Discussion
Background: Falcotentorial meningiomas are the tumours arising at the junction of dural folds in which straight sinus and both torcular and arachnoid granulations are embedded [1], projecting either anteriorly, inferiorly or posteriorly [2, 3, 4]. They are more common in women, regarded as a subgroup of tentorial meningiomas and extremely rare, constituting only 0.3% to 1.1% of all intracranial meningiomas [5, 6]. Further classified by neurosurgeons based on the surgical approach and vascular encasement and displacement by the tumour. Usually classified as:
Type I: Arises above the junction of the vein of Galen with the straight sinus, displaces the great vein of Galen and the internal cerebral veins inferiorly.
Type II: Arises from the undersurface of tentorium near the junction of the vein of Galen with the straight sinus, results in superior displacement of the Galenic venous system.
Type III: It is lateralised as it arises from the paramedian tentorial incisura. The great vein of Galen lies medial to the tumour.
Type IV: Arises from the FT junction along the straight sinus, causes contralateral displacement of the vein of Galen [7, 8].
MRI characteristics are the same as those of other meningiomas. Cerebral angiograms show they usually derive supply from internal carotid artery including the mengio-hypophyseal branch [9].
Clinical Perspective: Insidious onset of symptoms. The patient commonly presents with headache, papilloedema, gait disturbances and altered mental status. The pathophysiology is raised intracranial pressure and hydrocephalus [10].
Imaging Perspective: Imaging is needed to localise the origin of the lesion to convey the relationship of the lesion to the vein of Galen to the surgeons so it can guide them regarding the approach. Apart from conventional imaging features of meningioma, angiogram is essential to help localise the lesion, such as in our case, where its supply was from the artery of Barniskoni.
Outcome: Complete resection is the mainstay of therapy. Subtotal resection may be considered when the tumour invades or adheres to adjacent structures. Subtotal resection requires a close follow up. Reoperation may be required if the residual tumour regrows [11].
Thorough preoperative neuroimaging and knowledge of the nuances of the surgical technique are the key to an excellent outcome [12].
Our patient’s tumour was resected completely.
Take Home Message, Teaching Points:
Localisation is important as it helps the neurosurgeon with determining the appropriate approach.
