How a Stroke Causes Brain Damage

Strokes occur when the blood supply to the brain is interrupted. This can occur suddenly and cause serious damage quickly. Strokes may also prove fatal. A stroke is a medical emergency that requires immediate care.

Many factors contribute to your likelihood of stroke. They include lifestyle risks like smoking and underlying health conditions such as diabetes, high blood pressure, and irregular heart rhythms.

This article describes how a stroke can affect the brain, how these changes lead to the symptoms of a stroke, as well as what to do to lower your stroke risk.

Pet scans of the brain of a stroke patient

Types of Stroke

There are two main types of stroke that affect the brain. One is an ischemic stroke, which is due to a lack of blood flow to the affected area of the brain. The other is a hemorrhagic stroke that causes bleeding in the brain. Both types can lead to death to some of the nearby brain tissue.

Ischemic Stroke

An ischemic stroke happens when the blood flow to a part of the brain is blocked, interrupting its oxygen supply. This type of stroke occurs when one of two things happens in the blood vessels of the brain.

In the first type, called an embolic stroke, a clot travels from the heart or one of the blood vessels in the neck and becomes lodged in the brain. This causes a block in the brain's blood supply. It is the most common type of stroke to affect the brain.

The other type of ischemic stroke is known as thrombotic stroke. In this case, the clot forms in an artery that supplies blood to the brain. The clot then cuts off blood supply to that part of the brain, along with the oxygen needed by the nearby brain cells.

Hemorrhagic Stroke

A hemorrhagic stroke is caused by bleeding in the brain. The bleeding causes tissue damage while also limiting the flow of oxygen to the affected brain tissues. This type of stroke is less common, but it also has the potential to cause severe damage.

Is a TIA the Same Thing as a Stroke?

A transient ischemic attack, or TIA, causes symptoms that are similar to those of an ischemic stroke and have the same causes. The difference is that the TIA resolves quickly on its own and doesn't cause lasting damage. However, people who experience a TIA are at risk for another, perhaps more serious, event. It's important to reduce your stroke risk factors after a TIA occurs.

Changes in the Brain

When a stroke occurs, it will cause brain damage depending on its location. These changes can lead to speech difficulties, full or partial paralysis, mental confusion, and other impairments in the body.

The impacts of a stroke, and how they affect mobility and quality of life, are often quite visible. What's harder to see are the small chemical and cellular changes in the brain itself that lead to damage.

For example, brain cells that don't get enough blood can leak enzymes into the surrounding tissue. These enzymes are toxic to brain cells and can cause irreversible damage to them. Inflammation, along with other chemical processes in the brain, also may lead to damage.


When toxins attack the brain during a stroke, the brain naturally tries to repair itself. However, the brain's attempt to heal produces an exaggerated inflammatory response.

Ultimately, this brain activity can lead to swelling, or edema. This swelling is one of the reasons why healthcare providers carefully watch the amount of fluid intake in people who have had a stroke.

Excess Calcium

Calcium plays an important role in your body's health, including heart and bone health. It is one of the key minerals in the body known as electrolytes.

After damage from a stroke, calcium can leak into brain cells. This follows the disruption in the brain's blood flow and oxygen supply because of the stroke. The body is not able to maintain its optimal calcium levels and the amount of calcium in the brain becomes unbalanced.

Sodium Imbalance

Like calcium, sodium is a key mineral necessary for brain function. The balance of both minerals, along with potassium, may be disrupted when a stroke occurs and lead to additional damage.

These imbalances may contribute to the severity of a stroke, as well as whether or not a stroke may prove fatal. One study of more than 8,500 people who experienced a stroke found that hyponatremia, or low sodium levels, were associated with an increased risk of death from stroke.

Electrolytes and Stroke

Research suggests that electrolyte imbalances may be related, in part, to what type of stroke you've had. Among 300 people in one study, those who had an ischemic stroke also had a higher incidence of low sodium levels. People with hemorrhagic stroke were more likely to have high potassium levels. With stroke, it's important for healthcare providers to determine if there are electrolyte imbalances right away.

pH Imbalance

The chemistry of your body involves what is known as the acid-base balance. A pH balance is the measure of how well your body is fine-tuning itself to the optimal levels of acid and alkaline for brain and other functions.

When a stroke happens, this balance is disrupted in the brain. The brain's own acid-base balance can affect blood flow through the brain. Cells that are not receiving enough oxygen begin to become acidotic. The body mechanisms that help you to compensate for these changes, including your breathing, also may be impaired.

Right after a stroke, your stroke care team carefully manages your nutrition and any medical conditions like diabetes that can interfere with your body's pH balance.

As with the other changes that cause stroke damage to the brain, your recovery and long-term prognosis will depend on how well these challenges are met after your stroke happens.


A stroke happens when the blood flow to a part of your brain is interrupted, cutting off the oxygen supply to the affected cells. This quickly leads to cell death and is a medical emergency that requires immediate attention.

Most strokes fall into one of two categories: ischemic or hemorrhagic. The first type is caused by a blockage such as a blood clot, while the second involves bleeding in the brain. Strokes lead to chemical changes within the brain that damage cells and interfere with their function.

A Word From Verywell

If you're concerned about stroke or its symptoms, discuss your risk with your healthcare provider. There are a number of tests and techniques that can help to identify high cholesterol, irregular heart rhythms, and other factors that may contribute to your stroke risk.

Frequently Asked Questions

  • What are common symptoms of a stroke?

    Symptoms that are common among people having a stroke include:

    • Severe and sudden headache
    • Facial drooping
    • Numbness or weakness of the face or limbs, often on one side
    • Vision changes in one or both eyes
    • Confusion and trouble speaking or understanding words
    • Difficulty walking or a loss of balance
  • What can I do to prevent a stroke?

    There are quite a few risk factors for stroke, some of which you can change. These lifestyle changes include losing weight, quitting tobacco use, getting more exercise, and taking medication for conditions like high blood pressure. You also can change your diet to limit fats and sodium, and add more fresh fruits and healthy grains.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Boehme AK, Esenwa C, Elkind MS. Stroke risk factors, genetics, and preventionCirc Res. 2017;120(3):472-495. doi:10.1161/CIRCRESAHA.116.308398

  2. American Stroke Association. Hemorrhagic stroke (bleeds).

  3. Soiza RL, Cumming K, Clark AB, et al. Hyponatremia predicts mortality after strokeInternational Journal of Stroke. 2015;10(SA100):50-55. doi:10.1111/ijs.12564

  4. Mansoor F, Kumar J, Kaur N, et al. Frequency of electrolyte imbalance in patients presenting with acute strokeCureus. 2021;13(9):e18307. doi:10.7759/cureus.18307

  5. Caldwell HG, Carr JMJR, Minhas JS, Swenson ER, Ainslie PN. Acid–base balance and cerebrovascular regulationThe Journal of Physiology. 2021;599(24):5337-5359. doi: 10.1113/JP281517

  6. American Stroke Association. Stroke symptoms.

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.