Para-Sports can Promote Functional Reorganization in the Ipsilateral Primary Motor Cortex of Lower Limbs Amputee

Abstract

Background. Drastic functional reorganization was observed in the ipsilateral primary motor cortex (M1) of a Paralympic long jumper with a unilateral below-knee amputation in our previous study. However, it remains unclear whether long-term para-sports are associated with ipsilateral M1 reorganization since only 1 athlete with amputation was investigated. Objective. This study aimed to investigate the relationship between the long-term para-sports and ipsilateral M1 reorganization after lower limb amputation. Methods. Lower limb rhythmic muscle contraction tasks with functional magnetic resonance imaging and T1-weighted structural imaging were performed in 30 lower limb amputees with different para-sports experiences in the chronic phase. Results. Brain activity in the ipsilateral primary motor and somatosensory areas (SM1) as well as the contralateral dorsolateral prefrontal cortex, SM1, and inferior temporal gyrus showed a positive correlation with the years of routine para-sports participation (sports years) during contraction of the amputated knee. Indeed, twelve of the 30 participants who exhibited significant ipsilateral M1 activation during amputated knee contraction had a relatively longer history of para-sports participation. No significant correlation was found in the structural analysis. Conclusions. Long-term para-sports could lead to extensive reorganization at the brain network level, not only bilateral M1 reorganization but also reorganization of the frontal lobe and visual pathways. These results suggest that the interaction of injury-induced and use-dependent cortical plasticity might bring about drastic reorganization in lower limb amputees.

Brain Reorganization and Neural Plasticity in Elite Athletes With Physical Impairments

“…To further examine the relation between bilateral M1 activation and prosthesis use, Nakanish et al ( 12 ) recruited 30 individuals with unilateral lower limb amputations (14 transtibial and 16 transfemoral amputations) who regularly participated in sports activities and performed the same fMRI experiments as with Paralympic athletes. The authors found that 12 out of 30 participants demonstrated significant ipsilateral M1 activation, and there was a significant correlation ( P < 0.05) between years of participation in sports and the ipsilateral M1 activation level.…”

“…Another noteworthy result reported by Hordacre et al ( 13 ) was that the higher relative excitability of the ipsilateral M1 was associated with increased step-time variability for amputated and nonamputated limbs, suggesting that corticomotor projections from the ipsilateral M1 to alpha-motoneurons innervating the amputated limb quadriceps muscle would interfere with gait. It is uncertain whether the ipsilateral M1 activation on the amputated side observed in both Paralympic long jumpers and high jumpers is associated with higher prosthetic motor skills, although the result of Nakanishi et al ( 12 ) suggests that this activation is related to longer use due to sports activity. Future longitudinal studies are required to clarify the functional relevance of higher ipsilateral M1 excitability.…”