fold is usually located at the level of the crossing between the omohyoid muscle and the internal jugular vein (Fig. 5-28A). In fact, the

Figure 5-27 Upper fold of the carotid sheath at the internal jugular vein on the left side of the neck. To facilitate the dissection at this level, the tissue was dissected off the upper part of the internal jugular vein at the end of the spinal accessory maneuver. uf, upper fold; IJ, internal jugular vein; sa, spinal accessory nerve; S, specimen from the upper spinal accessory region.

Figure 5-27 Upper fold of the carotid sheath at the internal jugular vein on the left side of the neck. To facilitate the dissection at this level, the tissue was dissected off the upper part of the internal jugular vein at the end of the spinal accessory maneuver. uf, upper fold; IJ, internal jugular vein; sa, spinal accessory nerve; S, specimen from the upper spinal accessory region.

Figure 5-28 Danger points in the dissection of the carotid sheath. Lower fold over the internal jugular vein on the right side of the neck. (A) The lower fold develops at the crossing of the omohyoid muscle and the internal jugular vein. (B) Retraction of the omohyoid muscle facilitates the dissection of the lower fold. lf, lower fold; IJ, internal jugular vein; ca, carotid artery; vn, vagus nerve; oh, omohyoid muscle.

Figure 5-28 Danger points in the dissection of the carotid sheath. Lower fold over the internal jugular vein on the right side of the neck. (A) The lower fold develops at the crossing of the omohyoid muscle and the internal jugular vein. (B) Retraction of the omohyoid muscle facilitates the dissection of the lower fold. lf, lower fold; IJ, internal jugular vein; ca, carotid artery; vn, vagus nerve; oh, omohyoid muscle.

Figure 5-29 A middle thyroid vein drains into the internal jugular vein on the right side. IJ, internal jugular vein; CA, carotid artery; mt, middle thyroid vein draining into the internal jugular vein.

omohyoid muscle greatly contributes to this fold. Thus, if the omohyoid muscle is to be removed with the primary tumor, it can be transected at this moment to help the dissection of the lower part of the carotid sheath. On the other hand, when the omohyoid muscle is to be preserved, inferior retraction of the muscle allows better exposure of the lower part of the internal jugular vein and facilitates the dissection of the lower fold (Fig. 5-28B).

After both ends of the internal jugular vein have been freed, the dissection must be carried along the entire length of the vein, cutting obliquely with the scalpel over the tense wall of the vein. As the medial aspect of the vein is approached, several tributaries may be identified. The smaller veins can be cauterized, taking care not to injure the wall of the internal jugular vein, whereas the larger trunks need to be ligated and divided (Fig. 5-29).

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