Paralysis (also known as plegia) is a loss of

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

function in one or more

muscles Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of musc ...

. 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 states, a federal district, five major unincorporated territori ...

, 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 Palsy is a medical term which refers to various types of paralysisDan Agin, ''More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children;; (2009), p. 172. or paresis, often accompanied by weakness a ...

Causes

Paralysis is most often caused by damage in the

nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...

, 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 sp ...

. Other major causes are stroke,

trauma Trauma most often refers to: * Major trauma, in physical medicine, severe physical injury caused by an external source * Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic i ...

with

nerve injury Nerve injury is an injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injuries. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve f ...

, 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, stiff muscles, weak muscles, and tremors. There may be problems with sens ...

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

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 Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium ''Clostridium botulinum''. The disease begins with weakness, blurred vision, feeling tired, and trouble speaking. This may then be followed by weakne ...

spina bifida Spina bifida (Latin for 'split spine'; SB) is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy. There are three main types: spina bifida occulta, men ...

, multiple sclerosis, and

Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain oft ...

. 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 Curare ( /kʊˈrɑːri/ or /kjʊˈrɑːri/; ''koo-rah-ree'' or ''kyoo-rah-ree'') is a common name for various alkaloid arrow poisons originating from plant extracts. Used as a paralyzing agent by indigenous peoples in Central and South ...

, 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 Congenital syphilis is syphilis present ''in utero'' and at birth, and occurs when a child is born to a mother with syphilis. Untreated early syphilis infections results in a high risk of poor pregnancy outcomes, including saddle nose, lower extr ...

. 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 A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...

) are constant in nature; however, some forms of

periodic paralysis Periodic paralysis is a group of rare genetic diseases that lead to weakness or paralysis from common triggers such as cold, heat, high carbohydrate meals, not eating, stress or excitement and physical activity of any kind. The underlying mechanis ...

, including

sleep paralysis Sleep paralysis is a state, during waking up or falling asleep, in which one is conscious but is completely paralyzed. During an episode, one may hallucinate (hear, feel, or see things that are not there), which often results in fear. Episod ...

, are caused by other factors. Paralysis can occur in newborns due to a congenital defect known as

. 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: *

(another name for this condition is ''Landry's ascending paralysis'') * Tick paralysis Ascending paralysis contrasts with descending paralysis, which occurs in conditions such as

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'' 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 A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

, 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 ''Philanthus gibbosus'', which is commonly referred to as a beewolf due to its predation practices, is a species of bee-hunting wasp and is the most common and widespread member of the genus in North America. ''P. gibbosus'' is of the order Hymen ...

'', 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. ...

e when they hatch.

Vertebrates

A well-known example of a vertebrate-produced paralyzing toxin is the

tetrodotoxin Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovere ...

of fish species such as ''

Takifugu rubripes ''Takifugu rubripes'', commonly known as the Japanese puffer, Tiger puffer, or torafugu ( ja, 虎河豚), is a pufferfish in the genus '' Takifugu''. It is distinguished by a very small genome that has been fully sequenced because of its use as a ...

'', the famously lethal pufferfish of Japanese fugu. This toxin works by binding to

sodium channels Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the chann ...

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

nemertea Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many h ...

ns. 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 In medicine, paresis () is a condition typified by a weakness of voluntary movement, or by partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it can also be used to desc ...

, 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 Myelopathy describes any neurologic deficit related to the spinal cord. The most common form of myelopathy in humans, ''Spinal cord compression, cervical spondylotic myelopathy (CSM)'', also called ''degenerative cervical myelopathy'', results fro ...

. 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 Heart murmurs are unique heart sounds produced when blood flows across a heart valve or blood vessel. This occurs when turbulent blood flow creates a sound loud enough to hear with a stethoscope. Turbulent blood flow is not smooth. The sound di ...

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 Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nerv ...

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