**7.4 Intradural steps**

The dura mater is opened in a curvilinear fashion and the intradural portion of the tumor is progressively resected using conventional microsurgical methods, alternating debulking and peripheral dissection from the brain parenchyma and vessels. An additional dural incision directed medially toward the optic canal may cautiously be performed to complete the extradural anterior clinoidectomy. Once the optic canal has been widely opened intradurally (**Figure 5**), the tumor fragments at this level can be easily removed using a small blunt hook.

Complete resection is not always possible due to true intracavernous invasion (as opposed to a simple extension to the lateral wall) or excessive tumor adherence in the SOF or optic canal. In such situations, the key is to optimally decompress the ON so that the residual tumor can later be effectively treated with radiation therapy. The radiosensitivity of the ON justifies the creation of a safety zone around it, in order to avoid deleterious iatrogenic irradiation during radiation treatment. It is essential to preserve the function of the cranial nerves as much as possible, as their postoperative recovery is often uncertain.

### **7.5 Closure and reconstruction**

If the ethmoidal or sphenoidal sinuses are open during the extradural steps, either autologous fat or a temporal muscle graft should be harvested to plug the defect, depending on the size of the opening (for example, the muscle should be used for a small aperture of a pneumatized ACP and fat should be used for a large sinus opening secondary to intranasal tumor invasion). A synthetic fibrin sealant may be used in addition to these measures to prevent postoperative cerebrospinal fluid leakage. The dural and periorbital defects are ideally managed using a vascularized and pedicled pericranial graft that is rotated over the orbit. Alternative solutions include using the temporal fascia or synthetic dura patches. Finally, the remaining dead space left by the tumor removal can be filled with a fat graft.

Bone reconstruction for SOM is often more complex than for other meningiomas due to the extensive bony resection, which sometimes involves the superior and lateral orbital rims. Various options are available to perform cranioplasty and obtain a satisfactory cosmetic result. If the orbital margins are intact, the healthy part of the craniotomy can be replaced using grids that are cut to a suitable shape and serve as anchor points for the reinsertion of the temporal muscle. For larger defects, hydroxyapatite cement can be shaped easily. A custom-made polymethylmethacrylate or polyetheretherketone (PEEK) prosthesis can be ordered before the procedure, especially when the orbital rims are planned to be resected. The design of the prosthesis can also compensate for temporal muscle atrophy by incorporating an increased thickening at the level of the temporal fossa. Trimming of the edges of the prosthesis is often required to perfectly match the craniotomy. The zygomatic osteotomy must be reattached with standard plates before reinserting the temporal muscle and suturing the scalp in layers according to the usual technique.

### **8. Complications and postoperative care**

The first postoperative night is ideally spent in an intensive care unit, so that the patient can be closely monitored, and any respiratory, hemodynamic, or neurological failures can be detected at an early stage, particularly in the event of a surgical site hematoma. Most postoperative complications of SOM are related to the cranial nerves affected by the tumor. In their meta-analysis of retrospective series of operated SOM, Fisher *et al.* summarized the incidence of occurrence of these complications [12]. Ophthalmoplegia was frequent (16%) and mainly related to oculomotor nerves damage (oculomotor III 11%; trochlear IV 2%; abducens VI 6%; not specified 13%). In addition, ptosis or diplopia (neuropathic or restrictive) was observed in 17% of cases each. Regarding the optic nerve, visual field loss was described in 4% of cases, while visual acuity was decreased in 9%, and blindness was reported in 3% of cases. Trigeminal hypoesthesia was the most frequent complication (19%); in contrast, facial paralysis was rare (4%). Regarding complications related to the brain, the incidence of epilepsy was estimated to be 8%, while motor and phasic

#### *Spheno-Orbital Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.101983*

deficits, or diabetes insipidus were uncommon. Enophthalmos and cerebrospinal fluid leaks were encountered in 5% of cases each. Meningitis occurred in 7% and wound infections occurred in 3% of cases, which is consistent with the general rate of infection in cranial surgery, which was reported to be 9% [27]. Finally, pulmonary embolism was diagnosed in 4% of the patients who underwent an operation for SOM.
