Antiplatelet Agents Are Risk Factors for Cerebellar Hemorrhage in Patients With Primary Intracerebral Hemorrhage Hidetoshi Matsukawa, MD,* Masaki Shinoda, MD,* Daisuke Yamamoto, MD,* Motoharu Fujii, MD,* Atsushi Murakata, MD,* Ryoichi Ishikawa, MD,* and Fumio Omata, MD† Some reports have suggested that the location of primary intracerebral hemorrhage (ICH) is affected by oral antithrombotic agents (ATs). This is important, given the increasing use of ATs to treat arteriosclerotic disease. The aim of this study was to explore whether oral AT therapy increase the incidence of any specific location of primary ICH. A retrospective, single-institution study involving 410 Japanese patients with primary ICH was conducted between July 2003 and June 2009. Bivariate analyses (ie, Fisher’s exact 2-tailed test, Student’s t test, Welch’s test, Wilcoxon’s rank-sum test, Pearson’s c 2 test) and multivariate logistic regression analysis were performed for clinical characteristics of these patients. Of the 410 patients, 20% were taking ATs before the onset of primary ICH. The incidence of cerebellar hemorrhage (CH) exceeded that of other types of hemorrhage in patients taking ATs, and the difference was statistically significant on bivariate analysis (P , .0001). On multivariate analysis, only antiplatelet (AP) therapy was found to significantly increase the frequency of CH in patients with primary ICH (P 5 .0035). Our data indicate that taking APs before the onset of ICH a related factor for CH in Japanese patients with primary ICH. Key Words: Antiplatelet agent—cerebral hemorrhage—cerebellar hemorrhage. Ó 2011 by National Stroke Association Intracerebral hemorrhage (ICH) is one of the most common complications of treatment with antithrombotic agents (ATs). Advances in the treatment of arteriosclerotic disease prompted studies to investigate the association between ATs and ICH. ATs are known to increase the risk of ICH, 1-3 and may cause hematoma enlargement in the acute phase. 4-6 Studies have reported a 0.02%-0.47% annual incidence in the incidence of ICH in patients taking a single antiplatelet agent (AP). 7-14 The incidence of ICH is much higher in patients taking 2 APs. 15 In patients on warfarin therapy, the rate of ICH is between 0.3% and 0.6%. 8,9,11,12,16,17 Patients taking both APs and warfarin are at greater risk for hemorrhagic stroke compared with those taking warfarin alone. 15 Numerous underlying conditions are associated with ICH, including hypertension, amyloid angiopathy, vascu- lar disorders, older age, alcohol addiction, low serum cholesterol or triglyceride concentration, and decreased glomerular filtration rate (GFR). 18-21 Hypertension is the most important risk factor for the development of hemorrhagic stroke. 22,23 Hypertensive ICH often occurs in areas of perforating arteries, such as the basal ganglia, but locations may differ in patients who are taking ATs before the onset of ICH. None of the previous studies had sufficient statistical power to provide definitive results; however, some reported an association between warfarin therapy and cerebellar hemorrhage (CH), 24,25 and another found an association between APs and lobar hemorrhage. 26 On the other hand, the rate of CH is low From the *Departments of Neurosurgery, and †Clinical Epidemiol- ogy, St. Luke’s International Hospital, Tokyo, Japan. Received December 24, 2009; accepted February 15, 2010. Supported by St. Luke’s Life Science Institute Research Grant for Clinical Epidemiology Research 2007. The authors have no conflict of interest. Address correspondence to Hidetoshi Matsukawa, MD, Department of Neurosurgery, St. Luke’s International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo104-8560, Japan. E-mail: mahide@luke.or.jp. 1052-3057/$ - see front matter Ó 2011 by National Stroke Association doi:10.1016/j.jstrokecerebrovasdis.2010.02.005 346 Journal of Stroke and Cerebrovascular Diseases, Vol. 20, No. 4 (July-August), 2011: pp 346-351