Introduction
Phantom pain, sometime referred to as Phantom Limb Pain or simply 'PLP' is the pain felt by someone who has had a part of their body removed or amputated and where the pain is coming from, or seems to come from, the amputated body part.
It is most common where for example, a foot or a leg or finger or hand has been amputated, although can also occur for other parts of the body, for example after the removal of a breast (mastectomy) or part of the tongue or even removal of a tooth.
The existence of phantom pain has been known about for a long time, with reference to it dating back to 1551 when a French military surgeon called Ambroise Pare reported that amputees still felt pain in the amputated part of the body.
A closely associated but different form of pain is 'residual limb pain' sometimes called 'stump pain', which again is felt by amputees but the pain is clearly coming from the remaining part of the limb. Residual limb pain and phantom limb pain often happen at the same time. Some people who undergo amputation also report continuing to feel sensation from their removed limb – this is known as 'phantom limb sensation'.
Phantom pain is most closely associated with limb loss, either via amputation or from injury, however it can also affect people who are born without limbs due to a congenital birth defect, and people who have had some damage to either the spinal cord or a nerve root affecting a specific limb or part of the body.
Causes
For a long time, phantom pain was dismissed as being a psychological issue, but medical science now has a better understanding of why it happens and what causes it.
When a limb is amputated (or another part of the body is removed), the remaining nerve endings which used to supply that part of the body regrow and this seems in some cases to affect the normal communication between those nerves, the spinal cord and the brain.
Imaging scans of people with the condition using MRI (Magnetic Resonance Imaging) and PET (Positron Emission Tomography) scans show that the parts of the brain devoted to sensation from the amputated limb are active while the patient is feeling phantom pain.
There is also a theory that any pain felt in the limb before loss of the limb is retained in the brain afterwards and pain signals continue afterwards, and this is a known risk factor for developing phantom pain. Residual limb pain is also a known risk factor for developing phantom pain.
As with other types of pain, there are a range of triggers of phantom pain reported by people with the condition. These include for example…
- Weather conditions, including cold temperatures and changes in barometric pressure.
- Touching the remaining section of the limb / body part.
- Urinating or defecating.
- Smoking.
- Sexual activity.
- Angina.
- Shingles (herpes zoster).
- Chest pain (angina).
Symptoms
Phantom pain generally has the following characteristics…
- Generally, develops shortly after loss of limb / body part.
- Pain is generally a sensation of burning or stabbing pain in (or in some cases a feeling of crushing or squeezing of) the phantom limb.
- Accompanied by phantom limb sensation, i.e. it feels as if the limb is still there and for example moving, or a knee is bent etc., or is feeling hot or cold or is itching.
Sometimes the pain appears to come only from the extremity of the amputated limb, for example from the foot, not the rest of the leg.
Tests / Diagnosis
Phantom limb pain is relatively straightforward to diagnose, however it is important to distinguish it from residual limb pain, where the cause of the pain may be for example, an infection or the presence of a neuroma (which is a tangle of nerve endings that sometimes forms after amputation or loss of a limb).
Recognition that phantom limb pain is caused by a form of dysfunction of the remaining nerves, the spinal cord and/or the brain's ability to sense pain, means that this type of pain needs to be treated quite differently from other types of pain.