Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

, roughly 1 in 50 people have been diagnosed with some form of permanent or transient paralysis. The word "paralysis" derives from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

παράλυσις, meaning "disabling of the nerves" from παρά (''para'') meaning "beside, by" and λύσις (''lysis'') meaning "making loose". A paralysis accompanied by involuntary tremors is usually called " palsy".

Causes

Paralysis is most often caused by damage in the

nervous system In Biology, biology, the nervous system is the Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmitting action potential, signals to and from different parts of its ...

, especially the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...

. Other major causes are stroke, trauma with nerve injury, poliomyelitis,

cerebral palsy Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, spasticity, stiff muscles, Paresis, weak muscles, and tremors. There may be p ...

, peripheral neuropathy,

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

, 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. ''Pseudoparalysis'' (''pseudo-'' meaning "false, not genuine", from Greek ψεῦδος) is voluntary restriction or inhibition of motion because of pain, incoordination, orgasm, or other cause, and is not due to actual muscular paralysis. In an infant, it may be a symptom of congenital syphilis. Pseudoparalysis can be caused by extreme mental stresses, and is a common feature of mental disorders such as panic anxiety disorder.

Variations

Paralysis can occur in localised or generalised forms, or it may follow a certain pattern. Most paralyses caused by nervous-system damage (e.g., spinal cord injuries) are constant in nature; however, some forms of periodic paralysis, including sleep paralysis, are caused by other factors. Paralysis can occur in newborns due to a congenital defect known as spina bifida. Spina bifida causes one or more of the vertebrae to fail to form vertebral arches within the infant, which allows the spinal cord to protrude from the rest of the spine. In extreme cases, this can cause spinal cord function inferior to the missing vertebral arches to cease. This cessation of spinal cord function can result in paralysis of lower extremities. Documented cases of paralysis of the anal sphincter in newborns have been observed when spina bifida has gone untreated. While life-threatening, many cases of spina bifida can be corrected surgically if operated on within 72 hours of birth. Ascending paralysis presents in the lower limbs before the upper limbs. It can be associated with: * Guillain–Barré syndrome (another name for this condition is ''Landry's ascending paralysis'') * Tick paralysis Ascending paralysis contrasts with descending paralysis, which occurs in conditions such as botulism.

Other animals

Many animal species use paralyzing toxins to capture prey, evade predation, or both. In stimulated muscles, the decrease in frequency of the miniature potentials runs parallel to the decrease in postsynaptic potential, and to the decrease in muscle contraction. In invertebrates, this clearly indicates that, e.g., '' Microbracon'' (wasp genus) venom causes paralysis of the neuromuscular system by acting at a presynaptic site. ''

Philanthus Beewolves (genus ''Philanthus''), also known as bee-hunters or bee-killer wasps, are solitary, predatory wasps, most of which prey on bees, hence their common name. The adult females dig tunnels in the ground for nesting, while the territorial m ...

'' venom inhibits both the fast and slow neuromuscular system at identical concentrations. It causes a decrease in the frequency of the miniature potentials without affecting their amplitude significantly.

Invertebrates

In some species of wasp, to complete the reproductive cycle, the female wasp paralyses a prey item such as a grasshopper and places it in her nest. In the species '' Philanthus gibbosus'', the paralysed insect (most often a bee species) is coated in a thick layer of pollen. The adult ''P. gibbosus'' then lays eggs in the paralysed insect, which is devoured by the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...

e when they hatch.

Vertebrates

A well-known example of a vertebrate-produced paralyzing toxin 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, inhibiting 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. Paralysis can be seen in breeds of dogs that are chondrodysplastic. These dogs have short legs, and may also have short muzzles. Their intervertebral disc material can calcify and become more brittle. In such cases, the disc may rupture, with disc material ending up in the spinal canal, or rupturing more laterally to press on spinal nerves. A minor rupture may only result in paresis, but a major rupture can cause enough damage to cut off circulation. If no signs of pain can be elicited, surgery should be performed within 24 hours of the incident, to remove the disc material and relieve pressure on the

. After 24 hours, the chance of recovery declines rapidly, since with continued pressure, the spinal cord tissue deteriorates and dies. Another type of paralysis is caused by a fibrocartilaginous embolism. This is a microscopic piece of disc material that breaks off and becomes lodged in a spinal artery. Nerves served by the artery will die when deprived of blood. The German Shepherd Dog is especially prone to developing degenerative myelopathy. This is a deterioration of nerves in the spinal cord, starting in the posterior part of the cord. Affected dogs will become gradually weaker in the hind legs as nerves die off. Eventually, their hind legs become useless. They often also exhibit faecal and urinary incontinence. As the disease progresses, the paresis and paralysis gradually move forward. This disease also affects other large breeds of dogs. It is suspected to be an autoimmune problem. Cats with a heart murmur may develop blood clots that travel through arteries. If a clot is large enough to block one or both femoral arteries, there may be hind leg paralysis because the major source of blood flow to the hind leg is blocked. Many snakes exhibit powerful neurotoxins that can cause non-permanent paralysis or death. Also, many trees contain neurotoxins.

References

External links

{{Authority control Nervous system Motor control Cerebral palsy and other paralytic syndromes Neurology