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Letters and Responses |
Broetz and colleagues are correct, in that having no active movement of the fingers would make it challenging to transfer blocks during the Box and Block Test or to grasp during the Action Research Arm Test (ARAT). Prior to starting the intervention, the patient demonstrated trace active movement in wrist extension and flexion. He demonstrated no active finger movement (flexion or extension). During pretesting, he scored zero in all grasp portions of the Fugl-Meyer Test. Upon reviewing the video portions of the ARAT, we observed that the patient started in forearm pronation, which resulted in a relaxed open hand. From this position, he was able to achieve a "grasp" by changing his shoulder and elbow position, resulting in wrist and finger flexion. Although we don’t have video of the Box and Block testing, we assume that he used this same strategy for that test.
Two weeks before the task-specific training intervention started, the patient was pretested. One week before the task-specific training intervention started, the patient returned to the lab for orientation to the neuroprosthesis unit. He then took the unit home for 1 week to perform cyclic stimulation in order to ramp up his tolerance to the stimulation. During this week, he gradually increased the cyclic stimulation from 10 to 30 minutes daily; he did not perform task-specific activities during this week. The goal of this "ramp up" week was to acclimate him to the electrical stimulation in order avoid muscle fatigue during the intervention. This is common protocol for these neuroprosthesis units.
During a normal grasp, the wrist extensors provide stabilization for fingers to extend and flex. During the transport phases, the wrist can be in extension or flexion, depending on the task. During the release, the hand typically goes into a neutral position or even flexion; however, many tasks are functional with the wrist in extension. The neuroprosthesis helped the patient reach and grasp by stabilizing his wrist in a functional stationary extended position. The unit then stimulated his finger flexors and extensors to grasp and release. To facilitate normal motor learning, it would be ideal to not stimulate wrist flexion while finger flexors are being stimulated (as Broetz and colleagues are suggesting). Although the neuroprosthesis stimulates wrist flexion and extension during finger flexion and extension, respectively, this is minimized by electrode placement and stimulation intensity. Optimal contraction is achieved at the initial neuroprosthesis fitting session by selecting electrode placements that optimize finger contraction and minimize wrist contraction. The goal is to stimulate the primary finger muscles (eg, extensor digitorum and flexor digitorum superficialis muscles) and to minimize stimulation to the primary wrist muscles. Broetz and colleagues ask if there is "any adaptive skillful movement available after this." We believe that this refers to whether this type of activation facilitates motor learning. As we encourage patients to actively participate with the stimulation and do so in the context of feedback, motor learning can occur; however, activation may not resemble that of a "normal" hand due to the nervous system damage and subsequent control issues. This will depend on the patient. For example, someone with high wrist flexor spasticity may need much more extensor stimulation, making it difficult to isolate the finger extensors from the primary wrist extensors.
It is true that functional tasks are not performed in 7-second cycles as we used in this intervention program. These 7-second cycles, however, do allow for muscles to rest between contractions. Based on motor learning principles, we broke down the activity into components. First, the patient learned the stimulation timing (7 seconds "on" and 7 seconds "off"). Then he learned to do grasp and release during the stimulation timing. Education and feedback were provided during this learning period. The therapist observed whether the patient was doing the sequence correctly or fighting against the stimulation timing. The patient quickly learned to work with the stimulation timing. Once he learned to grasp and release simple objects using the stimulation timing, he progressed to components of functional activities. For example, with ironing, he initially worked on grasping the handle. Once that was achieved, he worked on moving the iron within the stimulation timing sequence. Once the sequencing of the subtask components were learned using the neuroprosthesis, he progressed to working on these subtask components without the neuroprosthesis. Finally, he worked on the complete task without stimulation (eg, the task of ironing). The therapist provided physical assistance as needed for safety. The therapist also provided verbal cues and encouragement but did not provide "hands-on" assistance to achieve the task (eg, hand-over-hand physical assistance). If the patient was unable to perform the activity without the neuroprosthesis, we returned to practice with the device.
The apparatus does not have any electromyographic (EMG) feedback system, nor did we use any other EMG feedback during the therapy. The device does have a feedback light that turns on when the device is stimulating. Our patient didn't need this, however, because he had intact sensation so that he could feel the stimulation, and he quickly understood the sequence pattern. In our experience, this feedback light has helped patients who have limited sensation.1
K Dunning, PT, PhD, is Assistant Professor, Department of Rehabilitation Sciences, College of Allied Health Sciences, University of Cincinnati Academic Medical Center, Ohio.
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