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. Methods— 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. Results— 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.

Background and Purpose— Pregnancy and the postpartum period are generally considered to be risk factors for cerebral venous thrombosis (CVT), but no controlled studies have quantified the risk. Methods— Case-control study using data of consecutive adult patients with CVT from 5 academic hospitals and controls from the Dutch MEGA study (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis). Men, women over the age of 50, women using oral contraceptives or with a recent abortion or miscarriage were excluded. We adjusted for age and history of cancer, and stratified for pregnancy versus postpartum, and 0 to 6 versus 7 to 12 weeks postpartum. Results— In total 163/813 cases and 1230/6296 controls were included. Cases were younger (median 38 versus 41 years) and more often had a history of cancer (14% versus 4%) than controls. In total 41/163 (25%) cases and 82/1230 (7%) controls were pregnant or postpartum (adjusted odds ratio, 3.8; 95% CI, 2.4–6.0). The association was fully attributable to an increased risk of CVT during the postpartum period (adjusted odds ratio, 10.6; 95% CI, 5.6–20.0). We found no association between pregnancy and CVT (adjusted odds ratio, 1.2; 95% CI, 0.6–2.3). The risk was highest during the first 6 weeks postpartum (adjusted odds ratio, 18.7; 95% CI, 8.3–41.9). Conclusions— Women who have recently delivered are at increased risk of developing CVT, while there does not seem to be an increased risk of CVT during pregnancy.