Study Of Microanatomy And Endoscope Anatomy Of Cerebelloponotine Angle Via Suboccipito-retrosigmoid Approach

There are many important structures like brain stem, cranial nerves and blood vessels in the cerebellopontine angle (CPA). It is difficult to expose because it is narrow and is obstructed by osseous structures like mastoid and labyrinthine o Retrosigmoid approach is often used to resects tumors in CPA, drilling the posterior wall of the internal auditory canal (IAC) without damaging the labyrinth in acoustic neuroma surgery via the retrosigmoid approach is very important on postoperative hearing, however the labyrinthine structures exhibit great antomic variability, there are no landmarks that indicate their exact locations within the petrous bone. Therefore, opening of the IAC via the retrosigmoid route is based solely on preoperative computed tomographic (or MRI) findings and the personal experience of the surgeon. Endoscopes-assisted microneurosurgery is an important part of the minimally invasive neurosurgery. As an assisted equipment, endoscope is a supplement to microscope in craniotomyo Anatomy with endoscope is not same as with microscope. Neurosurgeon should know well the endoscope anatomy, studying the anatomy of the CPA is helpful to protect the important structures there. For this purpose, we dissected five fresh cadaveric heads. To avoid the bias caused by moving the brain tissue, nerves or blood vessels, we study with endoscope in different angle of view first, then study and measure data between osseous landmarks with microscope. To provide anatomic support for surgery of this area.Objective To explore the shape of Chinese cerebellopontine angle and relationship of the structures in it, and provide anatomic base for retro-sigmoid approach. Methods The cerebellopontine angle and its structure were observed by neuro-endoscope and operative microscope on 5 fresh cadaveric heads via the retrosigmoid approach. The distance from the posterior inferior edge of internal acoustic port to the central point of the posterior edge of the sigmoid sinus and to the posterior edge of theposterior semicircular canal and to the jugular foramen were measured. Results The jugular foramen located on the lower part of petrous bone's inner surface, and its shape was irregular. Inferior petrosal sinus, sigmoid sinus, jugular veins, and IX > X > XI cranial nerves ran through it.internal acoustic port located on the center of the petrous bone's medial surface, the cranial nerve VII ran through the anterior superior part of the internal acoustic port, and the cranial nerve VIII ran through the posterior inferior superior part. The anterior inferior cerebellar artery (AICA) send out 1~3 Internal auditory arteries. The distance from the posterior inferior edge of internal acoustic port to the central point of the posterior edge of the-sigmoid sinus was 32.1 ?1.9mm on the left, and 33.3 ?1.7mm on the right, the distance from the posterior inferior edge of internal acoustic port to the posterior edge of the posterior semicircular canal was 12.5?.3mm mm on the left, and 13.2?.2mm on the right, the distance from the posterior inferior edge of internal acoustic port to the jugular foramen was 4.8 + 0.8 mm on the left, and 5.0+1.1 mm on the right. Conclusions To be familiar with the microanatomy of the cerebellopontine angle and structures in it is important to save the function of cranial nerves VII and VIII in the acoustic neuronal operation.