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Page 14 of 18 Avery et al. Mini-invasive Surg 2021;5:17 https://dx.doi.org/10.20517/2574-1225.2021.05

tuberculum sellae/planum sphenoidale meningiomas, transcranial approaches are limited in their ability to
visualize the inferomedial portion of the ipsilateral optic canal, where tumor invasion generally occurs.
Thus, we hypothesize that this discrepancy may be related to excessive manipulation of the optic apparatus
and/or insufficient decompression of tumor within the optic canal from above. An endonasal approach
provides direct access to the medial 180° of the optic canals, enabling the opportunity for effective
decompression and tumor removal. A summary of recent case series is presented in Table 2 [39,42,43,55-57,62] .

As mentioned previously, loss of olfaction (if not present pre-operatively) is virtually guaranteed with the
transcribriform approach due to disruption of the olfactory fibers. This sensory loss has been shown to have
a significant impact on quality of life [52,63] . While a unilateral transcribriform approach has been described to
preserve contralateral olfaction, the indications for this technique are highly specific and thus not applicable
[64]
to the vast majority of patients with olfactory groove meningiomas .
Complications
Aside from loss of olfaction, CSF leak and meningitis are the most common complications. While the rate
has decreased with the use of nasoseptal flaps, it remains a challenge for large olfactory groove meningiomas
with rates of 26% to 30% in the largest series [54,57] . Regarding most transcranial approaches for olfactory
groove meningiomas, CSF leak rates have ranged from 8.4% to 10%, while we have recently reported a 1%
CSF leak rate with the supraorbital craniotomy approach [10,58] . Other complications reported by
Koutourousiou et al. include hydrocephalus in 6%, new onset seizures in 4%, meningitis in 2%, cerebral
[57]
abscess in 6%, and deep venous thrombosis/pulmonary embolism in 20%. A high complication rate is
thought to be attributed to the long operative time required for this approach.

CONCLUSION
Endoscopic endonasal approaches to anterior skull base meningiomas have evolved substantially and are
commonly used today at many centers. While the indications are still debated, several advantages exist for
the endoscopic route over traditional transcranial approaches, including the ability to remove hyperostotic
bone, obtaining direct access to the dura and feeding arteries, minimal brain manipulation, excellent
visualization with the endoscope, displacement of critical surrounding structures away from the surgical
corridor, and improved vision outcomes with medial optic canal decompression. In our experience and that
of others, a majority of tuberculum sellae and posterior planum meningiomas can be safely and effectively
removed through an endoscopic endonasal approach, although requisite experience, instrumentation and
careful selection of appropriate cases is essential to success. In contrast, a minority of olfactory groove
meningiomas are ideally approached from an endonasal route, particularly for those in whom olfaction is
already absent, and they do not extend too far laterally. Otherwise, a transcranial route may be most
appropriate.

Careful patient selection is paramount to success in removing these anterior skull base meningiomas as
there are several important anatomic limitations of the transnasal corridors that must be identified. With
modern skull base reconstruction techniques, CSF leak rates are low, particularly for the
transplanum/transtuberculum approach. Utilizing endoscopic endonasal routes alongside minimally
invasive transcranial approaches, such as the supraorbital keyhole craniotomy, meningiomas of the anterior
skull base may be treated effectively with excellent oncological, functional and cosmetic outcomes. Thus,
both the endoscopic endonasal and endoscope-assisted supraorbital route should be considered part of the
modern surgical armamentarium for these challenging skull base meningiomas.