Research progress in motor neuron diseases.

The cause of amyotrophic lateral sclerosis is not known. However, there is increasing evidence that the syndrome has more than one cause. Many of the different categories of causation are dealt with in the papers presented in this symposium - including genetic and acquired forms, and multiple categories within those two major classes. The diversity of different causes gives hope that progress in one field will be followed by elucidation of other fields. As examples, there has been progress in understanding the genetic forms due to hexosaminidase deficiency and molecular genetics is being applied to other heritable motor neuron diseases. Among acquired diseases, in different parts of the world, there has been new evidence that persistent viral infection may be important, that dietary constituents may be important, and that paraproteinemia may be important.