Intracortical inhibition is modulated by phase of prosthetic rehabilitation in transtibial amputees

© 2015 Hordacre, Bradnam, Barr, Patritti and Crotty. Reorganization of primary motor cortex (M1) is well-described in long-term lower limb amputees. In contrast cortical reorganization during the rehabilitation period after amputation is poorly understood. Thirteen transtibial amputees and 13 gender matched control participants of similar age were recruited. Transcranial magnetic stimulation was used to assess corticomotor and intracortical excitability of M1 bilaterally. Neurophysiological assessments were conducted at admission, prosthetic casting, first walk and discharge. Gait variability at discharge was assessed as a functional measure. Compared to controls, amputees had reduced short-latency intracortical inhibition (SICI) for the ipsilateral M1 at admission (p = 0.01). Analysis across rehabilitation revealed SICI was reduced for the contralateral M1 at first walk compared to discharge (p = 0.003). For the ipsilateral M1 both short and long-latency intracortical inhibition were reduced at admission (p < 0.05) and prosthetic casting (p < 0.02). Analysis of the neurophysiology and gait function revealed several interesting relationships. For the contralateral M1, reduced inhibition at admission (p = 0.04) and first walk (p = 0.05) was associated with better gait function. For the ipsilateral M1, reduced inhibition at discharge (p = 0.05) was associated with poor gait function. This study characterized intracortical excitability in rehabilitating amputees. A dichotomous relationship between reduced intracortical inhibition for each M1 and gait function was observed at different times. Intracortical inhibition may be an appropriate cortical biomarker of gait function in lower limb amputees during rehabilitation, but requires further investigation. Understanding M1 intracortical excitability of amputees undertaking prosthetic rehabilitation provides insight into brain reorganization in the sub-acute post-amputation period and may guide future studies seeking to improve rehabilitation outcomes

Feasibility Study of a Wearable Exoskeleton for Children: Is the Gait Altered by Adding Masses on Lower Limbs?

We are designing a pediatric exoskeletal ankle robot (pediatric Anklebot) to promote gait habilitation in children with Cerebral Palsy (CP). Few studies have evaluated how much or whether the unilateral loading of a wearable exoskeleton may have the unwanted effect of altering significantly the gait. The purpose of this study was to evaluate whether adding masses up to 2.5 kg, the estimated overall added mass of the mentioned device, at the knee level alters the gait kinematics. Ten healthy children and eight children with CP, with light or mild gait impairment, walked wearing a knee brace with several masses. Gait parameters and lower-limb joint kinematics were analyzed with an optoelectronic system under six conditions: without brace (natural gait) and with masses placed at the knee level (0.5, 1.0, 1.5, 2.0, 2.5 kg). T-tests and repeated measures ANOVA tests were conducted in order to find noteworthy differences among the trial conditions and between loaded and unloaded legs. No statistically significant differences in gait parameters for both healthy children and children with CP were observed in the five “with added mass” conditions. We found significant differences among “natural gait” and “with added masses” conditions in knee flexion and hip extension angles for healthy children and in knee flexion angle for children with CP. This result can be interpreted as an effect of the mechanical constraint induced by the knee brace rather than the effect associated with load increase. The study demonstrates that the mechanical constraint induced by the brace has a measurable effect on the gait of healthy children and children with CP and that the added mass up to 2.5 kg does not alter the lower limb kinematics. This suggests that wearable devices weighing 25 N or less will not noticeably modify the gait patterns of the population examined here.Cerebral Palsy International Research FoundationStavros S. Niarchos Foundatio

Ipsilateral corticomotor excitability is associated with increased gait variability in unilateral transtibial amputees

Ipsilateral primary motor cortex (M1) reorganisation after unilateral lower-limb amputation may degrade function of the amputated limb. We hypothesised unilateral lower-limb amputees would have a bilateral increase in corticomotor excitability, and increased excitability of ipsilateral M1 would be associated with increased step-time variability during gait. Twenty transtibial amputees (16 male) aged 60.1 years (range 45-80 years), and 20 age- and gender-matched healthy adult controls were recruited. Single-pulse transcranial magnetic stimulation assessed corticomotor excitability. Two indices of corticomotor excitability were calculated. An index of corticospinal excitability (ICE) determined relative excitability of ipsilateral and contralateral corticomotor projections to alpha-motoneurons innervating the quadriceps muscle (QM) of the amputated limb. A laterality index (LI) assessed relative excitability of contralateral projections from each hemisphere. Spatial-temporal gait analysis was performed to calculate step-time variability. Amputees had lower ICE values, indicating relatively greater excitability of ipsilateral corticomotor projections than controls (P = 0.04). A lower ICE value was associated with increased step-time variability for amputated (P = 0.04) and non-amputated limbs (P = 0.02). This association suggests corticomotor projections from ipsilateral M1 to alpha-motoneurons innervating the amputated limb QM may interfere with gait. Cortical excitability in amputees was not increased bilaterally, contrary to our hypothesis. There was no difference in excitability of contralateral M1 between amputees and controls (P = 0.10), and no difference in LI (P = 0.71). It appears both hemispheres control one QM, with predominance of contralateral corticomotor excitability in healthy adults. Following lower-limb amputation, putative ipsilateral corticomotor excitability is relatively increased in some amputees and may negatively impact on function. © 2014 Federation of European Neuroscience Societies and John Wiley and Sons Ltd

Robotic Gait Training in an Adult With Cerebral Palsy: A Case Report.

Improved treatments and rehabilitation for cerebral palsy (CP) have led to an increased number of children with CP surviving into adulthood. Adults with CP show an increased prevalence of pain, fatigue, and musculoskeletal dysfunction, leading to a decrease in ambulatory function. Recent work has demonstrated the potential benefits of intensive task-specific gait training, including the use of robotic-driven gait orthoses, on motor recovery in children with CP [1 and 2]. In contrast, reports of interventions aimed at improving motor function in adults with CP are lacking. This case study reports on the outcomes of a 6-week intervention of robotic-assisted gait training administered to a 52-year-old woman with right hemiplegia attributable to CP. Improvements were noted in balance, walking speed, and time to negotiate stairs at posttraining and follow-up. Gait analysis showed an increase in step length and a reduction in the period of double support. In conclusion, robotic-assisted gait training may be beneficial in enhancing locomotor function in adults with CP