Epilepsy

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Description

An in-depth report on the types, causes, diagnosis, and treatment of epilepsy.

Highlights

What Is Epilepsy?

Epilepsy is a brain disorder that is marked by recurrent seizures. Seizures (also called fits or convulsions) are episodes of disturbed brain function caused by abnormalities of the brain’s electrical activity. There are many different types of seizures.

Epilepsy can affect people of all ages but is most common in young children and older adults. Some types of epilepsy are inherited and due to genetic factors. Other possible causes of epilepsy include brain injuries such as head trauma or oxygen deprivation at birth. In many cases, the cause of epilepsy is unknown (idiopathic).

A doctor will diagnose epilepsy based on a patient’s medical history, description of seizures, and various diagnostic tools. The most important diagnostic tool is the electroencephalogram (EEG), which allows doctors to record and analyze brain waves. Imaging tests such as computed tomography (CT) and magnetic resonance imaging (MRI) may also be used.

The goal of epilepsy treatment is to control seizures. Many different types of anticonvulsant drugs are available to treat epilepsy. Some patients need only one drug, while others may need to take several drugs. For patients who have not been helped by medication, surgery may be an option. Dietary changes, such as the ketogenic diet, have shown promise in helping some patients, especially children with severe epilepsy.

Anti-epileptic drugs (AEDs) can cause many side effects. Pregnant women with epilepsy need to take special precautions, because some of these drugs (particularly valproate) can cause birth defects.

In 2011, the FDA issued updated warnings on birth defect risks and AEDs:

  • Valproate  may have long-term effects on a child’s cognitive development if the mother takes it during her first trimester of pregnancy. Studies indicate that children born to mothers who took valproate during pregnancy had lower scores on IQ and other cognitive tests than children whose mothers took other types of AEDs. Valproate drug products include valproate sodium (Depacon), valproic acid (Depakene), and divalproex sodium (Depakote).
  • Topiramate  (Topamax, generic) may increase the risk for cleft palate or cleft lip when taken during the first trimester of pregnancy.

Drug Approval

In 2012, the FDA approved perampanel (Fycompa) as add-on treatment for partial seizures in patients ages 12 years and older. Perampanel is a new type of anti-epileptic drug that targets the AMPA glutamate receptor. It is taken once-daily as a pill at bedtime. In addition to typical AED side effects (dizziness, drowsiness), perampanel has a boxed warning to highlights risks of serious mood changes and mental disturbances, including violent thoughts and behaviors.

Introduction

Epilepsy is a brain disorder involving repeated, spontaneous seizures of any type. There are different types of epilepsy but what they all share are recurrent seizures caused by an uncontrolled electrical discharge from nerve cells in the cerebral cortex. This part of the brain controls higher mental functions, general movement and sensation, the functions of the internal organs in the abdominal cavity, perception, and behavioral reactions.

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The structures of the brain include the brainstem, consisting of the spinal cord, the medulla oblongata, the pons and the midbrain; the cerebellum; the cerebrum (one half, or hemisphere shown); and the diencephalon.

Seizures

Seizures are a symptom of epilepsy. Seizures ("fits," convulsions) are episodes of disturbed brain function that cause changes in neuromuscular function, attention, or behavior. They are caused by abnormally excited electrical signals in the brain.

A single seizure may be related to a specific medical problem (such as brain tumor or withdrawal from alcohol). If repeated seizures do not recur after this underlying problem has been corrected, the person does not have epilepsy.

A single, first seizure that cannot be explained by a temporary medical problem has about a 25% chance of returning. After a second seizure occurs, there is about a 70% chance of future seizures and the diagnosis of epilepsy.

Types of Epilepsy

Epilepsy is generally classified into two main categories based on seizure type:

  • Partial (also called focal or localized) seizures. These seizures are more common than generalized seizures and occur in one or more specific locations in the brain. In some cases, partial seizures can spread to wide regions of the brain. They are likely to develop from specific injuries, but in most

    cases the exact origins are unknown (idiopathic ).

  • Generalized seizures. These seizures typically occur in both sides of the brain. Many forms of these seizures are genetically based. There is usually normal neurologic function between episodes.

Partial Seizures (also called Focal Seizures)

These seizures are subcategorized as "simple" or "complex partial."

  • Simple Partial Seizures. A person with a simple partial seizure (sometimes known as Jacksonian epilepsy) does not lose consciousness, but may experience confusion, jerking movements, tingling, or odd mental and emotional events. Such events may include deja vu, mild hallucinations, or extreme responses to smell and taste. After the seizure, the patient usually has temporary weakness in certain muscles. These seizures typically last about 90 seconds.
  • Complex Partial Seizures. Slightly over half of seizures in adults are complex partial type. About 80% of these seizures originate in the temporal lobe, the part of the brain located close to the ear. Disturbances there can result in loss of judgment, involuntary or uncontrolled behavior, or even loss of consciousness. Patients may lose consciousness briefly and appear to others as motionless with a vacant stare. Emotions can be exaggerated; some patients even appear to be drunk. After a few seconds, a patient may begin to perform repetitive movements, such as chewing or smacking of lips. Episodes usually last no more than 2 minutes. They may occur infrequently, or as often as every day. A throbbing headache may follow a complex partial seizure.

In some cases, simple or complex partial seizures evolve into what are known as secondarily generalized seizures. The progression may be so rapid that the initial partial seizure is not even noticed.

Generalized Seizures

Generalized seizures are caused by nerve cell disturbances that occur in more widespread areas of the brain than partial seizures. Therefore, they have a more serious effect on the patient. They are further subcategorized as tonic-clonic (or grand mal), absence (petit mal), myoclonic, or atonic seizures.

Tonic-Clonic (Grand Mal) Seizures. The first stage of a grand mal seizure is called the tonic phase, in which the muscles suddenly contract, causing the patient to fall and lie stiffly for about 10 - 30 seconds. Some people experience a premonition or aura before a grand mal seizure. Most, however, lose consciousness without warning. If the throat or larynx is affected, there may be a high-pitched musical sound (stridor) when the patient inhales. Spasms occur for about 30 seconds to 1 minute. Then the seizure enters the second phase, called the clonic phase. The muscles begin to alternate between relaxation and rigidity. After this phase, the patient may lose bowel or urinary control. The seizure usually lasts a total of 2 - 3 minutes, after which the patient remains unconscious for a while and then awakens to confusion and extreme fatigue. A severe throbbing headache similar to migraine may also follow the tonic-clonic phases.

Absence (Petit Mal) Seizures. Absence or petit mal seizures are brief losses of consciousness that occur for 3 - 30 seconds. Physical activity and loss of attention may pause for only a moment. Such seizures may pass unnoticed by others. Young children may simply appear to be staring or walking distractedly. Petit mal may be confused with simple or complex partial seizures, or even with attention deficit disorder. [For more information, see In-Depth Report #30: Attention deficit hyperactivity disorder .] In petit mal, however, a person may experience attacks as often as 50 - 100 times a day.

Myoclonic. Myoclonic seizures are a series of brief jerky contractions of specific muscle groups, such as the face or trunk.

Atonic (Akinetic) Seizures. A person who has an atonic (or akinetic) seizure loses muscle tone. Sometimes it may affect only one part of the body so that, for instance, the jaw slackens and the head drops. At other times, the whole body may lose muscle tone, and the person can suddenly fall. A brief atonic episode is known as a drop attack.

Simply Tonic or Clonic Seizures. Seizures can also be simply tonic or clonic. In tonic seizures, the muscles contract and consciousness is altered for about 10 seconds, but the seizures do not progress to the clonic or jerking phase. Clonic seizures, which are very rare, occur primarily in young children, who experience spasms of the muscles but not tonic rigidity.

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Source: umm.edu

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