The Clinic Anatomical Study Of Skull Base By Maxillary Swing Approach

Objective To provide accurate skull base anatomical data in order to ensure the safety of surgery. Methods First, 10 cadaveric adult heads (20 sides) soaked with 10% formalin were undergone carotid artery and internal jugular vein perfusion with red latex and blue latex respectively. Second, parietal bone and brain tissue were removed to expose internal surface of skull base. Using maxillary swing approach to gradually expose the anterior, middle and lateral skull base, the relative anatomical data were measured. 1. Exposure of the anterior skull base: 1.1 Paries inferior orbitae and orbital internal periosteum was stripped and orbital contents were evaginated and removed to expose Dacryon point, frontomalar orbitale and orbital apex. The distances from Dacryon point and frontomalar orbitale to medial and lateral terminals of superior orbital fissure were measured respectively. 1.2 Nasal process of maxilla and lamina papyracea were resected and ethmoid sinuses were opened and enlarged to expose posterior wall of frontal sinus, ethmoid sinus and cribriform plate . The distances from the anterior border of comb to the midpoint of cribriform plate posterior border, the width of two sides of cribriform plate in comb posterior border were measured horizontally at the superior and inferior skull base. 2. Exposure of the middle skull base: 2.1 Dissecting infraorbital nerve to the external portal of foramen rotundum, then to the outlet of calalis pterygoideus by the interior and inferior of foramen rotundum, the distance from the posterior border of foramen rotundum to anterior border of the outlet of calalis pterygoideus was measured. 2.2 Resecting pterygoid process with root reserved, dissecting mandibular nerve to foramen ovale, then dissecting root of pterygoid process to foramen lacerum, the distances from anterior medial border of pterygoid process root to anterior border of foramen lacerum and from anterior lateral border of pterygoid process root to anterior border of foramen ovale were measured respectively. 2.3 Dissecting foramen rotundum and foramen ovale inside of skull base, the distance between the two foramens was measured. The relation between the line of the two foramens and cavernous sinus was observed and the relation between the root of pterygoid process and cavernous sinus was comprehended accordingly. 2.4 Opening sphenoid sinus and dissecting internal carotid artery, optical nerve in rear of ethmoid sinus or / and lateral side of sphenoid sinus, the distances from anterior nasal crest to superior horizontal part of internal carotid artery and from orbital portal to skull portal of optical nerve were measured. Dissecting optic-carotid recess, adjacent structures of which were observed. 3. Exposure of the lateral skull base: Resecting the ascending limb of inferior maxilla and exposing articular fossa of mandible, dissecting internal carotid artery and internal jugular vein to the external aperture of carotid artery and jugular foramen respectively, dissecting styloid process to skull base, the distances from the posterior border of foramen ovale to the anterior border of the external aperture of carotid artery and from the inner margin of articular fossa of mandible to the outer margin of the external aperture of carotid artery were measured. The relations between internal carotid artery and internal jugular vein and styloid process near skull base and in skull base were observed anteriorly to posteriorly. Results 1 1.1 The distances from Dacryon point to lateral and medial terminal of superior orbital fissure were 42.5±3.52mm, 37.2±2.52mm(left)and 42.8±3.90 mm, 37.8±2.57 mm(right) respectively .The distances from frontomalar orbitale to lateral and medial terminal of superior orbital fissure were 34.0±2.76mm, 49.3±3.02mm(left) and 35.0±4.30 mm,49.5±3.54mm(right) respectively. 1.2 The distances from anterior comb to the midpoint of posterior cribriform plate was 21.6±2.28 mm. The ultimate distance of cribriform plate posterior to comb was 8.8±2.32 mm. 2 2.1 The medial border of pteryoid process root was foramen lacerum .The lateral border of pteryoid process root was foramen ovale. The distances from medial border of pteryoid process root to anterior border of foramen lacerum were 11.9±2.35mm(left), 12±1.85 mm(right).The distances from lateral border of pteryoid process root to anterior border of foramen ovale were 14.4±1.87mm(left), 14.8±2.34 mm(right). 2.2 The distances from anterior nasal crest to superior horizontal part of internal carotid artery were 66.9±2.91 mm(left), 67.6±2.23 mm(right). The distances from orbital portal to skull portal of optical nerve were 8. 1±1.82 mm(left), 8.24±1.70 mm(right). 2.3 The distances from external portal of foramen rotundum to inferior medial portal of calalis pterygoideus were 5.08±2.04mm(left), 5.6±1.41mm(right). The distances from foramen rotundum to foramen ovale in skull were 7.43±1.49mm(left), 8.85±2.60mm(right). The line of the two foramen was identical with the lateral border of cavernous sinus and was approximal to the outer plate of pterygoid process. 2.4 Whether shaping a intumescentiae or not of internal carotid artery and optical nerve in rear of ethmoid sinus or / and lateral side of sphenoid sinus, both sides shaped recess ,optical- internal carotid artery recess, which formed the marker for earching internal carotid artery and optical nerve. 3. 3.1 The distances from the posterior border of foramen ovale to the anterior border of the external aperture of carotid artery were 9.6±1.85mm(left), 9.1±2.0mm (right). 3.2 The distances from the medial margin of articular fossa of mandible to the lateral margin of the external aperture of carotid artery were 12.3±2.95mm(left), 11.5±3.12mm (right). 3.3 Internal jugular vein was posterior lateral to internal carotid artery. Internal carotid artery was posterior to coronal plane at ultimate point medial border of articular fossa of mandible. Internal jugular vein exited jugular foramen medial to styloid process. Conclusions Using maxillary swing approach can thoroughly expose the anterior and middle and lateral skull base . Comb, cribriform plate, pterygoid process, optic-carotid recess,foramen rotundum, foramen ovale, internal carotid artery, optical nerve and their adjacent structures are important anatomical landmarks for anterior, middle and lateral cranial base. It is important to know the anatomical landmarks to ensure the safety of the skull base surgery.