Neuroplasticity Modifications Following a Lower‐Limb Amputation: A Systematic Review

Abstract

Background: Although there are studies that have examined brain functional reorganization following upper-limb amputation, understanding of the brain changes that occur in people with lower-limb amputation is limited. Objective: To investigate modifications in the brain following lower-limb amputation. Methods: We included case-control studies that evaluate neuroplasticity in the central nervous system using neuroimaging techniques. A literature search was conducted using MEDLINE, CINAHL, Web of Science, Scopus, and Cochrane. Results: Eleven articles were included (total n = 204 people with unilateral lower-limb amputation). These studies showed an increase in cerebellar gray matter volume in prosthesis users, as well as a decrease in thickness of the premotor cortex, orbitofrontal cortex, temporo-occipital junction, precentral gyrus, visual areas, and somatosensory cortex. Regarding white matter, the trials observed a decrease in the integrity at the corona radiata, the connections between the premotor areas, the fronto-occipital fasciculus and the corpus callosum. In addition, a decreased functional connectivity between cortical and subcortical areas has been described. Conclusions: Lower-limb amputation causes changes in several brain structures that may occur in the absence of pain and regardless of prosthesis use. The modifications observed include thinning or loss of gray matter volume, decrease in the integrity of the white matter connections between brain structures and changes in the functional connectivity between cortical and subcortical areas.

Parietal Lobe Reorganization and Widespread Functional Connectivity Integration in Upper-Limb Amputees: A rs-fMRI Study

“…Through seed-based whole-brain FC calculations we found that IPL_R and SPG_R regions in ULAs exhibit decreased functional connections with many areas throughout the brain, including lingual area, precentral area, frontal area, insula area, among others ( Figures 4 , 5 ). Related studies on post-amputation changes corroborate our finding that remodeling of brain function is not limited only to local sensorimotor areas in the brain that represent the respective limb ( Makin et al, 2015 ; Zhang et al, 2018 ; Molina-Rueda et al, 2019 ). How might these widespread changes be manifest behaviorally?…”

Energy flow analysis of amputee walking shows a proximally-directed transfer of energy in intact limbs, compared to a distally-directed transfer in prosthetic limbs at push-off

“…Recently however, studies have focussed on the kinetics and muscular activity of amputee gait to provide a more complete picture of the biomechanics of the limbs and trunk during amputee walking. Studies assessing the effect of different prosthetic components [6][7][8] and of amputation level [9][10][11][12][13][14] during amputee gait have led to consistent findings of reduced peak ankle plantar-flexion moment and power and increased peak hip power generation and absorption in amputees. This has led to several avenues of research, particularly the design and development of active (powered) prosthetic limbs [15][16][17].…”

“…An efficient gait will likely be dependent on energy conserving exchanges between limb segments and also on energy storage and return mechanisms, typically utilising strain energy in tendons and prosthetic components. In unilateral amputees, it is known that the intact limb often compensates for deficiencies on the prosthetic side, which leads to characteristic gait asymmetries of reduced stance time and increased swing time and step length on the prosthetic side [10,11]. However, despite these asymmetries, fit individuals with a trans-tibial amputation as a result of trauma often have a metabolic cost of walking that is close to that of healthy able-bodied controls [4,18], suggesting that, in certain cases at least, it is possible to overcome the deficiencies associated with the loss of limb.…”

Motor Imagery-Related Changes of Neural Oscillation in Unilateral Lower Limb Amputation

“…For example, one resting-state electroencephalogram (EEG) study showed that changes in the neural network of patients with right-sided amputations weakened the inhibitory effect of the sensorimotor area, and that connectivity of the right parietal lobe area increased ( Lyu et al, 2016 ). Moreover, recent studies have shown that amputees have structural and functional changes to multiple brain areas, such as the premotor cortex, and the supplementary motor area ( Molina-Rueda et al, 2019 ). These structural and functional changes can be interpreted as non-adaptive brain remodeling due to sensory deprivation and loss or decreased autonomous control ability ( MacIver et al, 2008 ; Raffin et al, 2016 ).…”