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Phantom limb pain (PLE) is defined as pain that is localized to a remote part of the body (arms or legs, less commonly elsewhere). This is a poorly understood clinical phenomenon that remains the subject of research due to the acute or chronic nature of the condition. The incidence has been reported to be as high as 60-80% in amputated patients, and risk factors include chronic limb pain prior to amputation, postoperative surgical pain, and psychological stress.
Phantom pains are often described by patients themselves as crushing, twisting of the toes, sensation of hot iron, burning, tingling, cramps, electric shocks, shooting pains, “pins and needles”. Pain is usually located in the more distal structures of the missing limb (eg, fingers and toes). According to experts, the problem occurs regardless of age, gender, level or side of the amputation, but only in adults.
What is phantom pain
Phantom pain is a painful sensation that seems to come from a part of the body that is no longer there (it was amputated due to injury or disease). Doctors once believed that this post-amputation phenomenon was a psychological problem, but experts now recognize that these actual sensations originate in the spinal cord and brain.
Most people who have had a limb removed report that they sometimes feel as if the amputated limb is still there. This painless phenomenon, known as phantom limb sensation, is not exactly the same as phantom pain.
In some patients, phantom pain resolves over time even without treatment. For others, managing phantom pain can be challenging. The patient and physician must work together to effectively treat phantom pain with medication or other therapies.
Causes of phantom pain in adults
The exact cause of phantom pain is unclear, but it appears to originate in the spinal cord and brain. During magnetic resonance imaging (MRI) or positron emission tomography (PET) scans of organs, parts of the brain that were neurologically connected to the nerves of the amputated limb become active when the person feels phantom pain.
Many experts believe that phantom pain can be explained, at least in part, as a response to mixed brain signals. After amputation, regions of the spinal cord and brain lose their influence on the missing limb and adapt to this loss in unpredictable ways. The result can trigger the body’s key message that something is wrong: pain.
Research also shows that after an amputation, the brain can remap that part of the body’s sensory circuits to another part of the body. In other words, since the amputated area can no longer receive sensory information, the information is transferred to another location, such as from the missing hand to the still present cheek. Therefore, when one touches the cheek, it is as if one were touching the missing hand. Since this is another kind of confusing sensory input, pain can be the result.
Phantom pain is thought to be influenced by a number of other factors, including nerve damage, scar tissue at the site of the amputation, and physical memory of pre-amputation pain at the site.
Not everyone has phantom pain after amputation. Some factors that may increase the risk of phantom pain include:
Pain before amputation. Some researchers have found that people who experienced limb pain before amputation are more likely to experience it later. This may be due to the fact that the brain stores the memory of pain and continues to send pain signals even after the removal of the limb.
Residual pain in limbs. People who have persistent pain in the remainder of a limb usually have phantom pain as well. Residual limb pain can be caused by abnormal growth of damaged nerve endings (neurinoma), often resulting in painful nerve activity.
Symptoms of phantom pain in adults
Characteristics of phantom pain include:
- onset within the first week after amputation, although pain may be delayed for months or longer;
- pain that comes and goes or is constant;
- symptoms affecting the part of the limb furthest from the body, such as the foot of an amputated leg;
- pain that may be described as shooting, stabbing, cramping, needles, crushing, throbbing, or burning.
Treatment of phantom pain in adults
Finding a treatment to relieve phantom pain can be difficult. Doctors usually start with medication and then may add non-invasive treatments such as acupuncture. More invasive options include injections or implanted devices. The operation is carried out only as a last resort.
Diagnostics
Although there is no medical test to diagnose phantom pain, doctors base the condition on the symptoms and circumstances, such as an injury or surgery that occurred before the pain began. An accurate description of the nature of the pain can help the doctor identify the problem. Although phantom pain and residual limb pain often occur at the same time, treatments for the two problems can differ, so an accurate diagnosis is important.
Modern treatments
While there are no drugs specifically designed to treat phantom pain, some drugs designed to treat other conditions have been helpful in relieving nerve pain. No medicine works for everyone, and not all medicines work in principle. The patient may need to try different medications to find what works for them.
Medicines used to treat phantom pain include:
Over-the-counter painkillers. Paracetamol, ibuprofen, or naproxen sodium may relieve phantom pain. These medicines should only be taken as directed by your doctor. Excessive consumption can cause serious side effects such as stomach bleeding.
Antidepressants. Tricyclic antidepressants can relieve pain caused by nerve damage. Examples include amitriptyline, nortriptyline and tramadol. Possible side effects include drowsiness, dry mouth, and blurred vision.
Anticonvulsants. Epilepsy medicines such as gabapentin and pregabalin can be used to treat nerve pain. Side effects may include dizziness, sedation, and mood changes.
Narcotic analgesics. Some people may take opioid drugs such as codeine and morphine. Taken in appropriate doses under the guidance of a physician, they can help control phantom pain. These drugs can cause many side effects, including constipation, nausea, vomiting, or sedation.
N-methyl-d-aspartate receptor antagonists (NMDA). This class of anesthetics works by binding to NMDA receptors on nerve cells in the brain and blocking the activity of glutamate, a protein that plays a large role in nerve signaling. In studies, NMDA receptor antagonists, ketamine and dextromethorphan, have helped relieve phantom pain. Side effects of ketamine include mild sedation, hallucinations, or loss of consciousness. No side effects have been reported from the use of dextromethorphan.
Other treatments
As with drugs, treating phantom pain with non-invasive methods is a matter of trial and observation. The following techniques may relieve phantom pain in some people:
Mirror box. This device has mirrors that give the impression that the amputated limb is still there. The box with the mirror has two openings – one for the intact limb and one for the residual limb. The person then performs symmetrical exercises while observing the movement of the uninjured limb and imagining that they are actually observing the movement of the missing limb. Some studies, though not all, have shown that this exercise can help relieve phantom pain.
Acupuncture. Researchers have found that acupuncture can relieve some types of chronic pain. In acupuncture, the practitioner inserts very fine, sterilized stainless steel needles into the skin at specific points on the body. Acupuncture is generally considered safe when performed correctly.
Repetitive transcranial magnetic stimulation. This therapy uses an electromagnetic coil placed against the forehead. Short pulses are sent through the coil, which induce small electrical currents in nerves located in a specially targeted area of the brain. Research suggests that this therapy may be useful for phantom pain, although it has not yet been approved specifically for this condition. The magnetic field is similar to that used in MRI. Side effects may include mild headache or dizziness.
Spinal cord stimulation. The doctor inserts tiny electrodes into the spinal cord. A small electrical current applied continuously to the spinal cord can sometimes relieve pain.
Operation. Surgery may be an option if other treatments have failed.
Brain stimulation. Deep brain stimulation and motor cortex stimulation are similar to spinal cord stimulation except that the current is delivered to the brain. The surgeon uses magnetic resonance imaging (MRI) to properly position the electrodes. Although data is still limited and these treatments are not approved specifically for phantom pain, brain stimulation appears to be a promising option for individuals.
Prevention of phantom pain in adults at home
Because the risk of developing phantom pain is higher in people who had pain in the limb prior to the amputation, some doctors recommend regional anesthesia (spinal or epidural) in the hours or days leading up to the amputation. This can reduce pain immediately after surgery and reduce the risk of persistent phantom limb pain.
Popular questions and answers
Answered popular questions about phantom pains neurologist at the clinic “Neplacebo”, teacher of neurology Elena Gayvoronskaya.