What is a seizure?
A seizure is a brief disruption in the brain’s normal electrical activity. The brain’s nerve cells send signals to communicate with your body and control how it works. During a seizure, those signals become sudden and disorganized, interrupting normal brain function for a short time. Some people have a single seizure in their lifetime. Others have a medical condition, such as epilepsy, that makes them more likely to experience repeated seizures.
At Penn Medicine, people with seizures receive care from specialists experienced in diagnosing and treating seizure disorders. Our Comprehensive Epilepsy Center is a Level 4 epilepsy center—the highest designation from the National Association of Epilepsy Centers—offering advanced testing and treatment for complex seizure conditions.
Signs and symptoms of seizures
Signs and symptoms of seizures vary depending on the area of the brain affected and the type of seizure. Some seizure symptoms are obvious, while others might not be noticeable at all.
People with seizures may experience one or more of the following symptoms:
- Abnormal or unpleasant taste or smell
- Hearing or seeing things that are not there
- Strange thoughts or experiences, such as déjà vu or sudden behavioral changes
- Involuntary movements of the arms or legs
- Spells of staring or unresponsiveness during which the person has difficulty communicating and may remember nothing
- Lip smacking or repetitive movements, for example picking or grasping movements
- Whole-body stiffening or shaking
- Drooling or frothing from the mouth
- Loss of bladder or bowel control
Common seizure triggers
Certain events or exposures called triggers may set off the abnormal electrical brain activity that causes seizures.
Common seizure triggers include:
- Alcohol or drug use or withdrawal
- Certain foods and medications
- Dehydration, physical exertion, or malnutrition
- Flashing lights or patterns (photosensitivity)
- High environmental temperatures
- Hormonal changes (such as those during menstruation)
- Illness or fever
- Sleep disturbance or stress
Types of seizures
Doctors categorize seizures into two main types—generalized seizures and focal seizures. The type of seizure depends on what part of the brain is affected and the symptoms a person has during the seizure.
Generalized seizures happen when abnormal electrical activity affects the entire brain at the same time. Generalized seizures include:
- Absence seizures: Also known as petit mal seizures, people who have absence seizures have staring spells or periods of unresponsiveness or "spacing out." When the seizure ends, the person has no memory of it.
- Atonic seizures: These types of seizures are also known as drop attacks. People having these seizures lose complete control of their muscles and fall suddenly to the ground or slump over if seated. These seizures carry a high risk of injury due to falls.
- Clonic seizures: These types of seizures involve involuntary muscle twitching or convulsions that happen seemingly out of nowhere, with no muscle tensing first.
- Generalized tonic-clonic seizures: Also called grand mal seizures, these most easily recognized seizures occur in two phases. In the tonic phase, muscles stiffen, and people fall unconscious. The clonic phase follows, with uncontrolled muscle jerking or convulsions.
- Myoclonic seizures: These types of seizures involve quick jerking or twitching of one muscle or a group of related muscles. If the jerking happens in a leg, it may lead to falling and possible injury.
- Tonic seizures: These types of seizures involve muscle stiffening and falling, but no convulsions. These are also sometimes known as drop attacks because they cause falling.
Focal or partial seizures begin in a region on one side of the brain. People who experience focal seizures will often experience auras, which are warning signs that a seizure is about to occur. Auras are also a type of seizure.
Focal seizures are divided into two categories:
- Focal onset aware seizures: During these seizures, formerly called simple focal or partial seizures, people remain conscious and are usually aware that the seizure is happening. Focal onset aware seizures may be motor seizures affecting movement of only one part of the body or purely sensory seizures known as auras. Some examples of auras include:
- Changes in vision (blurriness, dark spots, or partial loss of vision)
- Flashing lights
- Ringing or buzzing in the ears or hearing voices
- Sudden sensations (numbness, tingling, nausea, headache, or dizziness)
- Sudden strong emotions (joy, anger, sadness, or fear)
- Sudden tastes in the mouth (metallic, salty, bitter, sweet, or acidic)
- Unusual or unpleasant smells
- Focal onset impaired awareness seizures: These seizures, formerly called complex focal or partial seizures, cause a person to become unaware of what is happening. These seizures often follow an aura. They frequently include repetitive or involuntary movements of the limbs, face, or body.
Focal seizures may spread to the other side of the brain, causing a lack of awareness, body stiffness, and jerking movements. These types of seizures are called focal to bilateral tonic-clonic seizures. These are also called grand mal seizures. It can be difficult to distinguish focal to bilateral tonic-clonic seizures from generalized tonic-clonic seizures without additional testing.
What causes a seizure?
All seizures are caused by abnormal electrical activity in the brain. In some cases, the cause of seizures is unknown. In other cases, the abnormal activity can be caused by different factors.
Developmental and congenital abnormalities are conditions you are born with or develop during childhood. These conditions may include:
- Abnormal blood vessels in the brain (arteriovenous malformations)
- Congenital brain conditions that develop before birth
Acquired brain injuries occur as the result of a sickness or accident and can include:
- Brain infections (meningitis or encephalitis)
- Traumatic brain injuries (TBIs) from falls, car accidents, or other traumas
- Injuries to a baby's brain sustained during childbirth
- Strokes
Seizures can also occur as the result of exposing the body to certain external influences or events such as:
- Drug intoxication or overdose
- Electric shock
- Withdrawal from drugs, alcohol, or certain medications when taken for a long time
Other health conditions that may cause seizures include:
- Abnormal blood sugar or electrolyte levels
- Brain tumors
- Genetic, autoimmune, or metabolic disorders
- Eclampsia (very high blood pressure during pregnancy)
- Extremely high blood pressure (malignant hypertension)
- High fevers
- Liver or kidney failure
How are seizures diagnosed?
Some seizures have obvious symptoms, but others are subtle. Even when seizure symptoms are obvious, the cause often isn't. Precise diagnostic testing is the only true way to determine the cause of seizures.
We begin by reviewing your medical and family health history. You will be asked questions about your seizures, including how often they occur, what seems to trigger them, and what you experience during your seizures. Since many people with seizures do not remember them, we also ask family members or other witnesses what they observe when you have a seizure.
Your doctor will likely order brain imaging and other tests to pinpoint where abnormal electrical activity is happening in the brain and what is causing it.
- Neuropsychological testing: Seizure disorders can cause problems with memory, language, and attention. Neuropsychological testing allows us to evaluate whether you are experiencing cognitive problems because of seizures. The results of this testing can also help us identify where seizures are occurring in the brain and what's causing them.
- Inpatient seizure monitoring: If the cause of your seizure is unclear, your doctor may recommend inpatient monitoring in our Epilepsy Monitoring Unit (EMU). This specialized testing records brain activity over time to help your care team better understand your seizures and guide treatment. EMU monitoring may also help determine whether surgery could help control drug-resistant seizures.
Epilepsy Monitoring Unit
Sometimes, outpatient epilepsy testing isn’t enough to diagnose complex or unusual cases. Our EMU testing center provides continuous inpatient monitoring over several days to pinpoint a diagnosis and create the best possible care plan.
Comprehensive seizure treatment at Penn Medicine
The specialists at Penn Medicine's Comprehensive Epilepsy Center offer a variety of treatment options.
Many people try several different anti-seizure medications before finding the right option. But most seizures can be controlled using one or more anti-seizure medications (ASMs). These medications come in two categories:
- Broad-spectrum ASMs are useful for many kinds of seizures, including generalized seizures and focal seizures.
- Narrow-spectrum ASMs mostly target focal seizures.
Our Level 4 epilepsy center offers the full range of surgical treatment options for seizures that are not controlled with medication. Surgical treatment involves identifying and removing the tissue that causes the seizures or implanting devices that modulate (adjust) brain activity.
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