Vascular involvement in anterior clinoidal meningiomas : Biting the 'artery' that feeds

Anterior clinoidal (AC) meningiomas often encase internal carotid artery (ICA) and it branches. The aim of this study was to determine the efficacy of preoperative angiogram as a predictor of vessel wall adherence and feeders. Furthermore, defining the dangerous areas would provide insights to decrease vascular injury and achieve maximal safe resection.

21 cases of AC Meningiomas were evaluated for feeders, displacement, encasement/ narrowing of ICA and its branches. Intraoperative vascular involvement was noted. The reason and site of vascular injury, if any was evaluated.

Blush from ICA was seen in 15 patients. The ICA in its entirety beyond the bifurcation was encased in 11 patients. The radiological vascular encasement including narrowing didn't corroborate with intra-operative finding of vessel wall adherence. The tumor could be separated along the length of encased narrowed vessel except from ICA bifurcation in 6, where it had infiltrated adventitial layer. The adherent zone extended into anterior cerebral artery in 2 and middle cerebral artery in 2. There was major vessel injury in 2 patients and perforator injury in 2. GTR was achieved in 18 patients.

These tumours are often fed by supraclinoid ICA. It is possible to resect the tumor from vessel wall despite complete encasement/ narrowing on preoperative angiograms. The tumor often lethally embraces the ICA bifurcation making it the most dangerous zone for resection. This is possibly due to an arterial twig that arises close to the bifurcation to irrigate the clinoidal dura and the tumor infiltrates the adventitia at its origin.