Neuroepidemiology of amyotrophic lateral sclerosis: clues to aetiology and pathogenesis.

at La Salpetriere Hospital in Paris, first identified amyotrophic lateral scle- rosis (ALS) from among the heterogeneous group of the spinal muscular atrophies. Between 1872 and 1874, in his Lectures on the diseases of the nervous system (lectures XII and XIII), Charcot masterfully described the clinical and anatomopathological features of the disease that bears his name (Maladie de Charcot).' The growing complexity of this field is reflected in the current classification of the spinal muscular atrophies and other disorders of the motor neurons prepared by the World Federation of Neurology (WFN) Research Group on Neuromuscular Disorders.2 Like- wise, the difficulties in clinically separating cases of ALS from other related forms of the disease for epidemiological studies, for clinical research, and for therapeutic trials, led to the successful meeting in El Escorial, Spain, of a group of experts under the aegis of the WFN to define precise criteria for the clinical, elec- trophysiological, and neuropathological diag- nosis of ALS.3 El Escorial WFN criteria have been recently validated,4 and offer a solid foundation for future epidemiological studies of ALS.