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Left Lateral Exposure of Brain, Infratemporal Fossa, Pharynx, and Neck

Surgical Correlation

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Left lateral exposure of brain, infratemporal fossa, pharynx, and neck. The dura mater and arachnoid layers of the meninges have been removed to expose part of the brain. The tentorium cerebelli (not labeled) separates the cerebrum from the cerebellum. A portion of the sigmoid venous sinus is in view along with the superior petrosal vein. The latter drains the anterior and lateral surfaces of the brainstem and parts of suboccipital and tentorial surfaces and empties into the superior petrosal sinus. In the infratemporal fossa the lateral and medial pterygoid muscles have been removed. The tensor veli palatini and part of the superior pharyngeal constrictor have been removed to expose the interior of the pharynx. The maxillary artery, one of the terminal branches of the external carotid artery, traverses the infratemporal fossa giving rise to several branches, such as those shown here: inferior alveolar, middle meningeal, posterior and anterior deep temporal, posterior superior alveolar, and infraorbital arteries. The sphenopalatine artery continues through the pterygomaxillary fissure into the pterygopalatine fossa. The buccal and auriculotemporal branches of the mandibular nerve can also be seen as well as the inferior alveolar and lingual nerves that descend on the medial pterygoid to the mandibular canal and floor of the mouth, respectively. The inferior alveolar nerve gives rise to the mylohyoid nerve, motor to the mylohyoid and anterior digastric muscles. In the lateral neck, the common carotid artery divides into its external and internal carotid branches. The cervical segment of the ICA continues as the petrous segment once it enters the carotid canal. The internal jugular vein emerges from the nearby jugular foramen and descends in the neck. The hypoglossal nerve emerges between the IJV and proximal part of the ECA and courses forward superficial to the hyoglossus muscle. It then passes deep to the mylohyoid muscle to supply motor innervation to the intrinsic and extrinsic muscles of the tongue, except palatoglossus. The superior root of the ansa cervicalis (containing C1 nerve fibers) leaves the epineurial sheath of the hypoglossal and descends in the neck where it unites with the inferior root to supply motor innervation to most of infrahyoid muscles. The facial artery courses superficial to the hyoglossus and on the deep surface of the submandibular gland (not present) before emerging onto the face. Deep neck musculature has been removed to show the suboccipital muscles: obliquus capitis inferior and superior, which have common attachments to the transverse process of the atlas vertebra, and the rectus capitis posterior major. Part of the vertebral artery is exposed prior to entering the transverse foramen of the atlas. It is crossed superficially by the ventral ramus of the C2 spinal nerve. The greater occipital nerve (dorsal ramus of C2) is seen emerging from the lower border of the obliquus capitis inferior muscle. The ECA terminates as the superficial temporal and maxillary arteries near the neck of the mandible. The carotid sinus nerve, a sensory branch of the glossopharyngeal nerve, innervates the baroreceptors of the carotid sinus and the chemoreceptors of the carotid body. The proximal portions of the anterior and middle scalene muscles are in view. In the ventral neck, attached to the hyoid bone are the sternohyoid and superior belly of omohyoid muscles (out of view), and the thyrohyoid muscle overlying the thyrohyoid membrane, through which course the internal laryngeal nerve and superior laryngeal artery into the larynx. The superior horn of the thyroid cartilage can be seen along with a portion of the inferior pharyngeal constrictor muscle. (Image courtesy of PA Rubino)

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