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Detailed Superficial and Deep Dissection of the Left Side of the Head

Surgical Correlation


Detailed superficial and deep dissection of the left side of the head. The cerebellum, brainstem, and spinal cord are visible. Blood supply is provided by branches of the vertebral-basilar-internal carotid arteries. The transverse sinus overlies the posterior surface of the cerebellum and continues laterally as the sigmoid sinus to the jugular bulb. This continues through the jugular foramen as the internal jugular vein, which is accompanied by the glossopharyngeal, vagus, and spinal accessory nerves. In the neck, the internal carotid artery lies medial to this vein and enters the carotid canal with the perivascular carotid sympathetic plexus. Leaving the brainstem are 11 of the 12 cranial nerves (only the olfactory nerve is not visible). The largest of these, the trigeminal nerve, gives rise to its three divisions or branches at the Gasserian ganglion. The ophthalmic nerve travels to the orbit through the superior orbital fissure as do the oculomotor, trochlear, and abducens nerves. The maxillary nerve passes through the foramen rotundum to enter the pterygopalatine fossa. The mandibular nerve passes through the foramen ovale to enter the infratemporal fossa. In the orbit, the globe occupies the anterior half of this space and the optic nerve emerges from its posterior surface. In this view, the superior rectus, inferior rectus, lateral rectus, and inferior oblique muscles can be seen in addition to the levator palpebrae superioris to the upper eyelid. In the superolateral part of the orbit is the lacrimal gland receiving the lacrimal artery, a branch of the ophthalmic artery. The largest branch of the maxillary nerve is the infraorbital nerve. It is seen traversing the floor of the orbit. A window through the maxilla and nasal septum exposes the contralateral lateral nasal wall and the turbinates (superior, middle, inferior). Removal of portions of the mandible exposes the infratemporal fossa for views of the lateral and medial pterygoid muscles and the inferior alveolar nerve, artery, and vein. The pterygoid plexus drains the areas supplied by the branches of the maxillary artery before consolidating into the short maxillary vein. This passes behind the neck of the mandible to join the superficial temporal vein to form the retromandibular vein. Several branches of the external carotid artery can be seen including two branches, the posterior auricular and occipital, that arise from its posterior border. Extensive dissection of the posterior neck demonstrates the axis and atlas vertebrae, the obliquus capitis inferior and rectus capitis posterior major muscles, and the course of the left vertebral artery wrapping around the lateral mass to lay in a groove on the superior surface of the posterior arch. The suboccipital nerve (dorsal ramus of C1 spinal nerve) emerges between the arch and the artery. The artery continues through the foramen magnum to enter the posterior fossa. (Image courtesy of M Nunez)