Spontaneous thrombosis of a recurrent clipped intracranial aneurysm.

Spontaneous thrombosis of an intracranial aneurysm is a rare event. It is predominantly observed with aneurysms that are large and have relatively narrow necks. We report here a case of a 48-year-old woman presenting with subarachnoid hemorrhage (SAH) due to rupture of a 2-mm aneurysm of the anterior cerebral artery treated by microsurgical clipping. Six months after treatment of the aneurysm, the patient presented with severe headache. SAH was excluded, but computed tomographic angiography (CTA) revealed the recurrence of a large aneurysm (7 mm) that was confirmed by cerebral angiography (DSA). Endovascular treatment was scheduled for several days later, but DSA also revealed spontaneous occlusion of the recurrent aneurysm. On the control CTA performed one week later, the recurrent aneurysm had again reappeared, again confirmed by DSA, and was subsequently treated by coil embolization.