34
Alternatively, temporalis fascia may be har-
vested, or a free fascial graft may be harvested
from the abdominal wall or tensor lata.
Additionally, the use of dural sealants may be
necessary to ensure a watertight seal and prevent
postoperative CSF leak. All bony surfaces and
mastoid air cells are carefully waxed to limit the
risk of postoperative CSF rhinorrhea or
otorrhea.
Several studies have shown a lower incidence
of postoperative headaches and better cosmetic
outcomes when the dura is separated from the
overlying soft tissues, preventing tension on the
dura as the suboccipital muscular contracts [ 17 ].
We use a combination of titanium mesh and
hydroxyapatite cement impregnated with antibi-
otic powder to fashion a cranioplasty prior to
skin closure. This also serves to tamponade and
secures the dural reconstruction.
Complications
Aside from the typical complications associated
with any craniotomy, such as infection, postop-
erative hematoma, and parenchymal and/or neu-
rovascular injury, the retrosigmoid approach is
significantly associated with higher rates of CSF
leaks and postoperative headaches when com-
pared with other cranial surgical approaches [ 18 ,
19 ]. One recent meta-analysis of the three
approaches for acoustic neuroma surgery (trans-
labyrinthine, middle fossa, and retrosigmoid)
found that in >5000 patients in 35 studies, the
only significant complication differences between
the approaches were higher rates of CSF leak and
postoperative headache with the retrosigmoid
approach [ 18 ]. CSF leak is a known risk of poste-
rior fossa cranial procedures because of the need
for watertight dural closure. In addition to the
main concern for leaking from the dura and
through the incision or pseudomeningocele
development, the air cells of the mastoid are fre-
quent sources of CSF leak and must be waxed off
so that CSF cannot enter through them.
Postoperative headaches are also common
with the retrosigmoid approach; two of the more
common explanations are bone dust entering into
the posterior fossa from internal acoustic meatus
drilling and muscle-dural attachment and adhe-
sion after surgery [ 18 ]. Multiple studies have
shown decreased rates of postoperative retrosig-
moid headaches when a cranioplasty is per-
formed at the time of closure so that the muscles
cannot attach to the dura, but this benefit is only
seen after 1 year of increased headaches after sur-
gery [ 18 – 22 ]. Transverse and/or sigmoid sinus
occlusion after a retrosigmoid approach is a
potentially serious problem as it has been associ-
ated with headaches, increased intracranial pres-
sure, seizures, and even intracranial hemorrhage
[ 23 ]. There is a paucity of data involving rates of
sinus occlusion after retrosigmoid craniectomy.
One report in the otolaryngological literature
suggests it is not even of clinical significance,
and therefore they do not monitor for it or treat it
when it occurs [ 24 ]; however, reports in the neu-
rosurgical literature treat it as potentially lethal
and thus recommend treating it with anticoagula-
tion when it occurs. Pseudotumor cerebri can
occur occasionally after transverse-sigmoid sinus
occlusion, requiring subsequent treatment [ 24 ,
25 ]. Although more research needs to be done,
standard practice is to avoid sinus occlusion at all
costs, with some authors advocating initiating
non-bolus systemic heparin 24 h after surgery
once occlusion has been documented on postop-
erative imaging [ 23 ].Conclusions
The retrosigmoid approach is a workhorse for CP
angle pathology and lateral skull base surgery.
We review the anatomy of the various regions
accessed by this approach and demonstrate how
we position, pin, and perform the key surgical
steps while describing helpful surgical pearls.
For example, although the extent and size of
craniectomy varies depending on the pathology
of each particular case, anatomical studies have
shown that a burr hole placed inferior and dorsal
to the junction of the “mastoid line” and “zygo-
matic line” will usually be within 1 cm of the
transverse-sigmoid junction [ 8 ]. While recognizing
that there are a multitude of acceptable methodsC. Bowers et al.