High risk of cerebral-vein thrombosis in carriers of a prothrombin-gene mutation and in users of oral contraceptives

Abstract

Background: Idiopathic cerebral-vein thrombosis can cause serious neurologic disability. We evaluated risk factors for this disorder, including genetic risk factors (mutations in the genes encoding factor V and prothrombin) and nongenetic risk factors (such as the use of oral contraceptive agents). We compared the prevalence of these risk factors in 40 patients with cerebral-vein thrombosis, 80 patients with deep-vein thrombosis of the lower extremities, and 120 healthy controls. The G1691A mutation in the factor V gene and the G20210A prothrombin-gene mutation, which are established genetic risk factors for venous thrombosis, were studied. We also assessed the use of oral contraceptives and other risk factors for thrombosis.

Results: The prevalence of the prothrombin-gene mutation was higher in patients with cerebral-vein thrombosis (20 percent) than in healthy controls (3 percent; odds ratio, 10.2; 95 percent confidence interval, 2.3 to 31.0) and was similar to that in patients with deep-vein thrombosis (18 percent). Similar results were obtained for the mutation in the factor V gene. The use of oral contraceptives was more frequent among women with cerebral-vein thrombosis (96 percent) than among controls (32 percent; odds ratio, 22.1; 95 percent confidence interval, 5.9 to 84.2) and among those with deep-vein thrombosis (61 percent; odds ratio, 4.4; 95 percent confidence interval, 1.1 to 17.8). For women who were taking oral contraceptives and who also had the prothrombin-gene mutation (seven patients with cerebral-vein thrombosis but only one control), the odds ratio for cerebral-vein thrombosis rose to 149.3 (95 percent confidence interval, 31.0 to 711.0).

Conclusions: Mutations in the prothrombin gene and the factor V gene are associated with cerebral-vein thrombosis. The use of oral contraceptives is also strongly and independently associated with the disorder. The presence of both the prothrombin-gene mutation and oral-contraceptive use raises the risk of cerebral-vein thrombosis further.

PIP: The role of the prothrombin-gene mutation in idiopathic cerebral-vein thrombosis and its interaction with other risk factors was investigated in a study of 40 patients (9 men and 31 women) 15-64 years of age who presented to a thrombosis center in Milan, Italy, in 1991-97 after a first episode of this thrombosis. Also enrolled were 80 men and women randomly selected from patients screened at the same center during the study period after a first documented episode of proximal deep-vein thrombosis of the lower extremities. 120 healthy controls were matched to cerebral-vein thrombosis patients by sex, age, geographic origin, and education. 20% of patients with cerebral-vein thrombosis (odds ratio (OR), 10.2; 95% confidence interval (CI), 2.3-31.0), 18% of those with deep-vein thrombosis, and 3% of controls were carriers of the prothrombin-gene mutation. Factor V mutation was more prevalent in patients with cerebral-vein thrombosis (15%) than controls (3%) (OR, 7.8; 95% CI, 1.8-34.1), but the thrombotic risks associated with these two mutations were independent of each other. Oral contraceptive (OC) ever-use was more frequent among women with cerebral-vein thrombosis (96%) (OR, 22.1; 95% CI, 5.9-84.2) and deep-vein thrombosis (61%) (OR, 4.4; 95% CI, 1.1-17.8) compared with controls (32%). For the 7 women with cerebral-vein thrombosis who were both OC ever-users and had the prothrombin-gene mutation, the thrombotic risk rose to 149.3 (95% CI, 31.0-711.0). These findings show that there is a hypercoagulable state in 35% of patients with idiopathic cerebral-vein thrombosis. Although screening for the prothrombin-gene mutation in young women before they are prescribed OCs is unlikely to be cost-effective, carriers of the mutation who have had a thrombosis episode should discontinue OC use.