Health Topics A-Z

What Are Seizures?

A seizure is when electrical activity in the brain fires abnormally. Seizures may go virtually unnoticed or, in severe cases, produce a change or loss of consciousness and involuntary muscle spasms called convulsions. Seizures usually come on suddenly and vary in duration and severity. A seizure may be a one-time event, or you may have seizures repeatedly. Recurrent seizures are called epilepsy, or seizure disorder. Less than one in 10 people who has a seizure develops epilepsy.

Experts classify seizures into two general categories and numerous subtypes based on the pattern of the attack. Generalized seizures involve both sides of the brain from the start of the attack. Common subtypes include tonic-clonic (grand mal) and absence seizures (petit mal). Two types of generalized seizures — febrile and infantile spasms — occur almost exclusively in young children.

The second major seizure type is partial (or focal) seizures. These begin in a specific area of the brain and may be contained there or may spread to the entire brain. In simple partial seizures the person remains conscious; complex partial seizures involve impaired consciousness.

Alert on status epilepticus: Get immediate medical attention for someone experiencing a prolonged seizure or repeated seizures with intense muscle contractions and difficulty breathing. The person may be experiencing status epilepticus, which can cause permanent damage to their brain or heart.

What Causes Them?

Often the cause of a seizure is unknown. Many conditions can provoke seizures, including:

• Stroke.
• Brain tumor.
• Head injuries.
• Electrolyte imbalance.
• Very low blood sugar.
• Repetitive sounds or flashing lights, such as in video games.
• Medications, such as antipsychotics and some asthma drugs.
• Withdrawal from medications or alcohol.
• Use of drugs such as cocaine and heroin.
• Cancer.
• Brain infections such as meningitis.