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- perception
- pain
- limb
phantom limb syndrome
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What is phantom limb syndrome?
Phantom limb syndrome involves feeling sensations, including pain, in a limb that has been amputated. These sensations range from burning and shooting pains to tingling. First described in 1552 by Ambroise Paré, the syndrome's underlying phenomenon was later considered to be sensory perception.
In the 1990s, research showed that neuroplasticity, the brain's ability to modify its connections, could explain pain related to phantom limb syndrome. Specifically, map expansion neuroplasticity, or cortical reorganization, allows local brain regions to acquire areas of the unused phantom map.
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Why do people feel sensations in a limb that has been amputated?
Phantom limb syndrome involves feeling sensations in a limb that has been amputated. Even after amputation, the brain continues to act as if the limb is still present.
Researchers in the 1990s discovered that neuroplasticity—the brain's ability to modify its connections—can explain pain associated with phantom limb syndrome. Map expansion neuroplasticity (cortical reorganization) occurs when local brain regions acquire areas of the unused phantom map.
Nonpainful phantom limb sensations include perceived movement and external sensations like touch, temperature, and pressure. Painful sensations range from burning and shooting pains to tingling.
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How does the brain play a role in phantom limb syndrome?
In phantom limb syndrome, the brain plays a central role. After amputation, the brain can still feel sensations, including pain, in the missing limb. This occurs because of neuroplasticity, where the brain's neurons reorganize and modify their connections.
Specifically, local brain regions that once controlled the amputated limb can be taken over by other areas, leading to map expansion neuroplasticity, also known as cortical reorganization. This phenomenon can result in the perception of both painful and nonpainful sensations in the phantom limb.
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What happens to nerves after a limb is lost?
When a limb is lost, the nerves that once served that limb undergo several changes. If the nerve fibres are damaged, the blastema fails to develop, and instead, scar tissue forms. Severed nerve fibres outside the brain and spinal cord can regenerate, but complete regeneration is unlikely because most nerves are mixed motor and sensory paths, and regenerating fibres may take incorrect paths.
Phantom limb syndrome can occur following amputation, where the patient continues to feel sensations in the missing limb. Phantom limb pain is specifically explained by map expansion neuroplasticity (cortical reorganization), in which local brain regions can acquire areas of the unused phantom map. In these cases, the character of the sensory region of the cortex changes so that neurons that normally never cause pain when stimulated now invariably produce the pain from which the individual is suffering.
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How does the brain's sensory map change after an amputation?
After an amputation, the brain's sensory map undergoes neuroplastic changes, specifically map expansion neuroplasticity, also known as cortical reorganization. Brain regions, each with a specific function reflected in the cerebral cortex as "maps," can acquire areas of the unused phantom map. This means that the areas of the brain that previously processed sensory information from the amputated limb are taken over by neighboring areas. This phenomenon helps explain pain associated with phantom limb syndrome. The effects of cross-modal plasticity vary from person to person and depend on factors such as age, sensory experience, and the specific brain systems involved.
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What treatments try to help people with phantom limb pain?
Phantom limb syndrome is characterized by feeling sensations, including pain, in a limb that no longer exists. While the painful symptoms may resolve on their own, treatments are available to manage severe, chronic pain.
These treatments include analgesics, sedative-hypnotics, antidepressants, and anticonvulsants. Coping techniques such as hypnosis, progressive muscle relaxation, and biofeedback can help patients manage symptoms. Other nonsurgical options include acupuncture, shock therapy, and transcutaneous electrical nerve stimulation. For some, implantable treatments like deep brain stimulation, spinal cord stimulation, and intrathecal drug delivery systems may be used when noninvasive treatments fail. Mirror box therapy may also help alleviate pain associated with learned paralysis.
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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.
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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.