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Left Lateral Head Dissection with Brain In Situ

Surgical Correlation

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Left lateral head dissection with brain in situ. The brain and several cavities of the head are in view. The falx cerebri is a midline dural fold that separates the right and left cerebral hemispheres. In its superior margin is the superior sagittal sinus draining much of the adjacent superficial cortex. The sinus ends posteriorly at the torcula or confluens within the occipital attachment of the tentorium cerebelli, which separates the occipital lobes from the cerebellum. The transverse sinus continues laterally to the sigmoid sinus which ends as the jugular bulb just proximal to the jugular foramen. It passes through this foramen to continue in the neck as the internal jugular vein. Anterior to the vein here is the internal carotid artery entering the carotid canal. One of its terminal branches, the middle cerebral artery, is seen in cross-section in the Sylvian (lateral) fissure. The Lateral Fissure of Sylvius has been opened to expose the transverse temporal gyri (of Heschl) on the floor of the fissure, and the short and long insular gryi on the medial wall.  On the ventral surface of the brain anteriorly is the olfactory tract. The interior of the frontal sinus is seen in sagittal view between the outer and inner tables of the frontal bone. Inferior to the anterior cranial fossa in this view is the orbit. The eyeball or globe resides in its anterior half. The posterior half contains the optic nerve, extraocular muscles, and fat. The recti muscles (lateral, inferior, superior, medial) have their origins posteriorly from the annulus of Zinn. The inferior oblique muscle emerges from beneath the inferior rectus to insert into sclera. The levator palpebrae superioris muscle lies superficial beneath the periorbita and inserts into the upper eyelid to open the eyelids. The ophthalmic artery, a branch of the internal carotid, is shown ramifying in the orbit. One of its branches, the supraorbital artery can be seen accompanying the supraorbital nerve across the contents of the orbit toward the supraorbital foramen. The lacrimal gland can be seen in the supralateral portion of the orbit. The floor of the orbit borders on the roof of the maxillary sinus. At this junctional area courses the infraorbital nerve, the largest branch of the maxillary nerve, from the pterygopalatine fossa to the infraorbital foramen on the face. Windows in the maxillary bone have been made to view the lateral wall of the nasal cavity (and its superior, middle, and inferior turbinates), its floor (represented by the palate) as well as the midline nasal septum. The bones of the face bordering the orbit anteriorly include the frontal, zygomatic, and maxillary bones. The nasal bone articulates with the maxillary bone to form the margins of the anterior nasal or piriform aperture. Posterior to the maxillary sinus is the infratemporal fossa. A portion of the ramus of the mandible, the coronoid process, is visible establishing the lateral border of this space. Internally in this view are the two heads (superior and inferior) of the lateral pterygoid muscle with the buccal nerve to the cheek emerging between them. The distal end of the maxillary artery leaves this fossa to enter the pterygopalatine fossa. It gives rise to the posterior superior alveolar to the maxillary sinus and the sphenopalatine artery to the nasal cavity. In this fossa the maxillary nerve gives rise to the palatine nerves to the palate and oral cavity and the nasopalatine nerve to the nasal cavity. It "suspends" the sphenopalatine ganglion, a parasympathetic relay, that provides postganglionic secretomotor fibers that are distributed with the branches of the maxillary nerve. (Image courtesy of PA Rubino)

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