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Six Common Types of Generalised Seizures Explained

Epilepsy | September 9, 2014 | Author: The Super Pharmacist

epilepsy

Six Common Types of Generalised Seizures Explained

A seizure is the transient occurrence of signs or symptoms due to abnormal electrical activity in the brain, leading to a disturbance of consciousness, behaviour, emotion, motor function or sensation. Based on the type of behavior and brain activity, seizures are divided into two broad categories: generalised and partial (the term, 'focal' is now preferred). Generalised seizures are associated with impairment of consciousness and distortion of the electrical activity of the whole or a large part of both sides of the brain. Focal seizures begin with an electrical discharge in one limited area of the brain. There are six main types of generalised seizures:

  • Absence seizures (formerly known as petit mal seizures)
  • Myoclonic seizures
  • Clonic seizures
  • Tonic seizures
  • Tonic-clonic seizures (formerly known as grand mal seizures)
  • Atonic seizures (drop attacks)

What Are Absence Seizures?

Absence seizures (formerly called 'petit mal' seizures) are brief episodes of staring or daydreaming. During the seizure, awareness and responsiveness are impaired.

What Are Absence Seizures?There is no warning before the seizure, and the person is completely alert immediately afterwards. When people have absence seizures, they are unaware of what is going on around them. For example, they will not notice if someone tries to talk to them. If they were saying something when the seizure started, they may stop talking in the middle of a sentence. When an absence seizure ends, the person usually continues doing whatever they were doing before the seizure. 

This type of seizure usually begins in childhood between the ages of 4 and 12. Absence seizures may resolve on their own. Children who start having absence seizures before age nine are much more likely to outgrow them than children whose absence seizures start after age ten. Absence seizures can be provoked by one or two minutes of hyperventilation and may be terminated by a loud or repetitive stimulus. Sleep deprivation, drowsiness, and photic (flashing lights) stimulation may also precipitate seizures. There are two types of absence seizures: 

  • Simple absence seizures: These are staring spells which last for less than 10 seconds. Because they happen so quickly, it is very easy to overlook simple absence seizures or to confuse them with daydreaming or not paying attention.
  • Complex absence seizures: More common than simple absence seizures, these seizures are characterised by staring spells accompanied by automatisms, such as eye blinking, lip smacking, frequent swallowing, or picking at clothing. Complex absence seizures can last up to 20 seconds.

What Are Atypical Absence Seizures?

Atypical absence seizures usually occur in children who are developmentally delayed.

What Are Atypical Absence Seizures?They are often related to diffuse or multifocal structural lesions in the brain. Seizures usually last longer than 10 seconds, begin and end more gradually than typical absence seizures, and are not precipitated by hyperventilation. During an atypical absence seizure, consciousness may be only partially impaired, and it may be difficult to distinguish the seizure from the child's usual behavior.

What Are Myoclonic Seizures?

Myoclonic seizures are brief, shock-like jerks of a muscle or a group of muscles. “Myo” means muscle and “clonus” means rapidly alternating contraction and relaxation —jerking or twitching—of a muscle. Usually they do not last more than a second or two. There can be just one, but sometimes many will occur within a short time. Even people without epilepsy can experience myoclonus as in hiccups. Myoclonic seizures usually cause abnormal movements on both sides of the body at the same time. These seizures can be easily overlooked because they are so brief and appear as extra normal movements. These seizures can be mistaken for tics, tremors or clumsiness. Myoclonic seizures usually begin in childhood, but the seizures can occur at any age.

What Are Clonic Seizures?

Clonic seizures are rare. They consist of rhythmic jerking movements of the arms and legs, sometimes on both sides of the body. When a clonic seizure ends, the person may simply continue what he or she was doing when it began.

What Are Tonic Seizures?

Muscle "tone" is the muscle's normal tension at rest. In a "tonic" seizure, the tone is greatly increased and the body, arms, or legs make sudden stiffening movements. Consciousness is usually preserved. Tonic seizures most often occur during sleep and usually involve all or most of the brain, affecting both sides of the body. If the person is standing when the seizure starts, he or she often will fall. These seizures usually last less than 20 seconds. They are particularly common in people who have the epilepsy syndrome called Lennox-Gastaut syndrome, but they can occur in anyone.

What Are Tonic-Clonic Seizures?

This type of seizure is what most people think of when they hear the word "seizure." An older term for a tonic-clonic seizure is 'grand mal.' As implied by the name, they combine the characteristics of tonic seizures and clonic seizures. This type of seizure can affect children or adults. In the tonic phase, all muscles stiffen. The person loses consciousness and falls to the floor. The tongue or cheek may be bitten. After the tonic phase, the clonic phase is characterised by rapid and rhythmic jerking of the arms and usually the legs. After a few minutes, the jerking slows and stops. Bladder or bowel control may be lost as the body relaxes. Consciousness returns slowly, and the person may be drowsy, confused, agitated, or depressed. These seizures usually last one to three minutes. A tonic-clonic seizure that lasts longer than 5 minutes requires medical help. A tonic-clonic seizure that lasts longer than 10 minutes indicates a dangerous condition called status epilepticus and requires emergency treatment.

What Are Atonic Seizures?

Muscle "tone" is the muscle's normal tension. "Atonic" means "without tone," so in an atonic seizure, muscles suddenly lose strength. The eyelids may droop, the head may nod, and the person may drop things and often falls to the ground.

What Are Atonic Seizures?These seizures are also called "drop attacks" or "drop seizures." The person's body will get limp. If sitting, their head or upper body may slump over. If standing, the person many fall limply to the ground.

People who have seizures that cause them to fall rigidly (like a tree trunk) often have tonic seizures (involving sudden muscle contraction) rather than atonic seizures.

The person usually remains conscious. These seizures typically last less than 15 seconds. They often start in childhood yet last into adulthood. Many people with atonic seizures are injured when they fall, so they may choose to use protection such as a helmet.

How Are Generalised Seizures Treated?

After a single unprovoked seizure, a patient is advised to avoid common seizure 'precipitants' such as alcohol or sleep deprivation. Medication is not recommended unless the person has risk factors for recurrent seizures (e.g., an abnormal brain magnetic resonance imaging study (MRI) or an abnormal electroencephalogram (EEG).

Anticonvulsant medication is the mainstay of treatment for seizures. For patients who have had more than one unprovoked seizure, treatment with an anticonvulsant medication is recommended. The choice of anticonvulsant drug will vary with different seizure types and epileptic syndromes. The goal of treatment in individuals with recurrent seizures is to achieve a seizure-free status without adverse effects. This goal is accomplished in more than 60% of those who require treatment with anticonvulsant medication. However, a substantial minority may continue to experience seizures, and, unfortunately, adverse effects from these drugs are not uncommon. Patients who continue to experience seizures despite medical therapy may be candidates for the ketogenic diet, vagal nerve stimulation, an implantable neurostimulator, or neurosurgery.

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