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Paralysis is 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. The word comes from the Greek παράλυσις, "disabling of the nerves",[1] itself from παρά (para), "beside, by"[2] + λύσις (lusis), "loosing"[3] and that from λύω (luō), "to loose".[4]



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.

Pseudoparalysis (pseudo- meaning "false, not genuine", from Greek ψεῦδος[5]) is voluntary restriction or inhibition of motion because of pain, incoordination, or other cause, and is not due to actual muscular paralysis.[6] In an infant, it may be a symptom of congenital syphilis.[7]


Paralysis could 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.

Paralysis in the animal world

Many animal species use paralyzing toxins to capture prey, evade predation, or both. A well-known example is the tetrodotoxin of fish species such as Takifugu rubripes, the famously lethal pufferfish of Japanese fugu. This toxin works by binding to sodium channels in nerve cells, preventing the cells' proper function. A non-lethal dose of this toxin results in temporary paralysis. This toxin is also present in many other species ranging from toads to nemerteans. Another interesting use of paralysis in the natural world is the behavior of some species of wasp. To complete the reproductive cycle, the female wasp paralyzes a prey item such as a grasshopper and places it in her nest. She then lays eggs in the paralyzed insect, which is devoured by the larvae when they hatch. Many snakes also exhibit powerful neurotoxins that can cause non-permanent paralysis or death.

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