Case Presentation: A 20-year-old woman presented with 24 hours of severe left-sided headache associated with nausea, photophobia, and phonophobia. She was previously healthy and was taking only an oral contraceptive pill. On physical examination, she was tachycardic to 110 bpm, normotensive with a blood pressure of 108/64 mm Hg, and appeared uncomfortable. Neurological examination in the emergency department was unremarkable. Migraine headache was considered the most likely cause of her symptoms. After analgesia had improved her symptoms, the patient was discharged with instructions to return if her headache recurred or worsened. She returned 12 hours later with recurrent severe headache. Head computed tomogram (CT) without contrast demonstrated hyperdensities along the left tentorium and involving the left sigmoid sinus that were concerning for cerebral venous thrombosis (Figure 1A and B). A magnetic resonance (MR) venogram was recommended and showed thrombosis of the left transverse and sigmoid sinus and proximal internal jugular vein (Figure 1C and D). The clinical presentation and imaging findings established the diagnosis of cerebral venous thrombosis. Figure 1. Computed tomogram (CT) of the head without intravenous contrast demonstrating hyperdensities along the left tentorium (arrows, A ) and involving the left sigmoid sinus (arrowheads, B ) that were concerning for cerebral venous thrombosis. Magnetic resonance (MR) venography demonstrating thrombosis of the left transverse (arrowheads) and sigmoid sinus and proximal jugular vein (arrows) in the axial ( C ) and coronal ( D ) planes. Cerebral venous thrombosis, including thrombosis of cerebral veins and major dural sinuses, is an uncommon disorder in the general population. However, it has a higher frequency among patients younger than 40 years of age, patients with thrombophilia, and women who are pregnant or receiving hormonal contraceptive therapy. Annual incidence is estimated to be 3 to 4 cases per million.1 The incidence of cerebral venous thrombosis increases to 12 cases per …