The Role of MR Angiography in the Pretreatment Assessment of Intracranial Aneurysms: A Comparative Study

A 55-year-old woman presented with intractable pain and a complete right CN III palsy caused by pressure effect from a giant (25 mm), fusiform, intracavernous internal carotid artery aneurysm. The circle of Willis should be scrutinized as part of the assessment prior to endovascular balloon occlusion of the parent vessel.

A, TOF-MIP MRA (100/20/1) from above and slightly from the right. The right posterior communicating artery (arrow) cannot be differentiated from aneurysm by MIP-MRA findings. The ipsilateral anterior cerebral artery is also poorly demonstrated.

B, TOF-3D-isosurface MRA (100/20/1), similar projection to A. The posterior communicating artery (arrow) can now be clearly separated from aneurysm. The ipsilateral anterior communicating artery is of increased caliber compared with the MIP-MRA projection.

C, TOF-MPR MRA (100/20/1), parasagittal view. The relationship of the posterior communicating artery (arrow) to the aneurysm can be clearly seen along its whole length on this projection. The artery is in contact with aneurysm at its apex.

D, TOF-MPR MRA (100/20/1), coronal view. By scrolling along the posterior communicating artery (arrow) in the coronal plane, its relationship to the aneurysm is clearly depicted.

A 48-year-old woman presented with an SAH secondary to an anterior communicating artery aneurysm rupture. Diagnostic IA-DSA showed multiple aneurysms.

A, TOF-3D-isosurface MRA (100/20/1), right periorbital view. There is some minor artifact due to patient movement. The anterior communicating artery aneurysm (short broad arrow) appears to arise from the right A1/A2 junction. A terminal left internal carotid artery aneurysm is also visible (long thin arrow).

B, TOF-MPR MRA (100/20/1), coronal slice through the anterior communicating artery complex. Scrolling through, no communication is seen between the left A1 segment (thin short arrow) and aneurysm (short broad arrow). The aneurysm is continuous with the right A2 segment (long arrow).

C, IA-DSA, left periorbital projection. The anterior communicating and left terminal internal carotid artery aneurysms are clearly seen (arrows). There are also two discrete middle cerebral artery aneurysms. The anterior communicating artery aneurysm only filled from a left-sided injection. If one were to have planned endovascular treatment on the basis of the MRA findings, the approach would have been via the right internal carotid artery.

A 62-year-old woman presenting with a left CN III palsy due to posterior communicating artery aneurysm.

A, IA-DSA of left common carotid artery, lateral projection. A large left, saccular, posterior communicating artery aneurysm with a discrete narrow neck is seen well.

B, TOF-MIP MRA (100/20/1), similar projection to that of A. Streamlining artifact is seen within the internal carotid artery, and there is signal loss within the aneurysm itself.

C, TOF-3D-isosurface MRA (100/20/1), similar projection to that of A and B. The posterior communicating artery aneurysm (arrow) appears identical to its depiction by IA-DSA.

D, Axial-source TOF image (100/20/1). The true lumen of the posterior communicating artery aneurysm is depicted as high signal, but this is surrounded by concentric mixed signal rims representing intramural thrombus (arrow). The presence of thrombus is not appreciated on the IA-DSA image. The aneurysm is significantly larger than the IA-DSA and postprocessed MRA images suggest.