How a Mirror Can Cure Phantom Limb Syndrome, And What That Tells Us About the Brain

Phantom limb syndrome is a fascinating but unfortunate condition that affects amputees who have lost a limb during their lifetime (as opposed to losing one at birth). In cases of phantom limb, these individuals will have an arm or leg removed under anaesthetic, but will find that afterwards they continue to feel as though they still have the limb and can even move it.

This is their phantom limb and would not normally be a big issue, were it not for the fact that the limbs can also sometimes experience itching and even intense pain. Of course this is a serious problem as the patients have no way to scratch the arm or to ease the discomfort and as it can actually be quite distressing for them.

The good news though is that a new treatment discovered in 2012 has been able to treat the problem in most cases. And the even better news? The treatment may also be able to treat other conditions and even some cases of paralysis…

Understanding Phantom Limb

To understand how this treatment works, it is first necessary to understand where phantom limbs come from in the first place. Once, this was thought to be the result of ‘neuromas’ which are severed nerve endings caused by the amputation. The thought was that these could become inflamed and thus send anomalous signals to the brain. In some cases surgeons would even go as far as to remove part of the stump in an attempt to treat this problem, but all this would generally do would be to worsen the pain and in some case create two phantom sensations coming from both the missing limb and the newly missing stump.

Rather, the cause of the problem stems from the somatosensory cortex in the postcentral gyrus. This is essentially a map in the brain of our body parts that fires in response to signals. In this brain ‘map’, the region that manages the hand is right next to the region that manages the face. An expert in the field Vilayanur Ramachandran then found that when stroking certain parts of the face, he could create the sensation that parts of the phantom limb were being touched. This is due to a ‘reorganisation’ in the brain of the area. The nerves in the brain that are responsible for the arm are still present, but they are getting no feedback and are mixed with other signals. The interpretation of this by the brain is then often that the arm is stuck rigid an paralysed, and thus it experiences pain in accordance with that.

Ramachandran then postulated that it might be possible to try and ‘rewrite’ a patient’s body image using visual stimuli, and this is where the mirror box comes in.

The Mirror Box

The mirror box was first used in 2012 on a 57-year old woman who had been born with a right hand that was missing two fingers. At the age of 18 the woman had a car crash and had the entire hand removed, but began having phantom hand pain which eventually became unbearable. After 35 years she was referred for treatment and was put forward for an untested treatment lead by Ramachandran and colleague McGeoch.

Here the duo used a mirror box which consisted of a simple mirror at a particular angle positioned inside a box. The idea was that the patient would sit in front of the mirror box for 30 minutes a day, during which time the reflection of her good arm would make it seem as though she had a full hand and arm back in place.

Amazingly after two weeks past, she found that she could once again ‘move’ her phantom limb and that she had no remaining pain. Subsequently, patients have reported that the treatment has also helped them to move their phantom limbs, and even that they have had their phantom limbs ‘disappear’ altogether.

Implications and Further Findings

On its own, this is a fantastic discovery that will of course help many people suffering with phantom limb pain. However, the implications go further than that even and may help many more people still.

For one, these findings demonstrate the importance of the brain’s ‘body image’ and of course certain concepts can be ‘learned’. Painful phantom limbs are more common in people whose arms were paralysed or painful prior to their amputation. This suggests that the brain ‘learned’ the feeling of pain and paralysis, and that this played almost as important a role as the actual physical problem itself.

Ramachandran then went on to speculate that perhaps this treatment could then be useful for paralysed patients – that perhaps an element of their condition could in fact be ‘learned’. Early attempts to aid the treatment of paralysis has shown that techniques similar to the mirror box may be useful in overcoming the psychological element existent in some cases.

Another interesting note is that the original patient (the 57 year old woman) found that when she ‘regained’ her arm after treatment, her hand had a full set of healthy fingers. While it is possible that she learned this from seeing her other hand in full in the mirror box, Ramachandran and McGeoch speculate instead that perhaps we all have a ‘hard-wired’ template of a full human hand innately.

Brain Plasticity and Virtual Reality

Another study into phantom limb syndrome has some other rather amazing findings. In this study (conducted in 2009), psychologists asked patients to practice contorting their phantom limbs into ‘impossible’ positions. What they found was that the neural representation of the phantom limbs eventually altered in order to account for these new configurations, demonstrating something known as ‘brain plasticity’ (the ability of the brain to change shape in order to meet changing needs in the environment). What this shows is that the brain doesn’t even need any physical feedback in order to change shape – simply changing our belief about something can cause physical and structural changes to the brain. What else might we be able to teach ourselves then?

These studies show us a lot about the power of changing the brain’s ‘body image’ and of the extent of our brain’s plasticity. In the future though, technology more advanced than crude ‘mirror boxes’ is likely to be employed, and one of the most interesting suggestions is that we might someday use virtual reality in order to train the brain. Rather than seeing a mirrored version of your arm, you might be able to look down and see one that appears to be your own. And as these studies have shown, there may be many other uses for something like this too – even if you have all your limbs intact.


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