Banishing the phantom menace | Action Medical Research

Touching Lives - December 2003

Banishing the phantom menace

Our medical press officer Louise Brown reports on the results of an Action Medical Research project investigating phantom limb pain.

There are around six thousand amputations performed each year in the UK. The majority of these operations are on the legs and are caused by problems arising from diabetes, heart disease and cancer, although in younger people amputation occurs more typically due to injury.

Around 80 per cent of people who have a limb amputation suffer from what is known as ‘phantom limb pain’. This pain can include sensations of crushing, burning, itching and shooting pains. As well as phantom limbs there are also recorded instances of phantom breasts, ears and noses.

An Action Medical Research project at the University of Edinburgh has discovered that using a particular anaesthetic technique during amputation operations may reduce the chance of patients developing these painful sensations.

Pain ‘memories’

Doctors do not fully understand why phantom limb pain occurs although an amino acid called glutamate, which carries messages up the spinal cord to the brain, is believed to be involved. The brain and spinal cord are known to be capable of creating ‘memories’ of pain that cause the pain to persist.

It is thought that part of the brain carries a map of the body called the homunculus or ‘little man’ and this is connected to a corresponding part of the body. When this part of the body is lost the brain is not able to respond to the loss of information and ‘rewires’ itself in adjacent areas of the brain to make up for the lack of signals it no longer receives.

The effect of this is that a lost hand may be felt in the corresponding cheek. ^Other weird phenomena include the reported sensation of orgasm felt in a phantom foot!^ This can occur because the area in the brain for feet and the genitals are close together.

The research team, Drs Lesley Colvin, Sue Fleetwood-Walker, John Wilson and Alastair Nimmo, looked at an anaesthetic drug called ketamine which was administered near the spinal cord by epidural during the operation and for up to three days afterwards. Ketamine has a painkilling effect and has been found to block the effect of the glutamate involved in pain transmission.

The patients who were treated with ketamine as part of their operation were more pain free in the week after amputation than those who didn’t receive the drug. They also were generally less sensitive to touch on the stump than those who did not receive ketamine.

Exciting findings

Furthermore, using other very strong local anaesthetic blocks, with or without ketamine, the researchers found that the percentage of patients affected by phantom pain was generally reduced to around 40 per cent after six months.

It is hoped that a combination of using both ketamine and local anaesthetic around the spinal cord at the time of amputation will maximise the chances of preventing phantom pain development. Laboratory studies showed that this early treatment with ketamine can also make any remaining pain that does still develop more easy to treat with a new type of painkilling drug.

Dr Lesley Colvin told Touching Lives, “This is a very exciting finding for what is a devastating condition. Just changing the type of anaesthetic given to these patients has a really beneficial effect on their life after the operation. This drug seems to dramatically reduce the painful experiences that many of these people have and enables them to feel more comfortable afterwards.”

Dr Sue Fleetwood-Walker added, “Further study of the mechanism of action is required but ^we are very hopeful that this could prove to be a very effective way of helping people undergoing an amputation^. There are many treatment options that are currently used but with limited effectiveness. What we have done is look at a way of tackling the problem by studying the changes at the time of amputation that lead to phantom pain developing.”

Pain you can’t explain!

Paddy Devlin is 63 and had an accident two years ago which destroyed his left foot. There were complications and Paddy had to have a further operation when his leg was amputated to five inches below the knee.

Paddy takes up the story: “It took a while for the wound to heal and there was pain in the stump but then after a period of time I started to get pain in my foot that wasn’t there! It was worse at night after I had taken my prosthesis off and the pain was so bad that I couldn’t sleep at all.

“The doctors in hospital had told me about phantom limb pain, but ^unless it has happened to you, you just can’t explain it^. I get a terrible burning sensation in the bottom of my foot which is no longer there and sometimes I get a bad throbbing sensation. You know there is no foot there so you know you can’t have pain, and that is just so strange!

“Sometimes when it aches you look down at your feet and, although one is the prosthesis, just seeing two feet helps you to deal with the pain. When you first get it you wonder if there is anything else wrong with you and think you are going mad!

Pain control

“I took a mixture of drugs which helped with the phantom pain for a while and I have tried acupuncture. It’s funny but they actually do the treatment on your good leg. I would prefer not to take medication but then it is difficult to control the pain.

“After a year and half I went back into hospital and had some of the nerves cut where the wound was and that helped a lot as I could touch it then without it being painful. I’m so pleased at the advances Action Medical Research are making possible in this area of health care.

“I can drive an automatic car and walking is not too difficult on a level although stairs can be tricky. I really miss my job but I keep occupied playing musical instruments. I play the flute, clarinet, keyboards, guitar, accordion and bagpipes! In that respect I would feel a lot worse if I had lost one of my hands. I have met other people who have lost several limbs and it just makes me appreciate what I have got.”

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