Epileptic Seizures

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Epilepsy is a chronic neurological condition characterized by recurrent seizures that are caused by abnormal cerebral nerve cell activity. Epilepsy is classified as idiopathic or symptomatic.

Idiopathic epilepsy has no known cause, and the person has no other signs of neurological disease or mental deficiency.

Symptomatic epilepsy results from a known condition, such as stroke, head injury, poisoning, Lennox-Gastaut syndrome, and cerebral palsy.

Incidence and Prevalence More than 2 million people in the United States and over 50 million worldwide suffer from epilepsy. In the United States, more than 300,000 people with epilepsy are under the age of 14, and more than 500,000 are over the age of 65.

Seizure

A nerve cell transmits signals to and from the brain in two ways by:

  1. altering the concentrations of salts (sodium, potassium, calcium) within the cell.
  2. Releasing chemicals called neurotransmitters (gamma aminobutyric acid).

The change in salt concentration conducts the impulse from one end of the nerve cell to the other. At the end, a neurotransmitter is released, which carries the impulse to the next nerve cell. Neurotransmitters either slow down or stop cell-to-cell communication (called inhibitory neurotransmitters) or stimulate this process (called excitatory neurotransmitters). Normally, nerve transmission in the brain occurs in an orderly way, allowing a smooth flow of electrical activity. Improper concentration of salts within the cell and over activity of either type of neurotransmitter can disrupt orderly nerve cell transmission and trigger seizure activity.

Certain areas of the brain are more likely than others to be involved in seizure activity. The motor cortex, which is responsible for body movement, and the temporal lobes, including the hippocampus, which is involved in memory, are particularly sensitive to biochemical changes (e.g., decreased oxygen level, metabolic imbalances, infection) that provoke abnormal brain cell activity.

Seizure Phases

A seizure often has three distinct phases: aura, ictus, and postictal state. The first phase involves alterations in smell, taste, visual perception, hearing, and emotional state. This is known as an aura, which is actually a small partial seizure that is often followed by a larger event. The seizure is known as ictus. There are two major types of seizure: partial and generalized. What happens to the person during the seizure depends on where in the brain the disruption of neural activity occurs. Following a seizure, the person enters into the postictal state. Drowsiness and confusion are commonly experienced during this phase. The postictal state is the period in which the brain recovers from the insult it has experienced.

Types of Seizures

The International Classification of Epileptic Seizure identifies seizure types by the site of origin in the brain. The two main categories of seizures include partial seizures and generalized seizures. A partial seizure can evolve to a generalized seizure. There are several subtypes of each. Only the most common are described here.

Partial Seizures

The site of origin is a localized or discreet area in one hemisphere of the brain. The two most common types of partial seizure are simple partial and complex partial.

Simple Partial

These produce symptoms associated with the area of abnormal neural activity in the brain: motor signs, sensory symptoms, autonomic signs and symptoms (involuntary activity controlled by autonomic nervous system), and psychic symptoms (altered states of consciousness). There is no impairment of consciousness in simple partial seizures.

Complex Partial

Impairment of consciousness, characteristic of complex partial seizures (CPS), results in the inability to respond to or carry out simple commands or to execute willed movement, and a lack of awareness of one's surroundings and events. Automatisms may occur. An automatism is a more or less coordinated, involuntary motor activity. A simple complex seizure may begin as a simple partial seizure.

Generalized

At the onset, seizure activity occurs simultaneously in large areas of the brain, often in both hemispheres. Seizures can be convulsive or non convulsive. The two most common types are tonic-clonic and absence.

Tonic-clonic (grand mal)

There is loss of consciousness during the seizure. The tonic phase, consisting of increased muscle tone (rigidity), is followed by the clonic phase, which involves jerking of the extremities. Autonomic symptoms may also be present.

Absence (petit mal)

This type occurs most often in children, usually beginning between the ages of 5 and 12 years and often stopping spontaneously in the teens. The loss of consciousness is so brief that the child usually does not even change position. Most absence seizures last 10 seconds or less. There is no postictal state, but the person usually lacks awareness of what occurs during the seizure.

Myoclonic

These seizures are so brief that they may go unnoticed. They involve sudden muscle contractions that occur much more rapidly than clonic activity and are often confused with tics. Myoclonic seizures occur at all ages and are associated with epileptic syndromes such as West syndrome and Lennox-Gastaut syndrome.

Syndrome and Situation-Related Epilepsy

Infants and ChildrenEpilepsy is one of several symptoms that occur in West syndrome and Lennox-Gastaut syndrome. West syndrome, also called infantile spasm, is a rare disorder of infancy and early childhood. It is characterized by epilepsy, hydrocephalus, congenital anomalies, and mental retardation.

Lennox-Gastaut syndrome usually develops between the ages of 1 and 8 years old and is characterized by atonic, absence, and myoclonic seizures. Many of these children are developmentally delayed and have behavioral problems.

Adults Several medical conditions may precipitate epilepsy in adults, notably withdrawal from chronic alcohol and drug abuse, eclampsia, and stroke.

Symptoms of a seizure

A seizure is usually defined as a sudden alteration of behavior due to a temporary change in the electrical functioning of the brain, in particular the outside rim of the brain called the cortex. Below you will find some of the symptoms people with epilepsy may experience before, during and after a seizure. Seizures can take on many different forms and seizures affect different people in different ways. It is not implied that every person with seizures will experience every symptom described below.

Seizures have a beginning, middle, and an end.When an individual is aware of the beginning, it may be thought of as a warning or aura. On the other hand, an individual may not be aware of the beginning and therefore have no warning.

Sometimes, the warning or aura is not followed by any other symptoms. It may be considered a simple partial seizure by the doctor.

The middle of the seizure may take several different forms. For people who have warnings, the aura may simply continue or it may turn into a complex partial seizure or a convulsion. For those who do not have a warning, the seizure may continue as a complex partial seizure or it may evolve into a convulsion.

The end to a seizure represents a transition from the seizure back to the individual's normal state. This period is referred to as the "postictal period" an ictus is a seizure) and signifies the recovery period for the brain. It may last from seconds to minutes to hours, depending on several factors including which part(s) of the brain were affected by the seizure and whether the individual was on anti-seizure medication. If a person has a complex partial seizure or a convulsion, their level of awareness gradually improves during the postictal period, much like a person waking up from anesthesia after an operation.

 
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