Internal carotid artery dorsal wall aneurysm with configurational change: Are they all false aneurysms?

Aneurysms arising from nonbranching sites of the ICA, so-called dorsal wall aneurysm, are rare entity, and present as blister type or saccular type. Occasionally configurational changes have been observed on serial cerebral angiography: a small blister-like bulge on ICA wall on initial angiography progressing to a saccular appearance within a few weeks. Such aneurysm showing configurational change has been regarded as a false aneurysm with fragile wall just like blister-type aneurysm, and direct surgical approach has been considered highly risky.

A 42-year-old woman with a subarachnoid hemorrhage revealed small "blister-like" aneurysm at the medial wall of the ICA on initial angiography. After 12 days, the following angiograms demonstrated increased aneurysmal size and change of shape into a saccular configuration. Direct surgical approach was performed. The aneurysm had a relatively firm neck, and was successfully clipped without intraoperative rupture. The dome of aneurysm was resected after clipping and the histologic examination revealed it as a true aneurysm.

This case suggests that all dorsal wall aneurysms with configurational change are not false aneurysms, and that angiographic findings do not always correlate with the nature of the aneurysmal wall; therefore, we should give more credence to direct surgical observation rather than preoperative angiographic findings when considering the most suitable surgical option.