Etiology/Pathophysiology

Epilepsy (recurring seizures) has long been attributed to a group of abnormal neurons, known as the seizure focus, which undergoes spontaneous firing. Adjacent or distant areas of the brain are then affected as the firing spreads. If it spreads to involve the whole brain, a generalized seizure occurs. It is not clear what causes this abnormal firing, however, any stimulus that causes the cell membrane of the neuron to depolarize influences spontaneous firing. Regardless of the cause, the basic mechanism is the same: abnormal electrical discharges (1) may arise from central areas in the brain that affect consciousness; (2) may be restricted to one area of the cerebral cortex, producing manifestations characteristic of that particular anatomical focus; or (3) may begin in a localized area of the cortex and spread to other portions of the brain, which, if sufficiently extensive, produce generalized seizure activity.

While the cause is not known, we do know two things. (1) scar tissue is often found in areas of the brain from which epileptic activity arises. It is believed that these area are more likely to fire abnormally due to an interference of normal chemical and structural environment of the brain neurons. (2) a predisposition to the generation of an epileptic discharge is the activation of astrocytes by hyperactive neurons.

Seizures are classified as acute symptomatic, remote symptomatic, cryptogenic, or idiopathic Acute symptomatic seizures are associated with an acute insult such as head trauma or meningitis. Remote symptomatic seizures are those without an immediate cause but with an identifiable prior brain injury such as major head trauma, meningitis or encephalitis, hypoxia, stroke, or a static encephalopathy such as mental retardation or cerebral palsy. Cryptogenic seizures are those occurring with no clear cause. Idiopathic seizures are genetic in origin.

While we do not know what specifically causes the abnormal firing, there are many possible causes for epilepsy that vary by age.

• First 6 months: severe birth injury, congenital defects involving central nervous system, infections, and inborn errors of metabolism.
• 2-20: birth injury, infection, trauma, and genetic factors.
• 20-30: structural lesions such as trauma, brain tumors, or vascular disease.
• After 50: stoke and metastatic brain tumors.

Almost 30% of all epilepsy cases are idiopathic (idiopathic generalized epilepsy IGE). This means that they are not attributed to as specific cause. It is thought that genetic abnormalities may be the most important factor contributing to IGE. Because of the problem of separating genetic from environmental or acquired influences, the role of genetics in the cause of epilepst has been difficult to determine.

Hockenberry, M.J. & Wilson, D. (2011). Wong's nursing care of infants and children (9th ed). St. Louis: C. V. Mosby. (Wong-9th) pages 1652-1653

Lewis, M.S., Dirksen, S., & Heitkemper, M.M. et al. (2014). Medical-surgical nursing: Assessment and management of clinical problems (9th ed.). St. Louis: Mosby. (LDH-9th) page 1420

Epidemiology

What is epidemiology?

According to the National Institute of Health “Epidemiology is a branch of medical science that investigates all the factors that determine the presence or absence of diseases and disorders. Epidemiological research helps us to understand how many people have a disease or disorder, if those numbers are changing, and how the disorder affects our society and our economy”.

http://www.nidcd.nih.gov/health/statistics/Pages/epidemiology.aspx

The incidence of epilepsy looks at the number of new cases of epilepsy in a population over a period of time. It is often given in a ratio such as ‘X’ out of 1,000 persons develop epilepsy each year.

The prevalence of epilepsy looks at the number of people with epilepsy (existing cases) at any given point in time. This includes people with new onset epilepsy as well as those who have had epilepsy for some time. This is often given in a total number such as ‘X’ million’ people, but can also be given as a ratio.

We can use these numbers to show us the number of people affected right now (prevalence) or to show how often people are affected (incidence).

United States:

• At any given time 1.3 to 2.8 million people are living with epilepsy.

• Each year in the United States it is estimated that 150,000 (48 in every 100,000) people will develop epilepsy.

• The incidence of epilepsy is higher in young children, older adults, African Americans, socially disadvantaged youths, and males.  

• 1 in 26 people will develop epilepsy in their lifetime.

http://www.epilepsy.com/learn/epilepsy-statistics

Worldwide:

• World wide around 50 million people have epilepsy.
• In the general population an estimated 40 to 70 per 100,000 people are newly diagnosed with epilepsy yearly. In developing countries, this number is often close to twice as high.
• In developing countries 6 to 10 in 1000 have epilepsy.
• Close to 80% of epilepsy cases worldwide are found in developing regions.

http://www.who.int/mediacentre/factsheets/fs999/en/

What is epilepsy?

Epilepsy is a disorder which is characterized by spontaneous, recurrent, unprovoked seizures. Seizures are sudden surges of electrical activity in the brain caused by complex chemical changes that occur in brain neurons. These uncontrolled electrical discharges of neurons interrupt normal function.  This abnormal electrical activity can be seen as spontaneous, rapid firing of the neurons. This firing can spread to involve adjacent areas, distant areas, or even the whole brain. The factor that causes this abnormal firing is not clear. Epilepsy can affect everyone differently, this is due to a wide range of seizure types. Individuals with epilepsy can experience multiple types of seizures or a single type. Because of this, epilepsy varies from person to person.

Seizures are divided into two major categories: generalized and focal (partial). In generalized seizures, both sides of the brain are affected by sudden surges of electrical activity at the same time. In most cases the patient loses consciousness for a few seconds to several minutes. Generalized seizures can further be categorized as tonic-clonic, myoclonic, atonic, or absent. In focal seizures abnormal electrical discharge is limited to one area of the brain. Symptoms are directly related to the function of the area affected. Focal seizures can be further categorized as simple or complex.

Tonic-clonic seizures (grand mal): the most common type of generalized seizures are also the most dramatic.They are characterized by losing consciousness and falling to the ground if the patient is upright. Individuals often experience convulsions characterized by total body stiffening followed by a rhythmic jerking of the body. After the episode the person is usually confused, tired, and sore. The person will have no memory of the seizure.

Myoclonic seizures: are brief, sudden jerks due to rapid alternating contraction and relaxation of a muscle. Usually they don’t last more than a few seconds. People may experience a single one or many in a short time. Individuals who do not suffer from epilepsy may experience myoclonic seizures. The most identifiable examples are hiccups and the jerk that wakes you up just as you are falling asleep. However in epilepsy, these seizures cause abnormal movements on both sides of the body at the same time.

Atonic seizures (drop attacks): brief seizures that cause an unexpected and rapid drop to the ground. They result from stiffening or sudden loss of muscle tone. They are difficult to treat and have a great risk of injury.

Absence seizures (petit mal): brief and characterized by staring spells without motor movements. People tend to have a look of confusion and seem to be “out of it”. This type is common in children.

Simple partial epileptic seizures: abnormal electrical discharge is confined to a small part of the brain. Symptoms reflect the part of the brain being affected, the can be motor, sensory, autonomic, or psychic. People experience normal awareness of their surroundings.

Complex partial epileptic seizures: are also confined to a particular area of the brain, but have spread enough that individuals experience an impaired level of awareness about their surroundings.

Sources:

http://www.epilepsy.com/

http://www.thebarrow.org/Neurological_Services/Epilepsy/204351

LDH 1419-1421