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Page 2 of 18 Avery et al. Mini-invasive Surg 2021;5:17 https://dx.doi.org/10.20517/2574-1225.2021.05

illumination, image quality, viewing angle and dexterity over previous microscopic approaches. Since then,
endonasal techniques have expanded into both sagittal and coronal planes, including the anterior skull
[1-8]
base . This region endoscopically is defined posteriorly by the tuberculum sellae, anteriorly by the
posterior table of the frontal sinus, and laterally by the junction of the lamina papyracea and the fovea
ethmoidalis. The major divisions from anterior to posterior are the cribriform plate, planum sphenoidale
and tuberculum sellae, all of which are accessible with the use of straight or angled endoscopes.

Anterior skull base meningiomas are relatively common, with tuberculum sellae/planum sphenoidale
[6]
representing approximately 5%-10% of all meningiomas, and olfactory groove 8%-13% . Tuberculum
sellae/planum sphenoidal meningiomas frequently exhibit growth patterns that displace the optic nerves
and chiasm posteriorly and/or superiorly. Optic canal invasion is present in approximately two thirds of
[9]
cases . This growth pattern results in relatively early detection with small size. Olfactory groove
meningiomas, on the other hand, generally are much larger when at presentation due to initial lack of
critical mass effect on orbitofrontal cortex.

Traditionally, frontal fossa meningiomas have been approached through several transcranial approaches,
including frontal, bifrontal and pterional craniotomies. More recently, keyhole approaches, such as the
supraorbital craniotomy, have been utilized with success even for very large tumors [10,11] . Endoscopic
approaches are an extension of this minimally invasive keyhole philosophy and, in carefully selected
patients, they may be an excellent alternative due to the midline location of these tumors, offering a direct
line of site from an endonasal approach without brain retraction [5,6,8,12-14] . Furthermore, bilateral optic canal
decompression can be safely and effectively accomplished in patients with compressive optic neuropathy
from tumor extension into the medial optic canals [15-17] .

Here we describe both the transplanum/transtuberculum and transcribriform approaches for anterior skull
base meningiomas, including the indications, limitations and outcomes. We propose that a majority of
tuberculum sellae and posterior planum meningiomas can be removed with an endonasal approach given
the superior access to the medial optic canals. In contrast, only a minority of olfactory groove meningiomas
are ideal for the endonasal route given that the transcribriform approach will inevitably lead to anosmia in
[19]
[18]
the vast majority of patients. In fact, recent systematic reviews by Shetty et al. and Yang et al. of studies
comparing transcranial and endoscopic approaches for tuberculum sellae/planum sphenoidale and olfactory
groove meningiomas, respectively, found that 39% of the former are performed endoscopically vs. only 19%
for the latter. We also emphasize that the supraorbital “eyebrow” craniotomy is an excellent and
[10]
complimentary alternative for anterior skull base meningiomas .

TRANSPLANUM/TRANSTUBERCULUM APPROACH FOR TUBERCULUM & POSTERIOR
PLANUM MENINGIOMAS
Patient selection & surgical considerations
The optimal approach for symptomatic tuberculum sellae meningiomas remains controversial. While
conventional transcranial approaches are still widely used, minimally invasive “keyhole” approaches are
increasingly applied, but the ideal approach remains debated [11,13,20-27] . We and others have used the
endoscopic endonasal approach and supraorbital “eyebrow” approach, depending on certain tumor
characteristics for over 15 years. In our initial experience addressing this topic published in 2009 and using
an endoscope-assisted method, we concluded the endonasal route was preferred for smaller meningiomas
that did not extend beyond the supraclinoid internal carotid arteries (ICAs), while larger tumors that
extended more laterally were appropriate for supraorbital removal . During this time period, we
[11]
approached 75% of tuberculum sellae meningiomas by the supraorbital approach and 25% by an endoscope-