What is a Tonic Seizure?

D. Jeffress

A tonic seizure is a sudden, short-lived episode of unusual electrical activity in the brain that causes muscles to stiffen. An individual who experiences a tonic seizure is unable to control body movements and loses consciousness during the event. Most tonic seizures last for less than 20 seconds at a time and usually occur when a person is sleeping. It is important to seek medical evaluation after experiencing a seizure, so doctors can determine the underlying causes and administer the correct treatment.

EEG tests may be ordered to determine the underlying cause of tonic seizures and to develop a treatment plan.
EEG tests may be ordered to determine the underlying cause of tonic seizures and to develop a treatment plan.

There are many different types of epileptic seizures that are categorized according to the part of the brain that is affected and the symptoms involved. Tonic seizures are classified as generalized seizures, meaning that electrical activity is disrupted across the entire brain instead of in an isolated spot. They usually involve a loss of consciousness and a lack of memory for the fits after they occur. For reasons that are not well understood by doctors, tonic seizures are most likely to occur when people feel drowsy or shortly after they fall asleep.

A tonic seizure causes loss of consciousness.
A tonic seizure causes loss of consciousness.

A tonic seizure is also characterized by a sudden, sharp increase in muscle tone. During an episode, the muscles of the neck, shoulders, and extremities abruptly tighten, leaving the sufferer stiff and entirely unable to move for as long as 20 seconds. A sleeping person's legs can become fully extended and the arms might raise themselves above his or her head. A tonic seizure that occurs while an individual is awake may lead to a fall or some other injury.

People can experience tonic seizures at any age and for a number of different reasons. Children under the age of five who have frequent tonic seizures usually have a congenital form of epilepsy called Lennox-Gastaut syndrome. Seizures can occur later in life due to head trauma, brain tumors, or withdrawal from alcohol or drugs, among several other potential causes. It is rare for a person to experience a single tonic seizure in his or her lifetime; most people who are afflicted suffer from recurring episodes and have seizures of different types as well.

A person who experiences a tonic seizure should visit the emergency room or schedule an appointment with a primary care physician as soon as possible. A doctor can ask about symptoms, take blood samples for laboratory analysis, and conduct a series of diagnostic imaging tests. The doctor usually takes a computerized tomography scan of the patient's brain to check for physical abnormalities and performs an electroencephalogram to monitor electrical activity in the brain. When a clear diagnosis cannot be made, the physician may refer the patient to an epileptologist for further testing.

Treatment for tonic seizures depends on the underlying causes. Adult patients are typically given prescription anticonvulsant drugs and instructed to maintain good dietary, sleeping, and exercise habits to lessen the risk of recurring seizures. Children with Lennox-Gastaut syndrome may need to undergo brain surgery to correct congenital deformities and lessen the frequency and severity of future episodes. There is no clear cure for epilepsy, but taking medications and following a doctor's recommendations usually allows a patient to successfully manage symptoms and enjoy a normal, active lifestyle.

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