Temporal and Spatial Changes in Cerebral Blood Flow during Management for Preventing Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage: Serial Semiquantitative Analysis

Background Delayed cerebral ischemia is a major cause of morbidity after aneurysmal subarachnoid hemorrhage. The management for preventing the delayed cerebral ischemia is clinically difficult because of its multifactorial nature. We tested the hypothesis that spatial and temporal changes of regional cerebral blood flow after subarachnoid hemorrhage might relate to the incidence of the delayed cerebral ischemia and the clinical outcome. Methods Eighty-eight patients who underwent single-photon emission computed tomography twice during 14 days after the onset of aneurysmal subarachnoid hemorrhage were retrospectively analyzed. Regional cerebral blood flow was automatically analyzed in statistical imaging analyses using 3-dimensional stereotaxic region of interest template and 3-dimensional stereotaxic surface projection. Ratios were calculated by dividing the regional cerebral blood flow of patients by that of normal volunteers. We assessed the relation of changes in regional cerebral blood flow with the development of the delayed cerebral ischemia and the clinical outcome at 3 months. Results The regional cerebral blood flow of areas that eventually contained infarction significantly decreased, whereas those with significant increase were associated with transient neurological symptoms during the management for the delayed cerebral ischemia. Patients with both areas of regional cerebral blood flow increasing and decreasing during this period had worse outcomes than patients with a unidirectional change. Conclusions Cerebral perfusion may change temporally and spatially during the management for preventing the delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. Regional hypoperfusion refractory to the management might exist, which could impact on the clinical outcome. An additional therapeutic approach targeting on such regions may be required.