Return to Seizure Home Page

M. Kutscher, MD © 2004, 2006

    Get the complete book from Amazon or bookstores

Faced with a sudden neurological event, your doctors must first decide whether or not the event is a seizure. There is a  large and varied differential diagnoses that must be considered. Once the event has been determined to be a seizure, it must be classified to help determine appropriate work up, prognosis, and treatment.

Epidemiology and Classification

 Two different schemes are utilized in the classification of epileptiform events: classification by type of seizure and classification by epilepsy syndrome. The term "seizure" refers to the specific neurological event, such as an absence seizure or a tonic-clonic seizure. The term "epilepsy syndrome" refers to a full syndrome consisting of the type(s) of seizures seen in that syndrome, EEG findings, typical age of patient, typical prognosis, etc. For example, "absence seizure" refers to the specific event of staring for several seconds; whereas "petit mal epilepsy" refers to a syndrome of young, neurologically normal children whose EEG shows 3/second spike-wave discharges and who are likely to outgrow their seizures.

The seizures and their corresponding epilepsy syndromes are divided into two broad categories: generalized and partial. By definition, generalized seizures are those that start simultaneously from both hemispheres. Partial seizures start from one hemisphere. The epilepsy syndromes are similarly divided into the generalized and partial epilepsies. The classification of seizures and the major childhood epilepsies are summarized in Table 1.

Table 1:  Seizure/Epilepsy Classification

Partial (start in part of one hemisphere of the brain)

This distinction between generalized and partial seizures is important for several reasons; and affects the history, work up, and treatment of a child with seizures. During the history, we must ask if the seizure has any signatures of a focal onset: Did the seizure start or affect one part of the body more than the others? Was there an aura? The latter question is important since a well defined aura means that the seizure began focally. This is because the "aura" of a seizure is actually just its focal onset. During an aura, the rest of the brain is "watching" that part of the brain have its seizure. In contrast, a generalized seizure does not have a well defined aura. This is because consciousness requires one working cerebral hemisphere and a brainstem. A generalized seizure, though, affects the entire brain at its onset, and thus usually leaves "no one there" to be aware of the spell.

Determination of an aura, then, is extremely useful. We should remember to ask both the observer and the child about the specific onset of the seizure. Young children may be unable to verbalize an aura, and may just start acting unusually or run to their parent. Also, the aura or focal onset of a seizure may be so brief that it may not be noticed before there is secondary generalization of the seizure. Thus, a focal seizure does not necessarily have an identifiable aura.

Since focal seizures are more likely to have underlying focal structural abnormalities, classification of focal vs. generalized seizures may affect the child’s work up. In addition, different anticonvulsants are chosen on the basis of the type of epilepsy classification.

The Generalized Seizures

Absence seizures

Typical absence seizures are very "clean" seizures. Like all generalized seizures, there is no aura. They consist of brief (3-30 second) staring spells, accompanied by a cessation of activity. Sometimes, there is some eye fluttering, mild lip movements, or twitches. There is no post-ictal state after a typical absence seizure.

Tonic-Clonic seizures

"Tonic" refers to continuous stiffening of the extremities. "Clonic" refers to the rhythmic alternating contraction and relaxation of the muscles. A "tonic-clonic" seizure is one which starts with continuous tonic stiffening and is then followed by a clonic phase of rhythmic jerks. Note that partial seizures may have such rapid secondary generalization that they may be clinically indistinguishable from true primary generalized tonic-clonic seizures.

Minor Motor seizures

There are two basic types of "minor motor" seizures. Myoclonic seizures are brief jerks, often occurring in irregular flurries. Atonic (a.k.a. akinetic) seizures a drop attacks. They are so brief that consciousness has been regained by the time the child hits the floor.

The Partial Seizures

Partial seizures are classified into three types: simple partial, complex partial, and partial seizures with secondary generalization. Simple and complex partial seizures are, in effect, one big aura.

Simple partial seizures

Simple partial seizures begin focally in one hemisphere and do not impair the level of consciousness. They may consist of virtually any task of which the brain is capable, such as jerking of just one extremity, abnormal sensation of one part of the body, a feeling of deja-vu etc.

Complex partial seizures

Complex partial seizures (previously called "psychomotor seizures" or "temporal lobe epilepsy") begin focally in one hemisphere and do impair the level of consciousness. There is usually a well defined aura followed by confusion which is accompanied by lip smacking, fumbling, or eye fluttering. Unlike absence seizures, these spells tend to last several minutes and are accompanied by an aura and post-ictal states.

Partial seizures with secondary generalization

Although the secondary generalization may be the most striking feature to the family, it is the partial onset of these seizures that matter most to the clinician. A "Jacksonian march" is the label given to a seizure which spreads along the cortex with resultant spread of the clinical seizure along one hemisphere. The children may be aware of this focal spread along one side of their body, and then loose consciousness as the seizure spreads to the other hemisphere during secondary generalization.

Disclaimer: This web site is presented as a resource to patients by Pediatric Neurological Associates. There are no commercial sponsors.  This information does not constitute medical advice; nor is it a substitute for discussion between patients and their doctors.  The views of cited references do not necessarily represent  the views of our staff.  This information was last modified 06/10/06.

Return to Seizure Home Page

   Order the complete book from Amazon or your local bookstore

since 6/02