Tuberculum sellae meningioma (TSM)
J.Sales-Llopis
Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain
The site of origin of these tumors is only about 2 cm posterior to that of olfactory groove meningioma 1)
The tuberculum sellae is the bony elevation between the chiasmatic sulcus and the sella turcica. By definition, the limbus sphenoidale (which is the anterior margin of the chiasmatic sulcus) is the demarcation between the anterior and middle cranial fossa. Therefore these tumors originate in the middle fossa (unlike planum sphenoidale meningiomas which are in the anterior fossa).
They are traditionally grouped together with other suprasellar meningiomas diaphragma sellae meningiomas and the more anterior planum sphenoidale meningiomas
Suprasellar meningioma usually arises from the tuberculum sellae or the sulcus chiasmatis. Due to the close proximity to the optic apparatus, the same may be involved even when the lesions are small.
Tuberculum sellae meningiomas originate in the middle fossa (unlike planum sphenoidale meningiomas which are in the anterior fossa).
They are in a deep and sensitive location, proximity to critical neurovascular elements, hypothalamus with often dense and fibrous nature.
Characteristically lie in a suprasellar subchiasmal midline position, displacing the optic chiasm posteriorly and slightly superiorly, and the optic nerves laterally 2).
Although tuberculum sellae (TS) and diaphragma sellae meningiomas have different anatomical origins, they are frequently discussed as a single entity.
Epidemiology
Classification
Clinical Features
Diagnosis
Differential diagnosis
When a TSM grows posteriorly into the sella turcica it may be mistaken for a pituitary macroadenoma.
Magnetic resonance imaging has supplanted computed tomography as the imaging modality of choice for sellar lesions and parasellar lesions, but unenhanced MR imaging does not reliably distinguish between all tuberculum sellae meningiomas and pituitary macroadenomas. Accurate differentiation between these alternative diagnoses of a suprasellar mass is important because a tuberculum sellae meningioma always requires a craniotomy, whereas a transsphenoidal route is preferred for removing most pituitary macroadenomas. The gadolinium-enhanced MR images of seven patients with tuberculum sellae meningioma and seven with pituitary macroadenoma were reviewed retrospectively. Although no specific radiological feature was pathognomonic, a combination of several features allowed the correct diagnosis in all cases. Three characteristics of tuberculum sellae meningiomas distinguish them from pituitary macroadenomas: 1) bright homogeneous enhancement with gadolinium, as opposed to heterogeneous, relatively poor enhancement; 2) a suprasellar rather than a sellar epicenter of tumor; and 3) tapered extension of an intracranial dural base. Each of these findings can be subtle, but careful examination of gadolinium-enhanced, high-quality, thin section coronal and sagittal MR images of the parasellar region for this constellation of findings will allow the correct preoperative diagnosis in patients with either of these tumors 3).