91The venous drainage system must be carefully
evaluated before planning any skull base approach
to the PC region. In particular, the variations in
drainage patterns of the superficial middle cere-
bral venous and superior petrosal sinus systems
need to be appropriately assessed using either CTFig. 7.1 Case illustration of removal of petroclival tumor
via the retrosigmoid approach. (a, b) Coronal T1-weighted
MRI with gadolinium demonstrating large petrotentorial
tumor. (c) Axial T1-weighted MRI with gadolinium dem-
onstrating large petroclival tumor with brainstem com-
pression. (d) Surgical incision demonstrated in
relationship to transverse and sigmoid sinus. (e) Upon
exposure of the tumor, the VII and VIII nerve complex is
noted lateral to the tumor. (f) The posterior lip of the IAC
is drilled to assess the relationship between the tumor
attachment and the IAC. (g, h) The suprameatal protuber-
ance is drilled to afford exposure to the region of the
tumor attachment. (i) The trigeminal nerve is noted adja-cent to the attachment of the tumor. (j) The tumor is deb-
ulked using the ultrasonic aspirator. (k) The capsule of the
tumor is then dissected free of the cerebellum and brain-
stem. (l) The remaining tumor is removed from the attach-
ment to the petroclival-tentorial junction. (m, n) The
trochlear nerve is repaired using end-to-end suture tech-
nique. A 9-0 filament suture is used. (o) After tumor
removal is complete, the dura is closed in a watertight
fashion. Here, the authors have used autologous fascia as
a dural substitute. Note that the mastoid air cells have
been occluded with bone wax. (p, q) Axial FLAIR image
(p) and T1-weighted image with gadolinium (q) demon-
strating complete removal of the tumor7 Petroclival Meningiomas