Epilepsy Classification

By Dr Ananya Mandal, MD

Seizures are divided into two main types - generalised and partial. This is based on the International classification of epileptic seizures proposed by the Commission on Classification and Terminology of the International League against Epilepsy (ILAE) and approved in September 1981. This is based on the clinical features of the epilepsy as well as the EEG features.

Partial seizures

In partial seizures the abnormal electrical discharges start in a localized area of the brain. The symptoms depend on the part of the brain that is affected. These discharges may remain localized. In this case the case is of partial seizures.

If the impulses spread to the whole of the brain seizures become generalized. This is called secondary generalized seizures.

There may be presence of an aura before the seizure. A definite aura is an indication that the seizure is of focal (partial) onset. An aura comes few seconds to minutes before a seizure. There may be a variety of symptoms in the aura including intense fear, butterflies in the stomach, dreamlike experiences, unpleasant smells etc.

The partial seizures are further classified into two types and a third type that is a combination of the two:

Simple partial seizures

In this the patient does not lose consciousness. He or she is able to recount the episode of the seizure. If the motor areas of the brain are affected there may be twitching, starting in a limb or fingers/toes or the face. The twitching may remain there, or spread up the whole limb or become generalized to the whole body. The spreading is called a Jacksonian march (named after Huglings Jackson 1835 - 1911). There may be feelings of numbness, pins and needles or heat/ cold at the limb.

Complex partial seizures

Here the patient loses consciousness. There may not be a complete loss of consciousness, however, and the patient may be slightly aware of the surroundings. There is an aura. Sometimes the seizure occurs with hallucinations and automatic movements like picking at clothes, smacking lips etc. There is a slow recovery after a complex partial seizure, with a period of confusion.

Partial seizures secondary generalized

Both the simple partial seizures and the complex partial seizures may become generalized seizures.

Generalized seizures

The seizure here is generalized from the onset. The impulses start from both sides of the brain simultaneously. The primary generalized seizures are typified by loss of consciousness and the absence of an aura. They may come on abruptly and unexpectedly, and may make the patients fall.

There are six different types of generalized seizures:-

Primary generalized tonic-clonic seizure (GTCS)

This is the most common type of generalized epilepsy. The whole body stiffens (tonic phase) and the person loses consciousness and falls. This is followed by a violent uncontrollable shaking (clonic phase). With this jerking the patient might bite his tongue, pass urine, or sometimes stool. The clonic phase may last several minutes. After the clonic phase consciousness is regained.

Absence seizures

These are short periods of loss of consciousness lasting only a few seconds. They are of sudden onset. Absence seizures are commonly seen in children. There may be a blank stare, brief upward rotation of the eyes and freezing of the individual. The child has no memory of these seizures after they have passed. Earlier these seizures were called petit mal seizures, or pyknolepsy (because they occurred so frequently). The term “petit mal” (little illness) is no longer used.

Myoclonic seizures

This leads to sudden, brief seizures with shock-like muscle contractions leading to jerky movements. They may be single jerks, or jerks repeated over longer periods.

Clonic seizures

These seizures do not have the tonic phase (phase of stiffening of the muscles). There repetitive clonic jerks or uncontrollable shakings. When the frequency diminishes the amplitude of the jerks remain the same.

Tonic seizures

These are generalized seizures with only the tonic phase or stiffening of the muscles. The limbs are fixed in a strange position. There is immediate loss of consciousness. The eyes may deviate to one side of the head. The body may also be twisted.

Atonic seizures (astatic seizures)

In this type of seizure there is sudden loss of muscle tone causing the head or a limb to drop and the patient falls as a heap on the floor. These are also thus called “drop attacks”. There is loss of consciousness, a sudden onset of seizures.

Unclassified types of epileptic seizure

There are several unclassified types of epileptic seizures as well.

International classification of epileptic seizures

  • I. PARTIAL SEIZURES (seizures beginning locally)
    • A. Simple partial seizures (consciousness not impaired)
      • 1. With motor symptoms
      • 2. With somatosensory or special sensory symptoms
      • 3. With autonomic symptoms
      • 4. With psychic symptoms
    • B. Complex partial seizures (with impairment of consciousness)
      • 1. Beginning as simple partial seizures and progressing to impairment of consciousness
        • (a) With no other features
        • (b) With features as in A 1–4
        • (c) With automatisms
      • 2. With impairment of consciousness at onset
        • (a) With no other features
        • (b) With features as in A 1–4
        • (c) With automatisms
    • C. Partial seizures secondary generalized
  • II. GENERALIZED SEIZURES (bilaterally symmetrical and without local onset)
    • A. 1. Absence seizures
    • 2. Atypical absence seizures
    • B. Myoclonic seizures
    • C. Clonic seizures
    • D. Tonic seizures
    • E. Tonic-clonic seizures
    • F. Atonic seizures
  • III. UNCLASSIFIED EPILEPTIC SEIZURES (inadequate or incomplete data)

Reviewed by April Cashin-Garbutt, BA Hons (Cantab)

Sources

Further Reading

Last Updated: Jan 1, 2013

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