[Case of bilateral vertebral artery dissecting aneurysm presenting with subarachnoid hemorrhage].

Vertebral artery dissecting aneurysm (VADA) is a relatively rare cause of subarachnoid hemorrhage (SAH). Bilateral VADAs are even rarer, and there is no established treatment for this type of VADA. We report a case of bilateral VADAs with SAH. A 45-year-old man suddenly developed headache and consciousness disturbance and was referred to our hospital. CT scans demonstrated SAH mainly in the left cerebello-pontine cistern. Three dimensional computed tomographic angiography (3D-CTA) revealed fusiform dilatation of the bilateral vertebral arteries (VAs), suggesting dissecting aneurysms. The aneurysm on the left was larger in size than that on the right, and also had a bleb-like protrusion. Therefore, the left one was considered to be the cause of SAH. The patient was initially treated conservatively for one month to obtain spontaneous resolution of the aneurysms. On day 22, 3D-CTA revealed that the right VADA had decreased in size, however, the left VADA had slightly enlarged. On day 28, he underwent trapping of the ruptured left VADA. Postoperative course was uneventful. Occlusion of one VA may increase the hemodynamic pressure of the contralateral VA, inducing enlargement and subsequent rupture of the contralateral aneurysm. Therefore, both lesions of bilateral VADAs should be treated. However, if collateral blood flow through the posterior communicating artery is poor, occlusion of both VAs at the acute phase is considered to be intolerable. Therefore, waiting spontaneous resolution of the contralateral unnruptured dissecting aneurysm may be the treatment of choice for this type of lesion.