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

Surgical Correlation

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Left lateral exposure of brain, infratemporal fossa, and suboccipital 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 inferior frontal gyrus, represented by the pars orbitalis, triangularis, and opercularis, is separated from the temporal lobe and its superior, middle, and inferior temporal gyri, by the lateral or Sylvian sulcus. The precentral gyrus or primary motor cortex is the posterior portion of the frontal lobe. It is separated from the postcentral gyrus or primary somatosensory cortex of the parietal lobe by the central sulcus. The inferior portion of the postcentral gyrus merges with the supramarginal gyrus, a component of the multimodal somatosensory association cortex contributed also by the angular gyrus located immediately posterior to it. Together, they compose the inferior parietal lobule. 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 muscle has been removed; only the medial pterygoid remains. 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 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. Sandwiched between these vessels more inferiorly is the tip of the superior cervical sympathetic ganglion from which arises the internal carotid nerve carrying postganglionic sympathetic fibers. This nerve courses on the external surface of ICA, but has been pulled inferiorly out of position in this view. 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. 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. (Image courtesy of PA Rubino)

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