What is phantom limb. Ambrose Pare, a sixteenth century French Military surgeon first described the concept of phantom limb. Phantom limb is the sensation of an amputated part of the limb still attached to the body and moving appropriately with other body parts. [2] People who were amputated mostly will either feel a phantom sensation or phantom pain. Phantom sensation is different from pain where the person will experience a tingly, cramping, or itching feeling where the removed limb used to be. It is said that is a normal part of healing after the surgery procedure and it often goes away with time. [3] Phantom pain is a sensation of burning, crushing, or stabbing sensation where it can be a short-term or can last for a long time.3 Phantom limb sometimes also occurred when a part of organ is removed such as breast, teeth, or the eye. [4]
1.2 Pain theory
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As a person limbs been removed, how would the person felt the pain? To understand this, the basic concept of pain needs to be explored. Pain is described as an unpleasant sensation that may be associated with actual or potential tissue damage and may have physical and emotional components. [5] Ron Melzack and Patrick Wall suggest in 1962 that physical pain is not a direct result of activation of pain receptor neurons, but rather its perception is modulated by interaction between different neurons.5 By understanding the basic concept of pain, the relation of phantom limb and pain will be further discussed in the other section.
1.3 Incidence
There were an estimate of 1.6 million people with limb loss in 2005 and is expected to increase to 3.6 million by the year 2050 in a study done in USA.1 The number of traumatic amputation also increased due to the war in Iraq and Afghanistan.1 For the person that received amputation, the incidence of PLP reported to be in the range of 42.2% to 78.8%.1 Another studies in 62 suggest that this phantom incidence is less seen in early childhood due to the fact that in early childhood there is not enough time for the body image to ‘consolidate’. [7]
2.0 The Mechanism of phantom limb (patophysiology)
2.1 Introduction
To understand the factors that causing the pain in phantom limb the underlying basic of anatomy and physiology must be well known first. The phantom limb pain at first was taught just to be a result of psychiatric illness. However research after research was done to justify the theory behind the mechanism that causes the phantom limb. Multiple mechanism theory were suggested which involve peripheral mechanism, central mechanism and also psychogenic mechanism.
2.2 Peripheral mechanism
In the article “What is a Phantom Limb” from the news medical, the peripheral mechanism theory that was causing the pain was taught to be due to neuromas which is irritation in the severed nerved ending. The irritation was a result of many nerve endings are terminated at remaining stump when a limp is amputated. The inflamed nerves then will send signals to the brain that the brain perceived it as a pain. Based on this theory, treatments are done but the results were a failure. Some surgeon would perform a second amputation so that the inflamed nerved endings can be removed and may bring temporary relief but the result was that the phantom pain increased than they had previously. Some surgeon also attempts to remove the sensory nerved leading to spinal cord and in a more extreme cases, a surgeon would removed the part of thalamus that received the sensory signals from the body.2 In neuromas, there is a hyper-excitability and spontaneous discharge of sodium channels and drugs are used to block this sodium channels helps to reduce a little pain that led to this theory being supported.1 However this does not explain about the phantom limb pain in the patient with congenital absence of limb.1
2.3 Central Mechanism
The National Health Institute (NHI) in 1990 discovered that the brain would reorganize itself if the sensory input were being cut off. This then gives the idea that the phantom limb pain was due to cross wiring in the somatosensory cortex.2 Somatosensory cortex is located at the post-central gyrus and it receives input from the limbs as well the body. V.S. Ramachandran, a neuroscientist stated that when a person right hand is amputated, the input from the hand to the left somatosensory cortex would be stopped.2 However this person would experience a phantom limb feeling due to the somatosensory cortex near to the hand which is the arm and face will take over the right hand cortical region or known as remapping.2 This cortical reorganization at the level of brain partly explains the afferent nociceptive stimulation of neurons within the surrounding area produces the sensation in the missing limb.1 Another theory propose is that in the level of spinal cord there is an increase of N-methyl-D-aspartate (NMDA) receptor activity which leads to a neuronal firing of nociceptive neurons hence this exacerbate the phantom limb pain. [8]
2.4 Psychogenic mechanism
Another theory that was proposed in the article “Phantom Limb Pain: Mechanisms and treatment” from the pain research and treatment journal is through psychogenic mechanism. However this in not supported in some research although it was believed that stress, exhaustion, anxiety and depression would exacerbate phantom limb pain. In one cross sectional study, the results found that amputation in people with personality traits characterized by passive coping style and catastrophic behavior was found to be associated with the development of phantom limb pain independent of anxiety and depression.1
3.0 Pain Management
3.1 Introduction
As for the management of phantom limb pain, there are no definite treatments that can cure the pain completely. There are lots of treatments either through drugs or through a non-drugs intervention. Like other drugs, some may bring benefit and brings side effect to the patient. Thus, it depends on the doctors to make the decision based on the patient condition to gives what is the best treatment for their patient. For this pain management of phantom limb pain, all were from the same source, which is an article “Phantom Limb Pain: Anaesthesia Tutorial Of the week 229”. [9]
3.2 Drug intervention
3.2.1 Antidepressant
An example of an antidepressant is trycyclic antidepressants that the drug works by inhibiting the re-uptake of noradrenalin and serotonin and will potentiate the action of two important central anti-nociceptive pathways. There is however no studies specifically that examine the use of trycyclic antidepressant in phantom limb pain but they are commonly used and is thought to have the modest efficacy.
3.2.1 Sodium channel blockers and anticonvulsants
Gabapentin and Pregabalin are thought to be effective in variety of neuropathic pain problems. They act by binding to voltage gated calcium channels. However the side effects of this drug is somnolence and dizziness, which can be minimized by using gradual dose titration. Intravenous Lidocaine also has been reported that it bring good results in neuropathic pain. Mixiletine, an oral analogue of intravenous Lidocaine has been shown in a small study that is results in pain relief in phantom limb pain
3.2.3 Tramadol
A synthetically produced drug that has a monoaminergic and opiod activity and has less adverse effects compared to strong opiods. It is useful for neuropathic pain that involve multiple receptor process. It has shown in a number of studies that it helps reduce neuropathic pain including post-amputation pain.
3.3 Non-drug Intervention
3.3.1 Mirror Box
Mirror box is a non-medical treatments where a device containing a vertical mirror and is positioned so a reflection of the patient intact limb is superimposed onto the perceived position of the phantom limb. It is shown that the mirrored movements activate the contra lateral sensory motor cortex and cause a reduction in pain.
3.3.2 Mental imagery
This is a process of imagining motor sequences and is thought to work similar way as the mirror box. Studies have shown that it results in a significant reduction in pain.
3.3.3 Psychology
Psychology therapy such as hypnosis and cognitive behavioral therapy may also benefit patient in reduction of the phantom limb pain.
3.3.4 Electrical stimulation
Electrical stimulation of spinal cord, deep brain structures and motor cortex helps to relieve pain but its effectiveness decreases over time.
3.4 Prevention
In order to prevent the risk of developing phantom limb pain, doctors suggest the use of regional anesthesia through spinal or epidural few hours or days leading to the amputation. By doing this procedure it might helps to reduce the pain before the surgery hence reducing the risk of lasting phantom limb pain. [10]
4.0 Conclusion
Phantom limb pain is an issue that started a long time ago and has been discussed until nowadays. Lot of researched are done in order to find the right mechanism and the most efficient treatment to reduce the pain in a person with amputated limb. With the advanced technology nowadays, a lot of more scientist and research will come out with a new discovery in this studies of phantom limb pain. As for the anesthetic view of phantom limb pain, there are few research done that proves to help the pain management in phantom limb. A right decision by an anesthesia can helps and suggests a better treatment to be undergone by a patient with an amputated limb.
