Phantom Limbs and Virtual Reality
After watching the inspirational Paralympic games this September, it got me thinking about amputees and the challenges they face. As a neuroscientist, my immediate thoughts went to a condition called Phantom Limb Syndrome, a very peculiar sensation that occurs in around 90% of amputees. It made me wonder how on earth does this happen! It didn’t seem logical, so I looked into the background and causes of the syndrome and that led me to some very interesting treatments for patients – spanning a period of over 450 years!
What is a Phantom Limb?
Firstly, let’s get a little bit of background on the term Phantom Limb Syndrome. It is the sensation or feeling that a limb is still part of a person after that particular limb has been amputated. The feeling can be characterised into both painful and non-painful sensations. Non-painful sensations include the feelings of touch, temperature, pressure and often itching, whilst the painful sensations usually come in the form of burning and shooting pains. This phantom limb pain does not originate from the site of amputation; it is a completely separate experience. But for me it begs the question, how can you ‘feel’ anything in a limb that doesn’t physically exist?
Why does it occur?
This question has had scientists baffled since 1552 when the syndrome was first described, but to this day the exact causes still remain unclear. A little more recently, research using Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) scans has led current thinking to believe the feelings originate in the brain and spinal cord. It was found that the portions of the brain that had once been neurologically connected to the nerves in the amputated limb showed activity in the scans when the patient was experiencing their phantom pain. The patient was experiencing the genuine sensation of pain in a limb that shouldn’t be able to feel anything, a slightly confusing concept right? The explanation for this baffling condition is by no means set in stone, but it is mostly thought to occur due to a lack of sensory input from the missing limb. In everyday life when you produce movement via your limbs, the brain is constantly receiving sensory feedback from that moving limb. In a phantom limb patient, after the limb is amputated, comprehensive sensory input from the limb ceases to be sent; the brain becomes confused and so triggers the body’s most rudimentary response of pain. A different example is the noise heard by people suffering from tinnitus – individuals hear a high-pitched noise that doesn’t actually exist as no-one else can hear it – and current theory is that this is also caused by an anomaly in the brain and spinal cord.
Phantom limb pain is extremely prolific in amputees but varies in duration and seriousness between patients. Phantom pain is a type of nerve pain and can be extremely severe and debilitating. It is extremely common for phantom pain to severely affect patients quality-of-life with many people being driven to near madness from the constant pain. The condition is usually treated via drugs such as painkillers, sedative-hypnotics and anticonvulsants but sadly without much success, often leaving patients still having to cope with their chronic pain. An effective form of treatment is therefore very much in need. But what would happen if we could trick the brain into thinking the limb still existed? This concept was first used by neuroscientist Ramachandran in the 1990s whereby he placed a mirror between a patient’s limbs and asked the patient to move their healthy limb and phantom limb whilst looking at the mirror. This could effectively trick the brain into thinking that the phantom limb was moving, removing some of the discordance in brain signals and relieving the patient of pain.
Cutting edge treatments
Now usually, when thinking of the term ‘Virtual Reality’ (VR) I would immediately think of state-of-the-art video games, where users are completely immersed to the point where they think they are in the game. A recent study has allowed this technology to be used to help sufferers of phantom limb pain. Through VR, users are able to see an image of their moving (phantom) limb in their minds. The technology allows the virtual image to move in accordance with the intact parts of the limb creating a life-like and extremely believable sensation of an intact limb. This then tricks the brain, stops the confusion and therefore reduces the patients’ pain. It’s a more modern take on Ramachandran’s mirror therapy concept and has proven to be even more effective. It’s exciting to see how technology can improve people’s lives, what are your predictions for the future?
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