ABSTRACT
The Trans-labrynthine approach, through Otic capsule gives direct approach to the cerebellopontine angle (CPA) and internal auditory meatus (IAM) with preservation of the facial nerve. Mastering the approach to IAM in a cadaver with anatomical landmarks is important to the budding Otologist & Neurotologist to approach the CPA with functional preservation of the Facial nerve in patients with Vestibular Schwannoma & other procedures. Transitioning surgical skills and anatomic knowledge from surgical anatomy textbooks and laboratory training to the operative room is challenging. 30 adult wet human cadaveric temporal bones were studied by performing Trans-labrynthine approach to the IAM by using ZEISS microscope in a temporal bone dissection lab. Photographs were taken by HD phone camera, imported into computer & labeled the anatomical landmarks. Wide exposure & 3D visualization of complex anatomical landmarks were noted in each step by step approach from basic to advanced procedure of Trans-labrynthine approach to IAM. The step by step approach to the IAM from basic to advanced procedure in a cadaveric temporal bone offers great orientation & opportunity to become a master of the complex surgical anatomy of IAM and in acquiring a 3D orientation of the critical structures.
ABSTRACT
Facial recess approach through posterior tympanotomy is the most common & best appraoch for facilitating Cochlear Implant surgery through the round window. Sacrificing Chorda tympani nerve can be avoided by proper understanding of the anatomy of the Facial Recess & Chorda-Facial angles. Hence it is important to know the Chorda-Facial angle to prevent injury in Facial recess approach during Cochlear Implant surgery. Objective This study is done to know the Chorda-Facial angle variation with Round Window visibility during the Facial recess approach which is of relevance in Cochlear Implant surgery. Methods Thirty adult normal wet human cadaveric temporal bones were studied by performing by Posterior Tympanotomy & Facial Recess approach by using ZEISS microscope. Photographs were taken by digital camera of 26 megapixel, imported into computer, then Chorda-Facial angle were measured by Digimizer software & mean angle was calculated. Results The mean angle between the facial nerve & chorda tympani nerve was 20.232°. Bifurcation of chorda tympani nerve at the level of origin itself from the vertical segment of facial nerve was found in 6 Temporal bones out of 30. Round window visibility was noted in all 30 temporal bone specimens (100%). Conclusion The wide Chorda-Facial angle variations, especially the narrowest angle should be known to the otologist in particular to the Cochlear Implant surgeon, which may help avoid inadvertent damage to the CTN in facial recess approach during Cochlear Implant surgery & use diamond burr size of 0.6 mm or 0.8 mm.
