Hypertension, or high blood pressure, is the main risk factor for primary IPH, as it increases the likelihood that small vessels in the brain parenchyma will rupture. Another cause of primary IPH is cerebral amyloid angiopathy (CAA). In CAA, abnormal proteins called amyloids accumulate on the walls of the brain arteries, which can lead to rupture and subsequent hemorrhage.
Meanwhile, secondary IPH can occur as a result of various underlying conditions. Most commonly, it is the result of coagulopathy, or the inability to form blood clots due to either a coagulation factor deficiency or a severe platelet deficiency, the latter of which is known as thrombocytopenia. Secondary IPH may also be caused by sickle cell disease, an inherited red blood cell disorder that causes red blood cells to form into a sickle shape. The sickle-shaped red blood cells are unable to move easily through blood vessels, and they carry less oxygen. In other cases, secondary IPH may be due to brain tumors.
Yet another condition often associated with parenchymal hemorrhage is cerebral venous sinus thrombosis (CVST). CVST occurs when there is a clot in the vein responsible for draining blood from the brain. The clot causes the blood flow to back up, leading to leakage of blood into surrounding tissues.
Two other conditions that can lead to secondary IPH are arteriovenous malformation and Moyamoya disease. Arteriovenous malformation is characterized by abnormally formed connections between arteries and veins, which can disrupt normal blood supply to the brain and increase risk of rupture. Moyamoya disease, a rare condition seen most often in Japan, involves defective arteries in the brain, leading to arterial narrowing and increased risk of hemorrhage.
Additional significant risk factors include smoking, alcohol intake, and use of sympathomimetic drugs, such as amphetamines. Lastly, trauma or infection, particularly from the hepatitis C virus, can raise the possibility of parenchymal hemorrhages.
