Functional implications of corticospinal tract impairment on gait after spinal cord injury

Abstract

Objective: Maximum toe elevation during walking is an objective measure of foot drop and reflects the impairment of the corticospinal tract (CST) in persons with spinal cord injury (SCI). To determine if this measurement is functionally relevant to ambulatory abilities, we correlated maximum toe elevation with clinical physiotherapy tests. Setting: Cross-sectional study, laboratory and clinical settings. Methods: A total of 24 individuals with SCI (American Spinal Injury Association (ASIA) Impairment Scale D) were recruited. Maximum toe elevation during the swing phase of treadmill gait was measured with a kinematic system. CST function was assessed in a sitting position by measuring the motor-evoked potentials (MEPs) induced in tibialis anterior muscle with transcranial magnetic stimulation over the motor cortex. Clinical tests performed were 10-m and 6-min walk test (6MWT), Timed-Up and Go (TUG), Walking Index for Spinal Cord Injury, Berg Balance Scale, Lower Extremity Motor Score (LEMS) and sensory score of the L4, L5 and S1 dermatomes. Results: Participants with lower toe elevation during gait walked at a slower speed, took more time to perform the TUG test, and covered a shorter distance in the 6MWT. They also scored lower on the LEMS and showed impaired superficial sensitivity of the dermatomes around the ankles. Few correlations were observed between CST function and clinical tests, but the presence of MEP at rest was indicative of faster speed and longer distance in the 6MWT. Conclusion: These results indicate that maximum toe elevation, which is directly correlated with CST impairment, is functionally relevant as it also correlates with timed clinical tests, LEMS and sensory scores. induced by TMS reflects impaired transmission in CST. Although CST transmission is increased following specific interventions, 1,2 correlation between MEP characteristics and overall gait function is not all that clear. While motor function can remarkably improve during recovery, MEP latency remains pathologically prolonged. 3 Also, a recent study demonstrated lack of correlation between measures of MEPs and gait. 4 One reason might be that CST involvement is more prominent in discrete subtasks of the function rather than in the overall task, which requires concurrent input from many different systems. Identifying the precise role of CST within gait will enable a more specific assessment of incapacities following CST lesion. Previous studies and clinical assessment of stroke patients indicate that the CST is involved in foot elevation during swing and that its impairment induces foot drop. [5][6][7] We have recently shown that measurement of maximum toe elevation during swing can be used as a simple and objective measurement of foot drop and reflects CST impairment in persons

Disrupted Ankle Control and Spasticity in Persons With Spinal Cord Injury: The Association Between Neurophysiologic Measures and Function. A Scoping Review

“…There were seven studies that examined changes in CST function, all of which included measures of VAC (8,30,(32)(33)(34)(35)42). Six of seven performed correlation and/or association analyses to quantify the relationship between CST function and VAC (8,30,(32)(33)(34)(35). One study of CST transmission included subjects with stroke in addition to subjects with SCI without separating the data of those individuals prior to performing linear regression analysis, making it difficult to parse out SCI results from results of participants with stroke (32).…”

“…In contrast to the SRC studies, none of the CST transmission studies used an intervention; all had observational designs. Six of seven studies used direct measures of correlations or linear regressions to assess the relationship between CST transmission and volitional measures (8,30,(32)(33)(34)(35). Seven of 7 studies assessed MEP amplitude and latency in the TA.…”

“…Foot drop/toe drag can be assessed by measuring toe clearance and ankle angle during swing phase. Toe clearance during walking was measured in two articles that assessed CST transmission (8,30). Both articles demonstrated that maximum toe elevation was associated with MEP amplitude and latency.…”

“…Both articles demonstrated that maximum toe elevation was associated with MEP amplitude and latency. Lastly, 4/6 studies that contained some measure of gait parameters and stepping ability, presented evidence of an association with CST neurophysiology (8,30,35,42). Additional work is warranted in this area to understand how measures of CST transmission relate to ankle spasticity, as none of these studies included any spasticity measures.…”

Using Corticomuscular and Intermuscular Coherence to Assess Cortical Contribution to Ankle Plantar Flexor Activity During Gait

“…One reason for the dominant interest in the ankle dorsiflexor muscles is that paresis of these muscles and the resulting foot drop during gait are among the most common symptoms following stroke and other lesions of the corticospinal pathways (Barthelemy et al 2013;Everaert et al 2010). Ankle plantar flexor muscles on the other hand depend significantly on sensory feedback mechanisms in the maintenance of their activity when the foot is on the ground in the stance phase of gait (Christensen et al 2000;Nielsen and Sinkjaer 2002;Zehr and Stein 1999).…”