A stroke is a sudden medical event that occurs when the blood supply to part of the brain is disrupted, depriving brain tissue of oxygen and nutrients. This interruption results in the rapid death of brain cells, leading to sudden neurological symptoms. Since brain damage begins within minutes, recognizing the signs of a stroke and seeking immediate medical attention is essential. Prompt diagnosis and treatment limit damage and improve the chances of survival and recovery.
How Strokes Are Classified and the Prevalence Rate
Strokes are broadly categorized into two types based on the mechanism of blood flow disruption. The vast majority are ischemic strokes, which occur when a blood clot or blockage cuts off blood flow to a section of the brain. The other type is the hemorrhagic stroke, which involves bleeding into or around the brain.
Hemorrhagic strokes account for a small percentage of all stroke cases, typically ranging from 10% to 15% globally. Despite this lower prevalence, they are associated with a disproportionately higher rate of death and severe disability compared to ischemic strokes. The bleeding causes direct trauma to brain tissue and leads to a dangerous buildup of pressure within the skull.
The Two Main Types of Hemorrhagic Stroke
Hemorrhagic strokes are further subdivided based on where the bleeding occurs. The most frequent subtype is the Intracerebral Hemorrhage (ICH), constituting approximately 75% of all hemorrhagic strokes. This event involves a blood vessel rupturing and bleeding directly into the brain tissue itself (parenchyma). The resulting collection of blood forms a hematoma that compresses and damages surrounding brain cells.
The second subtype is the Subarachnoid Hemorrhage (SAH), which occurs when bleeding enters the subarachnoid space. This space is located between the brain and the thin membranes covering it. When bleeding occurs here, the blood irritates surrounding tissues and quickly increases pressure on the entire brain. SAH is characterized by bleeding around the brain, typically on the surface, rather than in the brain tissue like ICH.
Underlying Causes and Immediate Treatment Approaches
The primary causes for these two hemorrhagic stroke subtypes differ, influencing prevention and acute management. Intracerebral Hemorrhage is most commonly linked to chronic, uncontrolled high blood pressure, which weakens small arteries deep within the brain over time. This stress can lead to the formation of microaneurysms that eventually rupture.
Causes of Intracerebral Hemorrhage (ICH)
Other causes include the use of anticoagulant or antiplatelet medications, which reduce the blood’s ability to clot. Cerebral amyloid angiopathy, a condition where protein deposits weaken blood vessel walls, is also a factor.
For Subarachnoid Hemorrhage (SAH), the most frequent cause is the rupture of a cerebral aneurysm, a balloon-like bulge in an artery wall. These aneurysms are often located on the surface of the brain and burst, flooding the subarachnoid space with blood. Less common causes include arteriovenous malformations (AVMs), which are abnormal tangles of blood vessels that disrupt normal blood flow.
Acute Management
Acute care focuses on aggressively controlling the patient’s blood pressure, typically below 140 mmHg systolic, to prevent the bleed from enlarging. If the patient is taking blood-thinning medications, doctors must rapidly reverse the anticoagulation using specific agents like prothrombin complex concentrate or Vitamin K. This reversal is necessary to restore the blood’s clotting ability, contrasting sharply with ischemic stroke treatment where clot-busting drugs are used.
Surgical intervention is often considered to manage the bleeding and relieve pressure on the brain. For Intracerebral Hemorrhage, a neurosurgeon may evacuate the hematoma, surgically removing the pooled blood to reduce intracranial pressure. For Subarachnoid Hemorrhage, the ruptured aneurysm may be secured through surgical clipping or endovascular coiling, which uses a catheter and tiny coils to block blood flow and prevent re-bleeding.