Current research in neuro-epidemiology. Some main trends.

Recent epidemiological research has contributed to the understanding of the nature of common neurological disorders like multiple sclerosis, Parkinsonism, and amyotrophic lateral sclerosis. Viral etiology constitutes the most probable environmental factor in multiple sclerosis, but host-related genetic factors are also involved and determine susceptibility. In disorders like Parkinsonism, amyotrophic lateral sclerosis, and epilepsy, heredity seems to play a more important role than earlier believed, and segregation analyses indicate polygenic inheritance patterns. The subacute spongiform encephalopathies fit into a similar concept, and here the hunt for infectious agents has succeeded. Polygenic traits and dominantly inherited disorders seem to aggregate in genetic isolates, as shown through studies from different parts of the world. The reason for this is not quite clear, but selection through assortative matings or other mechanisms may be operating in these populations.