Key takeaways:
A stroke happens when there’s a lack of blood flow to a certain part of the brain. A seizure happens when there’s a sudden burst of electrical activity in the brain.
The symptoms of a stroke and seizure can look alike, and it can be hard to tell them apart. In rare cases, a stroke can cause a seizure.
Both strokes and seizures are medical emergencies. But understanding the difference can help you know what to do when someone nearby is having one.
Strokes and seizures can be hard to tell apart. And it can be a frightening experience when someone nearby is having either one. They both start suddenly, and they can completely change the way the brain and body behave. To make things even more complicated, a stroke can sometimes lead to a seizure.
If someone in your life is at risk for either or both conditions, it can help to understand the differences between the two. And more importantly, it’s good to know what to do when you see one.
What happens in the brain during a stroke vs. a seizure?
Strokes and seizures both affect the brain, but in different ways.
Stroke
During a stroke, there’s a sudden change in blood flow to the brain. This can come from a blockage in a blood vessel or even bleeding in the brain. Either way, this leads to a lack of blood flow (oxygen) to specific areas of the brain. And without blood flow, brain cells malfunction and die.
Since strokes tend to only affect a specific part of the brain, they tend to only affect a few brain functions — like speech or movement of an arm.
Seizure
During a seizure, there’s a surge of electrical activity in the brain. So, it’s a problem with electrical signals rather than blood flow. Seizures start in a specific part of the brain. But the disorganized activity usually spreads to the whole brain (known as a “grand mal” seizure). This is why seizures often lead to a full loss of consciousness.
What are the symptoms of a stroke vs. a seizure?
The symptoms of a stroke and seizure can be very similar. Overlapping symptoms include:
Headache
Confusion
Numbness or tingling sensations
Difficulty seeing or vision changes
Inability to speak
But there are still some key signs that can help you tell them apart.
How do you know someone is having a seizure?
To understand what a seizure looks like, it’s first important to know that seizures can be either:
Partial: also called focal seizures
Full: also called generalized or grand mal seizures
A partial seizure is less common than a generalized or grand mal seizure. Partial seizures affect only one part of the brain. These can lead to symptoms like:
A strange taste in the mouth
Trouble concentrating
Feelings of intense fear
Nausea
Staring episode
They can also look like a stroke, causing weakness or numbness in one part of the body. Partial seizures can also progress to a full seizure.
Full seizures affect the whole brain, so they cause someone to lose consciousness. During the seizure, the person will typically experience:
Stiffening of the body
Jerking movements of arms and/or legs (a hallmark sign of a grand mal seizure)
Drooling or frothing at the mouth
Teeth clenching, which can cause them to bite their tongue
Sudden, rapid eye movements
Loss of bowel or bladder control
A temporary pause in breathing
How do you know someone is having a stroke?
Unlike a seizure, a stroke usually starts without any warning or preceding symptoms. And it usually doesn’t result in loss of consciousness (passing out).
Symptoms that are more likely from a stroke than a seizure include:
Weakness in the face, arm, or leg on one side of the body
Numbness in one specific body part, which usually feels like a reduced sensation to touch
Slurred speech, or garbled speech that seems like “word salad”
Trouble walking, vertigo (room spinning sensation), or lack of coordination
Trouble swallowing
It’s important to note that these aren’t hard and fast rules. For example, someone who’s having a stroke can lose consciousness. And someone who’s having a seizure may just have weakness or numbness in one part of the body.
Can a stroke cause seizures?
It depends. Some people who’ve had a stroke may go on to develop seizures. This can happen in two different ways:
The lack of blood flow can interfere with the electrical signals in the brain. When this is the case, the seizures happen at the start of the stroke. More commonly, they happen in the first 1 to 2 days after the stroke occurred.
As someone’s brain is healing from a stroke, it can develop scar tissue where the brain cells died. Since the scar tissue can interfere with electrical activity, this can lead to seizures up to 2 or more years after the stroke.
Some people will have multiple episodes of seizures after a stroke and be diagnosed with epilepsy. Epilepsy is a brain disorder that leads to multiple episodes of seizures. But having one seizure after a stroke doesn’t mean that someone will develop epilepsy.
Can a seizure cause a stroke?
While a stroke can lead to seizures, seizures don’t lead to strokes. But right after someone has a seizure, they can have symptoms that look like a stroke. The medical term for this is Todd’s paralysis. This is when a seizure is followed by an episode of dysfunction as the brain recovers.
The paralysis is most often on one side of the body, which is what makes it look like a stroke. But it's only temporary and resolves quickly as the person returns to normal. They might have weakness in an arm or leg. Or they may not feel weakness or paralysis at all. They might just instead experience:
Confusion
Loss of memory
Trouble speaking
Numbness
Difficulty seeing
What should I do if someone is experiencing a stroke or a seizure?
If you think someone is having a seizure or stroke, the bottom line is the same: call 911.
A stroke is a medical emergency that always requires prompt care. The acronym FAST can help you recognize a stroke:
F = face drooping: Look for drooping or numbness of one side of the face. An uneven smile can also be a clue.
A = arm weakness: Weakness or numbness of one arm is concerning. If the person raises both arms, see if one sags downward.
S = speech difficulty: Speech may be slurred.
T = time to call 911: Acting quickly during a stroke is important.
A seizure isn’t always an emergency — especially for people who have them often and know what to do. But there are certain scenarios when emergency treatment for a seizure is important. Call 911 if the person:
Has never had a seizure before
Seizes for longer than 5 minutes
Has a second seizure after the first one
Has difficulty breathing
Has difficulty walking after the seizure
Is injured during the seizure, like falling and hitting their head
Is in water during the seizure
Has another health condition, like diabetes or heart disease
Is pregnant
At the end of the day, you aren’t expected to figure out if someone is having a stroke versus a seizure. The most important thing to do is call 911 as quickly as possible. But while you’re waiting for emergency personnel, there are a few more things you can do to help keep someone safe.
When someone is having a seizure, here’s what you should do:
Prevent them from hurting themselves by lowering them to the floor or clearing the area around them.
Loosen any constriction around the neck, like a shirt or tie.
Turn them on their side to help keep their airway clear. You may also help them breathe more comfortably by removing things like a mask, glass, or other objects around their face.
These guidelines also apply to someone having a stroke, especially if they have altered consciousness. And be sure to stay with the person until the ambulance arrives. This will help keep them safe and calm.
Frequently asked questions
Common tests that are done after a seizure can include:
Lab tests to measure blood counts and electrolytes
An EKG to check the rhythm of the heart
Tests for infection — like a blood culture, urine culture, or lumbar puncture
A CT scan and/or MRI of the brain
Keep in mind all of these tests aren’t always necessary. It depends on someone’s other medical conditions, their physical exam, and the likely cause of the seizure.
Yes, it’s safe to sleep after a seizure. In fact, most people will be very tired and need to rest or sleep after a seizure. This is because a seizure can be very taxing on the brain. Still, it’s important to keep a close eye on someone after they have a seizure. This includes monitoring their breathing and mental status as they rest and recover.
An MRI after a seizure may not show any changes or abnormalities. A small percentage of people may have temporary changes on an MRI as a result of the seizure. These changes are thought to be caused by the increase in energy metabolism and blood flow in the brain after a seizure. MRIs may also reveal the cause of a new seizure — like a stroke, bleeding, or a tumor.
Common tests that are done after a seizure can include:
Lab tests to measure blood counts and electrolytes
An EKG to check the rhythm of the heart
Tests for infection — like a blood culture, urine culture, or lumbar puncture
A CT scan and/or MRI of the brain
Keep in mind all of these tests aren’t always necessary. It depends on someone’s other medical conditions, their physical exam, and the likely cause of the seizure.
Yes, it’s safe to sleep after a seizure. In fact, most people will be very tired and need to rest or sleep after a seizure. This is because a seizure can be very taxing on the brain. Still, it’s important to keep a close eye on someone after they have a seizure. This includes monitoring their breathing and mental status as they rest and recover.
An MRI after a seizure may not show any changes or abnormalities. A small percentage of people may have temporary changes on an MRI as a result of the seizure. These changes are thought to be caused by the increase in energy metabolism and blood flow in the brain after a seizure. MRIs may also reveal the cause of a new seizure — like a stroke, bleeding, or a tumor.
The bottom line
It can be difficult to tell the difference between a stroke and a seizure, since many of their symptoms resemble one another. Both can happen suddenly and affect someone’s mental state or body movements. One of the easiest ways to tell the difference is that seizures often cause loss of consciousness. Strokes usually don’t. But even this isn’t a hard and fast rule. So, if you or someone nearby is experiencing symptoms of either one, call for help.
Why trust our experts?
References
American Stroke Association. (n.d.). Stroke symptoms.
Anathhanam, S., et al. (2017). Mimics and chameleons in stroke. Clinical Medicine Journal.
Buck, B. H., et al. (2021). Stroke mimics: Incidence, aetiology, clinical features and treatment. Annals of Medicine.
Chen, J., et al. (2022). Pathogenesis of seizures and epilepsy after stroke. Acta Epileptologica.
Kim, S. E., et al. (2017). Characteristics of seizure-induced signal changes on MRI in patients with first seizures. Seizure.
Kiriakopoulos, E. (n.d.). Focal aware seizures (simple partial seizures). Epilepsy Foundation.
Kiriakopoulos, E. (2019). Understanding seizures. Epilepsy Foundation.
National Institute of Neurological Disorders and Stroke. (2023). Todd's paralysis. National Institutes of Health.
Stroke Association. (n.d.). Seizures and epilepsy after stroke.
