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Cappabianca et al. Mini-invasive Surg 2020;4:83 I http://dx.doi.org/10.20517/2574-1225.2020.67 Page 5 of 11

inevitably lost during endoscopic endonasal approaches to the cribriform plate. It is worth mentioning
that patients harboring olfactory groove meningiomas frequently present with significant hyposmia and/
or invasion of the lamina cribra and roof of nasal fossae: in these cases, the endonasal approach should be
considered as a choice for surgical treatment. In patients with a subchiasmatic lesion and a prefixed chiasm,
the endonasal approach is the preferred route because any transcranial approach would require retraction
of the optic apparatus with the risk of visual decline.

Endoscope’s assistance also finds application in convexity meningiomas located in critical areas. Rolandic
and parasagittal meningiomas should be classified as higher risk tumors, as compared to other convexity
meningiomas that are associated with low surgical complication rates [2,4,62,63] . Even if maximal radicality
has to be attempted because of a proven higher recurrence rate after partial resection, the more important
goal is not to harm neurological functions. Radical resection may cause severe neurological impairment
because of direct mechanical trauma to the eloquent areas, especially if the tumor is tightly adhering to
the cortex and/or because of vascular arterial and venous impairment. The close-up view provided by the
endoscope may be helpful in the identification of the arachnoid plane at the tumor-cortex and tumor-
vessels interfaces and can contribute, together with the more established role of electrophysiological
mapping and intraoperative videoangiography, to pushing the boundaries of the maximal safe resection in
both achieving the best functional results and reducing the tumor remnant volume [42,63] .

Lastly, endoscopic spine surgery as an alternative to various open neurosurgical techniques gained
popularity in the management of degenerative disc diseases, while its application in treating spinal
meningiomas and other intradural lesions remains rather sparse [64,65] . The surgical procedure includes access
to the spine using tubular ports, parallel or expandable depending on the size of the lesion, thus obviating
the need of long skin incisions, paraspinal muscle dissection, and destabilizing dissection of ligamentous
structures. Tumor resection is achieved through small bony fenestration under endoscope-assisted
microscopic visualization, with occasionally reported pure endoscopic surgical procedures. The benefits
of the endoscope become particularly evident in the removal of intradural tumors located anterolaterally
to the spinal cord. The endoscope can obviate the use of much more complex anterior routes to the spine,
often associated with postoperative spinal deformity and the need for adjunctive fusion surgery, allowing
for visualization and removal of the ventrally located part of the tumor, with minimal retraction of the
spinal cord. Endoscopic surgery may result equally effective in terms of extent of resection and with similar
morbidity compared to open techniques [30,66] . The safety of spinal meningiomas removal is increased by the
use of intraoperative neuromonitoring that enables the continuous evaluation of the sensory and motor
functions of the spinal cord by means of somatosensory-evoked potentials, motor evoked potentials, and
[66]
D-waves . Therefore, intraoperative neuromonitoring should be considered as part of spinal meningiomas
surgery, regardless of the surgical approach.

Endoscopic endonasal surgery
Since the 1990s, continued improvements in illumination and magnification have led to the purely
endoscopic transsphenoidal approach to the sella, a development that has subsequently revolutionized
the treatment of lesions accessible through the skull base [42,43,67] . The introduction of extended endoscopic
approaches, technological advancements as well as improvements in skull base reconstruction techniques,
and increased experience have established the endoscopic endonasal approach as an important option for
anterior skull base meningiomas [68-73] . With further expansion of indications, in very selected cases, this
approach has entered into the broad spectrum of surgical options for cavernous sinus, petrous ridge, and
anterior foramen magnum meningiomas [74-76] .

The endonasal approach for anterior skull base meningiomas has several advantages and special anatomic
considerations to be underlined [69,71,77-81] . Aside from the cosmetic benefit of avoiding external scars, the