Quantitative comparison of retrosigmoid intradural suprameatal approach and retrosigmoid transtentorial approach: implications for tumors in the petroclival region.

Background Retrosigmoid transtentorial (RTT) and retrosigmoid intradural suprameatal (RISA) approaches have been used in the treatment of petroclival tumors. Objective To compare the area of exposure of brainstem and petroclival region obtained through RTT and RISA in cadaveric specimens. Methods Five cadaveric specimens with a total of 10 sides were analyzed. RTT and RISA were performed on five sides each. Brainstem and petroclival surface exposure were measured using both the approaches. These values were compared between the two approaches. Results Brainstem area exposure with RTT was 441 ± 63 mm(2) and that with RISA was 311 ± 61 mm(2). Student's t-test revealed that the difference was significant (p = 0.01). The area of petroclival exposure medial to the Meckel cave through RTT was 696 ± 57 mm(2), and that through RISA was 716 ± 51 mm(2) (p = 0.69). The area of brainstem exposure between V and VII-VII complex through RTT and RISA was 387 ± 86 mm(2) and 378 ± 76 mm(2) (p = 0.87). Conclusion The RTT approach is an excellent approach to ventrolateral brainstem and petroclival region. It provides greater superoventral exposure of the ventrolateral brainstem than RISA and provides similar petroclival exposure.