A, The medial part of the orbital rim is formed by the frontal bone and maxilla. The anterior part of the nasolacrimal canal is formed by the maxilla and the posterior part by the lacrimal bone, which joins the ethmoid bone posteriorly and the frontal bone above. B, The medial part of the orbicularis oculi muscle has been exposed. The anterior band of the medial canthal ligament, which crosses in front of the lacrimal sac, is attached to the frontal process of the maxilla medially and to the superior and inferior tarsi laterally. C, The medial part of the orbicularis oculi muscle and some of the maxilla have been removed to expose the lacrimal sac, nasolacrimal duct, and a small part of the nasal cavity and maxillary sinus. D, The anterior band of the medial canthal ligament has been reflected laterally to expose the superior and inferior lacrimal canaliculi joining the lacrimal sac. Additional maxilla has been removed to expose the nasal cavity and inferior turbinate medially and the maxillary sinus laterally. The nasolacrimal duct opens into the inferior nasal meatus. E, Some of the posterior and medial wall of the maxillary sinus has been removed to expose the pterygopalatine fossa, which contains the maxillary nerve and artery and their branches and the pterygopalatine ganglion. F, The approach has been directed through the nasal cavity medial to the pterygopalatine ganglion and fossa to the clivus, which has been opened to expose the basilar artery. (Images courtesy of AL Rhoton, Jr.)