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FOUNDATION OVERVIEW

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Epilepsy is a chronic disease of disturbed electrical activity in the brain, resulting in recurrent seizures with or without convulsions. Epilepsy is a disorder with profound impact on lifestyle, and patients are often dependent upon caregivers to assist with medications and transportation. All states impose limitations on driving for individuals who have recently had a seizure with impaired consciousness.

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The pathophysiology of a seizure is due to an unstable cell membrane in the gray matter of the brain. The cause of the unstable cell membrane has been linked to three causes: an abnormality in potassium conductance, an abnormality in voltage-sensitive ion channels, or a deficiency in membrane ATPases linked to ion transport. Excitatory neurotransmitters (glutamate, aspartate, acetylcholine, norepinephrine) enhance the propagation of seizures while inhibitory neurotransmitters (GABA, dopamine) decrease the propagation of seizure activity in the brain. The spread can be local (partial seizure) or throughout the entire brain (generalized seizure). The different types of epilepsies are due to the different pathophysiologic abnormalities.

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Epilepsy is classified by the seizure presentation (Table 51-1). The classification system is based on how the seizure begins; therefore, obtaining an adequate description from a third party is important. The classifications of epilepsy are:

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Table Graphic Jump Location
TABLE 51-1Classification and Management of Seizure Disorders
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  • Absence seizures (petit mal)—sudden interruption of activities and a blank stare.

  • Myoclonic seizures—brief shock-like contraction of a muscle group.

  • Clonic seizures—jerking motion while tonic seizures involve a sustained muscle contraction.

  • Tonic-clonic seizures (grand mal)—alternating muscle contraction and jerking.

  • Atonic seizures involve a sudden loss of muscle tone known as drop attacks.

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Epilepsy syndromes are another classification system of epilepsies based on seizure type and etiology. The syndrome approach provides a tool to aid clinical management and provide prognosis.

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  • Idiopathic epilepsy—no underlying etiology and is presumed genetic.

  • Symptomatic epilepsy—an underlying cause which is usually brain damage.

  • Cryptogenic epilepsy—presumed to have an underlying etiology that cannot be identified.

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Epilepsy is a clinical diagnosis made when the patient has recurrent seizures. An isolated seizure does not justify the diagnosis of epilepsy. Laboratory tests are evaluated to rule out treatable causes of seizures such as hypoglycemia, altered electrolytes, and infections. A seizure produced by treatable causes does not represent epilepsy. Electroencephalogram (EEG) can be useful to confirm a seizure and identify seizure types based on the spike and wave pattern generated; however, the EEG may be normal in some patients.

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The underlying etiology of epilepsy is unknown in 80% of patients. The ...

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