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Reduction of spastic hypertonus by controlled nerve ablation with implanted devices Open Access


Other title
spastic hypertonus
direct current
nerve lesion
Type of item
Degree grantor
University of Alberta
Author or creator
Ravid, Einat
Supervisor and department
Dr. Arthur Prochazka, Department of Physiology
Examining committee member and department
Jones Kelvin , Faculty of Physical Education and Recreation
Ashworth Nigel , Division of Physical Medicine and Rehabilitation
Kilgore Kevin, Cleveland FES center, Department of Biomedical Engineering, Case Western Reserve University
Gorassini Monica , Department of Biomedical Engineering
Bennett, David J. , Faculty of Rehabilitation Medicine
Department of Biomedical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Spastic hypertonus is a sensorimotor disorder characterized by involuntary muscle over-activity. Hypertonus emerges in the days and months following upper motor neuron lesions such as spinal cord injury, stroke or multiple sclerosis and affects millions of individuals around the world. Hypertonus impedes activities of daily life including mobility and self-care and may result in muscle contracture and pain if it remains untreated or if treatment fails. Current treatments for spastic hypertonus include physiotherapeutic approaches, anti-spastic drugs, surgery and nerve ablation with neurolytic drugs such as Phenol or Botulinum toxin A. Studies have shown a limited efficacy of these treatments, and it is unclear whether they lead to improvements in function. This dissertation deals with a novel approach to the treatment of spastic hypertonus, namely the use of direct current (DC) delivered with implantable electrodes, to ablate muscle nerves in a controlled fashion. This leads to an attenuation of the neural drive to the innervated muscle. Once a desired attenuation is achieved, functional electrical stimulation may be delivered via the same electrode to activate the muscle for the purpose of functional movement. The dissertation consists of three related studies. The first study (Chapter two) evaluates the feasibility of the suggested treatment. Proof of principle was demonstrated in anesthetized animals by producing controlled reductions in muscle force by applying DC to muscle nerves. The second study (Chapter three) explored DC parameters (amplitudes and durations) that would be both effective and clinically acceptable. DC nerve ablation was tested in the absence of anesthesia, and possible mechanisms were explored. The third part of the dissertation (Chapter four) describes the effect of DC on nerves of chronically implanted animals in the anesthetized and conscious states. Nerve conduction abolished by DC was found to recover completely after three months, consistent with nerve regeneration. A subsequent DC application again abolished conduction, with a similar 3-month recovery. Differences between results observed in anesthetized and conscious animals are discussed. In the conclusion (Chapter 5), it is argued that controlled nerve ablation with DC may be a cost–effective method for treating spastic hypertonus.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Ravid EN, Gan LS, Todd K & Prochazka A. (2011). Nerve lesioning with direct current. J Neural Eng 8, 016005 Epub 2011 Jan 19

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