Skull Base Surgery of the Posterior Fossa

32

maximize visualization of the cerebellopontine
angle and minimize retraction on the cerebellum.
For pathology that involves the foramen mag-
num, caudal extension of the exposure and
extensive bone removal as well as cerebrospinal
fluid (CSF) drainage from the cisterna magna

provides excellent exposure of the craniocervical

junction.

There are multiple methods of opening the

dura that are permissible as long as a watertight

dural closure is obtained. Although a single cur-

vilinear opening is probably the most popular

Fig. 2.6 (a) The asterion is identified on a right retrosig-
moid approach. The last centimeter of the three sutures,
whose intersection forms the asterion, has been marked in
black surgical marker with a pointer identifying it (lamb-
doid suture, occipitomastoid suture, and parietomastoid

suture). The beginning of the digastric groove has been

marked with black surgical marker as well (black arrow).

(b) The “zygomatic line” and a “mastoid line” marked out

on a right retrosigmoid approach as described by Tubbs

et al. [ 8 ]

Fig. 2.7 (a) Cadaveric specimen demonstrating large
single mastoid emissary foramen feeding the right sig-
moid sinus deep to the foramen. (b) Cadaveric specimen

showing the convergence of three mastoid emissary veins

as they drain eventually into the sigmoid sinus

C. Bowers et al.