Motor neuron diseases

A motor neuron disease (MND) is any of several neurological disorders that selectively affect motor neurons, the cells that control voluntary muscles of the body. They include amyotrophic lateral sclerosis (ALS), hereditary spastic paraplegia (HSP), primary lateral sclerosis (PLS), progressive muscular atrophy (PMA), progressive bulbar palsy (PBP) and pseudobulbar palsy. Spinal muscular atrophies (SMA) are sometimes included in the group by some neurologists but it is different disease with clear genetic cause.^[2]^[3] They are neurodegenerative in nature and cause increasing disability and eventually, death.^[4]

Terminology

In the United Kingdom, the term is also spelled motor neurone disease (MND).^[5]

While MND refers to a specific subset of similar diseases, there are numerous other diseases of motor neurons that are referred to collectively as "motor neuron disorders", for instance disease belonging to spinal muscular atrophies.^[4] However, they are not classified as "motor neuron diseases" by the tenth International Statistical Classification of Diseases and Related Health Problems (ICD-10), which is the definition followed in this article.

Motor neuron diseases affect either upper motor neurons (UMN) or lower motor neurons (LMN), or both:

Type	UMN degeneration	LMN degeneration
Amyotrophic lateral sclerosis (ALS)	Yes	Yes
Hereditary spastic paraplegia (HSP)	Yes^[6]	No^[6]
Primary lateral sclerosis (PLS)	Yes	No
Progressive muscular atrophy (PMA)	No	Yes
Progressive bulbar palsy (PBP)	No	Yes, bulbar region
Pseudobulbar palsy	Yes, bulbar region	No

^ Neilson, Stuart; Rose, Frank Clifford. Motor Neurone Disease: The 'at Your Fingertips' Guide. Class Publishing Ltd. p. 2. ISBN 9781859590478. Retrieved 4 August 2016.
^ "Motor Neuron Diseases Fact Sheet: National Institute of Neurological Disorders and Stroke (NINDS)". www.ninds.nih.gov. Archived from the original on 13 April 2014. Retrieved 7 November 2010.
^ Kimura, Jun (2013). Electrodiagnosis in Diseases of Nerve and Muscle: Principles and Practice. Oxford University Press. p. 599. ISBN 9780199969296.
^ ^a ^b Ellison, edited by Seth Love, David N. Louis, David W. (2008). Greenfield's neuropathology (8th ed.). London: Hodder Arnold. p. 947. ISBN 9780340906811. {{cite book}}: |first1= has generic name (help)CS1 maint: multiple names: authors list (link)
^ "Different types of MND". motor neurone disease association. Retrieved 4 August 2016.
^ ^a ^b "A Look at Upper Motor Neuron Diseases Hereditary Spastic Paraparesis and Primary Lateral Sclerosis" (PDF). sp-foundation.org. Archived from the original (PDF) on 25 March 2017. Retrieved 25 March 2017. {{cite web}}: Cite has empty unknown parameter: |dead-url= (help)