[Spontaneous resolution of the unruptured dissecting aneurysms of bilateral vertebral arteries with conservative treatment: analysis of the transient enlargement of aneurysmal dilatation].

A case of unruptured dissecting aneurysms of bilateral vertebral arteries was reported. A 47-year-old man was admitted to our hospital with right Wallenberg's syndrome. On the tenth hospital day, angiography revealed a pearl and string sign in the right vertebral artery and aneurysmal dilatation in the left vertebral artery. On the 38th hospital day, the pearl and string sign in the right vertebral artery was improved, but the aneurysmal dilatation in the left vertebral artery had enlarged. On the 222nd hospital day, angiography showed a spontaneous resolution of the aneurysmal dilatation in the left vertebral artery. He suffered no recurrence and returned to his previous life style. Because aneurysmal dilatation may be resolved spontaneously, especially in the chronic stage, surgery should not be undertaken lightly.