Impact of direct epispinal stimulation on bladder and bowel functions in pigs: A feasibility study.

AIMS: This study assesses the potential of epispinal (subdural) stimulation application in the treatment of urinary and bowel neurological disorders. Acute experiments were performed on a large animal model - the domestic pig - to develop a new methodology facilitating future results and technology transfers to human. METHODS: After rectal and bladder catheterization, four Landrace pigs (45-50 kg) underwent spinal cord surgery - that is, lumbosacral incision, laminectomy [L4-S4], dural opening and microsurgical arachnoid dissection. Three successive electrical stimulation sessions were carried out: 1) nerve roots stimulation, 2) epispinal stimulation with a matrix electrode, 3) epispinal stimulation with a small diameter needle electrode. Changes in rectal and bladder pressures were monitored throughout the various procedures to identify spinal areas inducing responses while evaluating the influence of electrode contacts size in the measured responses amplitudes. RESULTS: An interesting area was identified in the upper portion of the spinal myelomeres (ie, spinal cord segment delimited by two successive pairs of spinal roots) directly adjoining root with best pressures (either rectal or vesical). Significant responses (up to 40 cmH2 O) were also obtained with a needle electrode. Furthermore, bowel evacuation was triggered in one of the animals. Despite the use of smaller electrode contacts, no detrusor or rectum selective responses were observed in none of the sessions. CONCLUSION: This study showed, for the first time, that epispinal stimulation causes significant detrusor and rectal responses in pigs and allows considering further studies with the objective of treating urinary and rectal disorders in spinal cord injury patients.

An Intermediate Animal Model of Spinal Cord Stimulation.

Spinal cord injuries (SCI) result in the loss of movement and sensory feedback as well as organs dysfunctions. For example, nearly all SCI subjects loose their bladder control and are prone to kidney failure if they do not proceed to intermittent (self-) catheterization. Electrical stimulation of the sacral spinal roots with an implantable neuroprosthesis is a promising approach, with commercialized products, to restore continence and control micturition. However, many persons do not ask for this intervention since a surgical deafferentation is needed and the loss of sensory functions and reflexes become serious side effects of this procedure. Recent results renewed interest in spinal cord stimulation. Stimulation of existing pre-cabled neural networks involved in physiological processes regulation is suspected to enable synergic recruitment of spinal fibers. The development of direct spinal stimulation strategies aiming at bladder and bowel functions restoration would therefore appear as a credible alternative to existent solutions. However, a lack of suitable large animal model complicates these kinds of studies. In this article, we propose a new animal model of spinal stimulation -pig- and will briefly introduce results from one first acute experimental validation session.