Microscopic Anatomy Study About The Facial Nerve And Internal Auditory Canal Related To Acousitc Neuroma By Retrosigmoidal Approach

Objective To investigate the microsurgical anatomic research on the facial nerve inthe cisterna and the internal auditory canal and facial nerve,vestibular nerve and vesselwithin it, with which anatomical references were provided for surgery on acousticneurinomas.Method （1）15skulls were observed and measured on30the internal auditory canaland their adjacent bony structural anatomy parameters;（2） On24side of12cadaverheads, with the aid of surgical microscope and endosccope, the anatomic relationshipsof the facial nervers in the cisterna （3）In12cadaveric heads we simulatedsuboccipital retrosigmoid sinus approach to rub down posterior internal auditory canaland to dissect Internal auditory canal and facial nerve,vestibular nerve within it.At thesame time we undertook multi-angle observation and comparison by neuroendoscopy.（4）In the end, expand the exposure to CPAand measure relative data.Results (1)To the internal auditory canal the average distance from the facial nerveroot located in the brainstem is (12.15±2.37mm),and the length of the facial nerveinside internal auditory canal is (10.52±1.54mm). The brainstem end of the facialnerve has (2.62±1.32mm) apart from the one of the vestibulocochlear nerve, adistance of4.72±1.64mm from the trigeminal brainstem side,and3.82±1.44mmaway from the glossopharyngeal nerve brainstem side. Cerebellar flocculus,foramen ofLuschka and choroid plexus, appear in the rear and beneath the facial nerve brainstemside.(2) The length of internal auditory canal posterior wall is (9.88+0.85) mm, thetransverse ridge is (6.58+0.54) mm long, and vertical ridge is (2.67+0.31) mm. Theinternal auditory crossing has a distance about (46.3±5.10) from the sigmoid sinus corner,(6.88±3.77) mm away from meckel’s hole distance, from which the shortestdistance to the jugular foramen is (4.60±1.43) mm.(3)By neuroendoscopy we can seebrainstem ends of cranial nerves,including the vestibulocochlear nerve, the facialnerve,the glossopharyngeal nerve and choroid plexus.meanwhile,the facial nerve motorroot located in the cisternal segment and nerve intermedius from the brainstem side tointernal auditory crossing can be observed clearly; Nerves and vessels close to theinternal auditory crossing can be observed easily by neuroendoscopy.Conclusion：（1）Detailed dissection was performed on steady anatomy relationshipsbetween facial nerve and trigeminal nerver, vestibulocochlear nerve, glossopharyngealnerve,flocculus,choroid plexus. the facial nerve can be identified and protected by it’spermanent relationship in anatomical with vestibulocochlear nerve, glossopharyngealnerve, arteriae cerebelli inferior anterior, flocculus cerebelli, choroid plexus.（2）Therelative position between facial nerve and vestibular nerve inside Internal auditorycanal is constant; We can quickly find facial nerve by transverse ridge and verticalcrest;The structure inside Internal auditory canal can be observed from Inner listeningcrossing by neuroendoscopy.（3） Neuroendoscopy can extend the viewing angle ofthe facial nerve and internal auditory canal, and contribute to identify intraoperativefacial nerve.