Approximately 10% of all intracranial meningiomas involve parasellar structures, and approx 10% of all parasellar tumors are meningiomas. The majority are situated in the suprasellar region, taking their dural origin from the tubercu-lum sellae, planum sphenoidale, olfactory groove, diaphragma sellae, medial sphenoid wing, optic nerve sheath, and anterior fossa floor/orbital roof. Although intrasellar extension may be an occasional, and typically late, feature of menin-giomas arising at any of these sites, purely intrasellar meningiomas are exceptionally rare (1,7,37-40). The majority of meningiomas involving the sellar region tend to be large circumscribed lesions that are compressive of adjacent structures. Less often, and notably in the case of sphenoid wing meningiomas, they grow in an en plaque configuration, so insinuating themselves around cranial nerves and blood vessels that surgical removal becomes a formidable and frequently pointless challenge. Erosion, hyperostosis, or frank invasion of bone may be features of any meningioma of the skull base, although they are especially prominent in the en plaque variety. All histopathologic variants of meningioma occur in and around the sella. Meningiomas in the parasellar region have also occurred after radiation therapy for a pituitary adenoma.
Although meningiomas situated at different parasellar sites will have, to some degree, certain unique site-specific presentation patterns, some clinical features are common to all meningiomas occurring in the region. Insidiously progressive visual loss is a common presenting symptom (see Chapter 6). Alterations in mental status may accompany those massive lesions compressing the basal frontal lobes or those large enough to cause elevated ICP. Hypopituitarism is uncommon and generally late in occurrence. Hyperprolactinemia on the basis of hypothalamic or pituitary stalk compression may occur and has, in some instances, been associated with the amenorrhea-galactorrhea syndrome. Lesions involving the cavernous sinus may present varying components of a cavernous sinus syndrome.
The CT, MRI, and angiographic characteristics of meningiomas are sufficiently well known that their preoperative diagnosis can usually be made with some degree of certainty (Fig. 2).
Rarely meningiomas of intrasellar origin and occasional suprasellar menin-giomas descend into the sella, causing considerable diagnostic difficulties and may be mistaken for pituitary adenomas or other intrasellar pathologies.
In the past, parasellar meningiomas, whether primarily arising within the sella or secondarily extending into it from the cavernous sinus or a more superior site, were considered to fall exclusively within the domain of transcranial surgery. Indeed, when such meningiomas have been mistaken for pituitary adenomas, the transsphenoidal approach has proven disappointing. The inability to secure their vascular supply, together with their fibrous nature, which prevents their descent into the operative field, was believed to effectively contraindicate transsphenoidal removal. Accordingly, in such circumstances, after a frozen section has confirmed the diagnosis of meningioma, traditional teaching advises abandoning the procedure in favor of a transcranial approach at a later date. Whereas this traditional wisdom still holds true for many sellar region meningiomas, the development of the extended transsphenoidal approach now places selected meningiomas within the domain of transsphenoidal respectability (41,42). This is usually so for small or medium tumors that are centered on or above the sella without significant parasellar extension. Using the same operative strategy employed for cran-iopharyngiomas, with resection of the sellar diaphragma, one can now completely resect such tumors transsphenoidally.
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