Early Onset of Cerebral Venous Sinus Thrombosis in a 27-Year-Old Woman Receiving Norethisterone: A Rare Case Report.

Introduction: Cerebral venous sinus thrombosis (CVST) is a rare but serious manifestation of venous thromboembolism (VTE), accounting for 0.5-1% of all strokes. While typically affecting younger females, its diagnosis remains challenging due to nonspecific presentations. Risk factors include hormonal therapy, thrombophilia, and hematologic disorders, with emerging links to COVID-19/vaccine-induced thrombotic thrombocytopenia and polycystic ovarian syndrome. Although combined oral contraceptives are known to increase thrombotic risk, the association between progestogen-only agents such as norethisterone and CVST remains less clearly defined, particularly in the presence of additional risk factors. Case Presentation: A 27-year-old female on 1 month of norethisterone for menstrual disorders (plus unsupervised levothyroxine) presented with severe headache, visual disturbances, and imbalance - initially misdiagnosed as gastritis. She had a family history of VTE and COVID-19 vaccination. CT showed hyperdense venous sinuses; MRV confirmed extensive thrombosis (superior sagittal, transverse, straight sinuses). Laboratories revealed marked TSH suppression (<0.005 µIU/mL). Management included therapeutic enoxaparin, levetiracetam prophylaxis, and levothyroxine discontinuation. The patient demonstrated rapid clinical improvement within 24 h, with near-complete radiographic resolution at 1-month follow-up after transitioning to apixaban. Conclusion: Norethisterone may precipitate early-onset CVST in patients with multiple prothrombotic risk factors, warranting cautious use and careful clinical evaluation.