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INTRODUCTION

ESSENTIALS OF DIAGNOSIS

  • Occurrence of an aura.

  • Alteration in or impaired consciousness or behavior.

  • Abnormal movement.

  • Interictal trauma or incontinence.

  • Eyewitness account.

  • Presence of fever.

  • Postictal confusion, lethargy, sleepiness, or paralysis.

  • Diagnostic electroencephalogram.

  • Abnormality on neuroimaging.

GENERAL CONSIDERATIONS

Despite an alarming appearance, a single seizure rarely causes injury or permanent sequelae or signals the onset of epilepsy. The lifetime risk for seizure is about 10%, but only 2% of the population develops unprovoked, recurrent seizures (epilepsy). Epilepsy is usually defined as repetitive, often stereotypic seizures, but even a single seizure coupled with a significant abnormality on neuroimaging or a diagnostic electroencephalogram (EEG) can signify epilepsy. Seizure incidence is high in childhood, decreases in midlife, and then peaks in the elderly. The annual number of new seizures during childhood is 50,000–150,000, only 10,000–30,000 of which constitute epileptic seizures. In 2010, active epilepsy afflicted 1% of all adults in the United States and 1.9% of those with family incomes below $35,000. During childhood the incidence of partial seizures is 20 per 100,000; generalized tonic-clonic seizures, 15 per 100,000; and absence seizures, 11 per 100,000.

Only ~30% of children get a medical evaluation after a single seizure. In contradistinction, >80% of children with a second seizure obtain medical assistance. Approximately 50% of adults with epilepsy have seen a neurologist. A recognizable, treatable seizure etiology; a negative family history; a normal physical examination; a lack of head trauma; a normal EEG; and normal neuroimaging indicate a low risk for seizure recurrence. Each year approximately 3% of 6-month-old to 6-year-old children have a febrile seizure, the most common childhood seizure entity. The likelihood of these children developing epilepsy is extremely low even if the febrile seizure recurs.

PATHOGENESIS

A seizure results from an abnormal, transient outburst of involuntary neuronal activity. Anoxic degeneration, focal neuron loss, hippocampal sclerosis (common in temporal lobe epilepsy), and neoplasia are examples of pathologic central nervous system (CNS) changes that can produce seizures. Why a seizure spontaneously erupts is unclear, but abnormal ion flow in damaged neurons initiates the event.

Seizures are either generalized (a simultaneous discharge from the entire cortex) or partial (focal, a discharge from a focal point within the brain). Generalized seizures impair consciousness and, except for some petite mal (absence) spells, cause visible abnormal movement, usually intense muscle contractions termed convulsions. Because generalized convulsions occur most commonly in the absence of a focal defect, the initiating mechanism of a generalized seizure is less well understood than that of a partial seizure initiating from a focal CNS lesion. Partial seizures may either impair consciousness (complex) or not (simple) and can start with almost any neurologic complaint, termed the aura, including abnormal smells, visions, movements, feelings, or behaviors such as nonresponsiveness. Partial seizures can progress to and thus mimic generalized seizures, a fact that sometimes obscures the true nature ...

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