Chapter 2 Epidemiology and Classification of Epilepsy: Gender Comparisons

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Publisher Summary

Epilepsy is a common disease. Over the past number of decades, a pattern has emerged in relation to gender difference in the epidemiology of epilepsy worldwide. It appears overall that epilepsy is slightly more common in males than in females. The chapter discusses that certain epilepsy syndromes have a greater association with females, and that sometimes the same epilepsy syndrome may behave differently in women than in men. This has implications both for prognosis and for the understanding of seizure pathophysiology. The chapter reviews the classification of epilepsy to explain some methodological principles that are important in interpreting epidemiologic studies of epilepsy. The behavior of some common epilepsy syndromes such as mesial temporal sclerosis may differ between genders with isolated auras more common among females and secondary seizure spread more likely in males. Trends toward gender differences are also seen in other important aspects of epilepsy. These include the incidence of status epilepticus, incidence of sudden unexpected death in epilepsy (SUDEP), prognosis, and mortality.

Introduction

Over the last number of decades, a pattern has emerged in relation to gender difference in the epidemiology of epilepsy worldwide. It appears overall that epilepsy is slightly more common in males than in females. Beyond this, however, it seems that certain epilepsy syndromes have a greater association with females, and that sometimes the same epilepsy syndrome may behave differently in women than in men. This has implications both for prognosis and for our understanding of seizure pathophysiology. Before going into details of these interesting differences, it is important to briefly review the classification of epilepsy, and to explain some methodological principles that are important in interpreting epidemiologic studies of epilepsy.

Section snippets

Classification of Epilepsy and Seizures

Classification of seizures and epilepsy syndromes is an important part of clinical work. Appropriate classification relies on detailed history and a collateral account, neurologic examination, and the interpretation of specialized tests—notably electroencephalography (EEG) and neuroimaging. Accurate classification allows for optimal medical therapy of a seizure disorder and provides important prognostic information for the patient. From an etiological viewpoint, classification and “phenotyping”

Methodology of Epidemiologic Studies in Epilepsy

A number of problems have been described in relation to published epidemiologic studies of epilepsy (Sander and Shorvon, 1987). Broadly, these center around problems of case ascertainment and nonuniformity of case definition. This relates to: the definition of epilepsy itself (often not stated in studies); the inclusion or exclusion of febrile, neonatal, or acute symptomatic seizures; classification of same‐day seizures as single or multiple events; and definition and inclusion of “active

Incidence of Epilepsy

Incidence studies are especially useful in epilepsy epidemiology because they give information on etiology and prognosis of epilepsy and seizures. They are methodologically demanding however, and are ideally planned prospectively or are derived from rigorously maintained population‐based records such as the database of the Rochester epidemiologic project in Minnesota.

The estimated median incidence of epilepsy is 43.4/100,000 among industrialized countries and 68.7/100,000 in the developing

Summary

In summary, epilepsy is overall slightly more common in males than in females, largely relating to males' greater risk exposure to causes of lesional epilepsy. Mortality is also increased for males than females, although SUDEP appears to have an equal gender incidence. IGEs are more common in females.

Glossary

Given the stated importance of accurate and consistent terminology within epidemiological studies a glossary of terms is included here, which comprises selected clinical and epidemiological concepts referred to within this chapter. The definitions are reproduced from the 1997 report of the ILAE commission on epidemiology and prognosis in epilepsy. Terms that have been clearly defined in the main text are omitted.

Status epilepticus
A single epileptic seizure >30 min in duration or a series of

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