Endoscopic Internal Auditory Canal and Cerebellopontine Angle Surgery

Introduction and Background

Approaches to the internal auditory canal (IAC) and cerebellopontine angle (CPA) require an intimate knowledge of the anatomy and its potential variations to obtain the best outcomes and to minimize complications. The operating microscope has long been the primary means used by the surgeon to visualizes the operative field and has the advantage of both providing depth perception and allowing the surgeon to use both hands. The microscope provides a line-of-sight view but does not allow one to see around corners without removing the overlying bone or significantly changing the angle of visualization. The illumination of the operative field is achieved with a light source adjacent to the microscope lens and decreases with magnification. Endoscopes provide superb magnification, illumination, a wide-field view, and the ability to look around corners. The advantages of the endoscope lend itself well to the complex anatomy of the temporal bone and CPA. The disadvantages of the endoscope are the potential for thermal or mechanical injury with the tip of the scope, lack of depth perception, and adapting to one-handed surgery since the non-dominant hand holds the endoscope. The three standard microscopic approaches to the IAC and CPA include the retrosigmoid (RS), middle fossa (MF), and translabyrinthine (TL) approaches, with the indications varying among surgeons. The use of the endoscope as an adjunctive means of surgical field visualization in lateral skull base surgery was first reported in the 1970s. More recently, endoscopes have been used as the primary tool for CPA and IAC visualization and dissection by several centers.

Endoscopic Approaches to the Internal Auditory Canal and Cerebellopontine Angle