Anatomical Study Of Orbitozygomatic Subtemporal Approach For The Anterior Space Of Tentorial Incisura

Aneurysms and skull base tumors are the routine lesions in the anterior space of teniorial notch. It has traditionally been technically challenging because of the depth of the workspace and the criticals srtructures that obstruct visualization of this area. With advent of skull base techniques,many new approach has emerged as useful in managing lesions of the region. The operartion mortality and morbidity are decreased,tumors resection are changed better .It is important to apply the natural spaces of vessles,nevres and brain to access to the lesions.It is necessary to study the anatomy change.In the study,we research the anatomic relationship of the vessles nerves and brain stem and hypothalmaus,we also performed orbitozygomatic subtemporal approach,traditional subtemporal approach, extension of obitozygomatic subtemporal approach on cadaver head Specimens. On the study,we disscued some nunaes to manage the lesions in the region. Two parts are fellowed:Part1:The difference between obitozygomatic subtemporal approach and traditional subtemporal approach on anterior space of tentorial notch.Objective:1.To compare the different surgical exposure of obitozygomatic subtemporal approach,traditional subtemporal approach and extensional obitozygomatic subtemporal approach,and to explore their clinical indications.2.Observation of temporal bridging vein shape,and the location.Analysis the impact on operation.Methods:Ten(20sides) adult cadaveric specimens which perfused with colored silicone.Stepwise dissections via the obitozygomatic subtemporal approach,traditional subtemporal approach and extensional obitozygomatic subtemporal approach. Observe the difference of the anatomical characteristics.Analysis the surgical technique of the three approaches. Compare the field view angle between obitozygomatic approach traditional subtemporal approach and extentional obitozygomatic approach in the target being optic-carodic complex, the basilar bifurcation and the P2 segment of the posterior cerebral artery. Compare the between the three approach,and analyse the using scope. Expose temporal bridging veins,observe and measure under the microscope. Statistics the number of vessels, and their were classified.Result:1.The field view angle of the obitozygomatic subtemporal approach on optic-carodic complex higher 7.7°than traditional subtemporal approach, the field view angle increase 91.7%;on the basilar bifurcation higher 10.7°,the F.V.A increase 46.7%;on the P2 segment of the posterior cerebral artery higher 9.2°,the F.V.A increase 83.6%.2.There are 107 temporal bridging veins in the 20 sides of specimens.55 in the left side,52 in the right side. There were three configurations.The "separated type",the "bundle type" and the "multiple type", defined as the temporal bridging veins.and the second type was the major configurations.The locations of terminations of the bridging veins were divided into 4 groups:the transverse sinus group(55%),the posterior tentorial group(22%),the superior petrosal sinus(17%),and the anterior tentorial group(6%).Conclution:1.The obitozygomatic subtemporal approach expores more on anterior space of tentorial notch.2.extension of the FTOZ approach included the posterior root of the zygoma and the lateral part of the glenoid fossa. En bloc resection of the glenoid fossa and root of the zygomatic arch, together with the FTOZ osteotomy, facilitated reconstruction of the temporomandibular joint and increased the amount of exposure obtained with this FTOZ osteotomy. Comprehensive understanding of functional outcomes awaits further clinical study.3."Anterior drainage of the vein of Labbe" is a special type of the temporal vein,which is of clinical significance in operative exposure.The preoperative venous phase angiogram or magnetic resonance venogram should be scrutinized carefully.It is recommended to preserve all venous structures during petrosal approachesPart2:The microanatomical study of anterior space of tentorial incisura.Objective:To study the neural,cisternal,ventricular,arterial and venous relationship of the middle incisural space of the region of the tentorial incisura,as well as the cranial nerves and tentorial artery.To search the anatomical landmarks of these important neurovascular structures.Methods:Ten adult cadaveric heads were examined using 6 to 40 magnification after perfusing the arteries and veins with colored latex.In each,the relationship of the neural structures,cisterns,ventricles,arteries,veins and the tentorial artery were observed.The distances separating the important neursovascular structures and landmards were measured.Results:The important cranial nerves related to the middle incisural space of the tentorial incisura are the oculomoter,the trochlear and the trigeminal nerves.And the important arteries related to the middle incisural space are the anterior choroidal,posterior cerebral and superior cerebellar arteries.Superior cerebellar artery,the medial posterior choroidal artery and the long circumflex branches of posterior cerebral artery course middle incisural space parallel to the posterior cerebral artery.The important veins in this region is basal vein.The entrance site of oculomotor nerve to the roof of the cavernous sinus located at 11.2±4.3mm posterior to the anterior clinoid process,4.4±1.4mm laterally posterior to the posterior clinoid process.The entrance site of trochlear nerver located at 23.3±3.0mm posterior to anterior clinoid process,14.5±3.9mm laterally posterior to the posterior clinoid process.The entrance site of oculomotor nerver located at 6.3±1.6mm posterior to the sheath of internal carotid artery,while entrance site of the trochlear nerve 17.9±3.5 to the sheath of internal carotid artery.The entrance site of trochlear nerve located at 17.9±3.5mm posterior to the entrance site of oculomotor nerve.Before entering the cavernous sinus,one part of the trochlear never courses the middle incisura space 1.9±0.4mm medial to the free edge of the tentorium. Superior cerebellar artery usually passes below the level of the free edge with the distance 5.1±2.3mm away from the level of the free edge.The main trunk of the posterior cerebral artery is usually 3.3±1.7mm higher than the level of the free edge.The tentorial artery (Bernasconi-Cassinari artery)is existed at the 90% of the total cadaveric heads.In four sides of the specimens,besides the mening hypophyseal trunk,the artery that supplies the tentorium is also aring from the posterior cerebral artery.Conclusions:Anterior clinoid and posterior clinoid process-the two main points that construct the oculomotor trigone are the important landmarks for the surrounding important neurovasuclar structures.The sheath of internal carotid artery is also the landmark for the entrance site of the oculomotor and trochlear nerve.In the middle incisural space of the region of the tentorial incisura,the trochlear nerve is usually hided under the free edge of the tentorium.Then it should be very cautious when incising the tentorium.Besides the anterior and posterior clinoid process,the entrance site of the oculomotor can be used as the lankmark for the entrance site of the trochlear nerve during operation.The superior cerebellar artery,the posterior cerebral artery with its important branches,which are the medial posterior choroidal artery and the long circumflex branch are all closely related to the middle incisural space,and should not be injured during operation.The tentorial artery (Bernasconi-Cassinari artery)is still the major artery that supplies the tentorium.There are varied origins for the arteries that supply the tentorium.