Forelimb Training To Improve Trunk Stability and Hindlimb

Forelimb Training To Improve Trunk Stability and Hindlimb Locomotion after Thoracic SCI Samantha 1 Walkin , 2, 3 Fisher , Lesley Eileen 2, 3 Phillips , Rochelle 2, 3 Deibert , Jing 3 Zhang , D. Michele Basso Ed. D, 2, 3 PT The Ohio State University 1 Neuroscience Undergraduate Program, 2 Center for Brain and Spinal Cord Repair, 3 School of Health and Rehabilitation Sciences INTRODUCTION BBB Subscore (mean + SEM) 5 • Forelimb training improved hindlimb consistent stepping during locomotion. This innovative approach could enable individuals with SCI to have increased walking ability. 4 * 3 * FL Ex Un Ex 2 1 Timepoint (days) Figure 1 The difference in an animal’s stance and pull force from the start to end of training. At the beginning, rats had no hindlimb support or trunk control and did not pull with much force. At the endpoint, the rats showed weight support on their hindlimbs, increased trunk control, and pulled with much greater force, requiring a more precise grasp. Average Sum of Forces per Session A 14000 12000 10000 Behavioral Outcome Measures: • Force quantification: The total force pulled (grams) for each session was summed for each animal to determine that training occurred. • Open field locomotion: quadrupedal test of trunk control and stepping improvements using BBB Locomotor Rating Scale (Basso, 1995) • Inclined plane: quadrupedal test of static posture standing balance and trunk control while attempting to remain still on a sloped plane for 10 seconds. Max angle completed successfully was reported for each animal. • Cylinder: bipedal test that measured upright posture while rearing. Rats were separated into high performing and low performing groups based on hindlimb extension and trunk instability. B 8000 6000 4000 2000 0 Force (g) + SEM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Session Number Figure 4 FL Ex group had a significantly higher average BBB subscore than the Un Ex group at 28 d and 35 d. This illustrates a greater improvement in fine locomotor control in the FL Ex group. (*= sig greater than Un Ex, p<. 05, Rep Meas ANOVA with Tukey’s post hoc) A 12 B Consistent Stepping * 10 8 14000 * 12000 10000 6000 4000 8 7 * Fl Ex Un Ex Figure 8 Forelimb training activates sensory afferents from the forelimbs 6 5 and trunk which enter the spinal cord. Some synapse on neurons and 4 others project to different brain regions. These afferents activate brain 4 3 neurons which send signals to the spinal cord. Exercise promotes 2 2 neuroplasticity via remapping of existing pathways in the spinal cord to 1 form new connections with neurons who lost their input due to injury. 0 0 Additionally, neuroplasticity occurs in the brain because exercise 28 d 35 d promotes cortical remapping to re-establish supraspinal input after brain Figure 5 Key aspects of the locomotor differences after forelimb training were axons were damaged in the spinal cord by the injury. The sensorimotor increases in hindlimb Consistent Stepping (A) and Toe Clearance (B). These cortex, cerebellum and brain stem will rewire to adapt for lost significant differences demonstrate an overall improvement in the FL Ex connections. This training-induced neuroplasticity above the SCI may group for gross motor (stepping) and fine motor components (toe clearance) promote advanced locomotor improvements through spared pathways of walking. (*= sig greater than Un Ex, p<. 05, 2 x 2 Chi-Squared) that reach the CPGs for locomotion. FL Ex Un Ex 6 – Trunk stability HIGH LOW FL Ex Un Ex 2000 0 First Session Last Session Figure 2 The average pulling force for each training session steadily increased across training sessions (A). FL Ex group pulled an average of 6, 317 g more force on the last day than on the first day of training (B). All animals learned the task. This increase shows that animals were continually challenged and that training has occurred. (*= sig greater than first session, p=. 003, Paired T Test) Figure 6 High performing rats moved into an upright posture with extended hindlimbs and maintained a straight trunk. Low performing rats had no hindlimb extension and the trunk was curved. White Matter Sparing 40 35 30 Low 33% 25 20 15 High 33% High 67% 10 5 Low 67% Figure 7 The upright posture performance was High for 67% and Low for 33% of the FL Ex group. Conversely, performance was Low for 67% and High for 33% of the Un Ex group. 0 FL Ex Un Ex Figure 3 White matter sparing (WMS) was not significantly different. This demonstrates that SCI severity was equivalent between the FL Ex and Un Ex groups. (p=. 145, One Way ANOVA) • Most animals in the training group had better dynamic trunk control while moving in and out of rearing in the cylinder task, exhibiting hindlimb extension and maintaining a straight trunk. Training did not improve static trunk control on the incline plane. 9 Cylinder Rearing for Upright Posture 8000 • Forelimb training increasing the amount of toe clearance could be a crucial advancement in locomotor recovery after SCI because no other training paradigm has caused an improvement in toe clearance. This could enable people with SCI to walk without assistive devices as the risk of tripping would be much less. Toe Clearance * Average Force of First and Last Training Session % WMS + SEM Statistics: Values reported as Mean ± SEM. Statistics were calculated using IBM SPSS. Exact test is reported for each data set. TRAINING PERIOD 0 Rats were randomized to forelimb trained (FL Ex; n=6) or untrained control groups (Un Ex; n=6). The training represents the independent variable. After SCI, the FL Ex group performed the reaching task 15 mins/day, 5 days/week for 4 weeks starting at 7 days post injury. Lever distance and force required were increased throughout training. Outcome analyses represent the dependent variables. White Matter sparing: The spinal cord myelin sparing at the injury epicenter was processed using Eriochrome Cyanine staining. White matter sparing was quantified as: white matter (um 2)/total cross sectional area (um 2) *100 using stereology with Stereo Investigator. • The overall increase in pulling force throughout training indicates that despite marked functional impairments after thoracic SCI, task learning did occur in the FL Ex group. Fine Locomotor Control 6 Force (g) Adult, female Sprague Dawley rats underwent a mild (250 kilodyne) contusion at the midthoracic (T 9) spinal level using an Infinite Horizons computer-controlled impactor. All rats were trained before injury to pull a lever to obtain a food reward using the Vulintus Moto. Trak device. Animals were food deprived throughout training, with food modifications to manage body weight at less than a 10% change. CONCLUSIONS Improvements in Hindlimb Stepping Number of Hindlimbs METHODS Proof of Training Number of Hindlimbs Spinal cord injury (SCI) affects thousands of individuals every year. Our lab is involved with the Neuro. Recovery Network at Ohio State University Wexner Medical Center where we focus on treadmill training as an intervention to improve locomotion after SCI. Although this treatment is effective in improving trunk stability, lower extremity muscle control and locomotion, persistent deficits remain. We found that treadmill training focused only on the legs produced surprising improvements in arm and hand function (Buehner et. al, 2012). It is unknown if the inverse effect is true, that training the uninjured arms will improve function below the injury for trunk control and locomotion. Therefore, we used a repetitive forelimb reaching task with rodents to investigate whether these improvements will occur after SCI. We hypothesized that forelimb training will improve trunk control, stability, and balance after thoracic SCI. Additionally, it may improve lower extremity motor control and locomotion. RESULTS • A caveat of the study was that average BBB scores for locomotor performance were significantly different before training began at 7 d (FL Ex: 6. 33± 1. 31, Un Ex: 3. 25± 1. 36) despite random assignment to groups. It is difficult to say with certainty that locomotor improvements were due to the training itself and did not include spontaneous natural recovery. However, there is evidence that spontaneous recovery may not have influenced our results at endpoint: • Although BBB scores are different at 7 d, minimal biological difference occurred because both groups demonstrated only joint movements and no weight support or stepping. • There was no difference in BBB results between the two groups at 1 d and 3 d (before training began). • There was no difference in injury severity between the groups measured by tissue sparing and injury biomechanics. • Spontaneous recovery plateaus around 21 d post injury. The significant findings occurred at 28 d and 35 d post injury. • The individual performance at 7 d does not necessarily indicate performance at endpoint. The trained animal with the lowest BBB score at 7 d had consistent stepping and toe clearance at 35 d, while the trained animal with the highest BBB score at 7 d didn’t have toe clearance at 35 d. • These findings indicate that force-generating reaching by uninjured limbs above the injury may address serious impairments that resist recovery with other rehabilitation methods. BIBLIOGRAPHY Inclined Plane for Static Posture Inclined plane test did not show any significant differences in gross trunk stability as both groups reached same maximum angle (FL Ex: 57. 9°± 1. 76, Un Ex: 56. 3°± 2. 64)(p=. 611, One Way ANOVA ) 1. Buehner JJ et al. (2012) Arch Phys Med Rehabil. 93(9)1530 -1540, doi. org/10. 1016/j. apmr. 2012. 035 2. Basso DM et al. (1995) J Neurotrauma. 12(1): 1 -21, doi. org/10. 1089/neu. 1995. 12. 1 School of Health and Rehabilitation Sciences