Reduction of spastic hypertonus by controlled nerve ablation with implanted devices

• Author / Creator

  Ravid, Einat

• 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.

• Subjects / Keywords

  • Spastic hypertonus
  • Nerve lesion
  • Direct current

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R38M6T

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.