What Causes Seizures in Adults: Brain Tests & EEG Diagnosis

Experiencing a seizure for the first time in adulthood can be unexpected, especially in someone who has never had epilepsy before. While a seizure itself may last only a few seconds or minutes, it often points to an underlying medical condition that needs attention. This is why doctors first focus on finding what causes seizures in adults rather than treating the seizure alone.

The answer is different for every person. Some adults develop seizures after a stroke or head injury, while others experience them because of infections, brain tumours, metabolic disorders, or certain medicines. In many cases, identifying the underlying cause helps doctors decide the right treatment and reduce the risk of another seizure.

The most common seizure causes in adults include the following.

1. Stroke

Stroke is one of the leading answers to what causes seizures in adults, particularly in older adults. When blood flow to part of the brain is interrupted or a blood vessel bursts, brain cells become damaged. As the brain heals, the injured area may form scar tissue that can send abnormal electrical signals, leading to seizures.

The risk is generally higher after a severe stroke or when the outer part of the brain is affected. Some people develop post stroke seizures within the first few days, while others may experience their first seizure months later.

2. Traumatic Brain Injury

A serious head injury caused by a road traffic accident, fall, sports injury, or assault can damage brain tissue. Even after the visible injury heals, changes inside the brain may continue to affect normal electrical activity.

The chance of traumatic brain injury seizures is usually higher after severe injuries involving bleeding, swelling, or skull fractures. For some adults, the first seizure appears long after the accident, making the earlier injury easy to overlook.

3. Brain Infections

Certain infections can directly affect the brain and interfere with its normal function. In India, infections such as neurocysticercosis and tuberculous meningitis continue to be recognised as important seizure causes in adults.

Inflammation caused by these infections can irritate brain tissue and increase the likelihood of seizures. Early diagnosis and treatment are important because managing the infection often helps reduce seizure episodes.

4. Brain Tumours

A seizure may sometimes be the first sign of a brain tumour. Both non cancerous and cancerous tumours can disturb nearby brain tissue by increasing pressure or altering normal brain electrical activity.

Not every person with a brain tumour develops seizures, but when an adult experiences a first seizure without an obvious cause, brain imaging is often recommended to rule out structural problems.

5. Metabolic Disorders

The brain depends on a steady supply of oxygen, glucose, and essential minerals to function normally. Sudden changes in these levels can disturb normal brain activity and trigger a seizure.

Common metabolic causes include:

• Very low blood sugar
• Low sodium levels
• Kidney failure
• Liver disease
• Severe dehydration

These conditions may explain what causes sudden seizures in adults who have never experienced one before.

6. Alcohol and Certain Medicines

Heavy alcohol consumption, alcohol withdrawal, or sudden withdrawal from medicines such as anti anxiety drugs may trigger seizures in some adults.

Certain prescription medicines may also lower the seizure threshold, particularly when taken in high doses or combined with other medications. This is why doctors carefully review a person’s medical history and current medicines after a first seizure.

7. Degenerative Brain Disorders

Some neurological conditions that gradually damage brain cells can increase the risk of seizures later in life. As the brain changes over time, normal electrical communication between nerve cells may become disrupted.

Although these conditions are less common than stroke or head injury, they remain an important consideration in older adults with adult onset seizures.

8. When No Clear Cause Is Found

Despite detailed investigations, some adults have no obvious structural or metabolic abnormality. This does not mean the seizure should be ignored. Additional follow up, repeat EEG studies, or brain imaging may later identify the underlying cause.

In some people, doctors eventually diagnose epilepsy in adults, while others never experience another seizure.

Understanding what causes seizures in adults is the first step towards effective treatment. Once the possible causes have been identified, doctors use brain imaging, blood tests, and EEG to confirm the diagnosis and decide the next course of treatment.

Medical Conditions That Can Trigger Seizures

Not every seizure begins because of a structural problem inside the brain. Changes in blood sugar, body salts, kidney function, liver function, or certain medicines can temporarily interfere with brain function and trigger a seizure. In many cases, treating the underlying medical condition also reduces the risk of another seizure.

Low Blood Sugar

The brain depends on glucose for energy. When blood sugar falls to very low levels, brain cells cannot function normally, which may lead to confusion, unconsciousness, or a seizure. This is more common in people taking insulin or certain diabetes medicines.

Low Sodium Levels

Sodium helps brain cells send electrical signals. When sodium levels drop suddenly, the brain may swell slightly and electrical activity becomes unstable. Severe hyponatraemia is a recognised cause of what causes sudden seizures in adults.

Kidney and Liver Disease

Advanced kidney or liver disease allows waste products to build up in the bloodstream. These toxins can affect brain function and increase the likelihood of seizures until the underlying condition is treated.

Alcohol and Drug Withdrawal

Heavy alcohol use followed by sudden withdrawal can trigger seizures, particularly within the first two days of stopping alcohol. Withdrawal from certain prescription medicines, including some sleeping tablets and anti anxiety medicines, may have a similar effect.

Certain Medicines

Some medicines lower the brain’s seizure threshold, making seizures more likely in susceptible individuals. Taking higher than prescribed doses or combining certain medicines without medical advice may increase this risk.

These medical conditions are often reversible. Once the underlying problem has been identified and treated, many adults do not experience another seizure. This is why doctors do not diagnose epilepsy after every first seizure and instead focus on finding what causes seizures in adults before deciding the most appropriate treatment.

Can an Adult Have a Seizure Without Epilepsy?

Yes. A seizure does not always mean a person has epilepsy. Many adults experience a single seizure because of a temporary medical problem such as low blood sugar, alcohol withdrawal, high fever, or a head injury. Once the underlying cause is treated, they may never have another seizure.

Epilepsy is usually diagnosed only when a person has repeated unprovoked seizures or when brain tests show a high risk of future seizures. This is why neurologists first try to identify what causes seizures in adults before confirming epilepsy.

Some adults experience a seizure only once, while others need further investigations to determine whether the episode is linked to an underlying neurological condition.

How Do Doctors Find the Cause of Seizures in Adults?

The symptoms alone are rarely enough to identify what causes seizures in adults. Doctors usually combine the person’s medical history with brain imaging, blood tests, and EEG to understand why the seizure occurred and whether there is a risk of another episode.

The investigations recommended depend on the person’s age, symptoms, and suspected cause.

Medical History and Physical Examination

The first step is understanding exactly what happened before, during, and after the seizure. Doctors may ask about previous illnesses, head injuries, alcohol intake, medicines, family history, and whether anyone witnessed the seizure.

A neurological examination also helps identify signs that may point towards stroke, infection, or another brain disorder.

Blood Tests

Blood tests help identify temporary medical conditions that may trigger seizures.

These may include:

• Blood sugar levels
• Sodium and other electrolytes
• Kidney function
• Liver function
• Signs of infection

Correcting these abnormalities may prevent further seizures in some adults.

EEG

An Electroencephalogram (EEG) records the brain’s electrical activity using small electrodes placed on the scalp. It helps identify abnormal electrical patterns that support the diagnosis of epilepsy or other seizure disorders.normal EEG does not always rule out epilepsy. In some people, abnormal electrical activity appears only occasionally, which is why additional EEG studies may be recommended if symptoms continue.

MRI or CT Scan

Brain imaging helps doctors look for structural causes of seizures such as stroke, brain tumours, previous injuries, or infections.

MRI usually provides more detailed images of brain tissue, while CT scans are often used in emergency situations when rapid assessment is required.

The combination of medical history, neurological examination, EEG, and brain imaging gives doctors the clearest understanding of what causes seizures in adults and helps guide further treatment.

When Should an Adult See a Neurologist for a Seizure?

A seizure should never be ignored, even if it lasts only a few seconds or happens only once. While some seizures are triggered by temporary medical conditions, others may be the first sign of a neurological disorder that requires treatment. Consulting a neurologist helps identify what causes seizures in adults and whether there is a risk of future seizures.

Medical attention should not be delayed if any of the following situations occur:

A first seizure in adulthood

A seizure that happens for the first time should always be investigated. Even if the person recovers completely, tests may be needed to rule out conditions such as stroke, brain infection, tumour, or metabolic disorders.

More than one seizure

Repeated seizures increase the possibility of an underlying neurological condition. A neurologist may recommend additional investigations to determine the cause and decide whether anti seizure medication is required.

A seizure lasting longer than five minutes

A seizure that continues for more than five minutes or repeated seizures without full recovery between episodes is a medical emergency. Immediate hospital care is needed to prevent complications.

New neurological symptoms

Seek urgent medical attention if a seizure is followed by:

• Weakness in the arm or leg
• Difficulty speaking
• Loss of vision
• Persistent confusion
• Severe headache
• Difficulty walking

These symptoms may indicate a serious brain condition that requires immediate evaluation.

A seizure after a head injury

Any seizure following a recent head injury should be assessed without delay. Brain imaging and neurological evaluation help determine whether the injury has caused bleeding, swelling, or damage to brain tissue.

Early diagnosis makes it easier to identify the underlying cause and begin appropriate treatment before further seizures occur.

Expert Evaluation and EEG Services at Suri Neuro

Adults experiencing a first seizure or recurrent seizures should undergo a detailed neurological assessment to identify the underlying cause. At Suri Neuro, Defence Colony, South Delhi, patients receive expert evaluation supported by advanced diagnostic facilities, including routine EEG, sleep EEG, ambulatory EEG, video EEG monitoring, and brain imaging guidance when required.

The neurology team carefully reviews symptoms, medical history, and investigation findings to determine the cause of seizures and develop an individualised treatment plan. Early diagnosis and timely management can reduce the risk of recurrent seizures and improve quality of life.

Frequently Asked Questions

1. What causes seizures in adults?

Seizures in adults can be caused by stroke, head injury, brain infections, brain tumours, metabolic disorders, alcohol withdrawal, or certain medicines.

2. Can an adult have a seizure without epilepsy?

Yes. A single seizure does not always mean epilepsy. It may be triggered by a temporary medical condition.

3. Which test is used to diagnose seizures?

Doctors may recommend an EEG, MRI or CT scan, blood tests, and a neurological examination to identify the cause.

4. Can stress cause seizures in adults?

Stress alone is not a direct cause but may trigger seizures in people who already have epilepsy.

5. When should an adult see a neurologist after a seizure?

A neurologist should be consulted after a first seizure, repeated seizures, or if the seizure is followed by weakness, confusion, or difficulty speaking.