In this paper, the authors describe three cases of extremely rare aneurysm which were located in the C2 portion of the internal carotid artery and had no relation to arterial branches. From the operative findings, these aneurysms looked like “chimame” (blood blister) because of their extremely thin wall. Moreover, this aneurysm was not saccular but merely a protrusion. Because it has not been reported previously in the medical literature, the authors advocate calling it a “chimamelike aneurysm.” This aneurysm has a extremely high tendency to rupture prematurely during a radical operation. Special care should be taken to prevent tragic results.
All of the three patients were middle aged females who had a past history of hypertension. One of the most characteristic angiographic appearances was a small protrusion emerging from the upper wall of the internal carotid artery with more or less arteriosclerotic changes adjacent to the aneurysm. Complete angiographic investigation and careful analysis of the angiograms were necessary for the accurate preoperative detection of this type of unusual aneurysm.
The aneurysms were small protrusions without a distinctive neck. Because of the high tendency of premature rupture, it is advisable to occlude the proximal internal carotid artery temporarily during the brain protection using “Sendai cocktail”.Sometimes it is necessary to use multiple temporary clips in order to control the bleeding during surgery. These clips tend to disturb the operative field. Intravascular temporary balloon occlusion was very useful. As this aneurysm has a very thin and fragile wall and no distinct neck, it might be advisable to treat it by wrapping with a muscle piece, using Aron alpha adhesives (alkyl-alpha-cyanoacrylate monomer). Complete wrapping, including the portion behind the aneurysm, is also recommended.
