Navigation-Guided Microsurgical Anatomy Study Of The Facial Nerve Canal In The Combind Transpetrosal Approach

There are many important structures like brain stem, cranial nerves and blood vessels in the petrous and clivus area (PCA). It is difficult to expose because it is narrow and is obstructed by osseous structures like mastoid and labyrinthine. Combined transpetroal approach is often used to resect tumors in this area, because it can reach there at shortest distance and supply an extensive sight, this approach can observe the III-XI cranial nerves and main artery clearly, enlarge the scope of operation, decrease the complication post operation and advantageous for resect tumors. As a result, combined transpetroal approach get a widely use in the operation of tumors in the PCA. The anatomy study of PCA will improve the protection of important related structures. It is always a challenge for neurosurgen to get a precise 3-D localization of complicated structure and focal in nerve structures. Neuronavigation system (NNS) has a 3-D space localization system not only, it has a live navigation function too. It can be a supplement to microneurosurgery. So the appliance of NNS has become an important sign of the minimally invasive neurosurgery. Studying the anatomy of the PCA is helpful to protect the important structures there. Combined transpetroal approach is the most commonly used to resect tumors in the PCA. To protect the function of facial nerve in the operation is the objection of morden neurosurgeon .The focal point research of anatomy in this approach is microanatomy till now, there are few reports to combine the neuronavigation together. For this purpose, we dissected eight cadaveric heads in order to provide anatomic support for surgery guided by neuronavigation system in this area.Objective To study the use of neuronavigation in combined transpetroal approach, and to provide the observation of the anatomic structure of the facialnerve canal (FNC) for protecting nerve. Methods A cadaveric study was performed on 16 sides of 8 adults cadaveric heads by neuronavigation location through combined transpetroal approach, the anatomy of the facial nerve and the relationship of related structures were observed and measured between the FNC and the related structure by mimicking the actual surgical procedure. Results (1) All FNC were successful to be navigated, the mean error was less than 0.9mm. (2) The FNC can be divided into 3 portions: the labyrinthine, the tympanic and the mastoid. Lengths of the 3 portions were (3.6+1.2)mm, (11.2+2.5)mm and (16.1+3.6)mm; diameters of the 3 portions were (1.2+0.3)mm, (1.4+0.1)mm and (1.7+0.2)mm. Conclusion NNS can be used to protect the FNC, it can help to protect the nerve with the knowledge of the anatomic marks and characteristic of the FNC.