The loss of sensory input from the amputated limb leads to maladaptive reorganization of the sensory cortex, wherein the deprived area of the primary sensorimotor cortex responds to inputs received from cortical neighbors. Neuronal reorganization in the peripheral somatosensory nervous system leads to maladaptive supraspinal changes such as map remodeling of the sensory cortex, loss of neurons and/or neuronal function, and alterations in neural and glial activity, leading to pain.

Origin of Phantom Limb Pain 

In one type of phantom limb pain, the amputee thinks that the missing limb is twisted, which is why it is hurting. One treatment for such pain is placing a mirror reflecting the intact limb in the position of the missing limb. The patient repeatedly moves “both limbs,” allowing them to perceive the missing limb being untwisted, reducing pain. This suggests that visual stimuli may allow for the reinterpretation of pain arising from phantom limbs. 

Studies have suggested that the incorporation of neural prosthetics can also help alleviate phantom limb pain. 

Treatment of Phantom Limb Pain 

Between 1940-45 W.R. Henderson and G.E. Smyth conducted a study in prisoner-of-war hospitals and camps in Germany to study the phenomenon of "phantom limbs." Close contact with many amputation cases over a long period provided an opportunity to study the phantoms. A series of observations were made about the "natural phantom," the patients' perceived voluntary movements, and abilities of the phantom.
**Note: As addressed in the study itself, the detailed notes were unavoidably lost in Germany at the end of World War 2. The paper has therefore been compiled from memory (ie. the prepared statistics could not be recalled clearly).

Henderson and Smyth "Phantom Limbs" Study (1940)

Phantom Limb Pain Library


An example of neuropathic pain is Phantom Limb Pain, which is categorized as  constant pain, varying pain across the day, or as separate pain attacks differing in duration and intensity following the loss of a limb. 

•	Origin of Phantom Limb Pain 
•	Treatment of Phantom Limb Pain 


Grinnell College


Pain that sustains after a peripheral nerve injury is called neuropathic pain, also known as neuralgia. After peripheral injuries, microglial cells surround the synapses between pain fibers and neurons in the dorsal horn of the spinal cord, releasing chemicals that make the dorsal horn neurons hyper-excitable. This leads to neural signaling of pain in the hypothalamus. 

Cases of neuropathic pain can be considered disagreeable examples of neural plasticity since the nervous system (either the spinal cord or the cortex) amplifies its response to the pain signal. 

• Phantom Limb Pain 

• Migraines 


Neuropathic Pain 

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Phantom Limb Pain 


Migraines are defined as regularly occurring, intense headaches that typically affect one side of the head. Unlike other types of neuropathic pain, neuronal hyperexcitiation that spreads across the cortex does not particularly arise from injury. This wave of activity stimulates stimulates trigeminal nerves that normally signal damage in blood vessels, causing the experience of pain. Another theory states that the release of a neuropeptide called CGRP by the trigeminal nerves causes the pain. 

Migraines 

Sleep impacts both neuropathic and orofacial pain sensation.
Sleep quality is affected by pain and pain sensation is affected by a person's sleep quality.
One challenge that exists to clinicians today is finding treatment that will both improve sleep and reduce pain.
Opioids and antidepressants can reduce pain but may worsen sleep problems.

Relationship Between Sleep and Trigeminal Neuralgia

A patient suffered a severe nerve injury to their leg a year ago. The physical wound has completely healed, but they continue to experience intense, burning pain in the leg, even from a light touch. Which of the following provides the most accurate physiological explanation for this ongoing pain sensation?

A patient had a severe injury to their hand a year ago. The wound has completely healed, and medical imaging shows no remaining tissue damage. However, the patient continues to experience intense, burning pain in the hand, which is often triggered by a very light touch. Using your understanding of how the nervous system processes pain signals, explain the most likely underlying cause of this patient's ongoing pain.

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