Generalized seizures are episodes of disrupted or abnormal electric activity across the entire brain. They are distinguished from partial seizures, which tend to affect a specific area of the brain. There are six main types of generalized seizure: absence, myoclonic, clonic, tonic, tonic-clonic, and atonic. Each of these types invokes some degree of change in consciousness and muscle spasms, and can last anywhere from a fraction of a second to about five minutes. Emergency care is often needed during an episode to prevent an individual from hurting himself, and a follow-up medical evaluation usually is important to identify and treat the cause of generalized seizures.
Seizures can be caused by a number of different environmental factors and genetic conditions. A person might experience an isolated seizure due to a fever, severe infection, stroke, or from drug and alcohol withdrawal. More common are seizure disorders, where patients are prone to recurring episodes. An individual may acquire a seizure disorder after a traumatic brain injury or the onset of Alzheimer's disease, or because of a chronic condition like low blood sugar. Congenital and inherited conditions can also predispose people to generalized seizures.
Absence seizures rarely last more than a few seconds, and usually involve a momentary lapse in concentration and a minor facial spasm, such as an uncontrollable eye blink. Myoclonic and clonic seizures involve jerking muscle spasms in multiple parts of the body. A single myoclonic seizure lasts less than a second, though a person can experience multiple isolated seizures over the course of several minutes. Clonic seizures tend to last longer; 20- to 30-second episodes are common. In the case of a tonic seizure, muscle contractions cause the arms and legs to become rigid and the cheeks to tighten.
The most recognizable type of seizure is the tonic-clonic variety, also known as a grand mal seizure. An episode can last between 30 seconds and five minutes, and causes a loss of consciousness, interrupted breathing, severe muscle spasms, and rigid muscle contractions. It is common for a sufferer to fall down and appear to be flailing on the floor, though he has no control over the body and usually no recollection of the actual event. An individual typically becomes very sleepy and fatigued following a grand mal seizure.
The final category of generalized seizures, atonic, involves a sudden loss of muscle tone and consciousness. An individual's muscles go limp, causing him to collapse. Atonic seizures usually last less than 20 seconds, and are only dangerous if the person suffers a fall when standing or engaging in physical activity.
Individuals who experience generalized seizures typically need to be evaluated as soon as possible by a neurologist. Doctors usually can determine the cause of episodes and administer treatment accordingly. Many patients are prescribed anticonvulsant medications to reduce the risk of future episodes. Brain surgery usually is a last resort when other treatment measures are ineffective.