Cerebral hemodynamic parameters for patients with neurological improvements after extracranial-intracranial arterial bypass surgery: Evaluation usingpositron emission tomography

OBJECTIVE: The purpose of this study was to clarify the hemodynamic feature s of patients who experienced improved neurological function after extracra nial-intracranial arterial bypass surgery. With this aim, we retrospectivel y analyzed the results of their pre- and postoperative positron emission to mographic studies. METHODS: This study included 16 patients who exhibited stable neurological dysfunction just before extracranial-intracranial bypass surgery. All under went pre- and postoperative positron emission tomographic studies. They wer e divided into groups, i.e., patients who did (Group 1, n = 6) or did not ( Group 2, n = 10) manifest postoperative improvements in neurological functi ons. Positron emission tomographic parameters obtained in the middle cerebr al artery territories were compared between the two groups. RESULTS: Comparison of the preoperative hemodynamic values on the affected side and the contralateral side demonstrated that the mean regional cerebra l blood flow values were significantly lower on the affected side in both g roups (Croup 1, P < 0.005; Group 2, P < 0.05). For Group 1 patients, the me an regional oxygen extraction fraction (rOEF) and regional cerebral blood v olume values were significantly higher on the affected side than on the con tralateral side (P < 0.01 and P < 0.05, respectively). For Group 2 patients , the mean regional cerebral metabolic rate of oxygen (rCMRO(2)) value was significantly lower on the affected side than on the contralateral side (P < 0.05). The mean rOEF and rCMRO(2) values on the affected side were signif icantly higher for Group 1 patients, compared with Group 2 patients, before surgery (P < 0.05 and P < 0.05, respectively). The preoperative regional c erebral blood flow and regional cerebral blood volume values on the affecte d side were similar for the two groups. Postoperative changes in mean regio nal cerebral blood flow and mean rOEF on the affected side were statistical ly significant for both groups. The mean rCMRO(2) on the affected side for Group 2 was significantly lower than that for Group 1, even after bypass su rgery (P < 0.05). CONCLUSION: Bypass surgery may improve neurological function for patients w ith significantly elevated rOEF values and rCMRO(2) values near the normal level. These hemodynamic parameters may be useful for the identification of candidates for extracranial-intracranial bypass surgery.