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Endoscopic Approach to the Lower Clivus

Surgical Correlation

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A, An endoscope has been introduced through the inferior nasal meatus to view the posterior nasopharyngeal wall. The posterior part of the nasal septum has been detached from the sphenoid crest and removed. The mucosa on the right half of the posterior nasopharyngeal wall has been removed. The eustachian tubes open onto the lateral walls of the nasopharynx just anterior to the prominent and firm tubal elevations. The insertion of the longus capitis muscle to the clivus can usually be seen on the mucosal surface as a V-shaped elevation. The pharyngeal tubercle is located at this lower edge of the V (yellow arrow). There is a shallow, inverted-triangle–shaped depression on the mucosa above the insertion of the longus capitis muscle that corresponds to the site of the pharyngeal tonsil or adenoid in childhood. B, The nasopharyngeal mucosa on the right side has been removed. The pharyngobasilar fascia covers the longus capitis muscle and attaches firmly to the inferior surface of the occipital and temporal bones. As the fascia descends, it diminishes in thickness and gradually blends into the superior pharyngeal constrictor at the level of soft palate. At its upper edge, the pharyngobasilar fascia blends with the fibrocartilage around the border between the sphenoid and occipital bones and foramen lacerum. C, The pharyngobasilar fascia on the right side has been removed to expose the longus capitis attachment to the clivus lateral to the pharyngeal tubercle. This specimen has a vomerovaginal canal that shares its anterior end with the palatovaginal canal. The vomerovaginal canal is positioned between the vaginal process of the sphenoid and the ala of the vomer. D, 45-degree endoscope directed inferior. The upper edge of the superior constrictor is located at the C1 level at the border between the oropharynx and nasopharynx and is not usually opened for exposure of the lower clivus. The fossa of Rosenmüller projects laterally from the posterolateral corner of the nasopharynx behind the tubal elevation. The parapharyngeal segment of the internal carotid artery courses just deep to the lateral limit of the fossa of Rosenmüller. E, The longus capitis muscle and pterygoid process on the right side have been removed to expose the rectus capitis anterior muscle. F, Closer view. The rectus capitis anterior is a short, flat muscle that extends across the atlanto-occipital joint and connects to the lateral mass of the atlas and the basal part of the occipital bone. (Images courtesy of AL Rhoton, Jr.)

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