A common procedure to restore lateral pinch strength to persons with C5/6 tetraplegia is to transfer the distal tendon of the brachioradialis muscle to the tendon of the paralyzed flexor pollicis longus muscle (Br to FPL). Conventional post-surgical care is not well defined and some individuals are discharged before receiving a directed therapy program due to limitations in hospital stay. After surgery, the transferred Br is not fully activated to perform pinch tasks. Undoubtedly, this is one factor that leads to a range of functional outcomes, despite a successful surgery, that may be addressed by a focused re-training program. The mechanism(s) underlying successful re-training of the transferred muscle to perform a new task are unknown and may involve both motor and neural adaptation. Recent evidence suggests that task-based therapy can result in improved upper limb function by strengthening the existing neural connections and/or forming new ones. The proposed study will assess the neural response to a task-based therapy program for muscle re-education for Br to FPL tendon transfer recipients. This proposed pilot project is a critical step towards the broader objective to improve functional outcomes of tendon transfer procedures in tetraplegia. The purpose of the study is to obtain pilot data consisting of functional magnetic resonance imaging (fMRI) and functional performance measures to evaluate neural predictors and correlates of successful muscle re- education after tendon transfer. The participants will have chronic cervical SCI and have received a tendon transfer or meet the surgical criteria for transfer surgery. Patterns of neural activity from Br to FPL transfer recipients will be assessed (i) in those with poor versus good outcomes and (ii) before and after participating in the task-based therapy program designed to improve voluntary activation of the transferred Br in functional pinch tasks. Functional performance measures include quantitative electromyographic (EMG) measures of voluntary activation of the transferred Br, maximum effort pinch force in selected functional tasks, and a self- reported performance measure. The specific objectives are to: evaluate muscle re-education after Br to FPL transfer in individuals with good and poor outcomes, and to determine if the pattern of neural activity after the training program is comparable to those individuals wit higher pinch force measurements. The task-based training program is part of an ongoing study to improve Br to FPL surgical outcomes and preliminary results indicate positive changes in pinch force production and activation of the transferred Br in coordination with proximal muscles during functional tasks. Neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) have become important tools for understanding plasticity in the neuromuscular system and for assessing the neural changes in response to novel interventions. We propose that a directed task-based training program after Br to FPL transfer will drive neural changes that impact functional (pinch) ability. Establishing this relationship will allow for increased understanding of the mechanisms of successful interventions in patients and will suggest brain based dynamics that could be the focus of future treatments, such as biofeedback or brain stimulation. A more effective post-surgical rehabilitation program will lead to improved long-term functional outcomes following tendon-transfer in patients with both acute and chronic spinal cord injuries. These data will be used towards a broader study design for a prospective investigation of the effects of a focused rehabilitation intervention. Information gained from the proposed pilot study will be used to develop hypotheses and statistical power to guide a full-scale study to evaluate the capacity for improving surgical outcomes through task-based training.
The number of people in the United States who have survived SCI is estimated to be approximately 273,000 persons. Around 50% of the injuries are to the cervical spine resulting in tetraplegia. An important rehabilitation goal in this population is recovery of upper limb function which could decrease medical costs and improve their quality of life. Re-establishing active grasp and pinch strength to the hand can be accomplished by surgeries that transfer the tendon of a strong muscle to restore strength to a paralyzed muscle, but the outcomes of the surgeries are variable. We have demonstrated in an ongoing study, the functional gains after surgery can be improved with a focused therapy program to retrain the transferred muscle. The proposed study examines the cortical mechanisms that drive successful muscle re-education after surgery. Understanding the neural activity associated with functional performance can help to predict who will respond to therapy and will guide evidence-based rehabilitation programs to improve upper limb function in tetraplegia.