Kirkham, Alexander P S; (2004) Combined stimulation of afferent and efferent sacral nerves for bladder control in spinal cord injury. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

Aims: The Finetech-Brindley Sacral Anterior Root Stimulator is an effective method for achieving bladder emptying in patients with spinal cord injury (SCI). It is usually combined with a posterior rhizotomy of sacral roots 2 to 4 to increase bladder capacity and reduce detrusor-external sphincter dyssynergia (DSD). Although effective, rhizotomy abolishes reflex erections and is unacceptable to many patients. Neuromodulation, by stimulation of pudendal nerve afferents, has been shown to increase bladder capacity in SCI patients. The aim of this work was to develop an implant capable of bladder emptying (by high-level stimulation to activate the detrusor) and neuromodulation (by continuous low-level stimulation) to increase bladder capacity, while preserving the sacral roots. Methods: The response to neuromodulation was assessed preoperatively by stimulation of the dorsal penile nerve during serial cystometry in 17 patients. Conditional stimulation (where 1 minute periods of neuromodulation are repeatedly triggered by a rise in detrusor pressure) was compared with continuous, and a microtip transducer catheter used to measure urethral sphincter pressure. Five patients were implanted with a device capable of stimulating both anterior and posterior sacral roots (SPARS). Bladder emptying was assessed using interval voiding programs in the laboratory; neuromodulation was assessed both in the laboratory and in the long term at home. Results: Conditional neuromodulation was of similar efficacy to continuous: both significantly increased bladder capacity but neither markedly reduced DSD. In three patients with persisting postoperative detrusor hyperreflexia, neuromodulation was effective in the laboratory in two, and at home in one. In 3 out of 4 patients, bladder emptying was incomplete, with evidence of persisting DSD in the gaps between stimulations. Conclusion: Neuromodulation by continuous stimulation through the SPARS may be effective enough to replace posterior rhizotomy in some patients, but if DSD is present preoperatively it is likely to persist, preventing complete bladder emptying.

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