Bilateral Carotid and Vertebral Rete Mirabile Presenting with Subarachnoid Hemorrhage Caused by the Rupture of Spinal Artery Aneurysm

Rete mirabile (or carotid rete) is a normal structure that plays physiological roles in the lower mammals. However, the rete does not exist in the normal carotid circulation of humans. Carotid rote mirabile (CRM) is a rare condition compensating for congenital dysplastic internal carotid artery. Arterial plexus at the cavernous region, which supplies intradural internal carotid artery instead of the aplastic cavernous portion of internal carotid artery, looks like the "rete mirabile" seen in the lower mammals, and is a characteristic angiographical finding of CRM. In addition to the CRM, existence of segmental occlusion and tortuous collaterals of vertebral artery, so-called carotid and vertebral rete mirabile (CVRM), is a very rare condition. We report a 70-year-old female patient with bilateral CVRM presenting with subarachnoid hemorrhage (SAH) caused by the rupture of a cervical spinal artery aneurysm. Our patient is the oldest, compared with the previously reported four patients with CVRM. Moreover, this is the first report of ruptured spinal artery aneurysm as a cause of SAH associated with CRM/CVRM. To avoid rebleeding in the patient, we successfully treated the patients by performing coil embolization of the remaining spinal aneurysms. In patients with CVRM, aneurysm formation of the cervical spinal artery may be a reasonable consequence because of the hemodynamic stress on the spinal artery as a collateral pathway. Detailed evaluation of the cervical spinal arteries should be performed to detect or to rule out ruptured aneurysm in patients with SAH associated with CVRM.