Use of an implanted sacral nerve stimulator to restore urine voiding in chronically paraplegic dogs.

BACKGROUND: Loss of urinary control after spinal cord injury increases risk of urinary tract disease and is problematical for owners of affected dogs. OBJECTIVES: To design, implant, and test a sacral nerve stimulating device for controlling urine voiding in paraplegic dogs. ANIMALS: Nine pet dogs with severe thoracolumbar spinal cord injury causing paraplegia, loss of hindquarter sensation, and incontinence for more than 3 months. The procedure was offered prospectively to owners of suitable candidates after the irreversibility of the incontinence had been ascertained. METHODS: Open label clinical study. Surgically implantable electrode "books" were designed for insertion and retention of mixed sacral nerves. Sacral nerves were accessed via laminectomy and stimulated to test their ability to elicit detrusor contraction and then inserted into the electrode book, which was attached to a subcutaneously implanted, externally activated receiver. RESULTS: In 8/9 dogs, S2 nerves elicited the largest increases in intravesicular pressure with minimum stimulation and were placed in electrode books. Voiding efficiency was >90% in 8 of the 9 implanted dogs. No important detrimental effects of the procedure were observed. CONCLUSIONS AND CLINICAL IMPORTANCE: This sacral nerve stimulating implant is a simple and apparently effective neuroprosthetic device that restores urine voiding in paraplegic dogs.

Electrical stimulation for propelling endoscopes.

BACKGROUND: Methods are needed for propulsion of endoscopes and wireless video capsules along the small intestine. This work aims to test the hypothesis that electrical stimulation could propel an endoscope by stimulating muscular contraction. METHODS: Prototype acrylic ovoid-shaped devices were constructed with 2 stainless steel electrodes mounted on the tapered section. Five devices 15 to 23 mm diameter with a taper of 28 degrees to 40 degrees (included angle) were tested. When these devices were in contact with the bowel wall, electrostimulation was applied causing circular muscle contraction, which when applied to the taper of the ovoid resulted in forward propulsion of the device. The method does not induce peristalsis but works by stimulating local contraction. The device was tested in the small intestine and esophagus of anesthetized pigs. RESULTS: Electrostimulation caused the ovoid to advance rapidly (6 mm/sec) up and down the esophagus by inducing circular esophageal muscle contraction. When stimulated at 15 Hz with 30-ms pulses, the threshold for movement in the small intestine was 12 mA; at 20 mA the device moved reliably in either direction in the small intestine at speeds of up to 4.5 mm/sec and negotiated tight curves. CONCLUSION: Electrostimulation can move endoscopes in the small intestine.