Introduction
The goal of surgical intervention in meningiomas is complete resection and removal of dural attachments. Often attainment of this goal is complicated by factors such as tumor location, extent of dural attachments, and the complexity of tumor blood supply. Falcine meningiomas are often richly supplied by multiple terminal arterial branches of the middle meningeal artery, callosomarginal artery, pericallosal artery, and branches of the anterior falx artery which can complicate any surgical attempts at resection [
3].
Feeding arteries can be located medial or inferior to the tumor making control of bleeding difficult until the tumor is removed [
1‐
3,
8]. When the blood supply is predominantly pial and the artery is distal within the vascular tree, embolization can be difficult or impossible without significant risk. Surgical approaches to the main blood supply of tumors vary by location and size. Accessing the feeding artery on the inferior surface of a large tumor attached to an immobile membrane such as the falx is very difficult without extreme retraction or corticectomy. One option is a contralateral approach to the blood supply via the interhemispheric fissure.
We report the case of a highly vascular meningioma with a large callosomarginal feeding artery successfully removed following surgical clipping of this vessel via a contralateral interhemispheric approach. Successfully addressing this vessel prior to any debulking allowed for en bloc Simpson Grade 1 tumor removal with minimal blood loss and short term tumor control without evidence of recurrence at 2 year follow up.
Discussion
Meningiomas are the most common benign intracranial tumor accounting for 13–26% of all primary intracranial neoplasms with approximately 5% arising from the falx [
4,
5]. The nidus of falcine meningiomas originally derives its rich vascular network from the dural vasculature and later parasitizes the pial vascular supply as the periphery of the tumor grows [
1‐
3,
5,
6,
10].
Preoperative angiography is often useful in helping plan the surgical approach in cases of falcine meningiomas by delineating the tumor’s arterial feeding pattern. Furthermore, cerebral angiography evaluates displacement, of the pericallosal artery and whether arterial branches contribute to the tumor’s vascular supply [
1,
3,
8,
9]. The venous phase can establish whether the tumor has invaded the superior sagittal sinus, determines sinus patency, and provides critical information about the courses of large draining veins [
1,
9].
In the present case, preoperative embolization was incompletely effective at limiting the tumor’s blood supply, largely due to a massive callosomarginal feeding vessel unsuitable for embolization. A direct approach to this artery on the ipsilateral side by dissecting the ill defined arachnoid plane on the anterior surface of the tumor and then retracting the tumor still attached to the falx was thought to be too difficult preoperatively. A contralateral interhemispheric approach was thought to be easier with incision of the lower falx to provide exposure of the artery as it entered the tumor on its inferior surface.
There are other reports of contralateral interhemispheric approaches to intra-axial lesions and intra-ventricular tumors [
4,
7]. The anterior location of this tumor lowered the risk associated with damaging the parasagittal draining veins.
A majority of meningiomas are supplied by ipsilateral meningeal arteries, however, falcine tumors are more likely to also have a contralateral vascular supply. Hattori et al in there study clarifying the characteristics of contralateral blood supply of paramedian meningiomas found that 56% of falcine meningiomas had a significant degree of contralateral vascular supply [
3]. They hypothesize the secretion of angiogenetic factors, such as vascular endothelial growth factor, induce neovascularization, establishment of arterial anastomoses in the falx between the right and left meningeal network, and the subsequent recruitment of contralateral dural arteries [
3].
Meningiomas of the anterior two thirds of the falx frequently receive their vascular supply from the anterior falx artery, which itself arises from the ethmoid artery. Since the ethmoid artery arises from the ophthalmic artery there is no way to safely embolize the falcine artery tumor supply.
The prognosis of patients with falcine meningiomas is dependent on the Simpson grade at the time of resection [
2]. One case series of 68 patients by Chung et al indicated the majority of patients who underwent subtotal resection had a tumor that involved the superior sagittal sinus, torcula, or cortical draining vein, were attached firmly to the falx, or were intimately involved with vital arterial structures. This case provides an excellent example of one approach to directly dealing with large, deep interhemispheric feeding vessels unsuitable for embolization allowing for en bloc Simpson grade 1 tumor removal.
In conclusion we present the case of a falcine meningioma with a large callosomarginal feeding branch which was successfully removed following surgical clipping of this vessel via a contralateral interhemispheric approach. Intra-operative control of the vascular supply and complete tumor resection was critical to excellent long term prognosis in this patient. We provide a three dimensional animation of the surgical approach for instructional purposes.
Acknowledgments
The first author thanks Bethany Carlson M.S. R.N. for her helpful comments regarding this manuscript. This work was supported by National Institutes of Health National Center for Research Resources Grant TL1 RR024129-01. Computer animation provided by Kenneth Probst, an employee of the Department of Neurological Surgery at the University of California, San Francisco.