What is phantom limb pain?

Phantom limb pain refers to the neuropathic pain some people experience after the surgical amputation of a limb. The pain may be associated with feelings that the amputated limb is still attached to the body. Phantom limb pain is often hard to distinguish from stump pain (pain felt in the stump remaining after amputation).

Statistics on phantom limb pain

Phantom limb pain affects 50-80% of all amputees. The occurrence is similar in males and females. It also occurs independently of age, level or side of amputation. Patients with short lasting pre-amputation pain and patients who did not have pain in the limb the day before the amputation have a significantly lower incidence of phantom pain.
Phantom limb pain can also affect children. Recent studies have reported that it is present in at least 20% of congenitally limb-deficient children (those who are born without one or more limbs) and in half of all children who undergo amputation before the age of 6 years.

Risk factors for phantom limb pain

Several factors have been identified which increase the risk of developing phantom pain:

  • Preamputation limb pain – the presence of pain in the limb the day prior to amputation.
  • Persistent stump pain – pain felt at the end of an amputated limb’s stump, due to nerve damage.
  • The presence of other pains, e.g. headache, bone, or joint pain.
  • Bilateral limb amputations – having limb amputations on both sides of the body, eg. having both legs amputated.
  • Lower limb amputations – amputation of the leg or part of the leg.

Progression of phantom limb pain

Phantom limb pain usually develops within the first few days after amputation. However, in some cases the onset is delayed for months or even years. It is often associated with the phenomenon of “phantom sensation”, where patients perceive that their limb is present in its pre-amputation form. It may be associated with vivid feelings of movement in the missing limb. Over time, these sensations may change, with the distal part of the limb being felt to ‘telescope’ into the stump.

Symptoms of phantom limb pain

Phantom limb pain is a type of neuropathic pain. This means that the pain is being caused not by a real injury but by a malfunction of the nervous system. Neuropathic pain is often described as having a burning or shooting quality and may be associated with bothersome paraesthesias (unusual sensations such as tingling or pins and needles). The pain reported may also be similar to the pain in the limb prior to amputation.
The pain is generally intermittent in nature, with only a minority of patients experiencing constant pain. Phantom pain is usually felt in the distal (far) part of the missing limb; for example, in lower limb amputation, phantom pain is usually felt in the toes, ball and top of the foot, and ankle.
Some patients with phantom limb pain are reluctant to discuss their symptoms with their doctor for fear that they will be told the pain is “all in their head”. However, it is a well-recognised pain syndrome for which treatment is available, so it is important to mention any pain that may be experienced.

Clinical examination of phantom limb pain

It is important for the medical practitioner to examine the limb stump for complications such as infection, bone spurs, or skin problems which may be contributing to the sensation of phantom limb pain.

Prognosis of phantom limb pain

The probable outcome of phantom limb pain is poorly understood. It is thought that phantom limb pain reduces or vanishes in most cases in the two years following amputation. However, persistent phantom limb pain may occur in approximately 5% of amputees. Even in these persistent cases, the pain usually becomes less severe over time.

How is phantom limb pain treated?

Phantom limb pain is often difficult to treat. There are several different types of treatment available, and a pain specialist is usually involved in the patient’s care to help coordinate pain management.  

Drug treatments

Simple analgesics such as paracetamol can be beneficial in some patients, but provide little pain relief in most. Opiate analgesia has been shown to be effective, but should be used with care in patients with chronic pain.
Anticonvulsants such as pregabalin (Lyrica) and gabapentin have proved beneficial in the treatment of other forms of neuropathic pain. It is suggested that these medications may also be effective for phantom limb pain, though further research is needed.
Tricyclic antidepressants such as amitriptyline are also known to be effective in the treatment of other forms of neuropathic pain, and may be tried in the management of phantom limb pain.
Calcitonin and ketamine have been shown to be effective for the reduction of phantom limb pain.

Non-drug therapies

In some patients, prosthesis revision can provide significant pain relief. Other techniques including acupuncture, heat and cold, ultrasound, massage and stump manipulation have been described in case reports. Transcutaneous electrical nerve stimulation (TENS) has been used with some success in the treatment of phantom limb pain.
Other techniques such as sympathetic nerve blockade and spinal cord stimulation have been used with inconsistent results. Prevention of phantom limb pain has also been attempted, with suggestions that preoperative epidural anaesthesia can reduce the incidence of phantom limb pain in the first few years following amputation.
Stump pain, which may trigger phantom limb pain, can be treated by identifying the trigger point on the stump and treating it locally.
All patients suffering from chronic pain are at increased risk of depression, and this should be identified and treated.

References

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