Partially thrombosed giant basilar tip aneurysm that remarkably decreased in size after stent-assisted coiling associated with the disappearance of neovascularization.

Endovascular treatment for partially thrombosed giant basilar tip aneurysms has not been established because of its low cure rate and numerous associated comorbidities. Although some authors reported the growth mechanism of partially thrombosed aneurysm, there is no report for the process of its shrinkage after treatment. We describe a case of a partially thrombosed giant basilar tip aneurysm presenting with disturbance of consciousness because of a mass effect and brain edema. The patient underwent stent-assisted coiling using a low-profile visualized intraluminal support stent (Terumo). Although pre-operative magnetic resonance imaging (MRI) and angiography revealed prominent neovascularization of the inner aneurysmal layer, this vessel was absent on follow-up angiography 1 month after treatment. Repeat angiography demonstrated the gradual recanalization of the aneurysm. However, repeat MRI examinations showed remarkable shrinkage of the thrombosed aneurysm, and the complete disappearance of the thrombosed component was noted 6 months after treatment. The disappearance of neovascularization 1 month after the treatment may have contributed to the shrinkage of the thrombosed aneurysm. Stent-assisted coiling combined with alteration caused a hemodynamic change in this aneurysm, and the flow-diverting effect might have controlled this partially thrombosed giant aneurysm.