Those patients who experienced the amputation of their limbs often report the presence of the phantom limb pain. The researchers associate the phantom limb pain with the certain features of nerves and different types of fibers in nociceptors (Flor, Diers, & Andoh, 2013, p. 308). Thus, even if the stump or the severe injury was healed, the patient can experience the pain in the limb that was amputated long ago (Vaso, Adahan, Gjika, Zahaj, & Zhurda, 2014). The theorists of such type of the pain and researchers note that such experiences can be associated with the hyperactivity, as well as hypersensitivity, of the nerves that were cut or injured significantly before or during the process of amputation (Flor et al., 2013; Vaso et al., 2014). Such peripheral nerves can also regenerate, and new formations can appear in them while causing the phantom pain (Flor et al., 2013). As a result of such regenerations in the peripheral nerves, the central nervous system receives and analyzes the pain from the amputated limbs because such signals are transmitted by the injured nerves.
Nociceptors can be discussed as nerves that are responsible for responding to different types of stimuli according to which they can be categorized (Dubin & Patapoutian, 2010). It is possible to identify such main types of nociceptors as thermal, mechanical, and chemical nociceptors (Dubin & Patapoutian, 2010). These nociceptors are usually characterized by the small diameter of axons in neurons that react to stimuli (Vaso et al., 2014). Each of these types of nociceptors has different nerve fibers that allow responding to various stimuli. The majority of nociceptors depend on the work of C-fibers, and this type of fibers is characteristic of thermal, mechanical, and chemical nociceptors (Dubin & Patapoutian, 2010). A-fiber nociceptors or Aδ-fiber nociceptors respond to the temperature and mechanical stimuli, but they rarely respond to the cold (Dubin & Patapoutian, 2010; Vaso et al., 2014). C-fiber nociceptors can be viewed as reacting to stimuli slower than A-fiber nociceptors do.
It is possible to state that the phantom limb pain is associated with both types of fibers, but they play the key role at different stages of the process of healing or recovery. The woman whose leg was amputated several months ago experienced the phantom pain caused by A-fiber or Aδ-fiber nociceptors after the operation because these signals are associated with the intense pain (Vaso et al., 2014). At the current stage, the patient can experience the phantom pain associated with C-fibers because the intensity of the pain can become lower, and the overall reaction to the stimuli is also slower (Dubin & Patapoutian, 2010). When the left leg of the patient was injured and then amputated, she also felt the pain associated with A-fibers, and that pain was acute. When the phantom pain is observed during a long period of time, it is possible to speak about the pain that is caused by C-fibers in nociceptors because of the prolonged character of the pain without the observed progression (Dubin & Patapoutian, 2010). The specific nature of the phantom limb pain causes difficulties when the treatment is proposed because the possibility of the sensory effects is limited, and traditional approaches to relieving the pain can be ineffective. Therefore, it is necessary to refer to the specific type of the fiber that can be a possible cause of the certain type of the pain.
References
Dubin, A. E., & Patapoutian, A. (2010). Nociceptors: The sensors of the pain pathway. The Journal of Clinical Investigation, 120(11), 3760-3772.
Flor, H., Diers, M., & Andoh, J. (2013). The neural basis of phantom limb pain. Trends in Cognitive Sciences, 17(7), 307-308.
Vaso, A., Adahan, H. M., Gjika, A., Zahaj, S., & Zhurda, T. (2014). Peripheral nervous system origin of phantom limb pain. Pain, 155(7), 1384-1391.