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Epilepsy- Definition, history, incidence, etiology, precipitating factors, pathophysiology

Seizures

Time-limited paroxysmal events that result from abnormal, involuntary, rhythmic neuronal discharges in the brain

Seizures are usually unpredictable

Seizures usually brief ( < 5 minutes) and stop spontaneously

Convulsion, , event, spell, attack and fit are used to refer to seizures

Definition of Epilepsy

A disease characterized by spontaneous recurrence of unprovoked seizures (at least 2)

Seizures are symptoms, while epilepsy is a disease, so those terms should not be used interchangeably

Epilepsy = “seizure disorder”

Epilepsy is a Syndromic disease

Each epilepsy syndrome is determined based on;

type of seizures, age at seizure onset, family history, physical exam, EEG findings, and neuroimaging

Brief History of epilepsy

The Babylonian view as the forerunners of the Greek concept of “the sacred disease”as described in famous treaties by Hippocrates. The term “seleniazetai ” was used to describe people with epilepsy, who were viewed with fear, suspicion and misunderstanding and were subjected to social stigma

Psychiatry concept of epilepsy was developed as a brain disorder .A hospital for ”paralized and epileptic “was established in London in 1857. Humanitarian approach to epilepsy was started .The foundation of all modern understanding of dearrangement of epilepsy was also laid in 19th century with work of HIRLINGS JACKSON. In 1873 this London neurologist proposed that seizures were the result of sudden brief electrochemical discharges of the brain. In 1928 HANS BERGER developed EEG ,which helped to locate the different sites of seizure discharge. During 1st half of the century main drug of treatment were phenobarbitones. Since 1960 there has been an accelerating process of drug discovery .

In world out of 50 million people of epilepsy only 35 million have assess to appropriate treatment ,this is either because non existent of services or epilepsy is not viewed as a medical problem or a treatable brain disorder .

In 1997 international league against epilepsy ILAE and international bureau for epilepsy joined with WHO to establish global campaign against epilepsy.

Incidence of epilepsy

Prevalence of epilepsy varies from 2.5 to 11.9 per 1000 population in different parts of India.India is the home to 10 million epileptics, accounting for one to fifth of global burden.

The incidence rates are high during the first year of life, declining through childhood and adolescence, pleatue in middle age and rise sharply among the elderly. The population with the highest prevalence of new-onset epilepsy is those over the age of 60.

Etiology of Epilepsy

Any process that alters the structure (macroscopic or microscopic) or the function of the brain neurons can cause epilepsy

Processes that lead to structural alteration include

  • Congenital malformation
  • Degenerative disease
  • Infectious disease
  • Trauma
  • Tumor
  • Vascular process

In majority of patients, the etiology is proposed but not found

Precipitating factors of epilepsy

  • Particular odor
  • Flashing lights
  • Certain types of music. If specific stimulus is identified then the pattern is known as reflex epilepsy.
  • General triggers
  • Fatigue
  • Sleep deprivation
  • Hypoglycemia
  • Emotional stress
  • Electrical shock
  • Febrile illness
  • alcohol consumption
  • Certain drugs
  • Constipation
  • Menstruation
  • hyperventilation

Pathophysiology of epilepsy

Ropper and Brown note that seizures require three conditions

  1. A population of pathologically excitable neurons
  2. an increase in excitatory glutaminergic activity through recurrent connections to spread the discharge
  3. a reduction in the activity of the normal inhibitory GABA projection(gamms aminobutyric acid)

The Pathophysiology of recurring seizures has long been attributed to a group of abnormal neurons (seizure focus) that seems to undergo spontaneous firing. This firing spread by physiologic pathways to involve adjacent or distant areas of the brain. If this activity spreads to involve the whole brain, a generalized seizure occurs. The factor that causes this abnormal firing is not clear. Any stimulus that causes the cell membrane of the neuron to depolarize induces a tendency to spontaneous firing. Often the area of the brain from which the epileptic activity arises is found to have scar tissue (gliosis) the scarring is thought to interfere with the chemical and structural environment of the of the brain neurons, making them more likely to fire abnormally.

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