Site of deafferentation and electrode placement for bladder stimulation: clinical implications

Based on the clinical experience of treating neurogenic bladders by the electrical stimulation of the ventral sacral roots, neuroanatomical and neurophysiologic studies were designed to study the mechanism of detrusor-sphincter dyssynergia during electrical stimulation of the sacral roots. An experimental model was developed to decrease the stimulation response of the pelvic floor and external urethral sphincter muscles while preserving bladder contraction. The significance of the site of deafferentation and electrode implantation was evaluated under functional and clinical aspects. Our results indicate that a combination of intradural deafferentation and extradural electrode implantation may offer maximal deafferentation efficiency with minimal surgical risk. Intradural deafferentation is facilitated by a consistent arrangement of sacral roots with the dorsal roots running laterally to the ventral roots at the site of their exit from the dura. Detrusor-sphincter dyssynergia can be reduced by selective division of ventral sacral rootlets innervating the striated musculature of the pelvic floor and the urethral sphincter.