Overview of Phantom Limb Pain

From Mayo Clinic

Phantom pain is pain that feels like it’s coming from a body part that’s no longer there. Doctors once believed this post-amputation phenomenon was a psychological problem, but experts now recognize that these real sensations originate in the spinal cord and brain.

Most people who’ve had a limb removed report that it sometimes feels as if the amputated limb is still there. This painless phenomenon, known as phantom limb sensation, isn’t the same as phantom pain.

For some people, phantom pain gets better over time without treatment. For others, managing phantom pain can be challenging. You and your doctor can work together to treat phantom pain effectively with medication or other therapies.

Symptoms

Characteristics of phantom pain include:

• Onset within the first week after amputation, though it can be delayed by months or longer
• Pain that comes and goes or is continuous
• Symptoms affecting the part of the limb farthest from the body, such as the foot of an amputated leg
• Pain that may be described as shooting, stabbing, cramping, pins and needles, crushing, throbbing, or burning

Causes

The exact cause of phantom pain is unclear, but it appears to come from the spinal cord and brain. During imaging scans — such as magnetic resonance imaging (MRI) or positron emission tomography (PET) — portions of the brain that had been neurologically connected to the nerves of the amputated limb show activity when the person feels phantom pain.

Many experts believe phantom pain may be at least partially explained as a response to mixed signals from the brain. After an amputation, areas of the spinal cord and brain lose input from the missing limb and adjust to this detachment in unpredictable ways. The result can trigger the body’s most basic message that something is not right: pain.

Studies also show that after an amputation the brain may remap that part of the body’s sensory circuitry to another part of the body. In other words, because the amputated area is no longer able to receive sensory information, the information is referred elsewhere — from a missing hand to a still-present cheek, for example.

So when the cheek is touched, it’s as though the missing hand is also being touched. Because this is yet another version of tangled sensory wires, the result can be pain.

A number of other factors are believed to contribute to phantom pain, including damaged nerve endings, scar tissue at the site of the amputation and the physical memory of pre-amputation pain in the affected area.

Risk factors

Not everyone who has an amputation develops phantom pain. Some factors that may increase your risk of phantom pain include:

• Pain before amputation. Some researchers have found that people who had pain in a limb before amputation are likely to have it afterward. This may be because the brain holds on to the memory of the pain and keeps sending pain signals, even after the limb is removed.
• Residual limb pain. People who have persistent pain in the remaining part of the limb usually have phantom pain, too. Residual limb pain can be caused by an abnormal growth on damaged nerve endings (neuroma) that often results in painful nerve activity.

Prevention

Because the risk of developing phantom pain is higher for people who have experienced pain in the limb before amputation, some doctors recommend regional anesthesia (spinal or epidural) in the hours or days leading up to amputation. This may reduce pain immediately following surgery and reduce the risk of lasting phantom limb pain.

Diagnosis

Although there’s no medical test to diagnose phantom pain, doctors identify the condition based on your symptoms and the circumstances, such as trauma or surgery, which occurred before the pain started.

Describing your pain precisely can help your doctor pinpoint your problem. Even though it’s common to have phantom pain and residual limb pain at the same time, treatments for these two problems may differ — so an accurate diagnosis is important.

Treatment

Finding a treatment to relieve your phantom pain can be difficult. Doctors usually begin with medications and then may add noninvasive therapies, such as acupuncture.

More-invasive options include injections or implanted devices. Surgery is done only as a last resort.

Medications

Although no medications specifically for phantom pain exist, some drugs designed to treat other conditions have been helpful in relieving nerve pain. No single drug works for everyone, and not everyone benefits from medications. You may need to try different medications to find one that works for you.

Medications used in the treatment of phantom pain include:

• Over-the-counter (OTC) pain relievers. Acetaminophen (Tylenol, others), ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve) might relieve phantom pain. Take these medications only as directed by your doctor. Overuse can cause serious side effects, such as stomach bleeding.
• Antidepressants. Tricyclic antidepressants may relieve the pain caused by damaged nerves. Examples include amitriptyline, nortriptyline (Pamelor) and tramadol (Conzip, Ultram). Possible side effects include sleepiness, dry mouth and blurred vision.
• Anticonvulsants. Epilepsy drugs — such as gabapentin (Gralise, Neurontin) and pregabalin (Lyrica) — may be used to treat nerve pain. Side effects may include dizziness, sedation and mood changes.
• Narcotics. Opioid medications, such as codeine and morphine, may be an option for some people. Taken in appropriate doses under your doctor’s direction, they may help control phantom pain.However, you may not be able to take them if you have a history of substance abuse. Even if you don’t have a history of substance abuse, these drugs can cause many side effects, including constipation, nausea, vomiting or sedation.
• N-methyl-d-aspartate (NMDA) receptor antagonists. This class of anesthetics works by binding to the NMDA receptors on the brain’s nerve cells and blocking the activity of glutamate, a protein that plays a large role in relaying nerve signals.In studies, NMDA receptor antagonists ketamine and dextromethorphan helped relieve phantom pain. Side effects of ketamine include mild sedation, hallucinations or loss of consciousness. No side effects were reported from the use of dextromethorphan.

Medical therapies

As with medications, treating phantom pain with noninvasive therapies is a matter of trial and observation. The following techniques may relieve phantom pain for some people:

• Mirror box. This device contains mirrors that make it look like an amputated limb exists. The mirror box has two openings — one for the intact limb and one for the residual limb.The person then performs symmetrical exercises, while watching the intact limb move and imagining that he or she is actually observing the missing limb moving. Some studies, though not all, have found that this exercise may help relieve phantom pain.
• Acupuncture. The National Institutes of Health has found that acupuncture may ease some types of chronic pain. In acupuncture, the practitioner inserts extremely 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 (rTMS). This therapy uses an electromagnetic coil placed against the forehead. Short pulses are sent through the coil that cause small electrical currents in the nerves located in a specifically targeted area of the brain.Research suggests that this therapy may be helpful for phantom pain, though it isn’t yet specifically approved for this condition. The magnetic field is similar to the one used in MRI scans. Side effects may include a mild headache or lightheadedness.
• Spinal cord stimulation. Your doctor inserts tiny electrodes along your spinal cord. A small electrical current delivered continuously to the spinal cord can sometimes relieve pain.

Surgery

Surgery may be an option if other treatments haven’t helped. Surgical options include:

• Brain stimulation. Deep brain stimulation and motor cortex stimulation are similar to spinal cord stimulation except that the current is delivered within the brain. A surgeon uses a magnetic resonance imaging (MRI) scan to position the electrodes correctly. Although the data are still limited and these treatments aren’t specifically approved for phantom pain, brain stimulation appears to be a promising option in selected individuals.

Potential future treatment

Newer approaches to relieve phantom pain include virtual reality goggles. The computer program for the goggles mirrors the person’s intact limb, so it looks like there’s been no amputation. The person then moves his or her virtual limb around to accomplish various tasks, such as batting away a ball hanging in midair.

Although this technique has been tested only on a small number of people, it appears to help relieve phantom pain.