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Focal Onset

Aware | Impaired

Awareness

Motor Onset

automatisms

atonic

clonic

epileptic spasms

hyperkinetic

myoclonic

tonic

Nonmotor Onset

autonomic

behavior arrest

cognitive

emotional

sensory

Focal to bilateral

tonic‐clonic

Generalized Onset Motor

tonic‐clonic

clonic

myoclonic

myoclonic‐tonic‐clonic

myoclonic‐atonic

atonic

epileptic spasms

Nonmotor (absence)

typical

atypical

myoclonic

eyelid myoclonia

Unknown Onset Motor

tonic‐clonic

epileptic spasms

Nonmotor

behavior arrest

A fundamental distinction is whether the seizure is of focal onset or generalized onset. This distinction may be important clinically because focal onset seizures may imply focal or structural CNS abnormalities and because different medications are effective in different seizure types. In focal onset seizures, clinical information indicates that seizure onset is limited to one part of the brain. Focal seizures may be further divided into seizures with awareness preserved and seizures with impaired awareness. In aware focal onset seizures, the patient remains at normal consciousness. Focal seizures with sensory symptoms include some patients with episodic paresthesias. Special sensory symptoms with focal seizures may have gustatory, olfactory, or auditory symptoms. The recent classification system uses the term seizures with impaired awareness in place of complex partial seizures. Symptoms of these patients often include altered mental status with confusion and simple repetitive motor movements such as lip smacking or picking at clothes. Sometimes, prolonged confusional states occur from seizures with impaired awareness, one of the types of nonconvulsive status epilepticus [18].

Generalized onset seizures imply that the cerebral cortex is bilaterally involved at seizure onset. This often requires EEG evaluation for definitive diagnosis. However, some seizure types are typical enough in appearance that they can be classified by observation alone. Focal‐onset seizures with secondary generalization are the most common type of generalized seizure in adults. An example of a focal onset seizure with secondary generalization would be a patient with onset of finger twitching, progression of movements to the arm and face, and then a subsequent generalized convulsive seizure. Unfortunately, often this secondary generalization occurs too rapidly to be appreciated by witnesses or in the field.

A few words concerning terminology are in order. Convulsion refers to the motor movements associated with a seizure. Tonic refers to the stiffening of the extremities seen in convulsions. Clonic is the rhythmic, synchronized movements of the extremities. Some patients experience an aura, which is the initial subjective perception of a seizure. Grand mal is generally used in a manner to be synonymous with a generalized convulsion. Petit mal, however, is so frequently misused by patients and physicians that perhaps that term is best not used. Correctly used, it is synonymous with absence seizures, a generalized onset seizure that has a characteristic EEG three‐cycle‐per‐second pattern. In common usage, however, petit mal is corrupted by association with the word petite, meaning “small,” so that fragments of seizures or partial seizures are incorrectly labeled petit mal seizures.