Phantom limb pain relieved when amputated arm is put back to work

Max Ortiz Catalan has developed a new method for the treatment of phantom limb pain (PLP) after an amputation. The method is based on a unique combination of several technologies, and has been initially tested on a patient who has suffered from severe phantom limb pain for 48 years. A case study shows a drastic reduction of pain.

People who lose an arm or a leg often experience phantom sensations, as if the missing limb were still there. Seventy per cent of amputees experience pain in the amputated limb despite that it no longer exists. Phantom limb pain can be a serious chronic and deteriorating condition that reduces the quality of the person´s life considerably. The exact cause of phantom limb pain and other phantom sensations is yet unknown.

Phantom limb pain is currently treated with several different methods. Examples include mirror therapy, different types of medication, acupuncture and hypnosis. In many cases, however, nothing helps. This was the case for the patient that Chalmers researcher Max Ortiz Catalan selected for a case study of the new treatment method he has envisaged as a potential solution.

The patient lost his arm 48 years ago, and had since that time suffered from phantom pain varying from moderate to unbearable. He was never entirely free of pain.

The patient´s pain was drastically reduced after a period of treatment with the new method. He now has periods where he is entirely free of pain, and he is no longer awakened by intense periods of pain at night like he was previously.
The new method uses muscle signals from the patient´s arm stump to drive a system known as augmented reality. The electrical signals in the muscles are sensed by electrodes on the skin. The signals are then translated into arm movements by complex algorithms. The patient can see himself on a screen with a superimposed virtual arm, which is controlled using his own neural command in real time.

”There are several features of this system which combined might be the cause of pain relief” says Max Ortiz Catalan. “The motor areas in the brain needed for movement of the amputated arm are reactivated, and the patient obtains visual feedback that tricks the brain into believing there is an arm executing such motor commands. He experiences himself as a whole, with the amputated arm back in place.”

Modern therapies that use conventional mirrors or virtual reality are based on visual feedback via the opposite arm or leg. For this reason, people who have lost both arms or both legs cannot be helped using these methods.

”Our method differs from previous treatment because the control signals are retrieved from the arm stump, and thus the affected arm is in charge” says Max Ortiz Catalan. ”The promotion of motor execution and the vivid sensation of completion provided by augmented reality may be the reason for the patient improvement, while mirror therapy and medicaments did not help previously.”

A clinical study will now be conducted of the new treatment, which has been developed in a collaboration between Chalmers University of Technology, Sahlgrenska University Hospital, the University of Gothenburg and Integrum. Three Swedish hospitals and other European clinics will cooperate during the study which will target patients with conditions resembling the one in the case study – that is, people who suffer from phantom pain and who have not responded to other currently available treatments.

The research group has also developed a system that can be used at home. Patients will be able to apply this therapy on their own, once it has been approved. An extension of the treatment is that it can be used by other patient groups that need to rehabilitate their mobility, such as stroke victims or some patients with spinal cord injuries.

Scientists create phantom sensations in non-amputees

The sensation of having a physical body is not as self-evident as one might think. Almost everyone who has had an arm or leg amputated experiences a phantom limb: a vivid sensation that the missing limb is still present. A new study by neuroscientists at the Karolinska Institutet in Sweden shows that it is possible to evoke the illusion of having a phantom hand in non-amputated individuals.

In an article in the scientific periodical Journal of Cognitive Neuroscience, the researchers describe a perceptual illusion in which healthy volunteers experience having an invisible hand. The experiment involves the participant sitting at a table with their right arm hidden from their view behind a screen. To evoke the illusion, the scientist touches the right hand of the participant with a small paintbrush while imitating the exact movements with another paintbrush in mid-air within full view of the participant.

"We discovered that most participants, within less than a minute, transfer the sensation of touch to the region of empty space where they see the paintbrush move, and experience an invisible hand in that position", says Arvid Guterstam, lead author of the study. "Previous research has shown that non-bodily objects, such as a block of wood, cannot be experienced as ones own hand, so we were extremely surprised to find that the brain can accept an invisible hand as part of the body."

The study comprises eleven experiments that explore in detail the illusory experience and include 234 volunteers. To demonstrate that the illusion actually worked, the researchers would make a stabbing motion with a knife towards the empty space ‘occupied’ by the invisible hand and measure the participant’s sweat response to the perceived threat. They found that the participants stress responses were elevated while experiencing the illusion but absent when the illusion was broken.

In another experiment, the volunteers were asked to close their eyes and quickly point with their left hand to their right hand (or to where they perceived it to be). After having experienced the illusion for a while, they would point to the location of the invisible hand rather than to their real hand.

The researchers also measured the brain activity of the participants using functional magnetic resonance imaging (fMRI). Perceiving the invisible hand illusion led to increased activity in the same parts of the brain that are normally active when individuals see their real hand being touched or when participants experience a prosthetic hand as their own.

"Taken together, our results show that the sight of a physical hand is remarkably unimportant to the brain for creating the experience of one’s physical self," says Arvid Guterstam.

The researchers hope that the results of their study will offer insight into future research on phantom pain in amputees.

"This illusion suggests that the experience of phantom limbs is not unique to amputated individuals, but can easily be created in non-amputees," says the principal investigator, Dr Henrik Ehrsson, Docent at the Department of Neuroscience. "These results add to our understanding of how phantom sensations are produced by the brain, which can contribute to future research on alleviating phantom pain in amputees."

Amputee pain linked to brain retaining picture of missing limb

Changes in the brain following amputation have been linked to pain arising from the missing limb, called ‘phantom pain’, in an Oxford University brain imaging study.

Arm amputees experiencing the most phantom limb pain were found to maintain stronger representation of the missing hand in the brain – to the point where it was indistinguishable from people with both hands.

The researchers hope their identification of brain responses correlated with the level of phantom pain can aid the development of treatment approaches, as well as increase understanding of how the brain reorganises and adapts to new situations.

The Oxford University researchers, along with Dr David Henderson-Slater of the Nuffield Orthopaedic Centre, report their findings in the journal Nature Communications.

‘Almost all people who have lost a limb have some sensation that it is still there, and it’s thought that around 80% of amputees experience some level of pain associated with the missing limb. For some the pain is so great it is hugely debilitating,’ says first author Dr Tamar Makin of the Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) at Oxford University.

Treatments for phantom limb pain tend to be limited to standard drugs for pain relief. The origin of the pain is not well understood. There may be many factors that lead to the pain, including injured nerve endings where the limb was lost and changes in the brain areas connected with the missing limb.

Lynn Ledger, a 48 year old trained therapist and advisor to charities on management training from Nottingham, took part in the study. She had her left arm amputated halfway between the elbow and shoulder in May 2009 after radiotherapy for a rare form of cancer failed to deal with an extensive tumour in her arm. She experiences severe pain as if it was coming from the missing limb.

‘I’ve pretty much tried everything to deal with the pain but nothing has worked,’ Lynn says. ‘There are no drug treatments that work because the condition is not fully understood yet. I can only use various distraction techniques, breathing exercises and mental imagery techniques, to help me manage the pain.

‘It’s very hard to describe the pain to others. I have a nonexistent limb, but I still sense it and feel pain. It’s like: imagine you are wearing a lady’s evening glove that stretches from the fingers up the arm past the elbow. But everywhere the glove covers, it’s as if it’s constantly crushing your arm. There are also shooting pains and intensely painful burning sensations that come and go, but the crushing pain is constant.

‘When I heard about this study I wanted to be involved as it was trying to improve people’s understanding of the condition.’

Kirsty Mason from Bracknell is 22 and about to start a new job as a support worker for people with mental health problems, as well as being an assessor for disabled students for their assisted technology needs. She lost her right arm four years ago just below the elbow after blacking out at a train station and falling on to the rails just ahead of a train coming in. She woke to find a wheel stopped on her arm. Since then she’s learned to write with her left hand and began driving last year. She also took part in the brain imaging study.

‘With me it’s all or nothing,’ Kirsty says of her phantom pain. ‘I get the usual pins and needles and a constant niggling pain that I can shut out by doing other things. But the worst pain is a kind of burning. It’s less frequent but it’s intense: 90-100 on the scale. It sounds silly, but the only thing I can do is stick my hand in a freezer. It numbs it.

She says: ‘I can feel my fist clenching, my fingernails digging in. I can see the hand isn’t there but the sensation is so realistic. If someone throws me a ball, I’ll move both hands to catch it. I’ll put out both hands if I fall over.’

The Oxford University team used MRI imaging to study how the phantom limb pain felt by people who have had an arm amputated is related to changes in the brain.

They compared MRI data for 18 amputees, with differing levels of phantom pain, with 11 individuals born with one hand through a limb deficiency and a control group of 22 adults with two full limbs.

The amputations had been done 18 years ago on average, but the participants still experienced sensations for the missing arm. By asking them to move the fingers of the phantom limb while in the MRI scanner, the researchers were able to look at how the missing hand is represented in the brain.

They found that the brain maintained its representation of the hand, even though the limb was no longer there. The extent to which the representation was maintained was linked to the strength and frequency of the pain the amputees felt: those feeling the greatest pain retained the strongest representation of the missing hand.

‘We were astonished to find that in amputees experiencing strong phantom pain, the brain’s response was indistinguishable from that seen in people with intact limbs,’ says Dr Makin.

The researchers found that the amount of grey matter in the phantom hand area of the brain was reduced in amputees compared to those with two hands. But again this was linked to the amount of pain amputees felt. Those experiencing stronger pain showed less structural degeneration in the missing hand area following the loss of the limb.

However, while those with strong phantom limb pain maintained the local brain structure and function for the missing hand, there was evidence that connections to other parts of the brain were disrupted more.

In particular, the representation of the missing hand was more out of synch with the area looking after the other hand on the opposite side of the brain.

Dr Makin says: ‘Most people experience “phantom” sensations in a missing limb after amputation. This disconnect between the physical world and what they are experiencing appears to be linked to a functional detachment in the brain. There seem to be reduced connections between the missing limb part of the brain and the rest of the cortex that’s involved in movement.

‘Our results may encourage rehabilitation approaches that aim to re-couple the representation of the phantom hand with the external sensory environment.’