Shah, Nimish Chhaganlal; (2002) Electrical neuromodulation of detrusor hyperreflexia using dorsal penile nerve stimulation in spinal cord injury. Masters thesis (M.S), UCL (University College London).

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Abstract

Introduction: Detrusor hyperreflexia (recently renamed neurogenic detrusor overactivity by the Standardisation Sub-committee of the Incontinence Continence Society, Abrams et al 2002) commonly ensues after suprasacral spinal cord injury. Its pathophysiology is not well understood and all treatments have significant disadvantages. Electrical stimulation of the sacral afferents can inhibit detrusor contractions, but most studies utilising this technique have been poorly designed. This study was undertaken to assess the optimal parameters of stimulation of the dorsal penile nerve for successful neuromodulation and study the acute effects on detrusor hyperreflexia in spinal cord injured patients. We also assessed the onset, time to reach maximum cystometric capacity and poststimulation persistency of the suppressive effects of neuromodulation using serial cystometry. Methods: Fourteen patients with detrusor hyperreflexia met inclusion criteria for the study. Patients were prepared as for a urodynamic study and contractions were provoked by rapidly infusing 0.9% saline solution into the bladder. Optimal parameters were assessed in a few patients by independent variation of the current amplitude, pulse width and frequency of stimulation which resulted in maximal suppression. The acute effect of neuromodulation was successfully assessed in thirteen patients, and chronic effect over serial cystometry was assessed in six patients. Results: Optimal neuromodulation was achieved with stimulation frequency between 15 and 20Hz, currents at least twice the pudendo-anal reflex irrespective of the pulse width of stimulation. Acute suppression of provoked contractions was achieved in all thirteen patients with a reduction in the area under the pressure / time curve by 73–92%. Stimulation during serial cystometry resulted in rapid increase, maximising by the third cycle, in bladder capacity by 46–231% compared to the control in the six patients. Post-stimulation cystometry demonstrated a gradual decline in bladder capacity towards the pre-stimulated control value. Conclusions: Optimised electrical stimulation of the dorsal penile nerve, a pudendal afferent branch, acutely abolishes hyperreflexic contractions. Moreover, neuromodulation had an immediate effect and became maximal for volume over relatively few cycles of bladder filling and emptying, whilst the persistency following cessation of stimulation was relatively short lived.

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