Invasion of the internal carotid artery by cavernous sinus meningiomas

BACKGROUND Meningiomas are the most common tumor involving the cavernous sinus. Although these tumors have been known to invade adjacent structures such as bone, soft tissue, and brain, invasion of the internal carotid artery (ICA) by meningiomas has only been recognized recently. The authors evaluate the extent of carotid wall involvement in nine patients with cavernous sinus meningiomas encasing the ICA who underwent en bloc resection of the cavernous sinus. METHODS The en bloc tumor-ICA specimens were fixed in formalin, embedded in paraffin, and sectioned on a rotary microtome. Hematoxylin and eosin, EVG, and HVG stains were performed and evaluated by light microscopy. RESULTS There were four males and five females with a mean age of 47 years. Eight patients had not undergone previous surgery, whereas one patient had been operated on before. In this latter case, however, the cavernous sinus was not entered during the first operation. In all patients, stenosis of the ICA was confirmed by preoperative angiography and/or magnetic resonance imaging (MRI). In seven cases, the tumors were excised en bloc along with the stenotic ICA segment. A petrous-to-supraclinoid ICA bypass was performed in these seven patients. In two cases, the tumor was excised with the stenotic artery, but no bypass was performed. The final pathological diagnosis was meningothelial meningioma. In all cases tumor cells were found in the adventitia of the cavernous carotid with stenosis of the arterial lumen. Compression and/or obliteration of the vasa vasorum within the adventia was noted in all specimens. In four cases, the tumor was found to have invaded the external elastic lamina. In two instances the external elastic lamina was disrupted and the tumor focally extended into the media. CONCLUSIONS These findings suggest that in the case of cavernous sinus meningiomas with encasement and stenosis of the intracavernous ICA, invasion of the vessel wall has occurred. The effect of these findings on the management of cavernous sinus meningiomas and the involved ICA is discussed.