Large and giant intracranial aneurysms are vascular pathologies associated with high morbidity and mortality. The purpose of this study was to assess large and giant internal carotid artery (ICA) aneurysms and their intra-aneurysm thrombosis and turbulent flow on magnetic resonance (MR) imaging.

This study investigated the large and giant ICA aneurysms in 12 patients. MR images, angiograms, and their treatment were retrospectively reviewed.

MR imaging demonstrated high and intermediate signals in addition to the normal flow void. The heterogeneous MR intensities correspond to turbulent flow, laminar flow, or intramural thrombosis. Turbulent flow in 8 cases and intramural thrombosis in 4 cases. Angiography showed turbulent blood flow in saccular and fusiform aneurysms with smooth walls. Intra-aneurysm thrombosis was found in fusiform aneurysms associated with pathology of adjacent ICA wall. A growing saccular aneurysm of the ICA with regular wall involving a turbulent flow was observed.

The turbulent flow and thrombosis in large and giant aneurysms can be detected on MR images. Most large and giant aneurysm is not fill with thrombus but turbulent blood flow. Partially thrombosed lesions are caused by pathology vessel wall not turbulent flow. Aneurysm growth can be caused by turbulent blood flow and intra-aneurysm thrombosis.