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approach include removal of involved bone and
dura as a part of the approach, which allows a
Simpson Grade I resection. The surgeons must be
very careful when indicating an EEA for a petro-
clival meningioma as the cranial nerve VI may be
pushed medially blocking the safe access. The
cases where CN VI is pushed inferiorly (dorsum
sellae meningiomas) or superiorly (tuberculum
jugulare meningioma) are potential good indica-
tions for EEA. For the situations where the CN
VI is inside the tumor, we believe that a combina-
tion of approaches is more appropriate for safe
management of the tumor. We usually start with
the approach that will give us access to most of
the base of the tumor in order to provide better
devascularization. In these cases a retrosigmoid
approach would be indicated if most of the tumor
is based on the petrous surface and a second-
stage EEA would address the medial component.
On the other hand, a tumor with a wide clival
base would be approached with an EEA tran-
sclival approach primarily followed by a retrosi-
gmoid, far lateral, presigmoid, or anterior
petrosectomy to complement the resection
depending on the position of the residual tumor.
Although endoscopes do not allow a three-
dimensional perspective, they do provide a close
and wide view of the operative field from differ-
ent angles. However, endoscopes only allow for a
narrow operative field, which is surrounded by
critical neurovascular structures making the risks
of major intradural bleeding, CSF leakage, and
neural damage still possible [ 20 ].
The main disadvantages of EEA are related to
the resection of lateral extension of tumors and the
reconstruction of large dural and bone defects of
the posterior fossa, being CSF leak rates quite high
(ranging between 4% and 33.3%) [ 18 , 42 , 44 ].
The expanded EEA, in its current form, is not
a substitute of the posterior skull base approaches
in the treatment of ventral posterior fossa menin-
giomas. It is a safe alternative for the rare cases of
meningiomas with most part of its dural base at
the midline clival region, and it may be used as
solely or combination of other approaches. Thus,
appropriate case selection may optimize the
advantages of the approach and reduce morbidity
of this complex pathology.
Skull Base Reconstruction
Skull base defects can be divided into extradural
and intradural. Intradural defects are further sub-
divided into low- or high-flow leaks. A high-flow
CSF leak is defined by the communication of
multiple subarachnoid cisterns or a ventricle with
the dural defect. Extradural defects are defined
by the resection of the skull base bone with an
intact dura and, therefore, no CSF leak.
Reconstruction following resection of ventral
posterior fossa lesions is particularly challenging
due to the lack of gravity effect given the vertical
position of the brainstem, which limits the sup-
port available for the reconstruction provided by
the weight of the brain and supporting bony
structures to stabilize inlay grafts, in addition to
the associated large dural defects with the risk for
high-flow CSF leaks [ 45 ].
Regardless of the approach, the goals of
reconstruction of skull base defects are the same
and include:- Water and airtight closure to prevent CSF
leak, pneumocephalus, meningitis, and other
intracranial infections. - Complete separation of the cranial cavity and
the brain from the sinonasal tract. - Protection of the brain, cranial nerves, and
intracranial vessels from desiccation and
infection. - Accelerate the healing process especially if
the patient is scheduled to undergo postopera-
tive external beam irradiation. - Preservation and rehabilitation of function.
- Preservation or restoration of cosmesis.
- Avoidance of dead spaces that may contribute
to hematomas and infection.
Critical factors to be considered when recon-
structing defects following the resection of skull
base lesions are the size and location of the bony
and dural defect, high- versus low-flow CSF
leaks, prior radiation therapy or scheduled post-
operative radiotherapy, previous sinonasal or
skull base surgery, extent of invasion of sinonasal
structures, morbid obesity and obstructive sleep
apnea (requiring CPAP), and possibility ofA. Beer-Furlan et al.