FIG 2.

A 36-year-old woman admitted with an internal carotid artery blister aneurysm, misdiagnosed due to 2 forms of operator-dependent error. The initial DSA (A) shows a perceptual-type interpretive error in that a laterally projecting blister (white arrow) was not recognized. The blister was more evident on the second DSA (B) and perceived but misinterpreted as vasospasm due to developing vasospasm elsewhere (dashed arrows). Finally, the lesion (yellow arrow) was recognized on the third DSA (C) as vasospasm abated. Intraoperative photographs (D) confirm the rupture site (yellow arrow) secured with clipping.