24-03: Epilepsy

GENERAL CONSIDERATIONS

The term “epilepsy” denotes any disorder characterized by recurrent unprovoked seizures. A seizure is a transient disturbance of cerebral function due to an abnormal paroxysmal neuronal discharge in the brain. Epilepsy is relatively common, affecting approximately 0.5% of the population in the United States.

Patients with recurrent seizures provoked by a readily reversible cause, such as withdrawal from alcohol or drugs, hypoglycemia, hyperglycemia, or uremia, are not considered to have epilepsy.

CLASSIFICATION OF EPILEPSY

According to the International League Against Epilepsy classification system, recurrent seizures should be classified first by seizure type, second by epilepsy type, and third, if possible, by epilepsy syndrome. The etiology of recurrent seizures should be sought at each stage of classification (see Etiology of Epilepsy).

A. Seizure Types

The International League Against Epilepsy distinguishes seizures affecting only part of the brain (focal seizures) from those that are generalized.

1. Focal onset seizures

The initial clinical and electroencephalographic manifestations of focal (partial) seizures indicate that only a restricted part of one cerebral hemisphere has been activated. The ictal manifestations depend on the area of the brain involved. Focal seizures are classified by motor or nonmotor onset as well as by whether awareness is impaired.

A. MOTOR VERSUS NONMOTOR ONSET

Seizures with motor onset may be clonic, tonic, atonic, myoclonic, or hyperkinetic, or may manifest as automatisms or epileptic spasms. The most commonly observed focal motor seizures consist of clonic jerking or automatisms. Nonmotor seizures may be manifested by sensory symptoms (eg, paresthesias or tingling, gustatory, olfactory, visual or auditory sensations), behavior arrest, cognitive symptoms (eg, speech arrest, déjà vu, jamais vu), emotional symptoms (eg, fear), or autonomic symptoms or signs (eg, abnormal epigastric sensations, sweating, flushing, pupillary dilation). Focal sensory and motor seizures may spread (or “march”) to different parts of the limb or body depending on their cortical representation and were previously called “simple partial” seizures.

B. AWARE VERSUS IMPAIRED AWARENESS

Awareness is defined as knowledge of self and environment and of events occurring during a seizure. Impaired awareness may be preceded, accompanied, or followed by the various motor and nonmotor symptoms mentioned above. Such seizures were previously called “complex partial” seizures.

C. FOCAL TO BILATERAL TONIC-CLONIC

Focal seizures sometimes involve loss of awareness and evolve to bilateral tonic-clonic seizures, in a process previously called “secondary generalization.”

2. Generalized onset seizures

Generalized seizures are thought to originate in or rapidly ...