Phantom limb
A phantom limb is the sensation that an amputated
Amputation is the removal of a body extremity by trauma, prolonged constriction, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for...

 or missing limb
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....

 (even an organ, like the appendix) is still attached to the body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...

 and is moving appropriately with other body parts. 2 out of 3 combat veterans report this feeling. Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

ful. Phantom sensations may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast, extraction of a tooth (phantom tooth pain) or removal of an eye (phantom eye syndrome
Phantom eye syndrome
The phantom eye syndrome is a phantom pain in the eye and visual hallucinations after the removal of an eye .- Symptomatology :Many patients experience one or more phantom phenomena after the removal of the eye:...

). The missing limb often feels shorter and may feel as if it is in a distorted and painful position. Occasionally, the pain can be made worse by stress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

, anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

, and weather changes. Phantom limb pain is usually intermittent. The frequency and intensity of attacks usually decline with time.

A slightly different sensation known as phantom pains can also occur in people who are born without limbs and people who are paralyzed. Phantom pains occur when nerves that would normally innervate the missing limb cause pain. It is often described as a burning or similarly strange sensation and can be extremely agonizing for some people, but the exact sensation differs widely for individuals. Other induced sensations include warmth, cold, itching, squeezing, tightness, and tingling.

Clinical description

Although not all phantom limbs are painful, patients will sometimes feel as if they are gesturing, feel itches, twitch, or even try to pick things up. For example, Ramachandran and Blakeslee describe that some people's representations of their limbs do not actually match what they should be, for example, one patient reported that her phantom arm was about "6 inches too short".

Some people with phantom limbs find that the limb will gesticulate as they talk. (But whether they feel the weight of the phantom limb while gesticulating is unclear). Given the way that the hands and arms are represented on the motor cortex and language centers, this is not surprising. Some people find that their phantom limb feels and behaves as though it were still there; others find that it begins to take on a life of its own, and does not obey their commands.

Neurological basis

Until recently, the dominant theory for cause of phantom limbs was irritation in the severed nerve endings (called "neuromas"). When a limb is amputated, many severed nerve endings are terminated at the residual limb. These nerve endings can become inflamed, and were thought to send anomalous signals to the brain. These signals, being functionally nonsense, were thought to be interpreted by the brain as pain. Treatments based on this theory were generally failures. In extreme cases, surgeons would perform a second amputation, shortening the stump, with the hope of removing the inflamed nerve endings and causing temporary relief from the phantom pain. But instead, the patients' phantom pains increased, and many were left with the sensation of both the original phantom limb, as well as a new phantom stump, with a pain all its own. In some cases, surgeons even cut the sensory nerves leading into the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 or in extreme cases, even removed the part of the thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

 that receives sensory signals from the body.

By the late 1980s, Ronald Melzack
Ronald Melzack
Ronald Melzack, is a Canadian psychologist.After studying for his Ph.D. in 1954 with D. O. Hebb at McGill University in Montreal, he began to work with patients who suffered from "phantom limb" pain — people who feel pain in an arm or leg that has been removed...

 had recognized that the peripheral neuroma account could not be correct, and suggested that changes in a "neuromatrix" was responsible for phantom limb sensations, but explicitly rejected the idea that these changes occurred in primary somatosensory areas. In 1991, Tim Pons and colleagues at the National Institutes of Health
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...

 (NIH) showed that the primary somatosensory cortex undergoes substantial reorganization after the loss of sensory input. Hearing about these results, Vilayanur S. Ramachandran
Vilayanur S. Ramachandran
Vilayanur Subramanian "Rama" Ramachandran, born 1951, is a neuroscientist known for his work in the fields of behavioral neurology and visual psychophysics...

 theorized that phantom limb sensations could be due to this reorganization in the somatosensory cortex, which is located in the postcentral gyrus
Postcentral gyrus
The lateral postcentral gyrus is a prominent structure in the parietal lobe of the human brain and an important landmark. It is the location of primary somatosensory cortex, the main sensory receptive area for the sense of touch...

, and which receives input from the limbs and body. Ramachandran and colleagues illustrated this theory by showing that stroking different parts of the face led to perceptions of being touched on different parts of the missing limb.

Ramachandran argued that the perception of being touched in different parts of the phantom limb was the perceptual correlate of cortical reorganization in the brain. However, research published in 1995 by Flor et al. demonstrated that pain (rather than referred sensations) was the perceptual correlate of cortical reorganization. In 1996 Knecht et al. published an analysis of Ramanchandran's theory that concluded that there was no topographic relationship between referred sensations and cortical reorganization in the primary cortical areas Recent research by Flor et al. suggests that non-painful referred sensations are correlated with a wide neural network outside the primary cortical areas.

Because phantom limb pain (PLP) is a complex phenomenon that produces a wide variety of symptoms researchers have advanced a number of theories during the past twenty years. It is important to note that many neurological researchers now distinguish between PLP and phantom limb sensations such as movement and position. V.S. Ramachandran, who brought the subject of phantom limbs to a broad audience with his book Phantoms In The Brain, has advanced a number of theories to explain phantom limb pain. In particular Ramachandran and Hirstein have linked phantom limb pain to both cortical and peripheral mechanisms with a five source model that included 1) residual limb neuromas, 2) cortical remapping, 3) corollary discharge, 4) body image, and 5) somatic memories.

In 2009 Lorimer Moseley and Peter Brugger carried out a remarkable experiment in which they encouraged seven arm amputees to use visual imagery to contort their phantom limbs into impossible configurations. Four of the seven subjects succeeded in performing impossible movements of the phantom limb. This experiment suggests that the subjects had modified the neural representation of their phantom limbs and generated the motor commands needed to execute impossible movements in the absence of feedback from the body. The authors stated that:"In fact, this finding extends our understanding of the brain's plasticity because it is evidence that profound changes in the mental representation of the body can be induced purely by internal brain mechanisms--the brain truly does change itself."

Phantom limb pain

Theories that attempt to account for phantom limb pain fall into two broad classes: those that point toward peripheral nervous system mechanisms and those that point toward central nervous system mechanisms. The most commonly cited explanation for phantom limb pain is cortical reorganization. Pain researchers such as Herta Flor and Lorimer Mosely have developed theories of phantom limb pain that rely on the idea of cortical reorganization. Recently a group of researchers headed by Jack Tsao, MD. at Walter Reed Hospital
Walter Reed Army Medical Center
The Walter Reed Army Medical Center was the United States Army's flagship medical center until 2011. Located on 113 acres in Washington, D.C., it served more than 150,000 active and retired personnel from all branches of the military...

 has advanced a theory based on the concept of "proprioceptive memory." This theory argues that the brain retains a memory of specific limb positions and that after amputation there is a conflict between the visual system, which literally sees that the limb is missing, and the memory system which remembers the limb as a functioning part of the body.

In 2006, Herta Flor suggested that phantom limb pain involves a form of unconscious learning similar to motor reflexes and perception skills. Flor theorized that preventing the formation of painful memories might be the most effective approach to preventing phantom limb pain. She conducted an experiment in which patients who were scheduled to undergo amputations were given memantine, a drug that blocks the activity of NMDA receptors, which are important to many types of learning and memory. Thirteen patients took memantine for four weeks after their amputations. These patients were then studied over the course of a year. The results of the this study indicated that changes in the brain were reduced and that the incidence and intensity of phantom limb pain was reduced.


Some treatments include drugs
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

 such as antidepressants. Spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 stimulation (SCS) can be effective treatment for phantom pain. An electrical stimulator is implanted under the skin, and an electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

 is placed next to the spinal cord. The nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 pathways in the spinal cord are stimulated by an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

. This interferes with the impulses travelling towards the brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 and lessens the pain felt in the phantom limb. Instead, amputees feel a tingling sensation in the phantom limb.

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...

, acupuncture
Acupuncture is a type of alternative medicine that treats patients by insertion and manipulation of solid, generally thin needles in the body....

, hypnosis
Hypnosis is "a trance state characterized by extreme suggestibility, relaxation and heightened imagination."It is a mental state or imaginative role-enactment . It is usually induced by a procedure known as a hypnotic induction, which is commonly composed of a long series of preliminary...

, and biofeedback
Biofeedback is the process of becoming aware of various physiological functions using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will...

 may all be used to treat phantom pain but are often of little help. The pain can sometimes be helped by keeping busy and focusing attention on something else. Massaging the stump can sometimes help. For planned amputation, phantom pain can be reduced by preoperative pain management, effective control of pain by analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

 or neuroleptic is required. The brain seems to implant the sensations from the preoperative state.

One particularly novel treatment for phantom limb pain is the mirror box
Mirror box
A mirror box is a box with two mirrors in the center , invented by Vilayanur S. Ramachandran to help alleviate phantom limb pain, in which patients feel they still have a limb after having it amputated....

 developed by Vilayanur Ramachandran and colleagues. Through the use of artificial visual feedback it becomes possible for the patient to "move" the phantom limb, and to unclench it from potentially painful positions. Repeated training in some subjects has led to long-term improvement, and in one exceptional case, even to the complete elimination of the phantom limb between the hand and the shoulder (so that the phantom hand was dangling from the shoulder).

The success of the mirror method inspired a team of researchers at the University of Manchester
University of Manchester
The University of Manchester is a public research university located in Manchester, United Kingdom. It is a "red brick" university and a member of the Russell Group of research-intensive British universities and the N8 Group...

 in England to experiment a technology of "immersive virtual reality
Virtual reality
Virtual reality , also known as virtuality, is a term that applies to computer-simulated environments that can simulate physical presence in places in the real world, as well as in imaginary worlds...

" to combat the discomfort caused by phantom limb syndrome. The researchers reported that phantom limb pain can be relieved by attaching the sufferer's real limb to an interface that allows them to see two limbs moving in a computer-generated simulation. This works on the same principle as the mirror box
Mirror box
A mirror box is a box with two mirrors in the center , invented by Vilayanur S. Ramachandran to help alleviate phantom limb pain, in which patients feel they still have a limb after having it amputated....

 technique in that the somatosensory cortex is being 'tricked', except that the computer created illusion
An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people....

 is thought to be stronger. Another virtual reality research was reported in 2009.

See also

  • Body image
    Body image
    Body image refers to a person's perception of the aesthetics and sexual attractiveness of their own body. The phrase body image was first coined by the Austrian neurologist and psychoanalyst Paul Schilder in his masterpiece The Image and Appearance of the Human Body...

  • Mirror box
    Mirror box
    A mirror box is a box with two mirrors in the center , invented by Vilayanur S. Ramachandran to help alleviate phantom limb pain, in which patients feel they still have a limb after having it amputated....

  • Neuropathic pain
    Neuropathic pain
    Neuropathic pain results from lesions or diseases affecting the somatosensory system. It may be associated with abnormal sensations called dysesthesia, which occur spontaneously and allodynia that occurs in response to external stimuli. Neuropathic pain may have continuous and/or episodic ...

  • Phantom pain
    Phantom pain
    Phantom pain sensations are described as perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body. Limb loss is a result of either removal by amputation or congenital limb deficiency . However, phantom limb sensations can also occur following...

  • Phantom eye syndrome
    Phantom eye syndrome
    The phantom eye syndrome is a phantom pain in the eye and visual hallucinations after the removal of an eye .- Symptomatology :Many patients experience one or more phantom phenomena after the removal of the eye:...

  • Synesthesia
    Synesthesia , from the ancient Greek , "together," and , "sensation," is a neurologically based condition in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway...

  • Proprioception
    Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...

  • Frieder Kempe
    Frieder Kempe
    Frieder Kempe is a German scientist who designed a special metallic fabric called Farabloc that shields the human body from immediate shifts in the Earth's electromagnetic field. Published studies show Farabloc relieves pain...

  • Supernumerary phantom limb
    Supernumerary phantom limb
    Supernumerary phantom limb refers to a condition where the affected individual believes and receives sensory information from limbs of the body that do not actually exist, and never have existed, on the contrary to phantom limbs, which appear after an individual has had a limb removed from the body...

    , where sensations are felt in a limb that never existed

External links

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