Deafferentation may be defined as a loss of sensory input from a portion of the body and is usually caused by an interruption between the brain or central nervous system and the peripheral sensory nerve fibers that innervate that portion of the body. Amputations and similar injuries in which a portion of the body is removed often give rise to deafferentation with respect to the portion of the body that is lost. Additionally, brachial plexus injuries, spinal cord injuries, and strokes are common causes of deafferentation.
The loss of sensory input produces compensatory changes in associated portions of the central nervous system. These changes often produce aberrant sensory signals. For instance, patients who have had a limb amputated commonly complain of “phantom limb syndrome,” in which painful, itching, or tactile sensations are perceived to arise in the missing extremity.
A number of theories exist as to the cause of deafferentation pain. One theory proposes that the pain is likely due to neuromas—painful nodular proliferations of nerve tissue that result from the futile attempt of a proximal nerve fiber to reunite with its corresponding severed distal portion. Reorganization of A- and C-fiber terminals in the spinal cord is another possible cause of deafferentation pain.
Another possible cause of deafferentation pain involves neural plasticity and reorganization of brain function following deafferentation. Cortical and subcortical maps show that areas within the brain representing the damaged structure shrink while neighboring areas expand following deafferentation. Moreover, brain imaging studies have shown a strong correlation between the amount of somotosensory cortex reorganization and deafferentation pain.
A limited number of treatments for deafferentation pain have been developed. Traditional analgesics are usually ineffective at relieving deafferentation pain. However, anticonvulsants and antidepressants have shown limited success in managing the pain. Chronic epidural analgesia has also been shown to prevent some types of deafferentation pain. However, none of these treatments have been shown to be completely effective in treating deafferentation pain.