All the information which comes into our sensory system such as feelings like touch and pain is transmitted up to the sensory cortex of the brain, where the parts of the body have specific parts of the cortex dedicated to them. The diagram which results when the body parts are illustrated against the sensory cortex is called the homunculus, in which certain parts such as the lips and hands have much larger areas of brain devoted to them than average. This is because the importance for daily life of those areas is greater and more information is required from them to figure out what's going on.
An injured tissue releases inflammatory chemicals which both cause local pain nerves to fire off and wake up pain nerves which normally don't participate much. As the levels of nerve impulses increase up towards the spinal cord, the second stage nerves there become overexcited and begin to amplify the incoming messages, cranking up the pain levels transmitted up to the brain. This amplification of incoming nerve impulses is known as central sensitisation, occurring in every acute pain state but persisting in central pain states such as neuropathic pain, of which phantom pain is an example.
We don't feel pain until it reaches the higher brain centres and intrudes upon our consciousness. In a sense, all our pain is in our minds, as it does not exist unless it gets up to our conscious brain. Our pain is not imaginary, our brains are constantly creating a virtual reality for us to understand the world, a virtual visual reality, a virtual touch reality and also a virtual pain reality when it's appropriate. This concept is important in that it is the brain which constructs our pain reality and not the broken ankle, the slipped disc or the burnt hand.
When we have an amputation our nervous system is divided as well as our limb. The bone, muscle and ligaments which are cut through are easy to envisage, but we do not think about the nerves which have to be cut, the consequences of which can be very important. The nervous system does not like parts of it to be removed, it does not like it when an area which normally sends in loads of information suddenly stops doing so. When this occurs odd things start happening in the nervous system, things which can have unpleasant results.
When incoming impulses are completely prevented from reaching the second stage nerves, these nerves react by rapidly increasing their excitability. With no incoming messages due to the amputation or nerve transection, the second stage nerves start to fire off spontaneously, that is for no particular reason but just because they are over-excited. The leg nerves may be missing but all the central nervous system transmission nerves for the leg still exist. The areas of the brain looking after the missing part are still present and still capable of creating pain in that missing part.
When someone has an amputation the pain problem which is often generated afterwards in known as phantom pain, a pain syndrome which appears gradually over a period of months or weeks and which can be very difficult to manage. An example of a very unpleasant type of pain called neuropathic pain, phantom pain can be very deep or stabbing and is very hard to cope with as a sufferer. These neuropathic pains are being generated inside the nervous system and are not related to normal, tissue injury pain.
Drug treatment of phantom pain is difficult as the morphine chemicals such as morphine, fentanyl, tramadol and codeine are often not very effective. The nerve treatment agents such as amitriptyline, gabapentin and pregabalin are used against neuropathic pain with some effectiveness. Other treatments include transcutaneous electrical nerve stimulation (TENS), an electrode based stimulation treatment which can be self-managed. Cognitive therapy may also be useful to start to cope with what can be a long term problem.
Phantom pain can be an intractable, serious problem for anyone with an amputation, and having significant pain before the amputation may make the likelihood of phantom pain greater. A multidisciplinary approach involving a pain clinic is most likely to be helpful.
An injured tissue releases inflammatory chemicals which both cause local pain nerves to fire off and wake up pain nerves which normally don't participate much. As the levels of nerve impulses increase up towards the spinal cord, the second stage nerves there become overexcited and begin to amplify the incoming messages, cranking up the pain levels transmitted up to the brain. This amplification of incoming nerve impulses is known as central sensitisation, occurring in every acute pain state but persisting in central pain states such as neuropathic pain, of which phantom pain is an example.
We don't feel pain until it reaches the higher brain centres and intrudes upon our consciousness. In a sense, all our pain is in our minds, as it does not exist unless it gets up to our conscious brain. Our pain is not imaginary, our brains are constantly creating a virtual reality for us to understand the world, a virtual visual reality, a virtual touch reality and also a virtual pain reality when it's appropriate. This concept is important in that it is the brain which constructs our pain reality and not the broken ankle, the slipped disc or the burnt hand.
When we have an amputation our nervous system is divided as well as our limb. The bone, muscle and ligaments which are cut through are easy to envisage, but we do not think about the nerves which have to be cut, the consequences of which can be very important. The nervous system does not like parts of it to be removed, it does not like it when an area which normally sends in loads of information suddenly stops doing so. When this occurs odd things start happening in the nervous system, things which can have unpleasant results.
When incoming impulses are completely prevented from reaching the second stage nerves, these nerves react by rapidly increasing their excitability. With no incoming messages due to the amputation or nerve transection, the second stage nerves start to fire off spontaneously, that is for no particular reason but just because they are over-excited. The leg nerves may be missing but all the central nervous system transmission nerves for the leg still exist. The areas of the brain looking after the missing part are still present and still capable of creating pain in that missing part.
When someone has an amputation the pain problem which is often generated afterwards in known as phantom pain, a pain syndrome which appears gradually over a period of months or weeks and which can be very difficult to manage. An example of a very unpleasant type of pain called neuropathic pain, phantom pain can be very deep or stabbing and is very hard to cope with as a sufferer. These neuropathic pains are being generated inside the nervous system and are not related to normal, tissue injury pain.
Drug treatment of phantom pain is difficult as the morphine chemicals such as morphine, fentanyl, tramadol and codeine are often not very effective. The nerve treatment agents such as amitriptyline, gabapentin and pregabalin are used against neuropathic pain with some effectiveness. Other treatments include transcutaneous electrical nerve stimulation (TENS), an electrode based stimulation treatment which can be self-managed. Cognitive therapy may also be useful to start to cope with what can be a long term problem.
Phantom pain can be an intractable, serious problem for anyone with an amputation, and having significant pain before the amputation may make the likelihood of phantom pain greater. A multidisciplinary approach involving a pain clinic is most likely to be helpful.
About the Author:
Jonathan Blood Smyth is a Superintendent Physiotherapist at an NHS hospital in the South-West of the UK. He specialises in orthopaedic conditions and looking after joint replacements as well as managing chronic pain. Visit the website he edits if you are looking for physiotherapists in Leeds.
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