Phantom Limb Pain Information

Phantom limb pain ( pain appearing from where an amputated limb used to be) is difficult to treat. After amputation of a limb, an amputee continues to feel it and to experience sensations from it.

The pain is described in various ways: burning, aching, 'as if the hand is being crushed in a vice,' etc. Such words, however, cannot fully encompass the experience of living with such a pain. In those with chronic pain after spinal cord injury it is frequently the pain rather than the paralysis that interferes with work and social life.

Mechanisms
There may be many mechanisms underlying phantom limb pain. Damage to nerve endings is often important: subsequent erroneous regrowth can lead to abnormal and painful discharge of neurons in the stump, and may change the way that nerves from the amputated limb connect to neurons within the spinal cord. There is also evidence for altered nervous activity within the brain as a result of the loss of sensory input from the amputated limb.

New treatments
Recently, some potentially valuable treatments have arisen, based on new ways of perceiving the origin of the pain itself.

Flor's group has shown that the development of phantom limb pain is correlated with changes in the way peripheral areas of the body are represented in the sensory cortex. Although is not clear why this should lead to pain, they devised experiments to reverse this cortical plasticity to see whether pain sensations were also altered.

They found that use of an electrical prosthetic limb moved by signals from the patient's muscle reduced the pain if used for several hours per day. Brain imaging revealed that this effect was dependent on a reversion of the sensory cortex to its original state. A task involving repeated touching of the skin over the stump, to improve sensory discrimination there, also reduced phantom limb pain, possibly by replacing some of the sensory input to the brain lost following amputation.

Report RR399 Improved early pain management for musculoskeletal - ketamine as pain relief
(source drugs.gov.uk)