Seizures
Certain types of cancer and cancer treatments can increase your risk of seizures. This is rare, but it does happen. You, your family, and your caregivers should know the signs and symptoms of a seizure and what to do if you have one.
- What is a seizure?
- Why do some people with cancer have seizures?
- What are the signs and symptoms of a seizure?
- If you see someone having a seizure
- When to call 911 or go to the emergency room
- How seizures are treated
- Tips for preventing and managing seizures
- How to talk to your health care team about seizures
What is a seizure?
A seizure is a glitch in your nervous system caused by an uncontrollable surge of electrical activity in your brain.
One way to think of this is to imagine a traffic light during a power outage.
Your brain cells (neurons) communicate through electrical signals. These signals work a lot like traffic lights. During a power outage, the electricity going to a traffic light sometimes surges (increases suddenly for a short amount of time).
When this happens, the power surge causes a glitch in the traffic light, creating chaos and confusion. This is similar to what happens to your brain during a seizure.
There are two main types of seizures, depending on where in the brain they occur.
- Focal seizures happen in one specific area or side of the brain.
- Generalized seizures happen in both sides of the brain at the same time.
You might also hear the term epilepsy. Epilepsy is the medical name used if a person has 2 or more seizures at least 24 hours apart without a known cause.
Why do some people with cancer have seizures?
There are several reasons why a person with cancer might have seizures.
- Tumors in the brain or spine
- Brain injuries, including those caused by a stroke, head trauma, lack of oxygen, or brain surgery
- Certain types of chemotherapy, especially when given into the spinal fluid (intrathecal or IT chemo)
- Certain types of immunotherapy, such as checkpoint inhibitors and CAR T-cell therapy.
- Hormone changes due to any cause, especially hormone therapy or when sex hormones are affected
- High fevers and certain infections
- Blood sugar levels that are too high or too low
- Electrolyte levels (such as potassium or sodium) that are too high or too low
- Paraneoplastic syndromes (a group of side effects that develop in some people with cancer; these usually affect the nervous system and sometimes cause seizures)
What are the signs and symptoms of a seizure?
The most common signs and symptoms of a seizure are:
- A blank stare or rolled eyes
- Moaning or mumbling
- Falling or slumping over due to loss of consciousness
- Muscle twitching or jerking (especially arms and legs)
- Sudden loss of bladder or bowel control
- Confusion or memory loss
- Weakness or fatigue
Some people report that they can sense a seizure right before it starts. This is commonly called an aura. People who have auras often describe them as a strange or unusual feeling, emotion, or sensation.
If you see someone having a seizure
There are six important steps you should take if you are with someone when they have a seizure.
1. ?Check safety first. Make sure the person having the seizure is safe. Remove any sharp objects or hazards that could hurt them. Loosen any clothing around their neck.
2. ?Position carefully. Gently guide the person to lie down on their side. This helps prevent choking and allows any fluids to drain from their mouth.
3. Don’t restrain. Restraining a person during a seizure increases the chances one or both of you will get hurt. Avoid holding them or trying to control their movements.
4. ?Watch the clock. Note the time when the seizure starts and ends. Most seizures last a few minutes or less. Seizures lasting more than 5 minutes are known as grand mal seizures and can cause serious problems.
5. ?Comfort and support. Speak to the person calmly and reassure them. After the seizure ends, they might be confused or afraid.
6. Write it down. Pay attention to what happens during the seizure. Write down any signs or symptoms you notice. Keep this information to give to the person’s health care team.
When to call 911 or go to the emergency room
Call 911 right away if:
- This is the person’s first seizure.
- The seizure lasts longer than 5 minutes.
- They hit their head.
- They have any trouble breathing.
How seizures are treated
Medicines such as steroids, benzodiazepines, or antiseizure medications are sometimes used to prevent, treat, or manage seizures. The treatment depends on what is causing the seizure.
Repeated seizures
For repeated seizures, some people take antiseizure medicines, but many of these medicines can cause unpleasant side effects.
If you start antiseizure medicine, you and your health care team usually work together to find the best dose for you. The goal is to find a dose that prevents your seizures while causing the least amount of side effects.
Seizures caused by brain tumors
For seizures caused by brain tumors, sometimes treating the tumor (with chemo, radiation, or surgery) is an option. It depends on where the tumor is in your brain, and what other problems it’s causing.
Seizures caused by injury
For seizures caused by an injury, steroids might be used to help with swelling while your brain has time to rest and heal.
Seizures caused by electrolyte or blood sugar imbalances
If electrolyte or blood sugar imbalances are causing your seizures, you might get treatments to correct your levels.
Other seizure treatments
Treatments such as vagal nerve stimulation and deep brain stimulation aren’t usually used for people with cancer. They are typically used for people who have epilepsy or another chronic seizure disorder and haven’t responded well to other treatments and medicines.
Tips for preventing and managing seizures
Seizures aren’t common, but they can be scary when they do happen. If you have an increased risk of seizures, try to avoid common triggers. This can help lower your risk.
If you are having repeated seizures, there are also certain steps you might need to take to protect yourself and others.
To lower your risk of seizures
Avoiding common triggers could reduce your chance of having a seizure.
- Get plenty of sleep. Lack of sleep can increase your risk.
- Manage your stress. Distress and intense emotions can sometimes trigger a seizure. No one can avoid stress, but it helps if you have tools to manage it.
- Take your medicines. For people taking antiseizure medicines, missing doses is one of the most common triggers.
- Avoid alcohol, cigarettes, and illicit drugs. These are all known triggers of seizures. Drug and alcohol withdrawal can also cause seizures.
- Avoid external triggers. Bright flashing lights, video games, loud music, and extreme heat can all trigger seizures.
To protect yourself and others
If you have seizures repeatedly, you might also need to take these precautions.
- Stop driving or operating heavy machinery. Each state has its own rules around drivers who have seizures with loss of consciousness. Depending on where you live, you might have to stop driving until you’ve gone a certain amount of time without having another seizure.
- Avoid being in the water alone. If you have repeated seizures, it’s important to avoid water activities when you are by yourself. Don’t swim or go in hot tubs alone. Take showers instead of baths.
How to talk to your health care team about seizures
Ask your health care team if your type of cancer or treatment increases your risk of seizures. If you are at an increased risk, ask what you can do to lower that risk.
If you are treated for a seizure, make sure your health care team knows about it. It’s also important to ask them what they want you to do if you have another seizure.
For example: When should you go to the emergency room? Should you tell your health care team right away after every seizure? Or is it okay to wait until your next office visit? Your health care team can help you come up with a plan.
- Written by
- References
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
Dalmau J and Rosenfield MR. Overview of paraneoplastic syndromes of the nervous system. UpToDate. UpToDate; 2024. Updated September 25, 2023. Accessed June 18th, 2024. https://www.uptodate.com/contents/overview-of-paraneoplastic-syndromes-of-the-nervous-system
Drappatz J, Avila EK. Seizures in patients with primary and metastatic brain tumors. UpToDate. UpToDate; 2024. Updated March 8th, 2023. Accessed June 18th, 2024. https://www.uptodate.com/contents/seizures-in-patients-with-primary-and-metastatic-brain-tumors
Gonzalez Castro LN, Milligan TA. Seizures in patients with cancer. Cancer. 2020;126(7):1379-1389. Doi:10.1002/cncr.32708
Karsecki S. Initial treatment of epilepsy in adults. UpToDate. UpToDate; 2024. Updated April 30, 2024. Accessed June 18th, 2024. https://www.uptodate.com/contents/initial-treatment-of-epilepsy-in-adults
Roth P, Winklhofer S, Muller AM, et al. Neurological complications of cancer immunotherapy. Cancer Treatment Reviews. 2021; 97. doi.org/10.1016/j.ctrv.2021.102189
Rudà, R., Mo, F. & Pellerino, A. Epilepsy in brain metastasis: an emerging entity. Curr Treat Options Neurol. 2020; 22(6). doi.org/10.1007/s11940-020-0613-y
Schachter SC. Evaluation and management of the first seizure in adults. UpToDate. UpToDate; 2024. Updated May 2, 2024. Accessed June 18th, 2024. https://www.uptodate.com/contents/evaluation-and-management-of-the-first-seizure-in-adults
Last Revised: July 11, 2024
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