Headache and Papilledema Unmasking an Underlying Myeloproliferative Neoplasm: A Case of Chronic Recanalized Cerebral Venous Sinus Thrombosis.

Cerebral venous sinus thrombosis (CVST) is a potentially life-threatening condition that can present with clinical features mimicking idiopathic intracranial hypertension (IIH), as both may present with headache and bilateral papilledema, leading to diagnostic uncertainty. We report a case of a 50-year-old woman referred for suspected IIH in whom venous neuroimaging revealed chronic, partially recanalized CVST. Thrombocytosis on full blood count, previously uninvestigated, prompted hematological assessment and led to the diagnosis of a JAK2-positive myeloproliferative neoplasm, for which cytoreductive therapy was initiated alongside anticoagulation. This case underscores the importance of performing venous imaging in patients with headache and papilledema, even when features suggest IIH, and highlights that thrombocytosis should prompt evaluation for an underlying myeloproliferative disorder to guide long-term management and prevent recurrent thrombosis.