Cerebral hemodynamic parameters for patients with neurological improvements after extracranial-intracranial arterial bypass surgery: evaluation using positron emission tomography

The purpose of this study was to clarify the hemodynamic features of patients who experienced improved neurological function after extracranial-intracranial arterial bypass surgery. With this aim, we retrospectively analyzed the results of their pre- and postoperative positron emission tomographic studies. This study included 16 patients who exhibited stable neurological dysfunction just before extracranial-intracranial bypass surgery. All underwent pre- and postoperative positron emission tomographic studies. They were divided into groups, i.e., patients who did (Group 1, n = 6) or did not (Group 2, n = 10) manifest postoperative improvements in neurological functions. Positron emission tomographic parameters obtained in the middle cerebral artery territories were compared between the two groups. Comparison of the preoperative hemodynamic values on the affected side and the contralateral side demonstrated that the mean regional cerebral blood flow values were significantly lower on the affected side in both groups (Group 1, P < 0.005; Group 2, P < 0.05). For Group 1 patients, the mean regional oxygen extraction fraction (rOEF) and regional cerebral blood volume values were significantly higher on the affected side than on the contralateral side (P < 0.01 and P < 0.05, respectively). For Group 2 patients, the mean regional cerebral metabolic rate of oxygen (rCMRO2) value was significantly lower on the affected side than on the contralateral side (P < 0.05). The mean rOEF and rCMRO2 values on the affected side were significantly higher for Group 1 patients, compared with Group 2 patients, before surgery (P < 0.05 and P < 0.05, respectively). The preoperative regional cerebral blood flow and regional cerebral blood volume values on the affected side were similar for the two groups. Postoperative changes in mean regional cerebral blood flow and mean rOEF on the affected side were statistically significant for both groups. The mean rCMRO2 on the affected side for Group 2 was significantly lower than that for Group 1, even after bypass surgery (P < 0.05). Bypass surgery may improve neurological function for patients with significantly elevated rOEF values and rCMRO2 values near the normal level. These hemodynamic parameters may be useful for the identification of candidates for extracranial-intracranial bypass surgery.