Treating Phantom Pain

Untreated, phantom limb pain can become intractable and chronic; once it develops and persists the sensations are rarely improved by present medical treatments. Should the amputee feel that he or she is helpless to do anything about the pain it can grow at a seemingly uncontrollable rate. Destructive surgical procedures have been tried yet they prove to be of limited use. The procedures can be effective for a few months or more, but the phantom pains always return, frequently worse than before the surgery. These procedures that would cut the nerve endings in an attempt to alleviate the erroneous growth issues are therefore not advised and likely not covered by insurance.

Recently, some potentially valuable treatments have arisen, based on new ways of perceiving the origin of the pain itself.

Flor's group has shown that the development of phantom limb pain is correlated with changes in the way peripheral areas of the body are represented in the sensory cortex. Even though it is not clear why this should lead to pain, they devised experiments to reverse this cortical plasticity to see whether the pain sensations were also altered.

The study found that use of an electrical prosthetic limb moved by signals from the patient's muscle reduced the pain if used for several hours per day. Brain imaging revealed that this effect was dependent on a reversion of the sensory cortex to its original state. A task involving repeated touching of the skin over the stump, to improve sensory discrimination there, also reduced phantom limb pain, possibly by replacing some of the sensory input to the brain lost following amputation.

Visual tricks
In a recent publication, Patrick Wall suggested that pain might be considered a 'need state', like thirst, rather than simply a sensation. If that is so, then the 'need' might involve movement to avoid or reduce pain.

Evidence that stimulation of the motor cortex (the area that controls movement) can reduce phantom limb pain has been around for some time. Perhaps more surprising was a trial by Ramachandran and Rogers-Ramachandran in 1996. They asked people with amputations of the arm and phantom limb pain to place their arms inside a mirror box so that they saw their remaining arm mirror-reversed to look like their amputated one. When they moved their remaining arm in the box they were 'fooled' into thinking they were moving their amputated one, and their pain was reduced. Although this has proved less effective in some subsequent trials, it did suggest that phantom limb pain might reflect a loss of motor control to the limb, as well as loss of sensory input from it.

More recently the mirror box has been used with some success in pain that is not due to sensory loss. In fact, a box may not be required. In phantom limb pain due to a peripheral nerve injury (brachial plexopathy), Giraux and Sirigu have shown that merely training patients to imagine their paralysed arms moving in relation to a moving arm on a screen in front of them can relieve phantom limb pain.

They suggest that these attempts to link the visual and motor systems might be helping patients recreate a coherent body image, and so reduce pain as a result of reduced and disordered input. If this approach is successful, it may be that relatively simple treatments, such as patients imagining that they are swinging a golf club with their amputated limb, could have significant pain-relieving benefits.

Finally, in experiments still being developed, we are constructing an arm in virtual reality which subjects with phantom limb pain will move themselves using motion capture techniques. Movement of their stump will be captured by a movement-tracking device, and used to project the movement of the reconstituted limb in virtual reality. We anticipate that this will lead to a sense of re-embodiment in the virtual arm and hence to a reduction of the pain.

These new approaches are all based on a shift in emphasis in phantom limb pain away from the site of damage – the stump – to the centre of pain processing: the brain. It appears that disordered inputs from the limb's sensory systems, combined with disrupted motor signal back to the limb, generate a mismatch between the brain's built-in map of the physical body and what is actually perceived. For some reason, this mismatch results in pain.

Whichever of these new techniques proves effective – and simple enough to be used – the prospects for relief from pain are probably brighter than at any time since Weir Mitchell first coined the term phantom limb pain in 1872.

What is Phantom Pain?

Phantom limb pain – Pain appearing to come from where an amputated limb used to be – is often excruciating and almost impossible to treat. New approaches, based on a better understanding of the brain's role in pain, may be opening the way to new treatments.

What is Phantom Pain?
Following amputation of a limb, the amputee typically continues to have an awareness of the limb and to experience sensations that feel like they are coming from that limb. These are commonly referred to as phantom limb sensations and are also found to be present in children born without a given limb. This suggests that the perception of our limbs is 'hard-wired' into our brains and that feelings from our limbs become mapped into our brain networks as we develop.
If we consider that phantom limb sensations are normal then so too, is phantom limb pain. This pain feels quite real and occurs in a majority of those who have lost a limb. Phantom pain has also occurred in conditions in which the brain is disconnected from the body, such as peripheral nerve injuries and after spinal cord injury, when an area becomes insentient (and usually paralyzed). This may sound confusing but, no more than an amputee describes the pain he or she feels from the area where a limb that is no longer attached to the body used to exist.

The pain is described in various ways: burning, aching, itching, like lightening and cramping as though the hand, fingers, foot, or toes are cramping or being crushed in a vice. Such words, however, cannot fully encompass the experience of living with phantom pain. Traditional medicines will likely fail as the muscular skeletal structure is no longer there and cannot be affected by medications. In those with chronic pain after spinal cord injury it is frequently the pain rather than the paralysis that interferes with work and social life. One amputee has stated that paralysis does not stop life, but pain can certainly slow it down.

Nerve Endings
There could be several mechanisms underlying phantom limb pain, some physical, others could be mental. Damage to nerve endings would certainly be a physical cause: subsequent erroneous nerve re-growth could lead to abnormal and painful discharge of neurons in the stump. This random nerve ending re-growth could alter the way that nerves that once connected the amputated limb communicate with neurons within the spinal cord.
There is also evidence for altered nervous activity within the brain as a result of the loss of sensory input from the amputated limb. This might further be described as a pulse sent by the brain to the missing limb and not getting a ( required ) response and the pulse being sent repeatedly. Still not receiving a response, the brain might assume something is wrong and trigger a ‘pain alarm’; something to draw attention to the affected area. This would then be more of an emotional rather than physical sensation. Granted, this may sound unreasonable but, the mind is a very powerful thing and you need to be in control of it rather than the reverse.

As an amputee myself, I can easily relate to the sensation of phantom pains in my missing limb. The sensations are just that, sensations and not what I consider pain. Pain has the connotation of hurting; having a part of the body which is no longer there that hurts is simply not acceptable in my mind. The idea being that if I can’t see or touch the body part, then how am I to resolve it if not with my mind. I generally describe the sensations as sometimes having the tingling sensation of being ‘asleep’ other times it might be like fireworks or lightening strikes going through what used to be my foot. It requires effort and repetition but, the simple fact is that since my foot is not there, the ‘pain’ cannot exist. It may sound like a leap of faith but the other side of the coin is that if I let it ‘hurt’ then it could only get worse and that, is not acceptable.
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