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Chapter 49. Epilepsy

S. Scott Sutton; Holly J. Watson

Epilepsy is a chronic disease of disturbed electrical activity in the brain, resulting in recurrent seizures with or without convulsions. The age-adjusted prevalence of epilepsy is 4 to 7 cases per 1,000 persons, with approximately 125,000 new cases of epilepsy annually. Developing countries have higher rates of epilepsy related to poor health care and prenatal care, increased risk of neurologic trauma, and increased rates of infection.

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.1

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.1

Epilepsy is classified by the seizure presentation (Table 49-1).2-3 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:

TABLE 49-1 International Classification of Epileptic Seizures

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TABLE 49-1 International Classification of Epileptic Seizures

I. Partial seizures (seizures begin locally)
- A. Simple (without impairment of consciousness)
  - 1. With motor symptoms
  - 2. With special sensory or somatosensory symptoms
  - 3. With psychic symptoms
- B. Complex (with impairment of consciousness)
  - 1. Simple partial onset followed by impairment of consciousness, with or without automatisms
  - 2. Impaired consciousness at onset, with or without automatisms
- C. Secondarily generalized (partial onset evolving to generalized tonic-clonic seizures)
II. Generalized seizures (bilaterally symmetrical and without local onset)
- A. Absence
- B. Myoclonic
- C. Clonic
- D. Tonic
- E. Tonic-clonic
- F. Atonic
- G. Infantile spasms
III. Unclassified seizures
IV. Status epilepticus

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."

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.3