A thrombotic stroke is when a blockage in an artery disrupts blood flow to a part of the brain. Symptoms may differ depending on whether the blockage is in a small or large artery.

A thrombotic stroke is a type of ischemic stroke. This means a part of the brain gets injured because the artery that supplies blood to it gets blocked, so blood flow is reduced or stopped completely.

According to the American Stroke Association, about 87% of all strokes are ischemic. The remainder are typically due to bleeding in your brain from a torn or ruptured blood vessel. This is called a hemorrhagic stroke.

In a thrombotic stroke, the artery is blocked by a thrombus (blood clot) that forms there.

The other type of ischemic stroke is an embolic stroke. In this case, the blockage, called an embolus, forms in another part of the body. It moves with your blood to an artery in your brain, where it gets stuck and blocks off the artery.

Embolic strokes typically result from blockages in larger arteries as it is more difficult for an embolus to travel to a small artery, though it can happen.

Thrombotic strokes can result from blockages in either large or small blood vessels.

A thrombotic stroke can involve large or small arteries in your brain.

Large vessel thrombosis (LVO stroke)

Large arteries supply blood to bigger sections of your brain. When a blood clot forms in one, the damage can be significant and affect important body functions.

Most often, plaque builds up slowly over time without you noticing any symptoms. Symptoms occur when a clot suddenly forms, blocking the artery.

A blockage in a large artery is called a large vessel occlusion (LVO). LVO strokes make up 24–46% of ischemic strokes, though not all LVO strokes are due specifically to a thrombus.

Small vessel thrombosis (lacunar stroke)

Small arteries are found deep inside your brain. They supply blood to small areas of your brain. When they become blocked, lacunar strokes occur.

Research estimates that about 15–25% of all ischemic strokes are lacunar strokes.

General stroke symptoms may include:

Sometimes, there are no general symptoms.

Symptoms of large vessel thrombosis and LVO stroke

Everything your body does, such as move an arm, speak, and stay in balance, is controlled by a specific part of your brain. What symptoms you experience during a large vessel thrombotic stroke will depend on which parts of the brain are affected and how severe the stroke is.

Symptoms of a large vessel thrombosis usually occur suddenly, but they can also come on gradually. Symptoms may include:

  • weakness or paralysis of your arm, leg, or face on one side of your body (hemiparesis)
  • numbness or loss of sensation on one side of your body
  • loss of part of your vision in one or both eyes
  • balance problems that can affect walking, standing, and staying upright while sitting
  • difficulty speaking clearly (dysarthria), finding the right word to say, or understanding what you hear or read (aphasia)
  • loss of coordination

Symptoms of small vessel thrombosis and lacunar stroke

Typically, small vessel thrombosis has no symptoms. The condition worsens until a lacunar stroke occurs.

Lacunar strokes usually cause one of five classic syndromes:

  • pure motor hemiparesis: weakness or paralysis of the face (facial droop), arm, or leg
  • pure sensory stroke: impaired sensation
  • sensorimotor stroke: weakness or paralysis and loss of sensation
  • ataxic hemiparesis: weakness and clumsiness in the arm or leg
  • dysarthria-clumsy hand syndrome: inability to form or pronounce words and clumsy hand movements

The symptoms of each syndrome usually affect only one side of your body.

Thrombotic strokes are caused by inadequate blood flow to a part of your brain due to a thrombus blocking an artery.

A thrombus often forms due to the hardened buildup of cholesterol and other substances called plaque. The disease causing the buildup is called atherosclerosis.

Your body sees this buildup as an injury, so it responds by sending clotting factors to form a blood clot. When it gets big enough, the clot blocks the artery.

The risk factors for a thrombotic stroke are the same as for atherosclerosis. They include:

Your risk is also higher if you or someone in your family has had a thrombotic stroke. Your risk increases as you get older. Strokes are more common in males at younger ages and in females at older ages.

The standard treatment for an ischemic stroke is a “clot-buster” medication called a tissue plasminogen activator (tPA). Healthcare professionals must administer a tPA within 4.5 hours of stroke onset. It breaks up the clot and opens the artery so blood can flow to the brain tissue again.

Doctors can administer tPA into a vein or directly into the area with the clot by inserting a catheter into the artery in your groin and threading it up to your brain.

When the large vessel thrombosis is in a carotid artery (in the neck) or the first part of the middle cerebral artery (in the brain), your doctor will perform a mechanical thrombectomy after tPA if possible. They must do this within 6–24 hours of the stroke.

In this procedure, a doctor removes the clot and places a stent to keep the artery open. If tPA isn’t an option, doctors can use thrombectomy alone to remove the clot.

If you’re at high risk or have had a previous thrombotic stroke, your doctor will probably prescribe an antiplatelet medication to make it harder for your blood to clot to help prevent a future stroke. These medications include:

  • aspirin
  • clopidogrel (Plavix)
  • combination of aspirin and dipyridamole (Aggrenox)

While doctors may use anticoagulants like warfarin (Coumadin) to treat embolic strokes, they don’t typically use them for thrombotic strokes.

Full recovery from a thrombotic stroke is possible if doctors can successfully treat the stroke within a few hours. But even with treatment, long-term complications are common. A stroke can leave you unable to walk, talk, or think clearly.

Research links LVO strokes with less favorable outcomes, including higher rates of dependence and death.

Lacunar strokes typically have a more favorable outlook. Still, they’re linked with a relatively high risk of future strokes, cognitive decline, and dementia.

The most important factor in your outlook is how quickly your medical team can remove the clot and reopen the artery. If too much time passes, some or all of the symptoms can be permanent, or you may not survive the stroke.

With prompt diagnosis and treatment, doctors can limit the damage. If the damage isn’t severe, it’s possible to regain some of the lost function caused by the stroke and have a better outcome.

You can reduce your risk of a thrombotic stroke by addressing some of the key risk factors. Steps you can take include:

A thrombotic stroke results from a blood clot in the arteries that supply blood to your brain. These can occur in large vessels (LVO strokes) or small vessels (lacunar strokes). LVO strokes are more severe, but lacunar strokes can also cause significant damage, particularly if you have several of them.

High blood pressure, high cholesterol, and diabetes are some of the major risk factors for a thrombotic stroke. Managing these conditions can help lower your risk of this type of stroke.