Paralysis is the complete loss of muscle function for one or more muscle groups. Paralysis can cause loss of feeling or loss of mobility in the affected area.
Paralysis is most often caused by damage to the nervous system, especially the spinal cord. Major causes are stroke, trauma with nerve injury, poliomyelitis, amyotrophic lateral sclerosis (ALS), botulism, spina bifida, multiple sclerosis, and Guillain-Barr syndrome. Temporary paralysis occurs during REM sleep, and dysregulation of this system can lead to episodes of waking paralysis. Drugs that interfere with nerve function, such as curare, can also cause paralysis. Many causes of this are varied, and could also be unknown. Pseudoparalysis (pseudo- meaning false, not genuine) is voluntary restriction or inhibition of motion because of pain, incoordination, or other cause, and is not due to actual muscular paralysis.] In an infant, it may be a symptom of congenital syphilis
Paralysis may be localized, or generalized, or it may follow a certain pattern. Most paralyses caused by nervous system damage (i.e. spinal cord injuries) are constant in nature; however, there are forms of periodic paralysis, including sleep paralysis, which are caused by other factors.