Motor neurone disease is a progressive degenerative disease of motor neurones leading to incapacitating neurological disability and death in over 1000 adults in Britain each year. About 5% of cases are familial; no specific treatment exists. The average length of survival from the onset of symptoms is only three years.

A recently reported controlled trial of riluzole, which inhibits release of glutamate,1 in the treatment of motor neurone disease (known as amyotrophic lateral sclerosis in the United States) raised patients' hopes. It concluded that riluzole slightly slowed the fall in muscle strength and increased survival at one year in a small subgroup of patients.2 Unfortunately, the overall results are not convincing of a significant benefit on a number of statistical and methodological grounds, and the findings of a larger, international trial are awaited.

The precise cause of motor neurone disease remains unknown. Excitotoxicity, oxidative stress, growth factors, and immunological abnormalities have all been included in pathogenetic theories, and current therapeutic trials are based on these concepts. The excitotoxic theory proposes that excess excitatory neurotransmitters, especially glutamate, …