A seizure happens when there is abnormal electrical activity in the brain, and it has numerous possible causes. In epilepsy, seizures happen without a clear cause.

About 10% of people experience a seizure at least once during their lifetime. After a first seizure, a person may wonder whether they have epilepsy. Epilepsy is a common cause of seizures, especially in people who have multiple seizures without another clear cause. However, epilepsy does not cause all seizures.

The numerous other causes of seizures include:

  • infections that affect the brain
  • a blow to the head
  • autoimmune conditions, such as lupus
  • severe malnourishment or nutritional imbalances

Doctors are not always able to determine the cause of a seizure, but when a person has multiple seizures over time, they usually diagnose epilepsy.

Keep reading to learn more about seizures and epilepsy, including the differences between an epileptic seizure and a seizure with another underlying cause.

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The brain is a complex electrical system that uses electricity to send nerve signals throughout the body. Various chemicals called electrolytes help conduct electricity. Potassium, sodium, magnesium, and calcium each have a unique electrical charge, so the right balance of these electrolytes is important for brain functioning.

Learn more about electrolytes here.

A seizure occurs when there is a sudden burst of abnormal activity in the brain. This can interfere with certain brain functions or cause a surge of brain activity that leads to unusual movements, perceptions, or experiences.

The effects of a seizure depend on where in the brain they occur. Generalized seizures, or tonic-clonic seizures, affect both sides of the brain and may cause shaking, jerking movements or repetitive motions such as rapid blinking.

Focal seizures affect small regions of the brain, and doctors may refer to them as partial seizures. The symptoms can range from very subtle, such as a person smelling something that is not there, to more dramatic, such as the individual suddenly becoming unaware of their surroundings. Some focal seizures can spread, affecting other areas of the brain.

Most seizures last for less than 5 minutes, and many last for just a few seconds. It is essential to call 911 for a seizure that lasts longer than 5 minutes.

Learn more about what seizures look like here.

Epilepsy is a chronic seizure disorder. Doctors typically diagnose epilepsy when:

  • There is no other underlying cause of the seizures, such as a head injury or an infection.
  • A person has a minimum of two seizures that occur at least 24 hours apart. Multiple seizures within a 24-hour period do not indicate epilepsy.
  • Tests of the electrical activity in the brain show that the symptoms are clearly seizures.

Definitions of epilepsy and the criteria for diagnosing the condition vary slightly. However, as other medical conditions that can cause seizures may be life threatening, it is important to get an accurate diagnosis.

After experiencing their first seizure or seizures, a person should give a doctor a complete medical history, including details about each seizure, any underlying health conditions, and any recent illnesses or head injuries.

The specific symptoms of the seizure are less relevant to the diagnostic process. For instance, a person can have several mild, short seizures and still have epilepsy.

Epileptic seizure and seizures relating to other disorders have many factors in common, including:

  • The specific symptoms of the seizures may be the same. Symptoms alone cannot distinguish epilepsy from other seizure-causing disorders.
  • Both epilepsy and other conditions that cause seizures increase the risk of injury from falls, car accidents, and loss of consciousness.
  • In both epilepsy and other seizure disorders, the seizure itself is not usually dangerous. A seizure is only a medical emergency if it lasts longer than 5 minutes or causes injuries.
  • A person can have epilepsy and another condition that causes seizures, so it is important that doctors consider both possibilities.

Some important differences between seizures and epileptic seizures include:

  • Some medical conditions that cause nonepileptic seizures may be life threatening. A person could potentially die from dehydration, diabetes, or a brain injury.
  • When an underlying medical condition causes seizures, a person may have other symptoms prior to the seizure, such as high blood pressure or malnourishment.
  • Diagnosing epilepsy requires excluding other syndromes and diseases. When diagnosing some other conditions, a single test may offer clarity. For example, if a person has a seizure and very high blood glucose, a doctor may conclude that uncontrolled diabetes is the culprit.

Epilepsy is the only medical condition for which seizures are the main symptom. Other medical conditions may cause seizures, but seizures are not the primary symptom. Due to this, a person can have one of these conditions and never have a seizure.

In many cases, a person with another medical condition will only have a seizure when their condition is severe or not well-controlled. For example, in diabetes, dangerously high blood sugar levels may trigger a seizure.

Some potential causes of seizures other than epilepsy include:

  • Fevers: Especially in young children, a fever may trigger a seizure on its own. About 1 in 25 children experience at least one fever-related seizure.
  • Drugs and other chemicals: Exposure to medications and toxic chemicals may trigger a seizure, especially at high or toxic dosages.
  • Electrolyte imbalances: Severe dehydration and medical conditions that affect electrolyte balance, such as diabetes, may trigger seizures.
  • Serious infections: Severe infections, such as the blood infection sepsis or an infection in the brain, may cause seizures.
  • Brain injuries: A blow to the head, a stroke, oxygen deprivation, and anything else that damages the brain can all cause seizures. Sometimes, seizures happen in people with brain lesions or cancer.
  • Inflammatory diseases: Diseases that cause widespread inflammation in the body, such as lupus, may also cause brain inflammation, triggering seizures.
  • HELLP syndrome: This serious pregnancy condition causes hemolysis (destruction of red blood cells), elevated liver enzymes, and low platelets during pregnancy. Most people who get HELLP syndrome develop preeclampsia first and have symptoms such as high blood pressure, swelling, and headaches. Untreated HELLP syndrome can cause seizures.

A seizure is not usually a medical emergency, and it typically resolves on its own. However, the conditions that cause seizures — such as uncontrolled high blood sugar or HELLP syndrome — can require emergency treatment.

A person should go to the emergency room if they:

  • have an underlying medical condition
  • have other neurological symptoms
  • are pregnant
  • have just had their first seizure

A person with epilepsy or a seizure-causing condition who has previously had seizures does not need to call a doctor unless their seizure pattern changes or they suffer an injury during a seizure.

However, these individuals should contact a doctor if their seizure control medication stops working or the condition they have seems to be getting worse.

Although seizures and the conditions that cause them are often both treatable, some possible causes are emergencies. Prompt medical care can save a person’s life and give them quick answers about the reason for seizures. It is important not to self-diagnose seizures, as this can cause a person to overlook serious medical conditions.

A person who experiences a seizure for the first time should see a doctor. If they believe that they may have a serious underlying medical condition, they should go to the emergency room.