The causes of epilepsy: changing concepts of etiology of epilepsy over the past 150 years.

This paper provides a survey of the changing concepts of the etiology of epilepsy from 1860 to 2010, focusing on the first two 50-year periods and outlining more briefly major developments in the past 50 years. Among the concepts reviewed in the first 100 years are: the division between predisposing and exciting causes, idiopathic and genuine epilepsy, organic epilepsy, the concept of "cause" being equivalent to "causal mechanism," Russell Reynolds etiological classification, the neurological taint and theories of degeneration, the self-perpetuating nature of seizures, reflex theories of etiology, autointoxication, heredity and eugenics, epilepsy due to brain disorders, the role of EEG and of hippocampal sclerosis, psychological theories of causation, and the multifactorial view of epilepsy etiology. In the past 50 years, the major advances in studying causation in epilepsy have been: clinical biochemistry, neuroimaging, molecular genetics, studies of mechanisms of epilepsy, better statistical methodologies and classification. A number of general observations can be made: the identification of "cause" is not as simple as it might at first appear; progress in the study of causation has been often erratic and travelled up many cul-de-sacs; theories of causation are heavily influenced by societal influences and fashion, and is also heavily dependent on applied methodologies; the recently explored possibility that the underlying inherited mechanisms of epilepsy are shared with other neuropsychiatric conditions is in effect a reinvention of the concept of the neurological trait, and this has ethical and social implications. Considering and classifying cause in terms of causal mechanism, as was suggested by Hughlings Jackson, is an ultimate goal.