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Retromandibular Dissection, Exposure of the Posterior Fossa, and Proximal Neck Dissection, Left Side

Surgical Correlation


Retromandibular dissection, exposure of the 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 ramus of the mandible (masseter muscle has been removed), the buccinator muscle anterior to it, and the temporalis muscle. A portion of the skull and meninges have been removed deep to the temporalis to expose part of the cerebrum and the cerebellum, sigmoid sinus, and superior petrosal vein.  In the lower retromandibular region the external carotid artery can be seen ascending through the parotid gland, which has been removed. Behind the neck of the mandible it divides into its maxillary and superficial temporal branches. The latter vessel ascends on the temporoparietal fascia and divides into frontal and parietal branches to supply the scalp. The facial nerve crosses superficial to the external carotid artery and retromandibular vein (not present here) within the parotid gland and then gives off branches to facial muscles. Near the angle of the mandible the external carotid gives rise to the facial artery which first courses deep to the submandibular gland (removed) before emerging onto the face just anterior to the attachment of the masseter muscle to the mandible. Below the body of the mandible is the submandibular triangle bounded by this bone and the anterior and posterior bellies of the digastric muscles (posterior digastric has been removed). 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). The mylohyoid nerve, a motor branch of the inferior alveolar nerve, can be seen supplying the mylohyoid and anterior digastric muscles. Inferior to the body of the hyoid are the infrahyoid muscles (in the muscular triangle) represented here by the 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 to reveal the common carotid and internal and external 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 occipital branch 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. The styloglossus muscle can be seen entering the superolateral border of the tongue where it interdigitates with the hyoglossus. Removal of the sternocleidomastoid muscle exposes the anterior and middle scalene muscles. 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. Cut stumps of ventral rami of C3 and 4 spinal nerves are also visible. (Image courtesy of PA Rubino)