What is the relationship between Hormone Replacement Therapy (HRT) and Sagittal Venous Sinus Thrombosis?

From the Guidelines

Hormone replacement therapy (HRT) should be discontinued in patients with sagittal venous sinus thrombosis due to the increased risk of thrombosis associated with estrogen-containing medications. The relationship between HRT and sagittal venous sinus thrombosis is supported by studies that demonstrate an increased risk of venous thromboembolism (VTE) in women taking HRT 1. A meta-analysis of 12 studies found that HRT was associated with an increased risk for VTE, with a relative risk of 2.14 (95% CI, 1.64 to 2.81) 1. The risk was highest within the first year of use, with a relative risk of 3.49 (95% CI, 2.33 to 5.59) 1.

Key Points to Consider

• The increased risk of thrombosis with HRT is due to estrogen's effects on coagulation factors, including increased factors VII, VIII, X, and fibrinogen, decreased antithrombin III and protein S, and induced resistance to activated protein C.
• For patients with sagittal venous sinus thrombosis, immediate anticoagulation therapy is recommended, typically starting with low molecular weight heparin or unfractionated heparin, followed by oral anticoagulants like warfarin or direct oral anticoagulants (DOACs) for 3-12 months depending on underlying risk factors 1.
• Alternative non-hormonal treatments should be considered for menopausal symptoms, including selective serotonin reuptake inhibitors (SSRIs) like paroxetine or venlafaxine for vasomotor symptoms, or topical vaginal estrogen for genitourinary symptoms which has minimal systemic absorption.

Management of Menopausal Symptoms

• For women with severe menopausal symptoms who have completed anticoagulation therapy, any consideration of resuming HRT should involve careful risk assessment and discussion with both neurology and gynecology specialists.
• The decision to resume HRT should be based on the individual patient's risk-benefit profile, taking into account the increased risk of thrombosis and the potential benefits of HRT for menopausal symptoms 1.

From the Research

Relationship Between Hormone Replacement Therapy (HRT) and Sagittal Venous Sinus Thrombosis

• The relationship between HRT and sagittal venous sinus thrombosis is not directly addressed in the provided studies, as they focus on the treatment of dural sinus thrombosis 2, 3 and the risk of venous thrombosis associated with HRT 4, 5, 6.
• However, it is known that HRT increases the risk of venous thrombosis, including deep vein thrombosis and pulmonary embolism 4, 5.
• The risk of thrombosis with HRT is affected by the type of estrogen and progestogen used, as well as the route of administration 5.
• Women with a history of thrombosis or thrombophilia are at increased risk of venous thrombosis when using HRT, and the risk may be higher for those with prothrombotic mutations such as factor V Leiden 4, 6.
• The studies suggest that transdermal HRT may not be associated with an increased risk of thrombosis in healthy women, but the safety of HRT in women with a high background risk of thrombosis is not well established 5.
• There is limited information on the specific risk of sagittal venous sinus thrombosis associated with HRT, and further research is needed to fully understand this relationship 4, 5, 6.