COMPARATIVE ANALYSIS OF THE RETROSIGMOID AND LATERAL SUPRACEREBELLAR INFRATENTORIAL APPROACHES ALONG THE LATERAL SURFACE OF THE PONTOMESENCEPHALIC JUNCTION

Abstract

To quantitatively assess the working distance and angle of attack among the retrosigmoid (RS), lateral supracerebellar (LS), and extreme lateral supracerebellar (EL) views on the lateral surface of the pontomesencephalic junction. Eight sides of silicone-injected fixed cadaveric heads were dissected using the three approaches. All predetermined anatomic points were collected by use of a frameless stereotactic device. The length of exposure and the angle of attack were calculated and compared. Predissection imaging was obtained for illustration. The LS and EL approaches created a horizontal working space as compared with the vertical working space created by the RS approach. The RS view gained less posterior exposure margin than the LS and EL views (posterosuperior margin values: RS, 4.3 +/- 1.7 mm; LS, 6.4 +/- 2.0 mm; EL, 7.3 +/- 2.0 mm; P < 0.001; posteroinferior margin: RS, 2.7 +/- 2.7 mm; LS, 4.9 +/- 2.8 mm; EL, 8.3 +/- 2.5 mm; P < 0.001). When the tentorium is intact, transverse sinus retraction significantly accentuates the field of view by the EL approach compared with the LS approach at both the anteroinferior (P < 0.05) and posteroinferior (P < 0.001) margins. Between the supracerebellar types, the vertical angle of attack was significantly improved and the horizontal angle was significantly decreased when complete venous retraction was performed. The supracerebellar views offer greater advantage over the RS view when the surgeon is working more posteriorly on the pontomesencephalic junction. Between the supracerebellar views, venous retraction creates a significantly wider vertical angle and also improves the exposure when the surgeon is working more inferiorly.