These meningiomas involve the region of the anterior clinoid, adjacent medial sphenoid wing, superior orbital fissure, and cavemous sinus. They may grow into the orbit. The tumor often encases the intemal carotid and proximal middle and anterior cerebral arteries as well as the optic nerve and may compress or provoke edema in the temporal or frontal lobes.
Surgical management of giant medial sphenoid meningiomas (> or =5 cm in maximum dimension) is extremely challenging due to their intimate relationship with vital neural structures like the optic nerve, cranial nerves of the cavernous sinus and the cavernous internal carotid artery. Their surgical management is presented incorporating a radiological scoring system that predicts the grade of tumour excision.
20 patients of giant medial sphenoidal wing meningioma (maximum tumour dimension range: 5.2 to 9.5 cm; mean maximum dimension = 6.12 +/- 1.06 cm) with mainly visual and extraocular movement deficits, and raised intracranial pressure, underwent surgery. A preoperative radiological scoring system (range 1-12) was proposed considering tumour volume (using Kawamoto's method); extension into the surrounding surgical corridors; extent of cavernous sinus invasion (based on the tumour relationship to the cavernous internal carotid artery); associated hyperostosis and/or >50% calcification; and, associated brain oedema. Both the conventional frontotemporal craniotomy (n = 13) and its extension to orbitozygomatic osteotomy (n = 7) were utilized. The cavernous sinus was explored in 4 patients and the hyperostotic sphenoid ridge drilled in five patients.
Total excision was achieved in nine patients; small tumour remnants within the cavernous sinus, interpeduncular fossa or suprasellar cistern were left in eight patients; and less than 10% of tumour was left in three patients. A patient with a completely calcified meningioma died due to myocardial infarction. When the preoperative radiological score was > or =7, there was considerable difficulty in achieving total tumour excision. A mean follow of 17.58 +/- 15.05 months revealed improvement in visual acuity/field defects in three, stabilisation in 11, and deterioration of ipsilateral visual acuity in five patients. Symptoms of raised pressure, cognitive dysfunction, aphasia and proptosis showed improvement.
A relatively conservative approach to these extensive lesions resulted in good outcome in a majority of our patients. Both the standard as well as skull base approaches may be utilized for successful removal of giant medial sphenoidal wing meningiomas. A preoperative radiological score of > or =7 predicts a greater degree of difficulty in achieving complete surgical extirpation 4).
Resection of medial sphenoid wing meningiomas poses surgical challenges because of the close contact with important cerebrovascular structures. The standard treatment for large tumors is microsurgical resection. Complete removal includes maximal resection of the dura and any involved bone, but this approach is not always feasible when the tumor encases the arteries or cranial nerves. In these cases, there is evidence that a more conservative resection followed by radiation treatment can reduce operative morbidity with acceptable tumor control rates. In this 3-dimensional video (http://www.youtube.com/watch?v=owNVp-x_xOQ), the authors demonstrate their preferred technical nuances to resect a large middle to medial sphenoid wing meningioma 5).
A procedure employed in removing meningiomas of the ala parva and of meningiomas affecting simultaneously ala parva and ala magna is described. Materials derived from operative interventions in 78 patients are studied. The application of the microsurgical technique in separating meningiomas from basilar arteries made it possible to improve the effectiveness of operative interventions. The overall post operative lethality comprised 24.3 per cent 6).
Gum and Frueh report a case of unilateral exophthalmos and compressive optic neuropathy due to sphenoid ridge meningioma. The patient underwent transantral orbital decompression with removal of the orbital floor and medial wall that resulted in rapid, dramatic normalization of both visual acuity and visual field in the involved eye. Due to the slow-growing, noninfiltrative nature of meningiomas, we propose this procedure as an alternative, initial, palliative treatment for selected cases of compressive optic neuropathy due to meningioma compressing the posterior orbit. This procedure can provide restoration of visual function with less risk to the patient than neurosurgical resection 7).
Total removal of large global meningiomas at the medial aspect of the sphenoid ridge. Technical note 8).