(NewsNation) — When most people hear the word “stroke,” they automatically think of the most common type: An ischemic stroke, which occurs when an obstruction blocks blood flow to the brain.
A lesser-known, yet more deadly, type of stroke comes in the form of a hemorrhagic stroke.
A hemorrhagic stroke, which makes up only about 13% of stroke cases, occurs when a blood vessel ruptures and bleeds into the surrounding brain tissue. According to the American Stroke Association, the pressure from the bleed restricts the flow of blood — and the vital oxygen it carries — to the brain.
Yale Medicine reports that about half of patients who suffer a hemorrhagic stroke die within weeks of the event. If the stroke is caused by a ruptured aneurysm, about a third of patients die before reaching the hospital.
The most common cause of hemorrhagic strokes is untreated high blood pressure, according to the Cleveland Clinic.
Medical experts say hemorrhagic strokes are particularly dangerous because of the severity of the symptoms and the speed with which symptoms worsen. Without immediate medical care, they can kill or cause permanent brain damage.
Hemorrhagic strokes are themselves made up of two types: Intracerebral hemorrhages, which occur within the brain, and subarachnoid hemorrhages, which occur between the inner and outer layers of tissue covering the brain.
Recent studies have shown an alarming increase in hemorrhagic strokes, particularly among younger and middle-aged patients. The American Heart Association reported in 2022 that, over the past 15 years or so, there has been an 11% increase in intracerebral hemorrhage strokes.
The spike in cases indicates that conditions such as high blood pressure are poorly controlled in younger adults, according to the research.
High blood pressure ties in with other underlying conditions that can cause a blood vessel to weaken and increase the chances of a rupture. The first, an arteriovenous malformation, is a tangle of blood vessels in the brain that diverts blood from the brain tissue and directly from the arteries to the veins.
The vessels weaken and dilate over time, increasing the likelihood of a rupture, the Stroke Association reports.
Brain arteriovenous malformations are relatively rare, occurring in 10 to 18 per 100,000 adults.
The second condition, a cerebral aneurysm, occurs when a weak spot in a blood vessel “balloons” dangerously. If the aneurysm ruptures, it causes bleeding within the brain or the surrounding area.
Cerebral aneurysms occur most often in people between the ages of 30 and 60, and they are more common in women than in men. They can be caused by underlying conditions that weaken blood vessels.
They can also be caused by infections, the use of drugs like amphetamines and cocaine or direct brain trauma from an accident. About 30,000 ruptured cerebral aneurysms occur each year in the U.S.
According to the Stroke Association, up to 6% of the population may be living with an unruptured cerebral aneurysm.