Figure 17.2 shows the predominant symptoms at the time of initial evaluation depended on classification of SWM. The symptoms were most commonly visual disturbance (highest in groups 1 and 2 with 66.7 and 60.9 %, respectively) and headaches, regardless of their predominant location. Double vision was complained in 30.4 % of patients in group 2 compared to only 5.1 % in group 1. The average length of history of these patients until the first consultation with a physician ranged from 1 to 360 months with a mean of 26.45 months, but decreased over the years with frequent and early use of sophisticated diagnostic investigations (1992–2002, 24.07 months, range 1–96; 1980–1991, 38.03, range 1–360 months).

There was bony involvement in 41 % of cases in group 1 tumours and 42 % in group 2 tumours. Rate of hyperostosis or intraosseous involvement was not different between all groups. Increase of the internal carotid artery and its branches was observed in the majority of cases within the medial SWM (group 1, 2 and 6). Peritumoural oedemas on CT or MRI scans were observed in 22 % of SWM with intraosseous involvement, in 31 % within group 1 and 52 % within group 2 tumours. Tumour calcification was significantly higher in osseous SWM (41 %) than in patients with group 1 and 2 tumours (25.6 and 21.7 %, respectively). Additionally gadolinium-enhanced MRI images showed enhancement within the bone in the majority of cases, reflecting true intraosseous tumour masses.

Surgery is performed with general anaesthesia using an operating microscope and microsurgical instrumentation in all cases. For microsurgical tumour removal, the frontolateral and the pterional approaches are performed, techniques well described elsewhere (Fig. 17.3) [3, 14, 15]. For the frontolateral approach, a single burr hole is placed just posterior to the anterior temporal line using a high-speed drill, preventing to open the periorbita. The frontolateral approach provides a more medial view of the clinoid and suprasellar regions and thus early identification of the optic nerve in clinoidal meningiomas. For the pterional approach, the single burr hole is placed at the same location, but the craniotomy is performed more posteriorly, exposing the frontal and temporal lobe with the sylvian fissure and the sphenoid ridge. The lesser wing of the sphenoid is resected to the superior orbital fissure, depending on the tumour size, to allow exposure of the lesion with minimum brain retraction. The superior orbital fissure is similarly unroofed to expose the periorbital fascia, which is only opened in cases of obvious tumour infiltration of intraorbital structures. If there is marked hyperostosis around the optic canal, it is mandatory to perform first a partial clinoidectomy, then unroofing of the optic canal extradurally. The dura of the region of the tuberculum sellae and chiasmatic sulcus is carefully inspected for evidence of meningeal tumour infiltration in order to identify the optic nerve intradurally and incising the dural cuff of the optic nerve for a short distance, whenever there is evidence of tumour ingrowth. If protrusion of the tuberculum above the line connecting the surface of the nerves as they enter the optic canals is evident, it has to be removed in order to enlarge the transfrontal operative field.

Generally, great caution has to be taken when approaching meningiomas of the medial sphenoid wing because the carotid and middle cerebral arteries may be embedded in the tumour. The dura is opened in a trap-door fashion, and the tumour is approached through the sylvian fissure. The tumour is visualized laterally from above and a plane of dissection is established between the tumour and the frontal and temporal lobe. The tumour capsule is identified and coagulated. The capsule is then opened, and the tumour is debulked by piecemeal resection with the aid of bipolar coagulation, microscissors and ultrasonic aspiration. After the tumour has been debulked and branches of the middle cerebral arteries are encountered, the tumour capsule is carefully dissected off the branches of the middle cerebral artery. The tumour resection is continued along these branches proximally to reach the internal carotid artery (ICA), which may be completely embedded in the tumour. In that case, the vessel is microsurgically dissected free of the tumour. Usually, an arachnoidal membrane separates the tumour from the adventitia of the vessels, and microsurgical dissection can be performed without injury of the arteries. Microsurgical dissection along cerebral arteries may lead to visible vasospasm. In this case, local administration of nimodipine or papaverine sponges can be applied to prevent cerebral ischaemia. However, a systematic analysis concerning the effect of local vasodilator application on postoperative ischaemic events has not yet been performed.

After resection of the tumour, the dural attachment is resected, including hyperostotic bone of the lesser sphenoid wing or the anterior clinoidal process. In tumours involving the cavernous sinus (group 2), the intracavernous part of the tumour is not radically removed to prevent any new cranial neuropathies. Use of the endoscope in terms of an endoscope-assisted technique may be helpful for inspection and removal of hidden remnants [16]. In cases where only the lateral or superior sinus walls are involved, the wall was peeled off and carefully coagulated. After tumour removal, the dura is reconstructed with fascial grafts. In some cases, a muscle graft is required at the cranial base, augmented with fibrin glue, to achieve as watertight a closure as possible. In some patients, temporary postoperative lumbar drainage may be necessary to prevent a cerebrospinal fluid fistula. Bone flaps are repositioned after drilling of hyperostotic bone from the meningioma. Further reconstruction of the orbital roof is not necessary.

The extent of tumour resection is classified according to the Simpson classification [17]: grade I (total tumour resection with excision of infiltrated dura), grade II (total tumour resection and coagulation of dural attachments), grade III (gross total tumour resection without excising dural attachments or extradural extensions (e.g. infiltrated sinus or bone)) and grade IV (subtotal tumour resection).

A special issue in medial SWM is the tumour involvement of the optic canal (Fig. 17.4). MR imaging not always demonstrates the relationship between meningioma and optic canal. In our series of 58 parasellar meningiomas, standard MRI showed tumour growth inside the optic canal in 20 cases. In the remaining 38 cases, there was no optic canal involvement according to radiological criteria. However, in 19 cases the suspicion of tumour extension into the canal rose during surgical inspection and consequently the canal was unroofed. Seventeen times meningioma was detected and removed out of the canal. It can be stated that standard MRI does not show reliably intracanalicular meningioma extension. Fat-suppressed series with thin slices of the orbit enhance the reliability, but compared to the intraoperative assessment, we still detected both false-negative and false-positive cases. In our experience there is no ophthalmologic morbidity due to microsurgical unroofing of the optic canal. Extradural decompression of the optic canal with early intradural opening of the dural sheet enclosing the nerve seems to improve the visual outcome in patients with optic canal involvement [18].