Cerebral Venous Sinus Thrombosis Incidence Is Higher Than Previously Thought: A Retrospective Population-Based Study.BACKGROUND AND PURPOSE
 The incidence of cerebral venous thrombosis (CVT) varies between studies, but it is estimated to be between 2 and 5 per million per year.  A recent study in the Netherlands with comprehensive ascertainment suggested a much higher incidence.  It is uncertain whether these differing estimates reflect the quality of ascertainment or true variation.  The purpose of this study was to determine the incidence of CVT in Adelaide, using a novel clinical and radiological methodology.


 We retrospectively identified CVT International Classification of Diseases-coded cases from all Adelaide public hospitals from 2005 to 2011.  We also searched all neuroimaging studies (259 101) from these hospitals for text variations containing venous thromb.  All potential cases were reviewed, and cases of incident CVT ascertained.  Associations and outcomes were determined.


 Of 169 possible cases, 105 cases of CVT were confirmed (59 cases by both coding and neuroimaging, 40 from neuroimaging alone, and 6 from coding alone).  In our population of 953 390 adults, this represented an incidence of 15.7 million per year (95% confidence interval, 12.9-19.0), the highest incidence reported.  Of these cases, a possible procoagulant predisposition was identified in 48%.  Fifty-five of 105 cases occurred in females.  Relative risk of CVT in females of reproductive age was insignificantly higher than in males (1.18 [95% confidence interval, 0.94-1.48]).


 CONCLUSIONS
 Cerebral venous sinus thrombosis in our study was more common than previously reported, perhaps because of more complete ascertainment.  Future CVT incidence studies should include comprehensive capture and review of neuroimaging.
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