Dissection Of The Deep Cervical Muscles

If the previous steps have been properly performed, we will now have two main blocks of the dissection. The upper part includes the submandibular and submental triangles (area I), as well as the upper jugular and spinal accessory regions (upper part of areas II and V). The lower block includes the supraclavicular fossa (remaining part of area V). A small bridge of tissue still separates these two blocks and connects the specimen to the deep cervical muscles (Fig. 4-41). This bridge usually goes from just below the entrance of the spinal accessory nerve into the sternocleidomas-toid muscle to a level just below Erb's point.

Figure 4-39 Variations in the branches of the thyrocervical trunk. tt, thyrocervical trunk; it, Inferior thyroid artery; tc, transverse cervical artery; s, superficial cervical artery; ds, descending scapular artery; sc, suprascapular artery; th, internal thoracic artery.
Figure 4-40 Anterior view of the anatomic landmarks on the right supraclavicular fossa. BP, Brachial plexus; pn, phrenic nerve; tc, transverse cervical artery; sn, supraclavicular branch of the cervical plexus; oh, omohyoid muscle retracted inferomedially.

Figure 4-41 Lateral view of the bridge of tissue between the upper and the lower parts of the specimen on a right functional neck dissection. br, bridge of tissue between the upper and lower parts of the specimen; US, upper part of the specimen (submandibular, upper jugular, and upper spinal accessory regions); LS, lower part of the specimen (supraclavicular area); SC, sternocleidomastoid muscle retracted laterally; IJ, internal jugular vein; sa, spinal accessory nerve; sn, supraclavicular branch of the cervical plexus.

Figure 4-41 Lateral view of the bridge of tissue between the upper and the lower parts of the specimen on a right functional neck dissection. br, bridge of tissue between the upper and lower parts of the specimen; US, upper part of the specimen (submandibular, upper jugular, and upper spinal accessory regions); LS, lower part of the specimen (supraclavicular area); SC, sternocleidomastoid muscle retracted laterally; IJ, internal jugular vein; sa, spinal accessory nerve; sn, supraclavicular branch of the cervical plexus.

Using a scalpel, this bridge is transected and the fascia of the levator scapulae muscle is identified. This maneuver creates a single block that must be dissected free from the deep muscles toward the carotid sheath (Fig. 4-42). The dissection that follows will be performed using sharp dissection. Thus, the specimen is grasped with forceps and adequate traction is applied.

As the dissection proceeds medially, several branches of the cervical plexus are found. A thorough knowledge of neck anatomy is essential to combine oncological radicalism with functional surgery. As already mentioned, to achieve optimal shoulder function, the deep branches from the second, third, and fourth cervical nerves that may anastomose with the spinal accessory nerve should be preserved (Fig. 4-43). In the same manner, the contribution to the phrenic nerve from the third, fourth, and fifth cervical nerves should also be preserved. This is best achieved by keeping the dissection superficial to the scalene fascia, where the branches of the cervical plexus usually lie. On the other hand, the superficial or cutaneous branches of the cervical plexus will be transected as the dissection approaches the carotid sheath.

The dissection of the deep cervical muscles must be stopped as soon as the carotid sheath is exposed. Continuing the dissection posterior to the carotid sheath carries a high risk of damage to the sympathetic trunk (Fig. 4-44).

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