Racial Differences in Cerebral Vasospasm: A Systematic Review of the Literature

OBJECTIVE: Despite a significant body of clinical research and the widespread use of early intervention with aggressive postoperative management, cerebral vasospasm (CV) continues to contribute significantly to the morbidity and mortality of aneurysmal subarachnoid hemorrhage (aSAH). Many studies have evaluated predictive factors, although none to date has investigated a possible difference in the incidence of CV between Asian and white patients. We present a review of the modern aSAH literature to examine the incidence of CV in Japan and Europe, two highly researched populations. METHODS: A literature search was performed using the Medline and PubMed databases. Studies conducted in Japan or Europe published between 1990 and 2004 that reported an incidence of CV after aSAH were subjected to a thorough review. Data from included studies were categorized by origin (Japan or Europe) and method of CV diagnosis (angiography, delayed ischemic neurological deficit, or new infarct attributable to CV), and then were combined. Recorded incidences then were compared using a Χ 2 test, and estimates of the relative risk of vasospasm were computed. RESULTS: The initial literature search identified 102 studies, and 32 studies met all inclusion criteria. The incidence of vasospasm diagnosed by angiography, delayed ischemic neurological deficit, and computed tomography was significantly greater in Japanese studies (all P < 0.001). The relative risks for Japanese patients as compared with European patients were 2.04, 2.07, and 1.53 for angiographic CV, delayed ischemic neurological deficit, and new infarct, respectively. CONCLUSION: Patients in Japanese studies were more likely to experience CV after aSAH across diagnostic methods. This may be a manifestation of genetic differences between Japanese and European populations. Clinicians should consider possible patient differences when interpreting CV research conducted in these populations.