Transcranial Doppler Examination Following EIAB in Patients with Hemodynamic Cerebral Ischemia

ABSTRACT

OBJECTIVE: The aim of this study is to evaluate the effects of intracranial-extracranial arterial bypass(EIAB) surgery on cerebrovascular reserve capacity(CRC) in patients with hemodynamic cerebral ischemia and to assess the significance of transcranial doppler(TCD) examination before and after EIAB surgery. METHODS: In 29 consecutive patients who underwent EIAB surgery due to symptomatic internal carotid artery or middle cerebral artery(MCA) occlusion, 21 patients were studied using preoperative and postoperative digital subtraction angiogram(DSA), SPECT, and TCD examination. After measuring mean radioactivity count of a region of interest, relative regional cerebral blood flow(rrCBF) was quantitated by the following formula lesional radioactivity count/contralateral radioactivity count x 100%. CRC was calculated as the percentage change from baseline flow after a vasodilatory challenge. RESULTS: Postoperative DSA showed good collateral circulation through the bypass except 4 patients. Preoperative mean value of rCRC improved significantly after EIAB surgery from -14.8+/-2.6% to 6.9+/-2.7%(p<0.01). Intraoperatively, flow velocity of superficial temporal artery(STA) and MCA just after anastomoses increased remarkably in comparison with the values just before anastomoses(p<0.01). There was no correlation between the change of pre- and postoperative flow velocity and the change of rrCBF. In patients with the increase of flow velocity after surgery manifested good collateral circulation through the bypass. The difference was statistically significant(repeated measures ANOVA, p<0.05). Over a mean follow-up period of almost 3 years, no patient had another episode of brain ischemia. CONCLUSION: We believe that the measurement of flow velocity is expected a good method to evaluate the degree of collateral circulation through the bypass.