Overview of motor neuron disease: classification and nomenclature

Amyotrophic lateral sclerosis (ALS), although a disease that has been well recognized for nearly 150 years, still causes problems of diagnosis and management, as there is no definitive diagnostic test, and the disease is pleomorphic. Research criteria were developed for the categorization of definite, probable, and possible ALS at the El Escorial Workshop (published in 1994). The principal features are upper and lower motor neuron signs at several levels of the neuraxis, without involvement of other neurological systems. Separation of ALS or motor neuron disease (MND) from the spinal muscular atrophies or hereditary spastic paraplegia can be difficult. The relatively rapid progression to death in an average of 5 years is one of the hallmarks of ALS. However, some cases are relatively more benign. The recent finding that mutations of the SOD1 gene underlie about 20% of familial cases of ALS has allowed the recognition that all phenotypes can occur in different members of the same family with the same mutation, clarifying earlier suggestions that different phenotypes represent different diseases. Until the cause and cure of ALS are found, neurologists and rehabilitation specialists must continue to provide essential support for patients with this devastating disease.