Paralysis is the complete loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling (sensory loss) in the affected area, if there is sensory damage as well as motor.
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 is most often caused by damage in the nervous system, especially the spinal cord. Other major causes are stroke, trauma with nerve injury, poliomyelitis, amyotrophic lateral sclerosis (ALS),botulism, spina bifida, multiple sclerosis, and Guillain-Barré 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. There are many known causes for paralysis, and perhaps more yet to be discovered.