Role of ILAE in classification
The International League Against Epilepsy (ILAE) is a key organization leading the global fight against epilepsy since 1909. ILAE experts develop the unified terminology and recommended classifications used by physicians worldwide. Official cooperation between the League and the World Health Organization (WHO) began in 1971.
The chronology of taxonomy development includes several important milestones. The very first version was approved in 1969 in New York. Subsequent revisions took place, with the last mentioned one occurring in 1989 in New Delhi. Notably, the fundamental principles embedded in ICD-10 fully coincide with ILAE approaches.
The categorization is based on two strict criteria:
- Type of paroxysms. It is assessed whether the seizure is generalized (involving both hemispheres) or focal (with a localized onset).
- Nature of seizures. The origin is determined: idiopathic (without an established structural cause) or symptomatic (resulting from another brain lesion).
ICD-10 diagnosis structure (G40–G41)
According to the International Classification of Diseases, Tenth Revision, epilepsy and status epilepticus are coded in the range from G40 to G41. The categorization is structured logically and relies on ILAE principles:
- G40.0 — Focal idiopathic epilepsy with convulsive seizures. A typical example is childhood epilepsy, where the focus is localized in the occipital or temporal region.
- G40.1 — Focal symptomatic epilepsy. In this form, seizures occur without loss of consciousness, or secondary generalized seizures are observed.
- G40.2 — Focal symptomatic epilepsy, accompanied by twilight consciousness.
- G40.3 — Generalized idiopathic epilepsy. This includes myoclonic epilepsy, pyknolepsy, familial neonatal seizures, and primary generalized grand mal seizures.
- G40.4 — Other generalized epilepsy syndromes. This group includes salaam tic as well as severe forms: West syndrome and Lennox-Gastaut syndrome.
- G40.5 — Special epileptic syndromes. This category includes Kozhevnikov's epilepsy, as well as seizures triggered by external factors: alcohol intake, medications, sleep deprivation, major psychological trauma, or endocrinopathy.
- G40.6 — Unspecified grand mal seizures. May occur in combination with petit mal paroxysms.
- G40.7 — Unspecified petit mal seizures (strictly without grand mal).
- G40.8 — Seizures that, by their characteristics, cannot be classified as either focal or generalized.
- G40.9 — Epilepsy, unspecified.
- G41 — Status epilepticus.
Epidemiology and clinical course
The overall prevalence of epilepsy in the population ranges from 0.3% to 0.7%. The disease exhibits distinct age-specific patterns: the highest risk of development is observed in childhood and adolescence, when about 75% of all initial seizures debut.
The epidemiological curve of the disease is described by two key curves:
- Curve "B" (incidence / newly diagnosed cases): Has a bimodal (U-shaped) character. The maximum peak of manifestation occurs in the first year of a child's life. Then incidence gradually decreases, reaching a plateau in middle age (from 15 to 40 years). After this period (especially in the range of 40–75 years and older), there is a sharp and significant increase in the number of new cases in elderly and senile age.
- Curve "K" (cumulative prevalence / cumulative frequency): This curve demonstrates a continuous exponential growth throughout the patient's life. The cumulative frequency reaches its maximum value by age 75.
Briefly: answers to topical questions
What are the main differences between grand mal and petit mal seizures?
The main difference between grand mal and petit mal seizures lies in the presence or absence of a convulsive component, while both variants are classified as generalized seizures.
| Sign | grand mal | petit mal |
|---|---|---|
| Definition | Major convulsive seizure | Minor seizure (typical absence) |
| Clinical presentation | Sequential onset of tonic and clonic seizures | Non-convulsive paroxysm |
Both types of paroxysms begin without an apparent cause and are immediately accompanied by loss of consciousness.
To quickly recall ILAE criteria, answer two questions: "Where did it start?" (focal or generalized) and "What is the cause?" (symptomatic or idiopathic).
Class and exam questions
At what age does epilepsy most commonly begin?
In 75% of cases, the first seizure occurs in childhood or adolescence. The incidence curve is U-shaped with peaks in the first year of life and after 40–75 years.
What is the difference between categories G40.1 and G40.2?
In G40.1, focal symptomatic seizures occur without loss of consciousness, whereas in G40.2 they are invariably accompanied by twilight consciousness.
What falls under special epileptic syndromes (G40.5)?
This includes Kozhevnikov's epilepsy and seizures associated with sleep deprivation, alcohol intake, medications, endocrinopathy, or severe psychological trauma.
What else to study on this topic
- Clinical picture of primary generalized grand mal seizures
- Features of impaired consciousness in focal symptomatic epilepsy
- Pathogenesis and diagnosis of West and Lennox-Gastaut syndromes
- Triggering factors in special epileptic syndromes
- Criteria for diagnosing "status epilepticus" (G41)
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Other topics in "Chapter 20. Epilepsy"
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