Monday, August 22, 2016

Phantom Limb

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Phantom Limb
Multiple Responses:
1.
A phantom limb is the sensation that an amputated or missing limb (even an organ, like the appendix) is still attached to the body and is moving appropriately with other body parts.[1][2][3] Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are painful.[4] Phantom sensations may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast,[5] extraction of a tooth (phantom tooth pain)[6] or removal of an eye (phantom eye syndrome).[7][8] 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, anxiety, and weather changes. Phantom limb pain is usually intermittent. The frequency and intensity of attacks usually declines with time.[9]

Although not all phantom limbs are painful, people 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 person reported that her phantom arm was about "6 inches too short".[10]

A slightly different sensation known as phantom pain can also occur in people who are born without limbs, and people who are paralyzed.[11] 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 for people who are missing limbs. Other induced sensations include warmth, cold, itching, squeezing, tightness, and tingling.

2.
What is a Phantom Limb?
Phantom Limb
A phantom limb is the sensation that an amputated or missing limb (even an organ, like the appendix) is still attached to the body and is moving appropriately with other body parts. Approximately 5 to 10% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are painful. 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). 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, anxiety 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.

Phantom Limb 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 don't 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 is still there, others find that it begins to take on a life of its own, and doesn't obey their commands.

Phantom Limb Neurology
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 remaining stump. 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 or in extreme cases, even removed the part of the thalamus that receives sensory signals from the body.

In the early 1990s, Tim Pons, at the National Institutes of Health (NIH), showed that the brain can reorganize if sensory input is cut off . Hearing about these results,V. S. Ramachandran realized that phantom limb sensations could be due to "crosswiring" in the somatosensory cortex, which is located in the postcentral gyrus, and which receives input from the limbs and body. Input from the left side of the body goes to the right hemisphere and vice versa. The input from extremities comes into the somatosensory cortex in an ordered way, the representation of which is referred to as the somatosensory homonculus. Input from the hand is located next to the input from the arm, input from the foot is located next to input from the hand, and so on. One oddity is input from the face is located next to input from the hand.

Ramachandran reasoned that if someone were to lose their right hand in an accident, they may then have the feelings of a phantom limb because the input that normally would go from their hand to the left somatosensory cortex would be stopped. The areas in the somatosensory cortex that are near to the ones of the hand (the arm and face) will take over (or "remap") this cortical region that no longer has input. Ramachandran and colleagues first demonstrated this remapping by showing that stroking different parts of the face led to perceptions of being touched on different parts of the missing limb . Through magnetoencephalography (MEG), which permits visualization of activity in the human brain , Ramachandran verified the reorganization in the somatosensory cortex.

Phantom Limb Treatment
Some treatments include drugs such as antidepressants. Spinal cord stimulation (SCS) can be effective treatment for phantom pain. An electrical stimulator is implanted under the skin, and an electrode is placed next to the spinal cord. The nerve pathways in the spinal cord are stimulated by an electric current. This interferes with the impulses travelling towards the brain and lessens the pain felt in the phantom limb . Instead, amputees feel a tingling sensation in the phantom limb.

Vibration therapy, acupuncture, hypnosis and biofeedback 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 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 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).

More recently, virtual reality has been used to combat the discomfort caused by phantom limb syndrome. Scientists from the University of Manchester have shown 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 a similar principle to the mirror box technique in that the somatosensory cortex is being 'tricked' except that the illusion is stronger.

3.
Phantom limbs
If you had your arm amputated would you still feel its presence? Would it gesture as you talk and could it cause incredible pain?
Following amputation or paralysis of an arm or leg, most people still have a perception of their missing limb, and receive sensations from it.
For some people the phantom limb cannot move, for others it gesticulates when they talk and moves as before - even though the person knows the limb is missing or paralysed.
Phantom limb pain
About 80% of people with phantom limbs, feel excruciating pain from their missing limb, describing it as burning, aching, or 'as if my missing hand is being crushed in a vice’.
There is nothing phantom or imagined about the pain coming from a limb that is no longer there. The sensation is generated by the brain and as such is no different from pain elsewhere in the body.

“Paralysing my arm was very difficult to deal with, but what really interferes with my life is the crippling pain that comes from it”.
Paul, 24 who paralysed his arm in a motorcycle crash

How can a missing arm cause pain?
After injury: Invading other brain areas
The touch signals from the entire surface of your body are mapped on the surface of your brain – in a strip between your two ears called your sensory cortex. The area that ‘feels’ your hand is very close to the area for your face.
 
It seems there was a complete map of his missing phantom hand draped over his brain’s face map.

These critical changes might contribute to the pain from the phantom limb.
The idea was to trick his visual system into believing his paralysed arm was moving.
When the man watched the reflection of his good arm moving, he began to have the sensation that his paralysed arm was moving. That it had begun to obey his brains commands to move.
The man was able to take his arm out of its painful clenched position and reported a huge reduction in pain.

4.
Phantom limb syndrome, the ability to feel sensations and even pain in a limb or limbs that no longer exist. Phantom limb syndrome is characterized by both nonpainful and painful sensations. Nonpainful sensations can be divided into the perception of movement and the perception of external sensations (exteroception), including touch, temperature, pressure, vibration, and itch. Pain sensations range from burning and shooting pains to feelings of tingling “pins and needles.” While phantom limb syndrome occurs only in amputees, phantom sensations may be perceived in people who have survived strokes but lost function of certain body parts or who have spinal cord injury or peripheral nerve injury.

Phantom limb syndrome was first described in 1552 by French surgeon Ambroise Paré, who operated on wounded soldiers and wrote about patients who complained of pain in amputated limbs. The same syndrome was later observed and noted by French scientist, mathematician, and philosopher René Descartes, German physician Aaron Lemos, Scottish anatomist Sir Charles Bell, and American physician Silas Weir Mitchell, who tended to wounded soldiers in Philadelphia during the American Civil War. Scottish physician William Porterfield wrote a firsthand account of phantom limb syndrome in the 18th century, following the amputation of one of his legs. He was the first person to consider sensory perception as the underlying phenomenon of the syndrome.

In the 1990s researchers found that neuroplasticity—the ability of neurons in the brain to modify their connections and behaviour—could explain pain phenomena that had been observed in association with phantom limb syndrome. Phantom limb pain was found to be explained specifically by map expansion neuroplasticity (cortical reorganization), in which local brain regions, each dedicated to performing one type of function and reflected in the cerebral cortex as “maps,” can acquire areas of the unused phantom map.

Although the painful symptoms of phantom limb syndrome resolve on their own in some patients, other patients may experience severe, sometimes debilitating chronic pain. This may be controlled by drugs such as analgesics (e.g., aspirin, acetaminophen, and narcotics), sedative-hypnotics (e.g., benzodiazepines), antidepressants (e.g., bupropion and imipramine), and anticonvulsants (e.g., gabapentin). Certain drugs, such as ketamine (an anesthetic) and calcitonin (a hormone), administered prior to amputation surgery lessen the likelihood of development of later pain symptoms. Coping techniques, including hypnosis, progressive muscle relaxation, and biofeedback (a learned ability to regulate body functions), have helped some patients manage their symptoms. Nonsurgical treatments that may relieve phantom pain include shock therapy (or electroconvulsive therapy), acupuncture, and transcutaneous electrical nerve stimulation. Implantable treatments, generally used only after noninvasive treatments have failed, include deep brain stimulation, intrathecal drug delivery systems, and spinal cord stimulation.

The mirror box, a novel therapy for phantom limb syndrome developed in the mid-1990s, has been used by a small number of patients. The therapy has had some success in alleviating pain associated with “learned paralysis,” often experienced by patients whose missing limbs were paralyzed prior to amputation. The box, which does not have a roof, contains a mirror in the centre and usually has two holes, one through which a patient inserts his or her intact limb and one through which the patient inserts the phantom limb. When the patient views the reflection of the intact limb in the mirror, the brain is tricked into “seeing” the phantom limb. By moving the intact limb and watching its reflection in the mirror, a patient can train the brain to “move” the phantom limb and thus relieve the learned paralysis and associated pain. The changes in the brain that contribute to the success of this therapy are not completely understood, and information from long-term studies on the use of mirror box therapy is scant, although several patients have reported long-term relief.

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