Abstract
There seems to be a general agreement that unruptured cerebral aneurysms measuring more than 10mm should be treated surgically, although the situation regarding smaller lesions, especially those with a maximum diameter less than 5mm, is more controversial. We analyzed operative findings of 122 unruptured cerebral aneurysms found in 92 surgical cases to estimate whether such small aneurysms are prone to rupture. Among the 122, 32 (26%) were evaluated as having thick-walled sacs (type 1), 54 (44%) partially or entirely thin-walled sacs (type 2), and 36 (30%) partially or entirely very thin-wall sacs so that intra-aneurysmal blood turbulence was visible through the aneurysmal walls (type 3). The sizes were 9.6±1.3mm (mean±1 SD) for type 1 aneurysms, 4.8±0.3mm for type 2, and 5.3±0.9 mm for type 3, types 2 and 3 aneurysms being significantly smaller than type 1 aneurysms. Eighty-three percent of unruptured aneurysms less than 5 mm in diameter had partially or entirely thin-walled sacs. Ninety-eight percent of patients with surgical treatment for unruptured aneurysms less than 5 mm showed good recovery. Assuming that thin-walled aneurysms are at a high risk of subsequent subarachnoid hemorrhage, prophylactic surgical treatment for small unruptured aneurysms in otherwise healthy individuals may be recommended.
