Skull Base Surgery of the Posterior Fossa

33

method of dural opening because of the potential
of closing the dura with a running suture, we also
sometimes utilize a T-shaped dural opening to
allow for maximal visualization with the bottom
part of the T coming right up to the transverse-
sigmoid junction (Fig. 2.8, black lines). Once the
cerebellum is exposed, tenting sutures are placed
along the superior and ventral margins to increase
the angles and degree of exposure. Care should
be taken though, as these may completely occlude
the sinuses during the case, resulting in a trans-
verse sinus thrombosis.
Handheld retractors can be used to help with
the exposure of the petrous temporal bone and
the tentorium cerebelli, permitting sharp dissec-
tion/division of arachnoid tethering the cerebellar
hemisphere. If a lumbar drain was not preposi-
tioned into the subarachnoid space preopera-
tively, the arachnoid around the foramen magnum
may be sharply dissected, and additional brain
relaxation can be obtained by further drainage of
CSF from this cistern. Although retractionless
surgery is preferred, placement of a self-retaining
retractor over the surface of the cerebellum may
be required early on for visualization of key

neurovascular structures in the cerebellopontine

angle. The other key maneuver (aside from CSF

relaxation) for safely increasing exposure is to

control and divide the petrosal (veins) early in the

case. For large lesions or lesions within the supe-

rior third of the CPA cistern, these veins may be

sacrificed with relative impunity to further unte-

ther the hemisphere. The veins should be divided

closer to the cerebellar surface, leaving a “tail”

off their insertion into the sinus/tentorium; ampu-

tating the complex at its insertion results in a hole

in the wall of the petrosal sinus, which may be

difficult to control without packing it off with

oxidized cellulose.

Reconstruction and Closure

Obtaining watertight dural closure is important to

reduce the incidence of postoperative CSF leak.

In cases where the dura is thin or compromised,

the use of a dural patch with dural substitutes as

well as abdominal fat graft may be of benefit.

Regardless of type of dural opening, care should

be taken to keep the dural folds moist during the

case to help with future closure and utilize dural

grafts as needed to obtain a watertight dural clo-

sure (Fig. 2.9).

Fig. 2.8 A large right retrosigmoid craniectomy has been
performed, so the transverse sinus is completely exposed
(black arrow). The sigmoid sinus is exposed and covered
with thrombin-soaked Gelfoam pieces (black arrowhead)
for hemostatic purposes. The dural opening is outlined
with thick black lines

Fig. 2.9 Right-sided watertight dural closure with a

suturable dural graft after a retrosigmoid craniectomy was

performed for an acoustic neuroma resection

2 Retrosigmoid Craniotomy and Its Variants