A seizure is caused by an abnormal change in the brain’s electrical activity. The cause is often an event or condition that disrupts the communication between neurons in the brain. If you’re having a seizure, move to a safe area and seek medical attention right away.
Your brain relies on complex electrical signals to transmit information. These signals affect everything from how you process thoughts and experience sensory input to how you engage in movement.
During a seizure, the signaling pathways in the brain become disrupted, and your neurons start firing electrical impulses at an unusually rapid rate.
Depending on the areas of your brain involved, this wave of electrical signaling can cause a variety of symptoms such as erratic movement, loss of awareness, and jerking or muscle stiffness.
There are many kinds of seizures and many possible
- epilepsy
- brain infections
- traumatic brain injury
- medications
- sleep deprivation
- stress
Some seizures start in childhood, while others begin in adulthood. When seizures start as an adult, they’re called adult-onset seizures.
Read on to learn some of the common causes of seizures in adults for the first time.
Anyone can experience a seizure, and it’s not always possible to know why it happens or what caused it.
Adult-onset seizures are typically due to a specific condition or traumatic event. This is different from seizures that appear in childhood, which are usually due to idiopathic epilepsy or epilepsy related to an unknown cause.
Possible causes of adult-onset seizures include:
Stroke
A stroke occurs when a blood vessel in your brain bursts or becomes blocked. This interrupts blood flow, which injures the tissue.
The injury can also alter the electrical activity in your brain, resulting in a post-stroke seizure. Often, this type of seizure occurs within
The more severe a stroke, the more likely it is to cause a seizure. According to a
Central nervous system infection
Your central nervous system (CNS) includes your brain and your spinal cord. It’s the hub of neurological signaling in your body, directing electrical signals out into the peripheral nervous system (PNS), which connects all your other systems and tissues.
Severe CNS infections caused by bacteria, parasites, or viruses can trigger seizures. When these pathogens cause an infection in brain tissue, it can prompt an immune or inflammatory response that leads to abnormal changes in your brain’s electrical activity.
Examples of CNS infections that can lead to seizures include:
- CNS tuberculosis
- neurocysticercosis
- viral meningoencephalitis
- meningitis or encephalitis
- brain abscess
- cerebral malaria
- onchocerciasis (river blindness)
- cerebral toxoplasmosis
Not everyone with a CNS infection will experience a seizure. One study from 2022 found that out of 900 episodes of suspected CNS infection, only 14% presented with a seizure.
Brain tumor
Adult-onset seizures can be the first sign of a brain tumor. Brain tumors are abnormal clumps of cell growth in the brain or its surrounding tissues. They can disrupt electrical signals in their area of growth by putting pressure on surrounding neurons, causing bleeding, or adding their own irregular electrical patterns.
While around 1 million people in the United States live with a brain tumor, most are benign or not cancerous.
If seizures recur or worsen, it could indicate a tumor has grown or caused bleeding or swelling.
Different types of tumors cause seizures in different ways, and common brain tumors that can trigger seizures include:
- neuroglioma
- astrocytoma
- ganglioglioma
- oligodendroglioma
- glioblastoma
meningioma
Traumatic brain injury
Another possible cause of a first-time seizure is a traumatic brain injury (TBI). TBI occurs when an external force causes the brain to move within your skull, leading to bruising, swelling, or damage to brain tissue.
TBIs can be non-penetrating, like being hit in the head with a stick, or they can be penetrating, where an object pierces the skull and directly injures brain tissue.
After a TBI, the seizures may occur immediately. In other cases, they might happen within hours, days, or weeks after the injury. About 50% of TBI-related seizures happen within the first 24 hours.
More severe injuries are more likely to cause seizures. Other factors that increase your risk of seizures after a TBI include:
- being older than 65
- chronic alcohol use disorder
- injury that penetrates the skull
- contusion, which is a bruise of the brain
- bleeding in the brain
Depending on the injury, a TBI can trigger seizures by causing inflammation or damaging brain tissue. It may also cause seizures by disrupting the way your brain releases neurotransmitters.
Substance use and withdrawal
A first-time seizure in adulthood may be related to the use of certain substances or withdrawal from them.
When you introduce a substance into your body, it can affect your brain by crossing the blood-brain barrier, a membrane that helps protect your brain from harmful substances. Exposure to unfamiliar substances that cross this barrier can cause changes in the brain that affect electrical impulses.
If you’re experiencing withdrawal-related seizures, your body is responding to the sudden absence or lack of a substance the brain has been accustomed to receiving. Without the substance, there’s an imbalance in brain chemicals that can trigger unusual electrical activity.
Examples of common substances associated with seizures include:
- antidepressants
- diphenhydramine
- cocaine
- methamphetamine
- tramadol
- isoniazid
Certain substances can induce seizures by altering neurotransmitter activity. In other cases, a drug may modify electrolytes or blood flow in the brain, resulting in a seizure.
Some substances, like barbiturates, have a sedative effect on the brain. If taken regularly in high doses, suddenly stopping can cause a seizure. Stopping anti-seizure medications or taking them inconsistently can induce a seizure.
Alcohol poisoning and withdrawal
Alcohol poisoning, or an alcohol overdose, is when you drink a large amount of alcohol in a short amount of time. This can cause alterations in your fluid and electrolyte levels, resulting in seizures.
Alcohol withdrawal may also trigger a first-time seizure.
Heavy alcohol use can depress the central nervous system. Suddenly reducing alcohol consumption will affect the nervous system and can cause a seizure.
Lifestyle factors
Not all adult-onset seizures are related to a specific medical condition or trauma to the brain. Sometimes, patterns in your life can affect your body and your brain’s electrical activity enough to put you at elevated risk for a seizure.
Sleep deprivation and stress are examples of lifestyle factors that can contribute to seizure activity.
According to a review from 2022, sleep deprivation — when a person doesn’t get enough sleep to meet their body’s needs — is a well-documented risk factor for the development of epileptic seizures. Sleep is essential to your brain’s function and recovery, and missing out on too much sleep can alter neurotransmitters and hormones involved with electrical signaling.
Extreme stress is another risk factor for a seizure in some adults.
While experts aren’t clear on the underlying pathways between stress and a seizure, stress can affect chemicals in your CNS that are important to electrical signaling. It can also negatively impact your sleep, compounding your seizure risk.
There are many types of seizures that can occur in adults. These seizures are sorted into
Focal seizures
If the abnormal electrical activity begins on one side of the brain, it’s called a focal seizure.
Focal seizures that affect adults include:
- Focal aware seizures: During a focal aware seizure, you don’t completely lose consciousness.
- Focal impaired awareness seizures: This type of seizure causes loss of consciousness.
- Focal to bilateral tonic clonic seizures: This seizure starts in one part of the brain and then spreads to the other side. You might be aware at first, then lose consciousness.
Generalized seizures
Generalized seizures involve both sides of the brain. They usually cause loss of consciousness.
In adults, the most common types include:
- Generalized tonic-clonic (GTC) seizures: GTC seizures were previously known as grand mal seizures. They make the muscles rigid (tonic phase) and causes muscle jerking (clonic phase).
- Tonic seizures: A tonic seizure causes muscle stiffening, usually in the back, arms, and legs. It doesn’t involve a clonic phase.
- Clonic seizures: During a clonic seizure, your muscles repeatedly jerk.
- Myoclonic seizures: A myoclonic seizure causes jerking in one area of the upper body and limbs.
- Atonic seizures: An atonic seizure, or drop attack, causes sudden loss of muscle tone. You might fall to the floor, or your head might drop.
- Absence seizures: An absence seizure, previously called a petit mal seizure, causes blank staring and slight twitching. You might experience a brief change in consciousness.
- Gelastic and dacrystic seizures: A gelastic seizure causes uncontrollable laughing, while a dacrystic seizure causes uncontrollable crying. These seizures are often associated with a brain lesion called a hypothalamic hamartoma.
- Nonepileptic events: Nonepileptic events, like a migraine attack and fainting, can look like seizures. However, they’re usually caused by psychological and emotional stress instead of abnormal brain activity.
If you think you’re having a seizure for the first time, try to stay calm.
Focus on staying safe and avoiding injury. If possible, move away from furniture and large objects. Lie down on the floor and rest your head on a folded jacket or pillow.
If you’re driving or operating equipment, stop and find a safe area.
If possible, call emergency services or ask someone nearby to contact them for you. Not all seizures are medical emergencies, but if you’ve never experienced one before, having a professional medical team assess your overall condition can help detect potentially serious medical complications.
It’s possible for an adult without a history of epilepsy to experience a seizure.
Potential causes include central nervous system infections, brain tumors, stroke, and brain injuries. The use or stopping of certain substances, including alcohol, may also trigger a seizure.
The type of seizure depends on the cause. If you have a seizure for the first time, get medical attention as soon as possible. A healthcare professional can help determine the underlying cause and provide a treatment plan, if needed.