31across the long axis of the arm to open up the
angle between head and shoulders, maximizing
the surgeon’s angles of attack and visualization
of the operative space during the operation
(Fig. 2.4a, b).
We utilize a C-shaped, retroauricular incision
about two fingerbreadths medial to the mastoid
process, which extends from the pinna to the tip
of the mastoid (Fig. 2.5a, b). In most cases, we
prefer to raise a single myocutaneous flap with a
combination of electrocautery and sharp dissec-
tion. Although many authors prefer to raise a sub-
galeal flap and take the combined fascia/
periosteum at the insertion of the sternocleido-
mastoid as a separate local periosteal flap, we
harvest a separate free flap (temporoparietal fas-
cia or fascia lata) as necessary. The subperiosteal
dissection is carried down, and the asterion is
identified (which may also be confirmed with
intraoperative neuronavigation).
Craniotomy Technique
Prior to the marking of the skin incision, the posi-
tions of the transverse and sigmoid sinuses should
be approximated with anatomic landmarks or
confirmed with neuronavigation. A straight line
drawn from the root of the zygoma to the poste-
rior occipital protuberance (inion) defines the
course of the transverse sinus (Fig. 2.5b) [ 8 ]. The
asterior and digastric grooves are identified
(Fig. 2.6a). The “zygomatic line” and a “mastoid
line” as described by Tubbs et al. [ 8 ] and demon-
strated in Fig. 2.6b are marked with a surgical
marker at the time of surgery to approximate the
transverse-sigmoid junction.
In our experience, there is a lower likelihood
of tearing the dura or the lateral wall of a sinus
with craniectomy as opposed to a craniotomy. A
high-speed cutting burr such as a 6 mm fluted
ball or acorn bit is used to fashion a craniectomy
tailored to the size and scope of the lesion. Care
is taken to expose the sigmoid-transverse junc-
tion at the superolateral margin of the craniec-
tomy without violating the venous sinuses. Often,
the mastoid emissary vein (Fig. 2.7a) or a com-
plex of emissary veins (Fig. 2.7b) may be skele-
tonized and followed ventrally and superiorly to
its insertion near the junction of the sinuses.
Invariably, the mastoid air cells will be entered
prior to thinning out the bone over the sigmoid
sinus (“blue lining”) and should be packed with
wax during exposure (and again during recon-
struction) to prevent a postoperative CSF leak
(“wax in, wax out”).
Kerrison rongeurs are used to remove 4–6 mm
of bone overlying the sigmoid sinus (Fig. 2.8) toFig. 2.5 (a, b) A C-shaped retroauricular incision two
fingerbreadths medial to the mastoid process, extending
from the pinna to the tip of the mastoid. Figure b has a red
line drawn from the root of the zygoma to the inion,
approximating the course of the transverse sinus2 Retrosigmoid Craniotomy and Its Variants