Aneurysms arising remote from arterial divisions are rare. From January 1981 to December 1993. We operated on 271 internal carotid artery aneurysms (ICAA). Among them, we found nine of such unusual aneurysms protruding from the dorsal (six cases)
or
medial wall (three cases) of the internal carotid artery.
Angiographically, they were often misdiagnosed as the posterior communicating artery aneurysm or carotid artery bifurcation aneurysm due to small size and flat shape with broad neck. On operation, all three medial wall aneurysms showed severe
atherosclerosis, and moderate to minimal atherosclerosis was found in four dorsal wall aneurysms. In four cases, we experienced intraoperative premature rupture of the aneurysm, one during retraction of the frontal lobe due to adhesion of the
aneurysmal
dome to the base of frontal lobe, two during aneurysmal neck dissection and the other one during clip application. These aneurysms were difficult to operate on because of their fragility (thin or atherosclerotic wall) and relatively broad
aneurysmal
neck.
In conclusion. These aneurysms presented with difficulties in preoperative diagnosis by angiography due to small size and flat shape. In operation, special care should be taken to avoid premature rupture of the aneurysm due to thin or
atherosclerotic
fragile wall.
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