Magnetic Resonance Imaging and Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage: A Systematic Review and Meta-Analysis

The prognosis of aneurysmal subarachnoid hemorrhage (aSAH) has improved during the past decades. However, a recent hospital-based study showed that 90-day case fatality is still 30%.1 Determinants of functional outcome after aSAH may include the severity of the initial hemorrhage, rebleeding of the aneurysm, and cerebral ischemia that can be distinguished into (1) acute ischemia at the time of bleeding when intracranial pressure rises and cerebral perfusion pressure drops, (2) procedure-related ischemia from endovascular or neurosurgical treatment of the aneurysm, and (3) delayed cerebral ischemia (DCI), which can occur between days 4 and 14 after the hemorrhage.2,3 Magnetic resonance diffusion weighted imaging (MRI-DWI) is increasingly used for the evaluation of ischemia after aSAH. The aims of the present review were to (1) analyze the proportion of patients with MRI-DWI lesions within 72 hours after aSAH, both before and after aneurysm treatment; (2) study determinants of MRI-DWI lesions within 72 hours after aSAH; (3) analyze the proportion of patients with MRI-DWI lesions between 72 hours and 21 days after aSAH; (4) investigate the predictive value of MRI-DWI lesions within 72 hours for the development of DCI; and 5) investigate whether MRI-DWI can be used for the diagnosis of DCI in patients with clinical deterioration. ### Search Strategy We searched the PUBMED, EMBASE, and Web of Science databases with the following combination of variables: MRI OR magnetic resonance AND subarachnoid hemorrhage OR SAH OR DCI OR delayed cerebral ischemia OR DIND. The last search was performed in June 28, 2016. Only studies published after January 1, 2000, were included to assure a similar degree of image quality, given the technical developments in MRI hardware and sequences. Both prospective and retrospective studies were included. Eligible articles were identified according to the PICO criteria. Type of patient population (P): (1) >95% of patients …