What Causes Epilepsy?

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What Causes Epilepsy? From GABA to Zinc Epilepsy is "a diverse collection of disorders" (1). In the United States, there are close to one million people with epilepsy-- about 1 in 200 people around the world have epilepsy(3). This is a review of the emerging insights into the mechanisms underlying the most common form of epilepsy, complex partial epilepsy(1). Terminology and Classification of Epileptic Seizures The term seizure refers to a transient alteration of behavior due to abnormal synchronized and repetitive bursts of firing of neurons in the central nervous system. Epilepsy is syndrome of episodic brain dysfunction characterized by recurrent unpredictable spontaneous seizures. Partial seizures begin in a localized brain region, whereas generalized seizures show widespread involvement of both hemispheres. Examples of generalized seizures are absences (petit mal), myoclonic, or tonic-clonic (grand mal) seizures. A complex partial seizure is associated with impairment of consciousness while a simple partial seizure is not. Most complex partial seizures originate from the temporal lobe and are also called temporal lobe seizures. Epileptics frequently have more than one type of seizure. When simple partial seizure precedes a complex partial seizure, it is referred to as an aura. More recent classifications of epileptic syndromes incorporate such features as etiology, age of onset, and the different combinations of seizures that an epileptic has. Other commonly used terms include ictal (of seizure itself) and interictal (between seizures). Convulsion implies ictal behavior with vigorous motor activities. Status epilepticus denotes a very prolonged seizure or series of seizures occurring so frequently that full recovery of brain function does not occur interictally (1). Complex partial seizures constitute a major percentage of epilepsies and as a result of impaired consciousness are rather disabling. They are often medically intractable in that the administration of medication will not control the seizures. Most cases of complex partial epilepsy appear to stem from an abnormality in the temporal lobe, since partial resection of the temporal lobe, including the mesial structures, hippocampus, and amygdala, virtually eliminates seizures in more than 80% of selected patients. Examination of tissues of the surgical specimens and autopsy studies of patients with chronic temporal lobe epilepsy most often reveal sclerosis of the hippocampus, termed Ammons horn sclerosis, which is characterized by a marked loss of the principal neurons of hippocampus (1). Jackson and his Early Theory on Epilepsy and Brain Organization In the 1800s, it was noted by Jackson that epileptic seizures begin in isolated parts of the body such as the thumb and from there spread to neighboring regions perhaps the arm and then to the rest of the body.

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