The Two Main Types of Stroke

All strokes involve disrupted blood flow to the brain, but they happen in two very different ways. Understanding the type of stroke is critical because the treatments are completely different — and in some cases, a treatment that helps one type can be harmful for the other.

Ischemic Stroke

An ischemic stroke occurs when a blood vessel supplying the brain becomes blocked, preventing oxygen-rich blood from reaching brain tissue. Think of it like a dam forming in a river — the tissue downstream from the blockage is starved of what it needs to survive. The sooner the blockage is cleared, the more brain tissue can be saved.

There are several different causes of ischemic stroke, and identifying the cause is a critical part of treatment — particularly for preventing a second stroke. Your stroke care team will perform a thorough evaluation including brain imaging, heart monitoring, and blood tests to determine what caused your stroke.

Types of Ischemic Stroke

Large Artery Atherosclerosis (LAA)
A large vessel disease occurs when a major artery supplying the brain — such as the middle cerebral artery — becomes diseased, usually by a underlying atherosclerosis. The most severe version of these strokes are large vessel occlusions (LVO). LVO strokes tend to be severe and cause significant neurological deficits. They are the type of stroke most often treated with mechanical thrombectomy, a procedure in which a specialist threads a catheter through a blood vessel (usually in the wrist or groin) and physically removes the clot. UNMH is the only hospital in New Mexico offering mechanical thrombectomy 24 hours a day, 7 days a week.

Small Vessel (Lacunar) Stroke
Small vessel strokes, also called lacunar infarcts, occur in the tiny, deep blood vessels of the brain. They are often linked to chronic high blood pressure, which over time damages the walls of small arteries. These strokes tend to cause very specific patterns of weakness, numbness, or coordination problems depending on which small vessel is affected. Treatment focuses on controlling risk factors — particularly blood pressure — to prevent future events.

Cardioembolic Stroke
A cardioembolic stroke happens when a clot forms in the heart and travels to the brain. The most common cause is atrial fibrillation (AFib) — an irregular heart rhythm that causes blood to pool and clot in the heart's upper chambers. Other cardiac sources include a heart attack, heart valve disease, and certain structural abnormalities of the heart such as a patent foramen ovale (PFO), a small opening in the heart wall that normally closes after birth. When a cardioembolic source is identified, treatment typically includes anticoagulation (blood-thinning) medication to prevent future clots.

Cryptogenic Stroke (Unknown Cause)
In some cases, despite a thorough evaluation, no clear cause for an ischemic stroke is found. This is called a cryptogenic stroke. Your care team may recommend extended heart monitoring (for weeks or months) to look for intermittent AFib that was not detected during your hospital stay. Research in this area is ongoing, and at UNMH you will receive a comprehensive workup to look for all possible causes.

Transient Ischemic Attack (TIA)
A TIA — often called a 'mini-stroke' — produces stroke symptoms that resolve on their own, usually within minutes to an hour. Although the symptoms go away, a TIA is not harmless. It is a powerful warning that a full stroke may be coming. A TIA should be treated as an emergency: go to the nearest emergency room immediately, even if you feel completely normal afterward. At UNMH, we offer rapid TIA evaluation to assess your stroke risk and start preventive treatment right away.

Ischemic Stroke Treatment:  The main treatments for ischemic stroke are IV Tenecteplase (a clot-dissolving medication given through a vein in the arm, effective within 4.5 hours of symptom onset) and mechanical thrombectomy (a minimally invasive procedure to physically remove the clot, effective in selected patients up to 24 hours after symptom onset). Not every patient qualifies for both — your team will determine the fastest and safest approach for your specific situation.

Hemorrhagic Stroke

A hemorrhagic stroke occurs when a blood vessel in or around the brain ruptures and bleeds. Unlike ischemic stroke — where the problem is too little blood — hemorrhagic stroke involves blood leaking where it does not belong, creating pressure on brain tissue and causing damage. Hemorrhagic strokes are less common than ischemic strokes but tend to be more severe.

There are two main types of hemorrhagic stroke, defined by where the bleeding occurs.

Intracerebral Hemorrhage (ICH)
Intracerebral hemorrhage occurs when a blood vessel bursts inside the brain itself, causing blood to leak directly into brain tissue. This bleeding creates a clot (called a hematoma) that puts pressure on the surrounding brain. ICH accounts for about 10% of all strokes and carries a higher risk of death and disability than most ischemic strokes.

Common causes of intracerebral hemorrhage include:

• Hypertension: Uncontrolled high blood pressure (hypertension) — the most common cause. Chronic high blood pressure weakens small blood vessel walls over time until they rupture.
• Cerebral Amyloid Angiopathy: Cerebral amyloid angiopathy (CAA) — a condition in which a protein called amyloid builds up in the walls of blood vessels in the brain, making them fragile and prone to rupture. More common in older adults.
• AVM Rupture: Rupture of an arteriovenous malformation (AVM) — an abnormal tangle of blood vessels in the brain that can bleed. [Link to AVM page]
• Anticoagulation: Blood-thinning medications (anticoagulants) — medications like warfarin or newer blood thinners used to prevent clots in the heart can sometimes lead to bleeding in the brain.
• Other causes: Bleeding disorders, illicit drug use (particularly cocaine and methamphetamine), or brain tumors in some cases. 

Treatment for ICH focuses on controlling bleeding, reducing pressure on the brain, and managing the underlying cause. In some cases, surgery may be needed to remove the blood clot or relieve pressure. The UNMH neurocritical care team manages these complex cases around the clock.

Subarachnoid Hemorrhage (SAH)
Subarachnoid hemorrhage occurs when bleeding happens in the space between the brain and the thin tissues that cover it (the subarachnoid space). This is most commonly caused by the rupture of a brain aneurysm — a weak, balloon-like bulge in the wall of a blood vessel.

The hallmark symptom of a subarachnoid hemorrhage is a sudden, extreme headache — often described as 'the worst headache of my life' or a 'thunderclap headache' that comes on in seconds. This symptom should always be taken seriously and treated as an emergency.

Other symptoms of SAH may include:

• Nausea and vomiting
• Neck stiffness or pain
• Sensitivity to light (photophobia)
• Loss of consciousness or sudden collapse
• Neurological deficits such as weakness, speech problems, or confusion

Treatment of SAH caused by a ruptured aneurysm involves securing the aneurysm to prevent rebleeding — either through open surgery (surgical clipping) or a minimally invasive endovascular procedure (coiling, WEB device, or flow diversion). UNMH's neurovascular team has expertise in both approaches and will determine the safest treatment for each patient's specific aneurysm. Learn more about brain aneurysms.

Important:  Unlike ischemic stroke, hemorrhagic stroke should NOT be treated with tPA or most blood thinners — these medications can make the bleeding significantly worse. This is why emergency brain imaging is performed immediately for every stroke patient, so the correct treatment can be given as quickly as possible.