OBJECTIVE: There are many studies on postoperative cognitive function after surgical clipping (SC) and endovascular coiling (EC) for unruptured cerebral aneurysms, but few reports focusing on possible subclinical damage. The aim of the present study was to detect the subclinical damage after surgical intervention. METHODS: Patients with anterior circulation aneurysms who underwent either SC (SC group) or EC (EC group) were recruited. Imaging studies and evaluation of cognitive function were performed within 1 month preoperatively and at 6 months and 2 years postoperatively. The ipsilateral/contralateral cerebral blood flow (CBF) ratio (I/C ratio) calculated from values in four regions of interest (ROIs) placed on N-isopropyl-p-[ RESULTS: There were 14 patients in the SC group (mean age, 60.6 ± 11.7 years) and 33 patients in the EC group (mean age, 67.5 ± 7.2 years). All cognitive assessment results showed no significant reduction through the survey period. However, I/C ratios were restored by 2 years in the EC group not but in the SC group. I/C ratios at 6 months and 2 years were significantly lower in the SC group than the EC group (P <
0.01). CONCLUSIONS: 123IMP-SPECT revealed a statistically significant reduction in ipsilateral CBF in patients who had an uneventful clinical course and no cognitive problems. The subclinical consequence could persist for at least 2 years following SC, and was less pronounced following EC.