A Population-Based Study of the Incidence and Case Fatality of Intracerebral Hemorrhage of Undetermined Etiology.

BACKGROUND There is a paucity of reliable recent data regarding epidemiology of intracerebral hemorrhage (ICH) of undetermined etiology in population-based studies. OBJECTIVES To determine the incidence and case fatality of ICH of undetermined etiology using a population-based design. METHODS Medical records and neuroimaging data of all patients with ICH from Stearns and Benton Counties, Minnesota, between June 1st, 2012 and June 30th, 2014 were reviewed. Patients with a first-time diagnosis of ICH were categorized as of undetermined etiology if ICH was without features typical of hypertensive etiology with normal or no magnetic resonance imaging (MRI)/angiograms. We calculated the incidences of [1] probable and possible hypertensive ICH; [2] related to arteriovenous malformation, cavernous malformation, or aneurysmal rupture (angiographic or MRI diagnoses); [3] secondary to anticoagulation; and [4] of undetermined etiology adjusted for age and sex based on the 2010 US census. RESULTS Of the 50 identified ICHs among 136,654 resident populations, seven were true incident cases of ICH of undetermined etiology in this population-based study. The age- and sex-adjusted incidence of ICH of undetermined etiology was 2.6 [95% confidence interval (CI) 0.7-4.9] per 100, 000 person-years, which was lower than probable and possible hypertensive ICH incidence of 12.8 [95% CI 8.4-17.2] per 100,000 person-years. The age-adjusted case fatality rate at 1 month was 8.14 and 0.4 per 100,000 persons for probable and possible hypertensive ICHs and ICHs of undetermined etiology, respectively. CONCLUSIONS Our results should prompt further studies into identification of causes in ICH patients presently classified as ICH of undetermined etiology to reduce the incidence and case fatality of such ICHs.