| The anatomic and adjoining structures of the cerebellopontine angle(CPA) are so complexed and important that they have large clinic and practical value to know better anatomic realationship in the area and to identify and protect the nerves and blood vessels during operation.Objectives To study the shape of CPA and the realationship of the structures through imitating the operation of retrosigmoid approach under operative microscope and to measure cranial nerves and blood vessels and the figure related its operation to provide anatomic base for retrosigmoid approach. Methods The CPA and its structures were observed by operative microscope on 16 adule cadaveric heads via the restrosigmoid approach. Results (1) The CPA includes three cisterns: the prepontine cistern, the cerebellomedullary cistern, the cerebellopontine cistern.(2) The structures of nerves: There are facial, cochlear, vestibular and intermediate nerves through the CPA, whose top the trigeminus locates, whose cauda posterior group cranial nerves locate and which the abducens nerves lies in. Trigeminus, whose entire course in the cistern is (5.94±0.92)mm, locates the point (5.53±1.28)mm above the abducens nerve and (7.59±1.12)mm above cochlear nerve respectively, This distance from Dorello's canal to the midline and from facial nerve to the point at which the vestibulocochlear nerve join the brain stem is (3.56±1.28)mm and (2.46± 0.73)mm respectively. The length of facial and vestibulocochlear, glossopharygeal, vagus nerves are (14.57±2.89)mm,(13.51 ± 1.68)mm,(16.89 ±2.80)mm respectively. (3)The structures of blood vessels The AICA mainly originated from the basilar artery as a single (30CPAs,93.95%). The AICA gave rise to internal auditory arteries(23CPAs,72.5%). The PICA mainly originated from vertebral artery(25CPAs,78.75%). (4)Internal acoustic port located on the center of the petrous bone's medial surface, the cranial nerve Ⅶ,Ⅷ ran through the anterior superior part and the posterior inferior superior pare of the internal acoustic port respectively. Conclusions There are large differens 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 cochleare nerve. |
