A stroke happens when blood flow to the brain is blocked or slowed, which can cause sudden weakness, trouble speaking, or confusion. Myasthenia gravis (MG) is a condition that can sometimes cause similar symptoms to stroke, like slurred speech or weakness in the face, arms, or legs. In fact, MG can sometimes first appear with signs that look like a stroke.

Because both stroke and MG can be life-threatening medical emergencies that need immediate treatment, it’s important to know how to tell them apart. Keep reading to find out the differences between a stroke and MG.

MG Can Look Like a Stroke

Both MG and stroke can cause neurological symptoms — symptoms that affect the brain, spinal cord, and nerves. Because MG and stroke can share symptoms, MG may be mistaken for a stroke. In a 2023 study, researchers found that misdiagnosis of stroke was responsible for about 9 percent of delays in MG diagnosis.

People who have an exacerbation (flare-up) of MG may have symptoms similar to those seen in a stroke, such as:

• Increased muscle weakness
• Vision changes like diplopia (double vision) or ptosis (drooping eyelids)
• Difficulty walking
• Trouble with swallowing

If muscle weakness affects the respiratory muscles, it can also lead to trouble breathing. This medical emergency is called a myasthenic crisis. During a myasthenic crisis, a machine called a ventilator is needed to help with breathing in the hospital.

Symptoms like trouble swallowing and dysarthria (slurred or garbled speech) may lead healthcare providers to suspect a stroke instead of MG in some people. Other common symptoms of both conditions include:

• Blurry vision
• Double vision
• Facial muscle weakness
• Difficulty raising the arms
• Changes in facial expressions, like smiling
• Difficulty with coordination

MG and strokes can look different in different people. It’s not possible to make a diagnosis based on symptoms alone. Further testing is needed to rule out a stroke and confirm a diagnosis of MG.

Key Differences Between Stroke and Myasthenia Gravis

Although stroke — also known as a cerebrovascular accident (CVA) or a brain attack — and MG can share some symptoms, there are several key differences.

1. MG Is Autoimmune, and Strokes Are Caused by Lack of Blood Flow to the Brain

Stroke symptoms happen when there is a lack of blood flow to the brain. The symptoms depend on which part of the brain is affected. The most common causes of stroke are blood clots, known as ischemic strokes, or broken blood vessels, known as hemorrhagic strokes.

Most strokes are ischemic strokes, sometimes called transient ischemic attacks (TIAs) or mini-strokes. These strokes are often associated with other health problems, including atherosclerosis (clogged or hardened blood vessels), heart issues, and blood-clotting problems.

Another type of stroke, called a hemorrhagic stroke, is linked to high blood pressure, brain aneurysms (weak spots in blood vessels), and brain tumors.

Both types of stroke can block blood flow and oxygen to parts of the brain. If the brain is deprived of oxygen, brain cells begin to die. If too many brain cells die, the damage can be permanent.

In MG, symptoms are caused by an overactive immune system. MG is an autoimmune disease where the immune system makes abnormal antibodies (immune proteins) that attack the space where muscles and nerves meet. Damage to this area makes it harder for nerves and muscles to communicate, resulting in muscle weakness. Think of the communication between nerves and muscles like sending a message. In MG, the message doesn’t get through. That’s why your muscles feel weak or stop working right.

2. Strokes Are Preventable, MG Is Not

Up to 80 percent of strokes may be preventable with good health management and healthy lifestyle changes. Risk factors for stroke that may be changed include:

• Cigarette smoking or vaping
• Recreational or nonprescription drug use
• Alcohol use disorder
• COVID-19
• High blood pressure
• High cholesterol
• High blood sugar (type 2 diabetes)
• Atrial fibrillation, a problem with the heart’s rhythm that makes it beat fast and unevenly

To reduce the risk of stroke, the National Institute of Neurological Disorders and Stroke recommends the following:

• Staying physically active
• Eating a healthy diet
• Managing health conditions that increase your risk of stroke (for example, high blood pressure, high cholesterol, and type 2 diabetes)
• Not smoking

On the other hand, it’s not possible to prevent MG. Scientists aren’t exactly sure why and how the condition develops in some people. However, researchers have noticed it may develop after a triggering event, such as surgery or viral infections. People may be more likely to get MG if they have a thyroid disease or another autoimmune disease, such as lupus or rheumatoid arthritis.

3. MG May Be Harder To Diagnose in Older Adults

Strokes can happen at any age, but the risk of having a stroke increases as you get older. Most people who have strokes are older than 65 years. The National Institute of Neurological Disorders and Stroke has found that strokes are also more common in men compared to women.

Although MG can develop in people of all ages, it’s most commonly diagnosed in people of two different age groups. An article in the journal Heliyon found that women are more likely to be diagnosed with early-onset MG before the age of 40. Men are more likely to be diagnosed with late-onset MG after the age of 60, according to the Journal of Clinical Medicine.

MG can be harder to diagnose in older adults because the symptoms don’t always look the same. Many MG symptoms can also be caused by other health problems that are more common as people get older. Generalized weakness of MG in older people can be mistaken for normal aging. For example, drooping eyelids may not be as noticeable in older adults because of sagging skin around the eyes. Additionally, blurry vision and double vision caused by MG may be mistaken for age-related eye conditions, like macular degeneration and cataracts. Older adults are also more likely to have health conditions that increase the risk of stroke, such as heart disease and diabetes.

4. Stroke Symptoms Usually Start Suddenly, MG Is Often Gradual

The symptoms of a stroke are usually a sudden change from what’s normal. Stroke symptoms don’t usually get better until the blood flow has been restored to the brain.

Like stroke symptoms, MG symptoms can also start suddenly. However, MG symptoms usually get worse slowly over time and can come and go. In about half of people with MG, the first symptoms affect only the muscles around the eyes. This is called ocular MG. Within two years, about 80 percent of people with ocular MG develop muscle weakness in other parts of the body. This is called generalized MG.

Another factor that differentiates MG symptoms from stroke symptoms is muscle strength that improves with rest and gets worse with activity. Because of this, most people with MG feel stronger at the beginning of the day.

5. Strokes May Be Diagnosed Quickly, MG Diagnosis Is Often Delayed

Strokes are a medical emergency that requires fast medical care. If you or someone you know has stroke symptoms, it’s important to call 911 or emergency services right away. Emergency services will take you to the emergency department of the nearest hospital for diagnosis and treatment. Early stroke treatment can lead to better outcomes.

Tests to diagnose a stroke may include:

• Neurological examination — Tests to check how the brain and nerves are functioning
• Blood tests — Checks how your blood is clotting
• Brain imaging tests — For example, CT scan or MRI scan
• Angiography — Creates images of blood vessels
• Electroencephalogram (EEG) — Checks brain activity
• Electrocardiogram (EKG) — A test to check the electrical activity of the heart

If you have MG symptoms that look like a stroke, you may also end up in the emergency department for treatment. However, MG can be difficult to diagnose, and other conditions must be ruled out first. The process of ruling out other causes is called differential diagnosis.

A 2024 study found that the average time to receive an MG diagnosis was almost one year. Healthcare providers who aren’t familiar with MG and don’t refer people with MG symptoms to a proper specialist (such as a neurologist) may contribute to delays in MG diagnosis.

Tests that may help diagnose MG include:

• Blood tests — Check for abnormal antibodies
• Nerve tests — Check the signal between the nerves and muscles
• Imaging tests — Look for problems with the thymus gland associated with MG, such as an enlarged thymus or thymoma (thymus gland tumor)
• Ice pack test — A test to check for eye symptoms of MG

6. Stroke Treatment Helps Restoring Normal Blood Flow to the Brain

Successful treatment for stroke focuses on restoring normal blood flow to the brain. Treatment options for people with an ischemic stroke include medications or surgery to break up a clot. In a hemorrhagic stroke, treatments focus on controlling bleeding in the brain.

MG therapies focus on reducing symptoms of muscle weakness by improving the signal between nerves and muscles and decreasing inflammation. If MG is mistaken for a stroke or another condition, a person might get treatments that don’t help and could cause harmful side effects.

7. Strokes Are a Leading Cause of Death, Life Expectancy With MG Is Normal

Strokes are a leading cause of death in the United States, ranking fifth overall. A stroke is a life-threatening condition that needs quick treatment. Every three minutes and 11 seconds, someone in the U.S. dies from a stroke. Of those who survive, most will lose about 5.5 years of life expectancy.

On the other hand, MG is a rare disease that usually doesn’t shorten life expectancy.

Ask Your Doctor

If you notice symptoms like muscle weakness, drooping eyelids, or trouble speaking or swallowing, reach out to your doctor right away or head to the emergency department. MG can sometimes be mistaken for other conditions, but getting the right diagnosis is key. Your doctor can order tests and help you find treatments that ease symptoms and improve your daily life. If you ever feel unsure about your diagnosis or treatment plan, it’s OK to ask questions or get a second opinion.

Talk With Others Who Understand

MGteam is the social network for people with the autoimmune disease myasthenia gravis. On MGteam, more than 2,800 members come together to ask questions, give advice, and share their experiences with others who understand life with myasthenia gravis.

Have you had a stroke? Or did doctors initially suspect you had a stroke and diagnose you with MG instead? Share your story in the comments below, or start a conversation by posting to your Activities page.