Ferrarin, et al. (2001): Model-based control of FES-induced single joint movements

[Wise Young]

• Ferrarin M, Palazzo F, Riener R and Quintern J (2001). Model-based control of FES-induced single joint movements. IEEE Trans Neural Syst Rehabil Eng. 9 (3): 245-57. Summary: A crucial issue of functional electrical stimulation (FES) is the control of motor function by the artificial activation of paralyzed muscles. Major problems that limit the success of current FES systems are the nonlinearity of the target system and the rapid change of muscle properties due to fatigue. In this study, four different strategies, including an adaptive algorithm, to control the movement of the freely swinging shank were developed on the basis of computer simulations and experimentally evaluated on two subjects with paraplegia due to a complete thoracic spinal cord injury. After developing a nonlinear, physiologically based model describing the dynamic behavior of the knee joint and muscles, an open-loop approach, a closed-loop approach, and a combination of both were tested. In order to automate the individual adjustments cited above, we further evaluated the performances of an adaptive feedforward controller. The two parameters chosen for the adaptation were the threshold pulse width and the scaling factor for adjusting the active moment produced by the stimulated muscle to the fitness of the muscle. These parameters have been chosen because of their significant time variability. The first three controllers with fixed parameters yielded satisfactory result. An additional improvement was achieved by applying the adaptive algorithm that could cope with problems due to muscle fatigue, thus permitting on- line identification of critical parameters of the plant. Although the present study is limited to a simplified experimental setup, its applicability to more complex and functional movements can be expected. <http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=11561660> Centro di Bioingegneria, Fnd Don Carlo Gnocchi IRCCS ONLUS-Politecnico di Milano, Italy. ferramau@mail.cbi.polimi.it

[This message was edited by Wise Young on September 23, 2001 at 10:44 PM.]

[Wise Young]

• McCarron MO, Flynn PA, Pang KA and Hawkins SA (2001). Traumatic Brown-Sequard-Plus Syndrome. Arch Neurol. 58 (9): 1470-1472. Summary: BACKGROUND: In the 1840s Brown-Sequard described the motor and sensory effects of sectioning half of the spinal cord. Penetrating injuries can cause Brown-Sequard or, more frequently, Brown-Sequard-plus syndromes. OBJECTIVE: To report the case of a 25-year-old man who developed left- sided Brown-Sequard syndrome at the C8 level and left-sided Horner syndrome plus urinary retention and bilateral extensor responses following a stab wound in the right side of the neck. RESULTS: Magnetic resonance imaging demonstrated a low cervical lesion and somatosensory evoked potentials confirmed the clinical finding of left-side dorsal column disturbance. At follow-up, the patient's mobility and bladder function had returned to normal. CONCLUSION: This patient recovered well after a penetrating neck injury that disturbed function in more than half the lower cervical spinal cord (Brown-Sequard-plus syndrome). <http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=11559320> Department of Neurology, Quin House, Royal Victoria Hospital, Belfast BT12 6BA, Northern Ireland. mark.mccarron@royalhospitals.n-i.nhs.uk