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Panoramic Left Lateral Dissection of the Head, Face, and Neck

Surgical Correlation


Panoramic left lateral dissection of the head, face, and neck. The sagittal view of the brain depicts, from posterior to anterior, the occipital lobes of the cerebrum separated from the underlying cerebellum by the tentorium cerebelli. The transverse sinus is contained within the posterior attachment of the tentorium to the occipital bone. The lateral ventricle is seen in the right cerebral hemisphere in association with the corpus callosum and the fornix arches over the thalamus. The rostral portion of the midbrain is visible and the oculomotor and trochlear nerves are shown leaving it and coursing to the cavernous sinus and superior orbital fissure. Numerous vessels supplying brain tissue can be identified. Branches of the superior cerebellar artery encircle the superior surface of the cerebellum. The internal carotid terminates by dividing into the larger middle and, smaller, anterior cerebral arteries. A posterior communicating artery from the internal carotid artery connects it to the ipsilateral posterior cerebral artery as part of the arterial circle of Willis. The anterior choroidal artery arises from the posterior wall of the internal carotid between the origin of the posterior communicating artery and its termination. The anterior cerebral arteries course anteromedially to pass anterior to the genu of the corpus callosum to supply the medial surfaces of the cerebral hemispheres. Its first part (A1 segment) ends at the origin of the anterior communicating artery connecting the right and left anterior cerebral arteries. The second part (A2 segment) extends from this point anterior to the lamina terminalis. Lateral to the body of the sphenoid is the cavernous sinus and the cavernous segment of the internal carotid artery. Several cranial nerves are contained within the lateral wall of this sinus. From superior to inferior are the oculomotor, trochlear, and ophthalmic nerves. These course forward to enter the orbit through the superior orbital fissure. The lacrimal gland can be seen in the superolateral anterior portion of the orbit and the lateral rectus is shown inserting into the eyeball. A portion of the zygomatic arch and bone have been removed to expose part of the infratemporal fossa. The maxillary artery is in view near the pterygomaxillary fissure before entering the pterygopalatine fossa. Here, it gives rise to the posterior superior alveolar artery that enters the posterior wall of the maxilla. Superficially, the masseter muscle overlies and attaches to the ramus of the mandible. The transverse facial artery, a branch of the superficial temporal artery, is crossing the muscle below and parallel with the zygomatic arch. Part of the parotid gland lays upon the muscle and shown here are cut branches of the facial nerve emerging from the gland. Anteriorly, in the face are several muscles of facial expression as well as the facial artery. The artery, a branch of the external carotid, passes initially deep to the submandibular gland before crossing onto the face at the lower border of the mandible near the anterior border of the masseter muscle. The facial vein, on the other hand, crosses the submandibular gland superficially. In this specimen, it receives the external palatine vein draining the lateral tonsillar area and the superior thyroid vein before emptying directly into the internal jugular vein. Numerous vessels, nerves, and muscles are visible in the proximal neck. The common carotid artery terminates in the internal and external carotid branches. The internal carotid artery ascends medial to the internal jugular vein and will enter the carotid canal. It provides no branches in the neck. The proximal portion of the external carotid gives rise to the superior thyroid artery to the thyroid gland. The superior laryngeal artery is a branch of this artery that passes through the thyrohyoid membrane (in company with the internal laryngeal nerve) to supply the upper interior of the larynx. The occipital artery arises from the posterior border of the external carotid and, in turn, gives off a muscular branch to the upper part of the sternocleidomastoid muscle. In this relationship, this branch "hooks" the hypoglossal nerve as the nerve bends to course toward the oral cavity. From this bend in the nerve emerges the superior root (containing C1 fibers of the cervical plexus) of the ansa cervicalis to supply infrahyoid muscles. The superior belly of the omohyoid overlies a portion of the thyrohyoid muscle. The sternocleidomastoid muscle has been reflected to expose the muscles of the floor of the lateral cervical triangle, including the scalenus anterior, medius, and posterior, as well as the levator scapulae and splenius cervicis and capitis. Portions of the cervical plexus consisting of fibers from ventral rami of C1-C4 spinal nerves are in view as well as the upper portion of the brachial plexus, which are emerging between the scalenus anterior and medius muscles. The spinal accessory nerve is seen descending on the lateral surface of the internal jugular vein. It provides motor innervation to the sternocleidomastoid and trapezius muscles. (Image courtesy of M Nunez)