Skull Base Surgery of the Posterior Fossa

57

Skin Incision and Craniotomy

The skin incision is made starting from the zygo-
matic arch approximately 1 cm anterior to the
tragus and extending superiorly just behind the
hairline to the level of the superior temporal line.
The incision curves posteriorly about two finger
breadths above the pinna and two finger breadths
behind the mastoid before curving caudally and
stopping approximately 4 cm below the level of
the mastoid tip (Fig. 4.1). The skin flap is ele-
vated in a plane superficial to the temporalis fas-
cia and retracted inferiorly and anteriorly; the
superficial temporal artery is preserved. Next, the
temporalis fascia is dissected off the muscle and
kept in continuity with the sternocleidomastoid
(SCM) muscle forming a pedicled flap to be used
for the closure. The SCM muscle is released from
its attachment to the occipital bone and the mas-

toid and reflected down along with the pedicled

temporalis fascia. The temporalis muscle is then

elevated via subperiosteal dissection that pre-

serves its deep vascular supply [ 13 ] and is

retracted anteriorly and inferiorly. At this point,

the temporal fossa, the lateral aspect of the poste-

rior fossa and the mastoid along with the root of

the zygoma, is well exposed.

Burr holes are placed rostral and caudal to the

transverse sinus, one set laterally just behind the

level of the sigmoid sinus and one set medially as

allowed by the exposure for a total of four burr

holes. A drill with a footplate attachment is used

to liberate the temporal and occipital portions of

the craniotomy, while a drilling burr is used to

connect the cuts overlying the sinus. Once the

craniotomy is completed and the bone flap is ele-

vated, a mastoidectomy is pursued in order to

fully skeletonize the sigmoid sinus to the level of

Fig. 4.1 The skin incision is made starting from the
zygomatic arch approximately 1 cm anterior to the tragus
and extending superiorly just behind the hairline. The
incision curves posteriorly about two finger breadths
above the pinna and two finger breadths behind the mas-
toid before curving caudally. For the combined petrosal

approach, the incision is carried anteriorly to provide

additional access to the middle cranial fossa (blue dotted

line); for the posterior petrosal approach, the incision does

not need this additional curve and is carried up from the

zygoma (red dotted line). Both incisions have a common

posterior limb (black dotted line)

4 Posterior and Combined Petrosal Approaches