The retrolabyrinthine approach is a safe route to the cerebellopontine angle, which allows preservation of hearing and facial nerve function. However, it doesn't allow a straight view of the whole internal auditory canal (IAC) with the operating microscope. The endoscopes may be used to assess the IAC during retrolabyrinthine approaches. AIM: The objective of this study is to evaluate the capabilities of different angled endoscopes in assessing the IAC. STUDY DESIGN: Anatomic study. MATERIAL AND METHOD: We performed the retrolabyrinthine approach in 40 temporal bones and then we measured the hidden distance in every quadrant as seen with the microscope and the 0º, 30º and 70º endoscope. RESULTS: We observed that the hidden distances decreased, statistically, according to the optic used, in the following sequence: microscope, 0º, 30º and 70º endoscope. Only the 70º endoscope allowed a full view of the fundus of the IAC, which occurred in 27.5% of the cases. Partial view of the fundus of the IAC was possible in 67.5% of the bones with the 70º endoscope and in 12.5% with the 30º endoscope, whereas neither the 0º endoscope nor the microscope allowed any view of the fundus. The mean hidden distances at the superior-anterior quadrant measured with the microscope and the 0º, 30º and 70º endoscopes were, respectively: 10.4mm, 7.3mm, 4.3mm and 1.1mm. The 70º endoscope was significantly better than the others in the evaluation of the IAC and it should be considered the optic of choice in the assessment of the IAC during retrolabyrinthine approaches.
internal auditory canal; retrolabyrinthine approach; endoscopy
