Phantom Limb Pain

What is phantom limb pain?

Did you know that the majority of people who have had a limb amputated still report feeling some sensation in the removed limb, such as itching or tingling? As many as 80% of amputees experience a type of this phantom limb pain. This can manifest as almost any sort of pain, such as stabbing, throbbing, or burning. Pain can last anywhere from minutes to hours to days, with some amputees in constant pain for decades.

Ambrose Paré, a surgeon in the French military, first recognized the phenomenon in 1551 when some of his soldiers reported pain in their missing limbs for long periods of time. A surgeon in the Civil War, Silas Weir Mitchell, first coined the term “phantom limb” in 1871. It was once believed that phantom limb pain originated from painful neuromas (pinched nerves) from the original amputation surgery.

Symptoms

Although referred to as “pain,” many amputees also experience other sensations. These might include:

• Tingling
• Numbness
• Hot or cold
• Cramping
• Sharp, brief stabbing
• Burning

Symptoms may be mild for some, but other patients experience severe, painful, and debilitating phantom limb sensations. Of all possible sensations, the most common that patients continue to feel is pain in the missing limb.

Prevalence

The prevalence of phantom limb pain varies. It is more likely to occur in a lower limb amputation than an upper limb. Phantom limb pain usually occurs in the part of the missing limb that is farthest from the body. This means that even if an arm was amputated, the pain typically occurs in the missing fingers. Pain may also mimic the pain that was present in the limb prior to the amputation.

Overall, approximately 72% of amputees will experience some form of pain after surgery. These painful sensations can often diminish over time, but some people suffer from long-term pain that can be difficult to treat.

Risk factors

The main risk factors for the development of this condition include the following:

• Phantom sensations (other than pain)
• Pain in the stump (sometimes referred to as residual limb pain)
• Pain in the limb prior to amputation
• Use of a prosthetic limb
• Number of years since the original amputation surgery

Body parts most associated with the cortex of the brain (fingers and toes) also have a higher risk of developing phantom sensations.

How to treat phantom limb pain

While no one is quite sure what causes this form of pain, many experts suspect damaged nerves or scar tissue. Some also blame the mixed signals sent to the brain when an entire limb suddenly stops sending information. When the brain stops receiving input from a limb, it emits the most basic message it can to convey that something’s wrong: pain.

Phantom limb pain is a complex condition. Up until the early 1990s, it was routinely treated by performing additional amputations, shortening the stump, and removing any neuromas that might be causing pain.

In 1991, Tim Pons, a scientist with National Institutes of Health, discovered that the brain has the ability to reorganize itself if there is sensory deprivation from a part of the body. This revolutionized treatment in that it acknowledged the neurological aspect of the condition.

Understanding that the brain could be retrained was crucial to developing more successful treatment plans. Some treatments for phantom limb pain include:

• Medications
• Physical therapy
• Mirror therapy
• Phantom motor execution
• Interventional injections
• Neuromodulation

Medications

Studies have shown that tricyclic antidepressants, sodium channel blockers, and anticonvulsant medications can be useful in neuropathic pain conditions like phantom limb pain.

Most doctors agree that opioids cause more harm than good for chronic pain, but this is not necessarily the case with phantom limb pain. A study in 2013 found that intrathecal administration of buprenorphine/naloxone was very effective in many patients. This provided them with prolonged relief from phantom limb pain when other treatments were ineffective.

Physical therapy

Desensitization therapies (along with sympathetic nerve blocks) may provide relief for patients who have complex regional pain syndrome.

Physical therapy also ensures that prosthetics fit properly and that patients are using them effectively. This alone can help relieve many symptoms.

Mirror therapy

One of the more promising treatments for phantom limb pain is mirror therapy. Mirror therapy involves the use of a mirrored box with two openings: one for the amputated limb and one for the other limb.

The patient performs isometric exercises with the non-amputated limb, so it appears as though the amputated limb is moving as well. Research in 2018 found that mirror therapy is a simple, non-invasive, and effective way to drastically reduce phantom limb pain.

Recently, virtual reality (VR) programs have taken the place of traditional mirror therapy. Patients wear VR goggles while performing tasks with their remaining limb, but the goggles show the same tasks being performed by the missing limb instead. Alternatively, a patient can perform tasks in front of a screen with motion tracking equipment.

However, these therapies are useless for patients who have lost both arms or both legs, because there’s nothing for the mirrors to reflect or for the VR programs to mimic.

Phantom motor execution (PME) 

A new treatment for phantom limb pain takes this idea to new heights, while also providing a novel option for double amputee patients.

Max Ortiz-Catalan, a researcher at Chalmers University of Technology, recently carried out a case study with a patient who suffered from constant phantom limb pain for 48 years. The patient, who lost his arm below the elbow after a traumatic accident, had attempted drug therapy, acupuncture, traditional mirror therapy and even hypnosis, but his pain remained. Researchers attempted a new treatment method with the patient.

For the study, electrodes were attached to the patient’s arm stump. The patient was instructed to attempt eight different movements with his phantom arm and hand, such as opening and closing his hand or flexing his wrist. These attempted movements “trained” the researchers’ computer program to translate myoelectric muscle signals in the stump and allowed the patient to control a superimposed arm on a screen. The superimposed arm responded in real time, fooling the brain into thinking it was controlling a real arm.

Not only does this method allow a patient to visualize the amputated limb, as in existing mirror and VR therapy, but it also engages the areas of the brain that control the limb’s movement. This, suggests Max Ortiz-Catalan, is the reason that this method is more effective at treating phantom limb pain. Even when the superimposed arm wasn’t visible, such as while playing a racing video game, the patient achieved the same control over the arm. Additionally, this therapy method’s function is based on muscle signals in the stump, rather than the reflection of a remaining limb, so it will work just as well for double amputees.

After a study of 14 arm amputees with similar techniques, they found that:

“The patients were treated with the new method for 12 sessions. At the last session the intensity, frequency, and quality of pain had decreased by approximately 50 per cent. The intrusion of pain in sleep and activities of the daily living was also reduced by half. In addition, two of the four patients who were on analgesics were able to reduce their doses by 81 per cent and 33 per cent.”

Interventional injections

Injection therapy can be beneficial, especially when combined with other treatments. For upper extremity pain, interscalene blocks or stellate ganglion blocks may help. Lumbar sympathetic blocks can help lower extremity phantom limb pain.

Neuroma injections can also be beneficial for those who suffer with extremity neuromas.

Neuromodulation

Neuromodulation is a way to block nerve signals to the brain: even those signals that seem to be coming from a missing limb.

Transcutaneous electrical nerve stimulation (TENS) or spinal cord stimulation offers significant relief to many patients who have not had success with other treatment options. Of the two, TENS is the least invasive, using skin patches to deliver an electrical current to pain receptors in the brain. This mild electrical current replaces pain with a slight buzzing sensation.

For more intractable pain, spinal cord stimulation (SCS) technology works by introducing an electrical current into the epidural space near the source of chronic pain. Trial SCS leads are placed into the epidural space. These soft, thin wires connect to a stimulating device worn for five to seven days. If the trial successfully relieves your pain, your doctor can place a permanent SCS for long-term pain relief.