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Page 6 of 11 Cappabianca et al. Mini-invasive Surg 2020;4:83 I http://dx.doi.org/10.20517/2574-1225.2020.67

endonasal corridor is a direct path to the tumor, avoiding the need for brain retraction and reducing the
manipulation of neurovascular structures on the way to skull base. As part of the approach, an extensive
bony and dural resection is achieved and the major vascular supply to the meningioma is addressed before
the tumor excision. The main advantage of this surgical route is related to the possibility of achieving
an early decompression of the optic apparatus that seems to be associated with more favorable visual
outcomes. This is particularly true for tuberculum sellae meningiomas that usually present with visual
disturbance because of the intimate anatomical relation between the tumor and the optic apparatus. The
endoscopic endonasal technique allows for reduced manipulation of the compressed optic chiasm, and an
improved visualization and preservation of perforating vessels. In addition, it provides direct exposure of
the inferomedial aspect of the optic canals, allowing for quick decompression in cases of tumor extending
within. The main drawback remains the skull base reconstruction, whose failure results in cerebrospinal
fluid leakage and its related complications. In recent years, skull base repairing techniques including fat
grafts, synthetic materials, and vascular flaps (e.g., the pedicled nasal-septal flap) continue to improve,
expanding the indications for these approaches [82-84] .

Patient selection is critical for the success of an endoscopic endonasal approach. The question of which
tuberculum sellae meningioma should be resected transcranially and which should be approached
transsphenoidally remains paramount. Several series have compared approaches and attempted to define
which patients are best suited for each approach [61,68,85-89] . Larger tumors (> 3 cm) usually extend into
multiple areas, making complete removal through the transsphenoidal route challenging. Similarly, tumors
with encasement of the carotid arteries and/or anterior communicating artery complex, in the absence of
arachnoid plane between the tumor and the surrounding encased vessels, predicts more difficult resection
and may limit the efficacy of the endoscopic endonasal approach. The degree of tumor invasion into
the optic canal can be a relevant item when choosing the surgical route: whether invasion of the medial
inferior and superomedial aspects is present, transsphenoidal approach can be an option, but, if extensive
circumferential invasion is present, a craniotomy approach might be necessary. The role of the endoscopic
endonasal approach in the treatment of olfactory groove meningiomas is much more controversial and it is
still a matter of discussion in the current literature [69,85,90-92] . In patients with adequate preoperative olfaction,
the endonasal should be not preferred; conversely, the endoscopic approach offers supplementary value for
staged or combined procedures in the surgical management of giant olfactory groove meningiomas with
significant extension into the nasal cavities and paranasal sinuses.

Finally, advancements in endoscopy have further extended the possibilities of moving to regions outside
the nasal sinuses, namely the orbit and the spheno-orbital area. The endoscopic superior eyelid transorbital
corridor has recently been explored as a feasible route to address selected lesions at lateral middle fossa and
superolateral orbital region, with limited intracranial extension [93-96] . In meningiomas surgery, this approach
finds its main application in en plaque spheno-orbital tumors. Resection of en plaque meningiomas of
the skull base through transcranial approaches can cause significant morbidity, and complete removal is
often unattainable. The endoscopic transorbital approach has proven to be effective in greater sphenoidal
wing’s hyperostosis debulking, which is usually responsible for patient’s proptosis, oculomotor, and visual
impairment, due to optic canal, superior orbital fissure, and orbital compression. In these cases, clinical
benefit is the goal of surgery, rather than complete tumor removal. Extent of resection and symptoms
relief can be implemented by the combination with the endonasal transphenoidal approach, which allows
for drilling of the medial optic canal and lamina papyracea removal. Further studies with longer follow-
up are needed for a better definition of the pros and cons of this approach compared to more traditional
transcranial ones.

ADVANCES IN POSTOPERATIVE TREATMENTS
In the contemporary era, surgery remains the cornerstone of treatment for meningiomas. At the same
time, advances in imaging, treatment planning, and radiation delivery techniques have dramatically