The short answer
Seizures and personality changes are common effects of a brain tumor, its steroids, and its medications. Anti-seizure drugs, driving rules, and mood changes each need direct discussion with your team.
Seizures are one possible sign of a brain tumor, and small focal events are worth reporting.
Anti-seizure medication works best when taken steadily. NCI advises telling your team about a missed dose and not stopping suddenly.
Driving rules after a seizure vary by place. NCI advises asking your team whether seizures affect your ability to drive.
Mood and behavior changes can come from the tumor, from medicines such as steroids, and from the strain of illness. They are not a choice.
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This page is for people with a brain tumor, and the people close to them, who are dealing with seizures or changes in personality. It covers why these happen, living with anti-seizure medicine, driving, and personality changes.
Why a brain tumor causes seizures
A seizure is a burst of disordered electrical activity in the brain. A tumor irritates the tissue around it. That irritated tissue can then fire in an uncoordinated way. For some people a seizure is the first sign that anything is wrong.
Seizures are usually described as focal or generalized. In a focal seizure you may stay awake and aware while something specific happens. It might be a hand that will not obey you, an odd smell no one else notices, a wave of unreality, or a few seconds you cannot account for afterward. In a generalized seizure you lose consciousness, and there may be stiffening and jerking. Focal seizures are easy to miss or explain away. So describe every episode to your team, including the ones that felt too small to mention. Your team can use those details to plan your care.
Living with anti-seizure medication
Anti-seizure medication is preventive. It is not a rescue treatment. It works by keeping a steady level of drug in your bloodstream. That is why taking it as prescribed matters. Ask your team about the best times to take it and whether to take it with food. NCI advises telling your team if you miss a dose, and not suddenly stopping any medicine. Missed doses and sudden stopping are common causes of seizures.
Some of these drugs interact with chemotherapy, steroids, and other medicines. So check every new prescription and supplement against your list. If seizures continue, tell your team. They may adjust the plan. Raise any change with the prescriber or your pharmacist.
Household safety is worth a short conversation too, and what is worth changing depends on your seizure type, how much warning you get and who is around. Ask your team about safety at home and an emergency plan. Common suggestions include:
- Showering rather than bathing.
- Taking care on stairs and ladders.
- Making a simple plan for anyone who is with you.
If a seizure happens, help the person to the ground away from hard edges, do not put anything in their mouth, note how long it lasts, and afterward turn them onto their side. Call 911 if a seizure lasts longer than five minutes or seizures come close together.
Driving: the effect few people are warned about
Losing the ability to drive is often a hard practical change. Many people only discover the rules after the first seizure. NCI advises asking your health care team whether your seizures will affect your ability to drive. Rules differ by state and country, so also check with your local licensing authority, because the current local rule is the one that counts.
Ask your neuro-oncology team directly what applies where you live. Ask again if your medication changes. Driving when you are not allowed to may have legal and insurance consequences. It is better to plan for rides, transport services, or delivery than to guess.
Personality changes are a symptom, not a choice
Families often describe this as the hardest part. The person seems short-tempered, blunt, flat, tearful, unusually impulsive, or simply not themselves. This is not a character flaw, and it is not something anyone is choosing. Several things can be behind it, often at once, and untangling which is a question for the team. NCI lists changes in personality, mood, focus or behavior among the possible signs of a brain tumor. Steroids such as dexamethasone are often used to reduce swelling. MedlinePlus lists insomnia, restlessness, depression and anxiety among its possible side effects. Other medicines, fatigue and pain can add to it.
Naming the cause changes how a household copes. It moves the question from why someone is behaving this way to which part of it can be treated. Often some of it can be. Ask your team whether any medicine could be part of the problem. Do not change a steroid dose on your own, because MedlinePlus warns that stopping dexamethasone suddenly can cause problems. Ask about help with sleep, low mood and anxiety.
Bring specific examples to clinic rather than general impressions. Say that someone stopped starting conversations three weeks ago. Or that they have slept four hours a night since the steroid dose rose. That gives the team something concrete to act on.
Sources
Common questions
Can I drive after a brain tumor seizure?
Rules differ by state and country, and a seizure can change what is allowed. NCI advises asking your health care team if your seizures will affect your ability to drive. Also check with your local licensing authority, and ask again whenever your medication changes.
Why has my family member's personality changed so much?
A brain tumor can change mood and behavior. The steroid dexamethasone, which is often used for swelling, can cause insomnia, restlessness, depression and anxiety, according to MedlinePlus. Other medicines, pain and fatigue can add to it. It is a symptom of the illness and its treatment rather than a change in who someone is.
Will I have to take anti-seizure medication forever?
Not necessarily. That decision belongs to your care team. NCI advises against suddenly stopping any seizure medicine, because stopping suddenly is a common cause of seizures.
What should someone do if they see me have a seizure?
Help you to the ground away from hard edges, move objects out of the way, put nothing in your mouth, note how long it lasts, and afterward turn you onto your side. Call 911 if a seizure lasts longer than five minutes, if seizures come close together, or if there is injury or trouble breathing.
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Written by: Cancer ExplainedSources last checked: 2026-10-02 what this meansLast updated: 2026-08-19Next planned review: 2027-07-30
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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