Subarachnoid clot distribution in anterior wall saccular aneurysms of the internal carotid artery.

Anterior wall aneurysms of the internal carotid artery (AWAICA) are relatively uncommon. We investigated the distribution of the subarachnoid clot on computerized tomography (CT) scans in patients with ruptured AWAICA and compared the findings with those in patients with internal carotid artery aneurysms (ICAA) at other sites. Twenty-six ruptured ICAA patients were included in this study. Four (15.4%) of these had an AWAICA and 22 had an ICAA at other sites. Three of the 4 patients with AWAICA had an ordinary 'saccular type' aneurysm and the other had a 'blood blister-like' aneurysm. In all three patients with a 'saccular type' AWAICA, accumulation of the subarachnoid clot in the olfactory sulcus was noted on CT scan. In the patient with a 'blood blister-like' aneurysm and in 22 patients with ICAA at other sites, there were no specific correlations between focal accumulations of the subarachnoid clot and aneurysm location. The accumulation of subarachnoid clot in the olfactory sulcus on CT scan may suggest a ruptured 'saccular type' AWAICA.