**6. Complication avoidance**

Skull base surgery is technically complex and requires special training of the entire neurosurgical team. The procedure should be performed step by step, as each subsequent stage is possible only after the perfect execution of the previous ones. This form of organization as well as applying general principles of craniobasal surgery prevents the majority of surgical complications [36, 37]. Today, mortality after sphenoid wing meningioma surgery does not exceed 1.2% (0.6-1.8%).

In addition to technical aspects, the correct position of the body and head, the presence of neuronavigation and the intraoperative neuromonitoring system accompanied with a well-prepared neurophysiologist are no less important [38, 39]. The confidence with a set of special micro instruments and its appropriate application is crucial. Co-working with anesthesiologists is of great importance in managing the brain edema and consequences of nerves, meninges, and other immediately reactive structures irritation.

The most common complications after the removal of the sphenoid wing meningioma are deterioration of vision, 3rd nerve damage, vascular accidents due to vessels injury, and CSF leakage [36].

### **6.1 Optic nerve**

Visual impairment is usually the first and main symptom and the primary goal of surgery is to preserve and improve the visual function of these patients.

Thus, early extradural visualization following the anterior clinoidectomy and intensive irrigation while drilling to prevent thermal damage is extremely important.

Dissection of the optic nerve sheath, as well as the falciform ligament, allow to explore the nerve in the optic canal, remove the intracanal portion of the tumor, and to ensure the complete ON decompression in the bone canal. Subsequent intracranial dissection from the tumor should be gentle to cause minimal injury of the ON and chiasm.

Early visualization of the ON is challenging in the case of the intradural frontolateral approach as it is covered with a tumor. The fixation point of MAP often extends to the roof of the optic canal. The risk of thermal damage of the optic nerve is high during the attachment site coagulation. We coagulate and separate the meningioma not directly along the basal dura, but retreating a few millimeters into the tumor mass. This maneuver lowers the risk of ON sacrifice. Ophthalmic nerves could serve as a landmark to find the 2nd nerve as I and II nerves as they are always overcrossing.
