Study Of Microanatomy Of Facial Nerve Of Cerebelloponotine Angle Via Retrosigmoid Approach

The anatomic and adjoining structures of the cerebellopontine angle(CPA)are so completed and important that they have large clinic and practical value to know better anatomic relationship in the area and to identify and protect the nerves and blood vessels during operation.Objectives To study the shape of CPA and the relationship of the structures through imitating the operation of retro sigmoid approach under operative microscope and to measure cranial nerves and blood vessels and the figure related its operation to provide anatomic base for retro sigmoid approach.Methods The CPA and its structures were observed by operative microscope on 10 adults cadaveric heads via the restro sigmoid approach.Results(1)The length of facial and vestibulocochlear nerves are(13.56±0.63)mm, (11.22±1.01)mm in CPA,the distance from facial nerve to the point at which the vestibulocochlear nerve join the brain stem is(2.31±0.61)mm.In the inner surface of CPA citern,the facial nerve lie on the ahead anodic of vestibulocochlear nerve,and on the decoct later of nervus statoacusticus,the intermediary nerve walk inside the two nerves.The trigeminal nerve lie on the inner anodic ofⅦ,Ⅷcranial nerve,the distance of the two nerves is about (7.60±2.16)mm,theⅦ,Ⅷcranial nerve lie on the lateral of abducent nerve,the distance of the two nerves is about(8.76±1.42)mm,the distance of the starting point of facial nerve and the starting point of glossopharyngeal nerve is about(8.15±2.15)mm,the distance of the two nerves is about(3.95±0.77)mm in the entrance of auditory canal,the diameter of the cranial nerve is about(1.57±0.06)mm,the diameter of the nervus statoacusticus is about(2.51±0.09)mm. (2)The number of radix nervi facialis that is oppressed by the blood vessel around is 6 CPAs, the number of radix nervi facialis that is touched with the blood vessel around is 2 CPAs,the totle number is 8 CPAs(8/20).The main blood vessel is artery that oppress or touch the radix nervi facialis,and the arteriae cerebelli inferior anterior is been sow frequently(5/8),the next is posterior inferior cerebellar artery and dislocated vertebral artery.The AICA mainly originated from the basilar artery as a single(19CPAs).The PICA mainly originated from vertebral artery(18CPAs,).(3)The frequency of artery fillet that is formulated with AICA is about 90%.Conclusions There are large differents of the nerves and blood vessels in CPA.These anatomic study will help the neurosurgeon to correctly localize the facial and cochlear nerve during operations and to result in low morality and more higher anatomic and functional protection of the facial and cochleae nerve.