**7. Surgical outcomes and prognosis**

Sphenoid wing meningiomas are the group of tumors where the advantages of cranial base surgery over conventional transcranial surgery can be clearly demonstrated. The introduction of craniobasal approaches, which evolved from the fronto-temporal to the pterional and the fronto-temporo-orbitozygomatic, and from the unilateral subfrontal to the fronto-lateral supraorbital, significantly reduces both the mortality and postoperative complications rate. Thus, in the 1970s postoperative mortality was up to 43% in some reports [37]. In contrast, nowadays less than 2% are reported [36]. The complication rate is

dependent on involved structures and surgical approach but has markedly fallen over during the recent decades.

Analysis of the factors influencing the postoperative prognosis showed that histopathological characteristic of meningioma is one of the main determinants. Around 70% of meningiomas are benign (WHO grade I), while 28% are atypical (WHO grade II), and 2% are malignant (WHO grade III) [40]. Despite these wellknown prognostic groups, meningiomas could have up to 15 different histologic subtypes. These characteristics are marked prognostic predictors and define the treatment strategy.

Anterolateral skull base and convexity meninges are derived from the neural crest, but the rest of the skull base has mesenchymal origin (paraxial mesoderm and dorsal mesoderm) [41]. This correlates with different histological subtypes of tumors and even WHO grades. Interestingly, the recent studies demonstrate the link between topography (meaning mesenchymal or neural crest origin) and the main somatic gene mutations [42].

The radicality of the removal is the next important prognostic factor. However, the introduction of radiosurgical treatment of the residual tumor of the skull base has significantly decreased the recurrence rate in the described group [42, 43].

### **8. Radiotherapy and radiosurgery**

Surgical resection of MAC is the treatment of choice, but in some cases, surgery alone may not be radical due to the tumor invasion to the CS, ICA, and/or ON encasement. Subtotal resection with adjuvant postoperative radiotherapy may be preferable over complete resection.

High-dose fractionated radiotherapy and radiosurgery have been reported to achieve a tumor control rate between 93–97% and 91–98%, respectively [43]. Permanent complications after radiosurgery are rare and have been reported in 0–10.5% of patients. They mainly consist of delayed optic nerve neuropathy, trigeminal nerve dysfunction, cognitive deficits, and seizures [44]. Functional results after radiosurgery for meningiomas involving the CS have proved to be superior to those obtained after microsurgical resection. [45]

The growth pattern in progressive benign meningiomas after failed radiosurgery can be unusually aggressive. In the case of reoperation after radiotherapy, it is associated with a higher complication rate compared to primary procedures [46].

### **9. Conclusions**

Despite the great variety of existing approaches, the pterional extradural is the most common "workhorse" for meningiomas of the anterior clinoidal process excision. If there is no clinoid process hyperostosis and cavernous sinus invasion, the fronto-lateral approach will be an option. Overall, total clinoidectomy is the key procedure for visualization of all important structures during an extradural way to the tumor. All the peculiarities should be taken into account to move safely and prevent the thermal and mechanical injury of neural and vascular structures. Radicality of excision is limited by the ICA encasement rate and character, the cavernous sinus invasion, and an anterior semicircle of Willis ingrowth. Preserving the integrity of perforating arteries and surrounding veins is the main key to preventing complications. Finally, the radicality of surgery will never exceed the value of the functional result of surgery and the patient's postoperative quality of life.

*Surgery of Meningiomas of the Anterior Clinoid Process DOI: http://dx.doi.org/10.5772/intechopen.101945*
