The inherited epilepsies.

Our knowledge regarding the genetic bases of the human epilepsies is in a state of rapid flux. For some forms of epilepsy, epidemiologists are still trying to determine whether there is any familial (hereditary) predisposition. Other forms of epilepsy are known to run in families, but the mode of inheritance and degree of penetrance of the trait are still in doubt. Three forms of epilepsy have been tentatively localized to specific chromosomes, and several others are being analyzed with linkage analyses. In no case, has the gene responsible for any human epilepsy been isolated or characterized and we are not yet close to understanding how any specific genetically controlled biochemical or physiological parameter is responsible for the development of an epilepsy syndrome or of any specific epileptogenic increase in brain excitability. However, an extensive animal literature indicates that the mechanisms will be complex as a common phenotype can be the expression of multiple genes, and a single gene can be associated with several phenotypes (Buchhalter, 1993).