Extradural temporal lobe retraction in the middle fossa approach to the internal auditory canal - Biomechanical analysis

Hypothesis: The middle fossa (MF) approach is undergoing a marked resurgenc e in vestibular schwannoma surgery as a hearing conservation technique. It is widely recognized that the extradural temporal lobe retractors used in t his procedure, despite their cleverness of design, could be improved. Methods: To identify the characteristics of an ideal MF retractor, a system atic analysis of the safety and functionality of four commonly used retract ors (House-Urban, Fisch, Garcia-Ibanez, and UCSF) in a human anatomical mod el was conducted. Intensity of temporal lobe compression, width of exposure , angle of visualization, obstruction to instrument access, ergonomic conve nience of use, and adaptability to other subtemporal procedures (e.g. lesio ns of Meckel's cave and cavernous sinus) were quantified. Results: Because the intracranial portions of the retractors are similar, t he force transmitted to the brain differed little among the four retractors . Numerous differences were noted in the ergonomics of use and versatility of the various designs. Conclusions: The optimal MF retractor would incorporate the best features o f each of the existing systems: the integral suction of the Garcia-Ibanez, the bone contour-following design of the Fisch retractor base, the unobtrus iveness and adaptability of the UCSF, and the three-plane adjustability of the vintage House-Urban. Evolution of an "ideal" MF retractor requires furt her technical refinements and the development of an experimental model of e xtradural brain retraction to assess the optimal strategy for obtaining exp osure while minimizing the risk for temporal lobe injury.