Motor Neuron-Related Disorders

Motor neuron disease (MND) is a group of neurological disorders which is characterized by selectively progressive degeneration of motor neurons in the brain and spinal cord. On the basis of the degree of upper or lower neuron involvement, MND is broadly divided into several subtypes: pure upper neuron diseases (primary lateral sclerosis), pure lower motor neuron diseases (progressive spinal muscular atrophy, progressive bulbar palsy, spinal muscular atrophy, X-linked spinal and bulbar muscular atrophy, etc.), and mixed upper and lower motor neuron diseases (amyotrophic lateral sclerosis). Generally, MND can be sporadic, or it can occur as an inherited disorder. To date, a great number of genes have been identified to be responsible for inherited MND. The distinct causative genes usually result in different clinical phenotypes. Therefore, the genetic testing is crucial for inherited MND. In this chapter, we mentioned several cases of inherited motor neuron diseases and described the way how these definitive causative genes were identified. In addition, to make clear definition for MND, several other inherited neurologic diseases, such as hereditary spasticity paraplegia and inherited peripheral neuropathy, were also presented in this chapter.