By Heidi Fischer, MS, OTR/L, Jason Barbas, MPT, and Leonard Kahn, PhD
Each year, approximately 700,000 people in the United States experience a new or recurrent stroke. Stroke is a leading cause of long-term disability in the United States, with more than 1.1 million adults reporting functional limitations and difficulty with activities of daily living (ADLs).1 These limitations are most commonly due to motor dysfunction as a result of hemiparesis. Approximately 40% of stroke survivors experience chronic hemiparesis in the upper extremity, meaning the functional ability of the upper extremity is limited by deficits in motor control and coordination, synergy patterns, spasticity, and pain.2,3
Commonly, aggressive physical and occupational therapy addresses these functional deficits. While there are various approaches among clinicians and many techniques that may be applied to promote motor recovery following stroke, therapists most often use a combination of techniques depending on the client's particular needs and the background and training of the individual therapist.
COMMON THERAPY Neurofacilitation is a common approach used to aid in the recovery of upper extremity motor control. Two examples of neurofacilitation techniques include proprioceptive neuromuscular facilitation (PNF) and neurodevelopmental treatment (NDT). PNF aims to increase neuromuscular return through stimulation of proprioceptors using diagonal movement patterns. The NDT approach is based on inhibiting abnormal tone and facilitating normal movement, and uses weight-bearing positions to provide proprioceptive input and promotion of r extremity may include strengthening via resistive and active-assistive exercise, range of motion exercise, or neuromuscular electrical stimulation. In addition, orthotics and taping may promote proper upper extremity positioning to help manage pain, spasticity, and shoulder subluxation.
In spite of the prevalent use of these techniques among clinicians, a limited body of research supports the efficacy of these methods in the recovery of upper extremity motor function. Neuroplasticity, a core principle in neurorehabilitation, is the ability of neural systems to reorganize based on sensory and motor experience. Functional magnetic resonance imaging and transcranial magnetic stimulation studies provide evidence for functional adaptation of the motor cortex following injury.4-7 Emerging evidence in motor control research supports more recent treatment approaches such as shaping, massed practice or repetitive use of the affected limb, task-oriented reeducation, visual imagery, bilateral training, guided-force training, and constraint-induced movement therapy.8,9 Some of these techniques are used in conjunction with recent medical interventions such as botulinum toxin to manage spasticity.10,11 From a clinical standpoint, it is often difficult for therapists to provide opportunities for intense training or massed practice due to the amount of staff and time required. This is further complicated by the need to teach patients skills to be independent, which often involves teaching compensatory techniques.
TOP PRIORITY Independence is indeed the top priority for clients to return home; however, it is often done at the expense of recovery of motor control of the affected side. Therapists have the skills to minimize impairment of these extremities, but time and cost constraints often limit or shift this focus. In addition, the period of most intense rehabilitation following stroke is typically in the first month post injury, with intensity tapering down until about 6 months post injury.
This is most often the case as it is commonly believed that the therapeutic window for motor recovery is up to about 6 months post injury, with the most significant improvement taking place in the first month. Thus, most stroke survivors receive rehabilitation services only during this time period. However, several studies indicate that the brain has the ability to reorganize following neurological injury and may continue to do so during the chronic stages of recovery.12,13
ROBOTIC ALTERNATIVE Robotic devices have been investigated as tools in upper extremity rehabilitation for chronic stroke survivors14-17 and may allow rehabilitation professionals to focus on functional independence and increased motor recovery for their clients. Robotics emerged in an effort to provide opportunities for massed practice and repetitive exercise, and to allow rapid transitions between tasks. The first robot used as a therapeutic tool, the MIT-MANUS, demonstrated that arm function in stroke survivors benefited from interacting with a planar device in the sub-acute stages of recovery.18 Subsequently, two robots, the Mirror Image Movement Enabler (MIME)17 and the Assisted Rehabilitation and Measurement (ARM) Guide,16 expanded the investigations of therapeutic applications of robots into the chronic stroke population.
While the client performs reaching tasks with the hemiparetic arm, the ARM Guide provides guided force training by measuring reaching speed, distance, direction, and force, and by giving visual and manual feedback regarding their performance.
Studies with these machines verified that repetitive interaction with a mechanical device results in improved performance of functional tasks. However, specifically looking at unsupported and unassisted reaching movements, participants in the MIME study were able to reach farther toward a target, while users of the ARM Guide showed no change. After examining the differences between the methods in the two studies, we hypothesized that the fact that subjects consciously guided movement forces toward the reaching target during one of four methods employed by MIME may have been most responsible for the difference.19 We decided, therefore, to test this "guided force" method with the ARM Guide.
While the client performs reaching tasks with the hemiparetic arm, the ARM Guide provides guided force training by measuring reaching speed, distance, direction, and force, and by giving visual and manual feedback regarding their performance. The ARM Guide contains a forearm support with a hand piece that slides along a track connected to a motor. An attached force sensor records the movement, and a computer monitor displays this as visual feedback to the client. For example, if a client attempts to reach forward and instead internally rotates the shoulder, the robot prevents the movement and gives feedback on the screen in the form of an arrow that points them in the right direction to reach the target. If the client corrects the movement, the device may provide assistance to the target. It can also provide resistance to those performing at a higher level of function.
In the current study, we are investigating whether guided force training with the ARM Guide will result in significant gains in functional ability of the arm, superior to more conventional methods of therapy. In this study, chronic stroke survivors are randomly assigned to one of three training groups: guided force, free reaching, and occupational therapy. Outcome measures include kinematic, range of motion, force, limb stiffness, reaching distance, reaching speed, and observation of functional task performance.
Preliminary results indicate that subjects participating in all groups demonstrate improvements in reaching distance, smoothness, and speed, and decreased time to perform functional tasks. In addition, early outcomes suggest potentially greater improvements of ARM Guide users during performance of ADLs. These results indicate that focused, repetitive training with the hemiparetic arm can result in motor recovery years after stroke. Clinically, clients need opportunities for massed practice using their hemiparetic limb to facilitate motor recovery and improve their overall functional outcomes. Therapists may be able to incorporate motor control strategies such as shaping, active use of the limb, and repetitive practice into their current treatment programs for individuals with stroke. In the future, robotic devices have the potential to change stroke rehabilitation by incorporating evidence-based principles into a motor reeducation program with minimal supervision from a therapist. In addition, robots are able to provide quantifiable outcomes of client performance as well as a cost-effective means for extended periods of therapy long after the inpatient and outpatient therapy have been discontinued.
Heidi Fischer, MS, OTR/L, is a research occupational therapist at the Sensory Motor Performance Program and Center for Rehabilitation Outcomes Research at the Rehabilitation Institute of Chicago; Jason Barbas, MPT, is a physical therapist at the Center for Stroke Rehabilitation and the Sensory Motor Performance Program at the Rehabilitation Institute of Chicago; and Leonard Kahn, PhD, is a researcher in the Sensory Motor Performance Program at the Rehabilitation Institute of Chicago.
