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Left Lateral Exposure of Brain, Infratemporal Fossa, and Neck

Surgical Correlation


Left lateral exposure of brain, infratemporal fossa, and neck. The mandibular ramus, zygomatic arch, and portion of lateral skull and dura mater and arachnoid layers of the meninges have been removed to expose the brain. The tentorium cerebelli (not labeled) separates the cerebrum from the cerebellum. A portion of the superior petrosal vein is in view. It drains the anterior and lateral surfaces of the brainstem and parts of suboccipital and tentorial surfaces of the brain and empties into the superior petrosal sinus. In the infratemporal fossa the lateral pterygoid and medial pterygoid muscles have been removed. The maxillary artery, one of the terminal branches of the external carotid artery, traverses this space giving rise to several branches, such as those shown here: inferior alveolar, middle meningeal, 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 normally 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 cervical segment of the internal carotid artery 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. Coursing on the external surface of the ICA is the carotid sympathetic nerve plexus carrying postganglionic sympathetic fibers. The hypoglossal nerve emerges between the IJV and proximal part of the ECA and courses forward superficial to the hyoglossus muscle on its way to the oral cavity and tongue. 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 the infrahyoid muscles. Deep neck musculature has been removed to show portions of the suboccipital muscles: obliquus capitis inferior and superior muscles, 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 superior thyroid artery descends posterior and then deep to the thyrohyoid muscle to the upper border of the thyroid gland. It typically gives rise to a smaller superior laryngeal artery that passes through the thyrohyoid membrane in company with the internal laryngeal nerve to supply the upper interior of the larynx. The facial artery courses superficial to the hyoglossus and on the deep surface of the submandibular gland (not present) before emerging onto the face. The ECA terminates as the superficial temporal and maxillary arteries near the neck of the mandible. (Image courtesy of PA Rubino)