Seizures and Cancer: What to Know

Seizures can be a symptom of cancer, most often when cancer involves the brain. Brain metastases or primary brain tumors can disrupt normal brain electrical activity and trigger seizures. ^[1] As these tumors grow, they may press on or irritate surrounding brain tissue, leading to neurological symptoms such as headache, confusion, speech or vision changes, weakness, balance problems, and seizures. ^[1]

How Common Is It?

• Brain tumors frequently cause seizures, and this can persist even after treatment. Depending on tumor location, seizures may be accompanied by temporary issues with consciousness, movement, or speech. ^[2] Your care team may use an EEG (electroencephalogram) to monitor brain electrical activity if seizures occur. ^[3]
• Seizures are a recognized sign of brain metastases, including partial (focal) seizures that affect just one area of the brain and generalized seizures that involve the whole brain. ^[4] A tumor can affect the flow of electrical impulses and trigger sudden, uncontrolled changes this is the definition of a seizure. ^[5]

What Causes Seizures in Cancer?

Seizures in cancer have several potential causes:

• Direct brain involvement by a tumor (primary or metastatic) that alters or compresses brain tissue and disrupts electrical signaling. ^[1]
• Treatment-related effects such as radiation or chemotherapy to the brain that can irritate brain tissue and contribute to seizures or cognitive changes. ^[6]
• Metabolic and systemic factors including low blood levels of sodium, glucose, calcium, or magnesium, which can provoke seizures. ^[7]
• Other medical triggers such as stroke, brain infections (meningitis or encephalitis), high fever, or certain medicines and withdrawals. ^[8] Seizures can also occur with electrolyte imbalances and substance-related factors. ^[9]

What Do Seizures Look Like?

• Focal (partial) seizures may cause abnormal smells or tastes, tingling or numbness, trouble speaking, or localized jerking/stiffening. ^[4]
• Generalized (tonic-clonic) seizures often involve loss of consciousness, whole-body stiffening and jerking, and may be followed by confusion and fatigue. These can be triggered by brain tumors, strokes, infections, or metabolic disturbances. ^[7]

How Are Seizures Managed?

Management is tailored to both the seizure and the underlying cancer:

Symptom Control

• Anti‑seizure medications (ASMs) help control seizures when they occur. Clinicians often choose newer options that have fewer drug interactions with cancer therapies. ^[10] [PM23]
• Steroids (corticosteroids) may be used short‑term to reduce brain swelling from metastases, easing symptoms and sometimes helping seizures. ^[11]

Treating the Underlying Brain Tumor

• Surgery can remove as much tumor as safely possible, which may improve symptoms and aid diagnosis; seizure control often improves when tumor burden decreases. ^[10]
• Radiation therapy and chemotherapy aimed at the tumor can also reduce seizure frequency, especially in certain gliomas. ^[12] In low‑grade gliomas, surgery or radiotherapy typically reduces seizures, and chemotherapy has been shown to lower seizure rates in some cases. ^[13]

Ongoing Neurologic Care

• EEG monitoring may be used to evaluate persistent or unclear seizure activity and guide treatment adjustments. ^[3]
• Multidisciplinary follow‑up with neurology, neuro‑oncology, and neurosurgery supports coordinated care focused on seizure control and quality of life. ^[14] Many centers use integrated “onco‑epilepsy” approaches to simultaneously manage tumor and seizures. ^[15]

Practical Tips and Safety

• Seek urgent care for a first seizure, prolonged seizure (typically >5 minutes), repeated seizures without recovery, significant head injury, or breathing problems. These situations need emergency treatment.
• Medication consistency matters. Take ASMs exactly as prescribed and discuss side effects or interactions some drugs used in cancer care and some older ASMs can interact. Newer ASMs are often preferred to reduce interactions. [PM23]
• Track events. Keeping a seizure log (date, duration, features, triggers) helps your team fine‑tune treatment and assess response over time.
• Reduce triggers. Good sleep, staying hydrated, and managing electrolytes may help lower risk of provoked seizures. ^[8] Work with your care team on nutrition and lab monitoring, especially during chemotherapy.

Key Takeaways

• Seizures are a relatively common symptom when cancer affects the brain, and they can result from the tumor itself, treatment effects, or other medical triggers such as metabolic problems, stroke, or infection. ^{[1] [6] [8]}
• Management typically combines anti‑seizure medication, treatment of brain swelling, and therapies targeting the tumor surgery, radiation, and/or chemotherapy to improve seizure control and overall outcomes. ^{[11] [10] [13]}
• Ongoing, multidisciplinary care with attention to drug interactions and quality of life is important for effective control and safety. ^{[14] [15]}