A blood clot in the veins that drain the blood from the brain is called a sinus or cerebral vein thrombosis. It is an uncommon type of clot, affecting about 1500 people in the United States per year. Normally, blood is transported through arteries into the brain, where it delivers oxygen and nutrients. Once the blood has done its job, it collects into small veins (known as cerebral veins) that drain into large veins, called sinus veins (Figure 1). The sinus veins lead to the jugular veins in the neck, which carry the blood back to the heart. The sinus veins have nothing in common (except for the name sinus) with the sinuses of the face on both sides of the nose and above the eyes, which can get infected, leading to sinusitis. Figure 1. The anatomy and terminology of the cerebral and sinus veins. Reproduced with permission from Clot Connect.1 The obstruction of the blood flow from a clot in veins in the head leads to a back up of blood and increasing blood pressure in the blood vessels just before the obstruction. This is like water in front of a dam. The increased pressure leads to swelling of part of the brain, which results in headaches; the pressure can damage the brain tissue, leading to stroke-like symptoms. The increased pressure can also lead to rupture of the blood vessel and bleeding into the brain (Figure 2 …