An Unusual Presentation of Antiphospholipid Syndrome With Seizures and Sagittal Sinus Thrombosis: A Case Report.

Cerebral venous sinus thrombosis (CVST) is a rare but potentially life-threatening form of stroke. It may present with nonspecific neurological symptoms, including headache, seizures, or focal deficits. One of the rare but important underlying causes is antiphospholipid syndrome (APS), an autoimmune prothrombotic condition associated with persistent antiphospholipid antibodies: lupus anticoagulant (LA), anticardiolipin (aCL), or anti-β2 glycoprotein I (anti-β2GPI). APS-related CVST is typically seen in young women, often with systemic autoimmune disease such as systemic lupus erythematosus. We present a rare and atypical case of a 55-year-old man with no prior autoimmune history who developed new-onset seizures and right-sided weakness while visiting the UK. Imaging revealed a haemorrhagic infarct in the left frontal lobe secondary to superior sagittal sinus thrombosis. Initial thrombophilia screening identified an isolated positive lupus anticoagulant, with confirmatory repeat testing at 12 weeks fulfilling the revised Sapporo criteria for APS. The patient was managed with anticoagulation, antiepileptics, and specialist follow-up. This case is unusual due to several factors: the patient's demographic (middle-aged male), the absence of systemic autoimmune disease, presentation with seizures and intracerebral haemorrhage, and the isolated lupus anticoagulant positivity without triple antibody presence. It highlights the importance of considering APS in unprovoked CVST even in the absence of classic risk factors. Early diagnosis, appropriate imaging, and timely anticoagulation can improve outcomes. This case reinforces the need for autoimmune and thrombophilia screening in atypical stroke presentations.