Thrombophilia is a condition where the blood has an increased tendency to form clots. A blood clot within a vein is known as venous thrombus and the most common form is deep vein thrombosis, which is a blood clot in the deep veins of the leg.

If this blood clot breaks loose and travels to the lungs, it is known as pulmonary embolus and can be very dangerous.

A less common (and more severe) form of venous thrombus is known as cerebral venous sinus thrombosis, where a blood clot forms in the dural venous sinuses, which drain blood from the brain.