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INTRODUCTION
Spinal meningiomas are intradural extra-medullary lesions that arise from meningothelial arachnoid cells
within the spinal dura mater. They are the second most common intradural spine tumor, after neuromas,
accounting for two-thirds of all intraspinal neoplasms. Surgical treatment of spinal meningiomas
is associated with a favorable outcome, both in terms of progression-free survival rate and patients’
neurological post-operative status. Improvements in spinal meningiomas surgery are the results of the
continuing refinement of the surgical technique, the use of intraoperative neuromonitoring, and a better
[1-4]
understanding of meningiomas biological behavior . Spinal meningiomas have shown to be less likely
to recur than their intracranial analogs, with the majority of series reporting no significant difference in
[5]
recurrence rates between Simpson grade I and grade II resections . The negligible oncological benefit
of an aggressive surgical strategy that includes a wide removal of the dural attachment does not seem
to outweigh the risk of surgical complications and patients’ morbidity, especially for ventral and lateral
spinal meningiomas. For this reason, there has been an attitude shift toward less aggressive resections,
[6-9]
with the goal of minimizing morbidity . The safety of meningiomas surgery is increased by the use of
multimodal neuromonitoring: somatosensory-evoked potentials, motor evoked potentials, and D-waves
provide the opportunity to assess the functional integrity of the spinal cord during surgery, bearing the risk
of neurological complications. Therefore, intraoperative neuromonitoring adds to the modern treatment of
[10]
spinal tumors and should be performed in spinal meningiomas surgery .
Among all the technological advances, visualization, magnification, and the illumination of the surgical
field are the keys to any successful surgical procedure. After few years from the introduction of the
[11]
operating microscope by Yasargil and Krayenbuhl in the 1970s , Caspar demonstrated its usefulness for
spinal surgery : the advent of the operating microscope in spinal procedures brought terrific improvement
[12]
in terms of outcomes [13-16] . Since then, visualization tools have continued to evolve, along with the
inexhaustible research of less invasive surgical techniques to address cranial and spinal pathologies. In the
late 1990s, neurosurgeons began to use the endoscope, as a primary visualization tool or in assistance to
the microscope. Neuroendoscopy found its best application in skull base approaches and intraventricular
[9]
surgery [17-21] , while reports of endoscopic spinal surgery remain rather sparse in the literature . In recent
years, high-definition exoscope systems have entered the field of neurosurgery, as another tool in the
[22]
armamentarium of the contemporary neurosurgeon . Following preliminary convincing experiences
with the exoscope and subsequent technical refinements, reports of application of this device in the setting
of more complex cranial and spinal procedures have appeared in the literature [23-27] . Advantages and
disadvantages of the exoscope over the well-established visualization tools, i.e., the operating microscope
or endoscope, and the surgical settings in which it could be best indicated still need to be fully elucidated.
This article aims to provide a cogent review of the exoscope journey in neurosurgery, with a special focus
on spinal procedures and spinal meningioma surgery.

EXOSCOPE IN NEUROSURGERY
During the last three decades, telescopes have been recognized as a valid visualization tool in many surgical
fields. The telescope optical system is attached to a high-quality television camera and the surgeon operates
by visualizing the anatomic structures and instruments from a video monitor screen placed at an optimal
distance. Typical telescopes have very short focal distances and must therefore be introduced directly into
the body cavity. Because the lens sits within the body, these devices are usually referred to as endoscopes.
Endoscopic visualization in neurosurgery finds its main indication for the treatment of intraventricular
lesions and skull base surgery [17-19,28] . Exoscopes are telescope-based visualization tools that produce very
high-quality video images with large focal distance and wide field of view. One of the advantages of the
exoscope over the existing telescopes is that the exoscopes are positioned far away from the surgical field, at
a distance of approximately 25 to 30 cm. Distinctly from the endoscopic technique, exoscope facilitates the
passage of instruments under the scope and does not require dedicated instrumentation.