Applied Microanatomy Of The Facial Nerve Cerebellopontine Angle Segment Through Ventral Brainstem

Objective According to the latest anatomical section of the cerebellopontine angle segment of the facial nerve,the structure of the surrounding nerve and vessels in the cerebellopontine angle segment of facial nerve was exposed through the oropharynx to the ventral side of the brainstem.To study the anatomical relationship between cerebellopontine angle segment of facial nerve and surrounding neurovascular structures and to offer anatomic parameters for treating hemifacial spasm with microvascular decompression.Methods Fifteen adult head specimens were exposed to the ventral surface of the brainstem through oropharynx to clivus.Microscopic measurements were made on the sections and structures around the cerebellopontine angle segments of the facial nerve.The spatial relationships between the segments and the structures of vestibulocochlear nerve,the glossopharyngeal nerve and flocculus were observed and measured.Results The distance from root detachment point of facial nerve to root exit point of facial nerve,internal acoustic pore were 6.08mm±0.85 mm,11.55mm±1.11 mm.The distance from root detachment point of vestibulocochlear nerve to root enter point of vestibulocochlear nerve,internal acoustic pore were 6.86mm±0.91 mm,10.20mm±1.19 mm.The root exit point and root detachment point of facial nerve are important region of decompression of facial nerve,which are located in the inner side of root exit point of glossopharyngeal nerve,root detachment point of vestibulocochlear nerve,inside edge of flocculus.The distance from root exit point of facial nerve to root exit point of glossopharyngeal nerve,root detachment point of vestibulocochlear nerve,inside edge of flocculus were 2.12mm±0.44 mm,6.32mm±0.76 mm,5.65mm±0.99 mm,respectively.The distance from root detachment point of facial nerve to root exit point of glossopharyngeal nerve,root detachment point of vestibulocochlear nerve,inside edge of flocculus were5.95mm±0.70 mm,1.18mm±0.53 mm,2.98mm±0.73 mm,respectively.The proportion of different subsections of the cerebellopontine angle segment compressed by different blood vessels was disparate.anterior inferior cerebellar artery mainly oppress the root detachment point and attached segment of facial nerve.posterior inferior cerebellar artery mainly oppress the root detachment point and the root exit point of facial nerve.Conclusion The root exit point of the facial nerve and the root detachment point of facial nerve are the focal point of decompression and can avoid the damage during operation for it's closely related to the vascular compression and deep space.Glossopharyngeal nerve,vestibulocochlear nerve,flocculus are important signs for fast positioning of cerebellopontine angle segment of facial nerve to decompression in the operation.