A Rare Case of Spontaneous Thrombosis and Recanalization of a Ruptured Small Aneurysm in the Distal Posterior Inferior Cerebellar Artery

: The incidence of spontaneous thrombosis of intracranial aneurysm ranges from 1% to 2% of ruptured aneurysms. Most of them are giant or large aneurysms, and various factors have been discussed in previous literatures. Recanalization of thrombosed aneurysms may be rare, but its mechanism is poorly understood. Reports on recanalization of small aneurysms after spontaneous thrombosis are rare, and the natural history is still unknown. We describe a rare case of spontaneous thrombosis and recanalization of a ruptured small aneurysm of the distal posterior inferior cerebellar artery. Spontaneous aneurysmal thrombosis should not always be considered as a good or safe sign, as it may recanalize in a short time, resulting in re-rupture. In the acute stage, periodic follow-up of patients with a spontaneously thrombosed aneurysm is important.