Intradural aneurysm arising from the posterior genu of the cavernous carotid artery mimicking a posterior communicating aneurysm: case report.

OBJECTIVE AND IMPORTANCE: We present a rare case of an intradural aneurysm that arose from the posterior genu of the cavernous carotid artery and was diagnosed via angiography as originating from the internal carotid artery (ICA) at the level of the posterior communicating artery. Our review of the English-language literature found no other case of an intradural aneurysm that originated at the posterior genu of the cavernous ICA.

CLINICAL PRESENTATION: A 65-year-old woman presented with increasingly severe left retro-orbital headaches. Her family history included aneurysmal subarachnoid hemorrhage. Angiography revealed an 11-mm aneurysm, which was interpreted as arising from the left ICA at the level of the posterior communicating artery.

INTERVENTION: During a left pterional craniotomy, an aneurysm was identified underneath the oculomotor nerve; its neck seemed to arise from the posterior communicating artery segment. Despite clipping of the aneurysm attachment to the ICA and trapping of the posterior communicating segment, the aneurysm continued to fill. Further dissection revealed that the aneurysm's neck originated from the cavernous ICA. Placement of fenestrated clips around the oculomotor nerve successfully occluded the intradural portion of the aneurysm, as documented by an intraoperative angiogram.

CONCLUSION: We discuss this unique case to draw attention to the importance of the interpretation and adequacy of preoperative angiography, and we review pertinent vascular anatomy.