Abnormal paroxysmal neuronal discharge in the brain causing abnormal function. Isolated seizures are distinguished from the diagnosis of epilepsy. Epilepsy is a chronic disorder characterized by an abnormal tendency for recurrent, unprovoked seizures that are usually stereotypic. Approximately 3% of the population has epilepsy. Typically, provoked seizures result from treatable conditions, such as sleep deprivation, toxic exposure to stimulants, withdrawal from narcotics, barbiturates, or alcohol, fever, infection, metabolic disturbances, or SLE.
The approach to the evaluation of patients with a new-onset spell that may be a seizure, and the classification of seizures regardless of whether they are isolated seizures or part of a seizure disorder (e.g., epilepsy), are the same. The approach to treatment, however, is usually different. Although anticonvulsants are effective in controlling seizures acutely whether provoked or not, continuous prophylaxis is principally reserved for patients with epilepsy.
Seizures may occur with or without the loss of consciousness. Seizures are divided into partial and generalized. Partial seizures have clinical or electroencephalography evidence of a focal onset; the abnormal discharge usually arises in a portion of one hemisphere and may spread to the rest of the brain during a seizure. Primary generalized seizures have no interictal evidence of focal onset on electroencephalogram (EEG). A generalized seizure can be primary or secondary.
a. Primary generalized seizures (bilaterally symmetric and without local onset).
i. Tonic clonic (grand mal) or tonic or clonic.
ii. Atonic or astatic seizures.
iii. Absence seizures (petit mal).
Typical absences consist of abrupt onset and cessation of impairment of consciousness, with or without automatism, myoclonic jerks, tonic or autonomic components. A 3-Hz spike and wave discharge is usual EEG abnormality. Atypical absences have less abrupt onset and/or cessation of impaired consciousness and are more prolonged in tone with EEG abnormalities other than 3-Hz spike and wave discharge.
iv. Myoclonic seizures.
b. Partial or focal seizures (seizures beginning locally) (also referred to as Jacksonian, temporal lobe, or psychomotor seizure, according to type).
i. Simple, without impairment of consciousness. Depending on anatomic site of origin of seizure discharge, initial symptom may be motor, sensory, aphasic, cognitive, affective, dysmnesic, illusional, olfactory, or psychological..
ii. Complex, with partial impairment of consciousness, which may be simple at onset, followed by alteration or impairment of consciousness. Symptoms same as in i.
iii. Simple or complex may evolve to secondary generalized tonic/clonic seizures. Sometimes secondary generalization is so rapid that there is no clinical evidence of partial onset, only electroencephalographic.
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