Study Of Microsurgical Anatomy And Operative Approaches Of The Vertebro-Basilar Artery

Objective: 1.To study origin,diameter,course,main branches and variations of the vertebro– basilar artery, and therefore provide anatomical bases for relevant clinical operations in this area such as the aneurysms and the intervention operation. 2.Mimicking Subtemporal approach and Pterional approach,describle operative approaches of the scope of the superior segment of Vertebro-basilar artery and compare difference of these operative approaches.Methods: the vertebro-basilar artery of 15 formalin-fixed adult brain specimens (30 sides)with intact dura mater were dissected under the surgical microscope.The length,diameter were measured and counted;their shapes,courses,branches and connections were observed and recorded. Then, to observe and measure the relationship among the targeted neurovascular structures,to describle the scope of exposure of operative approaches of the posterior and lateral region of the brain stem and to compare difference of these operative approaches by using the standard median Subtemporal approach and Pterional approach under the microscope, respectively.Result: 1.The distance between the point VA entering the duramater and median line are (15.37±1.22)mm(left), (15.24±1.06)mm(right). 2. Significant asymmetry of caliber of V4 are 4 cases. (outerdiameter of one V4 being at least 1 mm larger than its counterpart);shifting and curve V4 are 3 cases. 3. The distances from the edge of tentorium incisura to the trochlear nerve, the superior cerebellar artery, the posterior cerebral artery and the trigeminal ganglion were (1.90±0.31)mm,(5.12±0.17)mm,(3.32±0.55)mm and (0.80±0.08)mm respectively. 4. The diameter of the posterior cerebral arteries were (2.25±0.17)mm (left), (1.92±0.15)mm(right),the left and the right posterior cerebral arteries were not significant different (P>0.05). 5. Anterior inferior cerebellar artery (AICA) was constantly present in all specimens(100%) , The incidence of AICA formed the loop of AICA near facial root was 83.3%. 6. The pterional approach could be available to expose the distal basilar-PCA-superior cerebellar artery and P1～P2 segment aneurysms,and the subtemporal approach for P2～P3 aneurysms. 7.The scope of expoure was widen to lateral middle of pons and the trigeminal ganglion after cutting tentorium. trochlear nerve,superior cerebellar artery, posterior cerebral artery have a difficult relationship to tentorium incisura,so a greater expoure will be obtained to these anatomical structure by cutting tentorium. 8. By drilling the posterior clinoid and cutting tentorium process in the orbitozygom- atic-cavernous sinus approach, the exposure of superior segment of the basilar artery can be increased.Conclusion: 1.Normal and variable vertebro-basial artery have important significance on neurosurgery and angiograms. 2.The pterional approach could be available to expose the distal basilar-PCA-superior cerebellar artery and P1～P2 segment aneurysms ,and the subtemporal approach for P2～P3 aneurysms. 3.In subtemporal approach,the scope of expoure was widen to lateral middle of pons and the trigeminal ganglion after cutting tentorium. trochlear nerve, superior cerebellar artery, posterior cerebral artery have a difficult relationship to tentorium incisura,so a greater expoure will be obtained to these anatomical structure by cutting tentorium. 4.By drilling the posterior clinoid and cutting tentorium process in the orbitozygomatic-cavernous sinus approach, the exposure of superior segment of the basilar artery can be increased.