RESUMEN
OBJECTIVE: We aim to evaluate the suitability of four electrodes previously used in clinical experiments for peripheral nerve electrical block applications. APPROACH: We evaluated peripheral nerve electrical block using three such clinical nerve cuff electrodes (the Huntington helix, the Case self-sizing Spiral and the flat interface nerve electrode) and one clinical intramuscular electrode (the Memberg electrode) in five cats. Amplitude thresholds for the block using 12 or 25 kHz voltage-controlled stimulation, onset response, and stimulation thresholds before and after block testing were determined. MAIN RESULTS: Complete nerve block was achieved reliably and the onset response to blocking stimulation was similar for all electrodes. Amplitude thresholds for the block were lowest for the Case Spiral electrode (4 ± 1 Vpp) and lower for the nerve cuff electrodes (7 ± 3 Vpp) than for the intramuscular electrode (26 ± 10 Vpp). A minor elevation in stimulation threshold and reduction in stimulus-evoked urethral pressure was observed during testing, but the effect was temporary and did not vary between electrodes. SIGNIFICANCE: Multiple clinical electrodes appear suitable for neuroprostheses using peripheral nerve electrical block. The freedom to choose electrodes based on secondary criteria such as ease of implantation or cost should ease translation of electrical nerve block to clinical practice.
Asunto(s)
Estimulación Eléctrica/instrumentación , Electrodos , Conducción Nerviosa/fisiología , Prótesis Neurales , Anestesia , Animales , Gatos , Impedancia Eléctrica , Estimulación Eléctrica/métodos , Masculino , Músculo Esquelético/fisiología , Bloqueo Nervioso/métodos , Reclutamiento Neurofisiológico/fisiologíaRESUMEN
AIMS: Dyssynergic reflexive external urethral sphincter (EUS) activity following spinal cord injury can prevent bladder voiding, resulting in significant medical complications. Irreversible sphincterotomies or neurotomies can prevent EUS activation and allow bladder voiding, but may cause incontinence or loss of sacral reflexes. We investigated whether kilohertz frequency (KF) electrical conduction block of the sacral roots could prevent EUS activation and allow bladder voiding. METHODS: The S2 sacral nerve roots were stimulated bilaterally to generate bladder pressure in six cats. One S1 nerve root was stimulated proximally (20 Hz biphasic pulse trains) to evoke EUS pressure, simulating worst-case dyssynergic EUS reflexes. KF waveforms (12.5 kHz biphasic square wave) applied to an electrode implanted distally on the S1 nerve root blocked nerve conduction, preventing the increase in EUS pressure and allowing voiding. RESULTS: Applying KF waveforms increased bladder voiding in single, limited-duration trials from 3 ± 6% to 59 ± 12%. Voiding could be increased to 82 ± 9% of the initial bladder volume by repeating or increasing the duration of the trials. CONCLUSIONS: Sacral nerve block can prevent EUS activation and allow complete bladder voiding, potentially eliminating the need for a neurotomy. Eliminating neurotomy requirements could increase patient acceptance of bladder voiding neuroprostheses, increasing patient quality of life and reducing the cost of patient care.
Asunto(s)
Terapia por Estimulación Eléctrica/métodos , Plexo Lumbosacro , Raíces Nerviosas Espinales , Uretra/inervación , Vejiga Urinaria Neurogénica/terapia , Vejiga Urinaria/inervación , Micción , Urodinámica , Animales , Gatos , Modelos Animales de Enfermedad , Terapia por Estimulación Eléctrica/instrumentación , Masculino , Conducción Nerviosa , Prótesis Neurales , Presión , Reflejo , Factores de Tiempo , Vejiga Urinaria Neurogénica/fisiopatologíaRESUMEN
AIMS: Uncoordinated contraction of the external urethral sphincter is prevalent in individuals with spinal cord injury and can prevent bladder voiding. The aim of this study was to demonstrate that complete and reversible sinusoidal high frequency alternating current (HFAC) conduction block of the pudendal nerves (PN) can eliminate external urethral sphincter activation and produce low residual bladder voiding. METHODS: In four cats, tripolar nerve cuff electrodes were implanted bilaterally on both pudendal nerves and on both extradural S2 roots. Bladder and urethral pressures, bladder volumes and flow were recorded. Bilateral HFAC was applied to determine voltage and frequency parameters resulting in bilateral PN conduction block. Sacral root stimulation provided bladder activation. Randomized sets of voiding trials were conducted with and without HFAC PN block. Additional voiding trials were conducted following bilateral PN neurotomy to eliminate somatic sphincter resistance and provide an estimate of voiding with complete block. RESULTS: Effective bilateral PN block and voiding was obtained in three of four animals. Application of bilateral PN HFAC stimulation improved voiding from 2 +/- 4% to 77 +/- 18% of the initial bladder volume and significantly (P < 0.001) reduced maximum bladder pressure during voiding. Voiding in trials with PN block was not significantly different from voiding following PN neurotomy (82 +/- 19%, P = 0.51). CONCLUSIONS: These results demonstrate that bilateral HFAC block of the PN can produce effective voiding. Neural prostheses using this approach may provide an alternative method for producing micturition for people with spinal cord injury.