Reading time: 5 minutes
Her alarm went off, and with a look outside of her window, she realized immediately that this was going to be a gloomy morning. How cozy it could have been to just stay in bed, turn around, and stay warm and comfortable. “But money doesn’t grow on trees,” she thought to herself and pushed herself out of bed. The moment she finally had found some motivation to tackle the day, she felt a sudden stitch-like pain running through her arm, something that had happened quite often lately. Once again she started thinking about whether she needs some time to rest and take a day off. “Get up. Isn’t this just all in your head?” she asked herself while pressing the turn-on button of her coffee machine. One hand still on the coffee machine, she felt it again. The sudden stitch in her left arm. This one feeling that just did not go away. The pain would have been her constant reminder. Her sweet little reminder of something that was not there anymore. Something that had gotten removed. She thought about that Tuesday in May on which the surgery had happened. That day they had to amputate it. Her whole left arm.
What this fictitious case illustrates here describes the lived reality of many people who have undergone amputation surgery. A painful or unpleasant sensation in the area the amputated limb used to be. This ironically striking discrepancy between the removal of a limb and the persistence of perceived pain in the absent area is called phantom limb pain (PLP).
While some might even consider this as impossible, PLP is not a rare neuropathic pain disorder. In fact, researchers have found about seven out of ten individuals who had undergone limb amputation surgeries to be affected by PLP.
The experiences of people suffering from PLP can differ in its guises and degree. However, regardless of the way PLP occurs, it always impacts the individuals and can cause serious consequences. These range from physical and mental health implications to the quality of life and the way PLP can slow down the process of rehabilitation after an amputation surgery. While for some individuals the pain occurs in a sudden manner, others describe it as a pain lasting for hours. Moreover, PLP can be experienced as a burning feeling, cramping, stinging like electric shocks, or even as a stabbing pain. For many people, this creates a perception of a limb that has never been amputated, something that is still present.
Who would not try to use a limb in which they just felt a sensation?
While this is a common experience among people with PLP, the feelings it evokes could not be more contrasting. On the one hand, for some individuals this ‘sweet reminder’ elicits a feeling of gratefulness. People compare this pain with their pre-amputation experiences, remind themselves of what they have been through, and are grateful to be alive. On the other hand, many individuals describe their frustration that comes with the pain and the way it triggers flashbacks of what has happened. Consequently, this constant reminder can impact their sleep behavior, cause sleep disturbances, affect their mood, and cause severe stress and depressive feelings.
But where does this distinct feeling/pain come from?
Although PLP had already been recorded in the 16th century, it still puzzles scientists today, as no single theory has been found to fully explain the pain experienced in the absent area. One of the first to popularize the view that pain is actively constructed by the brain was Ronald Melzack. In his neuromatrix theory, the Canadian psychologist proposed the concept of a ‘body-self neuromatrix,’ which is formed by an individual’s genes and their experiences. Regarding PLP, the theory holds that this combination, one’s genes and their experiences of pain, can leave a ‘neurosignature’ for a specific kind of pain in an individual’s brain. As this persists after the amputation of a limb, this neurosignature can still be generated. Accordingly, this may happen through cognitive inputs such as memories or stress, for example. Another influential theory that has shaped research in phantom limb pain is the cortical remapping theory. Different from the ‘self-body neuromatrix’, this theory proposes the persisting somatosensory map, which can be seen as a body map consisting of areas for every single touch and movement sensation. After amputating a limb, the corresponding area does not get sensory input anymore, and synapses from neighbouring areas invade the area that has lost its input. This invasion can lead to new input in the area corresponding to the amputated limb and thus lead to phantom sensation and phantom limb pain. In other words, if a person has had their arm amputated, they may feel a phantom sensation when touched on their face. This phantom sensation may be perceived as a consequence of the invasion of the silent area by the neighbouring representation of the face.
However, although both theories have been influential and have shaped exploration in pain and phantom limb pain, research has shown mixed evidence for both of them. While the neuromatrix theory does provide an overall framework, it misses a specific testable causal mechanism that explains the phenomenon of phantom limb pain. Similarly, research has not found sufficient evidence proving a causal relationship between phantom limb pain and cortical remapping.
Although research has set a starting point for the discovery of phantom limb pain, much more investigation is needed in both research on pain and on phantom limb pain specifically. This would help explain why one may wake up feeling a stitch-like pain in their left arm that has been amputated and could help develop appropriate treatments.
Amelie Happe
Bibliography:
Collins, K. L., Russell, H. G., Schumacher, P. J., Robinson-Freeman, K. E., O’Conor, E. C.,
Gibney, K. D., Yambem, O., Dykes, R. W., Waters, R. S., & Tsao, J. W. (2018). A
review of current theories and treatments for phantom limb pain. The Journal of
Clinical Investigation, 128(6), 2168–2176. https://doi.org/10.1172/JCI94003
Guémann, M., Olié, E., Raquin, L., Courtet, P., & Risch, N. (2023). Effect of mirror therapy
in the treatment of phantom limb pain in amputees: A systematic review of
randomized placebo‐controlled trials does not find any evidence of efficacy. European
Journal of Pain (London, England), 27(1), 3–13. https://doi.org/10.1002/ejp.2035
Limakatso, K., Ndhlovu, F., Usenbo, A., Rayamajhi, S., Kloppers, C., & Parker, R. (2024).
The prevalence and risk factors for phantom limb pain: a cross-sectional survey. BMC
Neurology, 24(1). https://doi.org/10.1186/s12883-024-03547-w
Melzack, R. (1990). Phantom limbs and the concept of a neuromatrix. Trends in
Neurosciences, 13(3), 88–92.
Trevelyan, E. G., Turner, W. A., & Robinson, N. (2016). Perceptions of phantom limb pain in
lower limb amputees and its effect on quality of life: a qualitative study. British
Journal of Pain, 10(2), 70–77. https://doi.org/10.1177/2049463715590884
A.P.E. 
Lascia un commento