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Page 2 of 11 Cappabianca et al. Mini-invasive Surg 2020;4:83 I http://dx.doi.org/10.20517/2574-1225.2020.67

INTRODUCTION
Meningiomas are the most common benign intracranial tumors, with an incidence rate reaching up
to 98/100,000 individuals per year [1-4] . They are much more prevalent than spinal meningiomas that
account only for 1.2%-12.7% of all meningiomas and 25% of all spinal tumors. Meningiomas originate
from arachnoidal (meningothelial) cells and, upon histological grading, the World Health Organization
(WHO) recognizes benign grade I tumors (75%), atypical grade II meningiomas (20%-35%), and the
[5]
malignant or anaplastic grade III subset (1%-3%) . The primary dural attachment site is another criterion
for meningiomas classification. Intracranial meningiomas arise most commonly at the convexity (34.7%),
often adjacent to the venous sinuses (22.3%), as compared to skull base tumors. Among infratentorial
meningiomas, the majority (50%) are at the cerebellar convexity. Spinal meningiomas are most frequently
located at the thoracic spine (67%-84%), followed by the cervical spine (14%-27%) and the lumbar spine
(2%-14%). Initially proposed by Harvey Cushing and Louise Eisenhardt, the classification of meningiomas
based on primary dural attachment helps describe the natural history, including the development of
[6]
signs and symptoms, and the plan for an appropriate management strategy . Clinical presentation
mostly depends on tumor size and location [1,2,4] ; tumors impinging the eloquent cortex often present with
seizures, whereas skull base lesions more often present with cranial nerve deficits. Being a space-occupying
lesion, all meningiomas can of course present with raised intracranial pressure. Spinal meningiomas may
present with signs of acute or chronic spinal cord compression, neurologic dysfunction, and progressive
myelopathy, according to the location. Seldom, meningiomas are found accidentally and without related
[7]
symptoms, in ca. 3% of the population . Contrast enhanced MRI of the brain diagnoses and defines the
details of meningioma; however, prediction of different histological subtypes of meningiomas is still not
possible by conventional or advanced (diffusion-weighted imaging, perfusion imaging, and magnetic
[8,9]
resonance spectroscopy) imaging techniques . Recently, radiomics-based machine-learning methods have
rapidly become a promising technique for analyzing medical imaging in clinical oncology. By analyzing the
spectral distribution of image pixels, valuable texture features of the meningioma, such as tumor cellularity,
degenerative changes, and neovascularization, can be extracted and correlated to prognostic score [10,11] .
Continuous advances in radiomics will provide more information in regard to the tumor clinical behavior
before surgery, with the potential impact of defining lesion clinical management.

Intracranial meningioma surgery with the goal of a radical resection has historically been performed
through invasive surgical approaches with considerable associated morbidities; improvements in terms
of both neurological outcome and extent of resection are the results of the continuous refinement
of neurosurgical techniques [12-15] . Nowadays, the surgical treatment philosophy for meningiomas
is multifaceted, thanks to several adjuvant treatments, i.e., endoscopy, image-guided surgery,
neuromonitoring, and radiosurgery. Moreover, recent developments of molecular biology have provided
new information in terms of prognosis and indications to secondary treatments, thus leading to innovative,
appropriate, and targeted adjuvant therapies granting better quality of life [16-19] .

Herein, we provide a cogent analysis of modern surgical indications for meningiomas, with special focus on
the role of the endoscopic technique and with a glimpse into the continuous improvement of postoperative
treatments.

SURGICAL INDICATIONS AND TECHNIQUES
Because of the benign nature of the vast majority of meningiomas, total removal leads to the most effective
cure, and it is claimed as the gold-standard treatment. The impact of the extent of resection on tumor
recurrence rates, traditionally categorized by the Simpson grading system, is the rationale behind aggressive
[20]
surgical strategies for the management of meningiomas . However, the tumor often involves surrounding
bone, dura, and neurovascular structures so that complete removal is challenging, sometimes risky, or even