Abstract
Injury to the cervical spinal cord results in complete or partial loss of arm and hand function, severely limiting the performance of daily activities. Deficits in hand function in individuals with cervical spinal cord injury (SCI) are primarily due to a loss of descending motor pathways that are vital for fine control of the hand and fingers. In addition to these deficits, secondary plastic reorganization may create further loss of function. This thesis will explore the following questions: 1. What are the similarities and differences between cortical organization of muscles affected by a cervical SCI to those not affected by the injury?; 2. Do individuals with cervical SCI improve in hand function and cortical organization after an intensive hand training intervention?; 3. Which physical therapy intervention provides the optimal conditions by which to improve hand function following cervical SCI? In chapter 2 we compare cortical motor maps of transcranial magnetic stimulation (TMS) evoked responses of muscles rostral and caudal to the injury to those of ND individuals. The cortical maps of the biceps brachii or the thenar muscles were constructed, and compared between ND individuals and individuals with SCI. The motor threshold (MT) for the thenar muscles in individuals with SCI was significantly higher than ND individuals. The purpose of the study described in chapter 3 was to compare the functional and cortical changes associated with two different interventions: unimanual or bimanual massed practice training, both combined with somatosensory stimulation. There was a significant difference between pre- and post-intervention scores on tests measuring unimanual hand function, bimanual hand function, and sensory function. This difference was associated with a difference between pre- and post-intervention cortical map area. The purpose of the study described in chapter 4 was to compare clinical and cortical changes associated with either a delayed intervention control period or a combined intervention of massed practice training with electrical stimulation. Participants were randomly assigned to one of two groups: delayed intervention control group or immediate intervention group. Participants were also randomly assigned to one of four groups: unimanual training with somatosensory stimulation, bimanual training with somatosensory stimulation, unimanual training with functional electrical stimulation, or bimanual training with functional electrical stimulation. There was a significant difference between the control and immediate intervention group on the test measuring unimanual hand function. Participants in the bimanual group performed significantly better on the test measuring bimanual hand function. There was a significant difference between the control group and immediate intervention group in cortical map area. In chapter 5 we discuss the clinical relevance of the results of the studies described in three prior chapters. Conclusions drawn include the idea that cortical maps of muscles caudal to the level of injury in individuals with SCI have higher motor thresholds than ND participants. Individuals with tetraplegia can improve in hand function and sensation with a physical therapy intervention of massed practice training combined with somatosensory stimulation. Finally, the type of training (unimanual massed practice or bimanual massed practice) influences the type of improvements gained, however the type of electrical stimulation does not influence the clinical outcome.