Limb telescoping

Limb telescoping is the progressive shortening of a phantom limb as the cortical regions are reorganized following an amputation. During this reorganization, proximal portions of the residual limb are perceived as more distal parts of the phantom limb. Such effect is responsible for increased phantom pain due to the discrepancy between the patient's body perception and their actual body. This effect may last from weeks up to years after post-amputation.

Neural reorganization

Brain cortex Following an amputation, there is a neurological reorganization of cortical regions in the brain, where brain regions that were responsible for the amputated limb start to manage remaining body parts, which are commonly related to the residual limb. The presence of this anatomical incongruence causes telescoping sensations because the body representation system is trying to adapt and reduce such mismatch by shortening the phantom limb, until it disappears. Consequently, the greater the limb telescoping effect, the more a phantom limb decreases. This shortening leads to increased phantom limb pain, which explains the correlation between limb telescoping and phantom limb pain.

Limb variance The amputation of upper limbs presents a quicker and more efficient neural reorganization than lower limbs. Upper limbs are connected to the brain through axons of the fasciculus cuneatus, while the lower limbs are connected to the brain through axons of the fasciculus gracilis. In addition, upper limb recognition is processed by the most anterior regions of the frontal lobe, which presents more neural connections and they are closely related to higher cognitive functions, such as goal-directed behaviors, working memory, attention, inhibition of distracting thoughts and actions. Meanwhile, the lower limbs are processed by a more posterior region of the brain, which presents a limited amount of connections in the brain. Therefore, the enhanced neural reorganization, combined with the smaller limbs, decreases the duration and the influence of the telescoping effect in upper limbs

Factors

Age

Younger patients with an amputation report phantom limb sensation less frequently than older patients, which leads to a lower incidence of telescoping among them. The primary explanation for this is neural plasticity, which is the ability of the brain to reorganize neural functions according to its necessities. Neural plasticity reduces with time due to a decline in prefrontal cortex (PFC) activity, synaptic connectivity, Ca2+ homeostasis, and network firing properties. In addition, exposure to novel experiences and new skills help individuals adapt and expand their neurological network. As young patients are exposed to new experiences more often, this boosts their neural plasticity, reduces the phantom limb sensation, and the duration of the telescoping effect. In addition, the size of the amputated limb plays a major role in the duration of the telescoping effect because the bigger the amputated limb, the longer limb telescoping takes for the phantom limb to disappear. Therefore, smaller limbs and greater neural plasticity help children overcome the telescoping effect more quickly and smoothly.

Traumatic amputation Traumatic amputations generally result from an accident and involve greater levels of pain. It has been observed that phantom limb pain is greater after a traumatic amputation. when compared to a scheduled amputation. During an accident, blast waves along with direct impacts cause nerve injuries, which lead to neurophatic pain. Moreover, displaced bone fragments, heterotrophic ossification, and scar tissue are additional factors that may contribute to greater pain sensation. Another common problem among traumatic amputations is the development of infections, which are more easily prevented during surgical amputation. Infections inhibit the healing process and the regrowth of nerve fibers. Overall, the nervous system faces additional challenges to recover due to greater levels of pain, deprived healing, and medical complications. Thus, the telescoping effect becomes longer (approximately 10 years post-amputation) and more predominant after traumatic amputations

Intervention

Induction An experimental research done by Dr. Laura Schmalzl and Dr. Henrik Ehrsson at the Karolinska Institute, in Sweden, showed that body ownership plays a major role in the development of telescoping. In this study, the body transfer illusion was combined with specific experiments and used to activate the telescoping effect. The patients' reactions under the telescoping effect were compared with their reactions when the effect was not present. Under the influence of the telescoping effect, patients with an amputation presented greater anatomical incongruence and pain. Although unrealistic, simulation of the presence of an amputated limb led to a better recognition of body parts, which was indicated by the proprioceptive drift of the induced hand in comparison with the telescoped hand. The induction of the telescoping effect helps us understand how it affects behavioral psychology and body modulation. Overall, the results obtained in this scientific study may help further develop therapeutic techniques for patients experiencing limb telescoping.

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