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Retromandibular Region, Posterior Fossa, and Proximal Neck Dissection, Left Side

Surgical Correlation


Retromandibular region, posterior fossa, and proximal neck dissection, left side. Skin, superficial fascia, and the parotid gland have been removed on the face and neck to reveal underlying structures. These include the masseter muscle covering the ramus of the mandible and subcutaneous fatty tissue containing some muscles of facial expression anterior to it. In the retromandibular region the facial nerve has been reflected where it crosses superficial to the retromandibular vein (not labeled) and external carotid artery (parotid gland has been removed). Below the body of the mandible is the submandibular triangle bounded by this bone and the anterior and posterior bellies of the digastric muscles (intermediate tendon has been divided). The floor of this triangle is formed by the hyoglossus (posteriorly) and mylohyoid (anteriorly) muscles. The principal content of this triangle is the submandibular gland (removed). Between the right and left anterior digastric muscles and body of the hyoid bone is the unpaired submental triangle whose floor is the mylohyoid muscle. Inferior to the body of the hyoid are the infrahyoid muscles consisting here of the superior belly of the omohyoid and the underlying thyrohyoid muscle. The latter muscle partially covers the thyrohyoid membrane into which passes the superior laryngeal artery and internal laryngeal nerve to supply the upper part of the laryngeal interior. The inferior pharyngeal constrictor muscle is shown as well before it attaches anterolaterally to the thyroid and cricoid cartilages of the larynx. The superior thyroid artery descends on the muscle enroute to the thyroid gland. In the lateral neck the internal jugular vein has been cut and reflected to reveal the common carotid and internal carotid arteries. The vagus nerve descends in the neck between the internal jugular and internal carotid vessels. The hypoglossal nerve descends deep to the posterior digastric muscle. Near the origin of the external carotid it courses forward toward the oral cavity superficial to the hyoglossus muscle and then deep to the mylohyoid before entering the tongue where it provides motor innervation to intrinsic and extrinsic muscles, except palatoglossus. Near the bifurcation of the common carotid can be seen the carotid sinus nerve, a sensory branch of the glossopharyngeal nerve. It innervates the baroreceptors of the carotid sinus and the chemoreceptors of the carotid body. Removal of the sternocleidomastoid muscle exposes the anterior scalene muscle. In addition, removal of deep neck musculature has exposed the suboccipital muscles, obliquus capitis inferior and superior and rectus capitis posterior major. A portion of the vertebral artery is shown before it enters the transverse foramen of the atlas. It is crossed superficially by the ventral ramus of the C2 spinal nerve. Posterior to this, the greater occipital nerve, the dorsal ramus of C2, emerges from the lower border of obliquus capitis inferior. A portion of the skull and meninges have been removed to expose the cerebellum, sigmoid sinus, and superior petrosal vein. (Image courtesy of PA Rubino)