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

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.