Motor neuron disease

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This article is about a group of diseases that affect the motor neurons. For the most common form of the disease, sometimes known as "motor neurone disease" (MND) in the UK, see Amyotrophic lateral sclerosis.
Motor neuron disease
Classification and external resources
Polio spinal diagram.PNG
spinal diagram
ICD-10 G12.2
ICD-9 335.2
DiseasesDB 8358
MeSH D016472

The motor neuron diseases (MND) are a group of neurological disorders that selectively affect motor neurons, the cells that control voluntary muscle activity including speaking, walking, swallowing, and general movement of the body. They are generally progressive in nature, and cause increasing disability and, eventually, death.


Terms used to describe the motor neuron diseases can be confusing. In the United Kingdom, motor neuron disease (sometimes spelled motor neurone disease) refers both to the group of motor neuron diseases which includes amyotrophic lateral sclerosis (ALS) and to ALS itself as motor neuron disease - this is simply because ALS is the most common form. The other four motor neuron diseases are primary lateral sclerosis, progressive muscular atrophy, progressive bulbar palsy and pseudobulbar palsy. In the United States, amyotrophic lateral sclerosis (ALS) is commonly used both for the specific disorder (sometimes referred to there as Lou Gehrig's disease) and as a umbrella term for the group of MNDs.[1] To avoid confusion, the annual scientific research conference dedicated to the study of MND is called the "International ALS/MND Symposium".

Although MND refers to a specific subset of pathologically similar diseases, there are numerous other afflictions of motor neurons that are pathologically distinct from MND, have a different clinical course and should not be confused with MND, such as spinal muscular atrophy, spinobulbar muscular atrophy, Charcot–Marie–Tooth disease, Guillain–Barré syndrome, and many others.


In the most common classification, the term "motor neuron disease" applies to the following five disorders which affect either upper motor neurons (UMN) or lower motor neurons (LMN), or both:

Type UMN degeneration LMN degeneration
Amyotrophic lateral sclerosis (ALS) yes yes
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

Even though diseases known as spinal muscular atrophies, including the most common spinal muscular atrophy (SMA), affect motor neurons and are classified as MND by the disease terminology classification system Medical Subject Headings (MeSH), they are not classified as such by the tenth International Statistical Classification of Diseases and Related Health Problems (ICD-10) published in 1992 and thus are not discussed in this article.


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