Microsurgical anatomy of the anterior subtemporal- medial transpetrosal approach to the petroclival region

Objective To obtain more detailed anatomic imformation about the anterior subtemporal transpetrosal approach to the upper brain stem and clivus. Methods Twenty sides of 10 adult cadaver heads fixed in formalin were used. The relationship of the main structures was observed and measured, and the actual surgical procedure was mimicked under the surgical microscope. Results The apical petrosal bone was removal via a subtemporal approach through the triangle area which surrounded by the superior petrosal sinus the greater superficial petrosal nerve and the edge of the mandibular nerve. The superior semicircular canal was located almost perpendicular to the petrosal edge under the arcuate eminence. The cochlea was located anterior to the internal auditory canal and posterior to the genu of petrosal carotid artery. The internal auditory canal was located in the line dividing the angle formed by the greater petrosal nerve and the superior semicircular canal. Two of the 20 sides facial genu had no bone cover. The average distance between the cochlea to the geniculate ganglion and the genu of petrous carotid was (3.03()0.79) mm and (2.48()1.14) mm, respectively. The average length of the internal auditory canal to petroclival suture was (16.03 () 1.94) mm, and the average height of the horizontal segment of petrous carotid to the superior petrosal sinus was (10.73()2.00) mm. Conclusion The anterior subtemporal-medial transpetrosal may improve the vison of the region of petroclival and ventral of the brain stem, but the exposure area is limited and There are also need a limited temporal lobe retraction and accidentally injury the cochlea, carotid artery and 6 to 8 nerves due to being unfamilliar with the anatomy. It must be considered carefully when using this appoach.