Motor neuron disease
|Motor neuron disease|
|Classification and external resources|
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 increasingly debilitating disability and, eventually, death.
Terms used to describe the motor neuron diseases can be confusing. In the United Kingdom, "motor neurone disease" (sometimes spelt as "motor neuron disease") refers both to amyotrophic lateral sclerosis and to the broader spectrum of related motor neuron disorders that includes progressive muscular atrophy, primary lateral sclerosis, and progressive bulbar palsy. In the United States, "ALS" is commonly used both specifically for amyotrophic lateral sclerosis (which is also referred to as "Lou Gehrig's disease") and as a blanket term for the entire spectrum. 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, and many others.
There are five recognized subtypes of motor neuron diseases. They are distinguished by the nerve cells affected, upper motor neuron (UMN) and lower motor neuron (LMN), and the symptoms that result from this damage:
|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|
The term "bulbar region" in the above table refers to the mouth, face, and throat.
The disease spinal muscular atrophy (SMA) as well as various other spinal muscular atrophies are classified as motor neuron diseases by the disease terminology classification system Medical Subject Headings (MeSH) but not by the tenth International Statistical Classification of Diseases and Related Health Problems (ICD-10) published in 1992; hence, they are not discussed in this article.
- "Motor Neuron Diseases Fact Sheet: National Institute of Neurological Disorders and Stroke (NINDS)". www.ninds.nih.gov. Retrieved 2010-11-07.