Limited value of bladder sensation as a trigger for conditional neurostimulation in spinal cord injury patients

Conditional stimulation of dorsal genital nerves suppresses undesired detrusor contractions (UDC) and consequently increases bladder capacity and prevents incontinence. No clinically applicable sensor exists for reliable bladder activity monitoring as a trigger for conditional stimulation. Primary objective of this study was to determine whether bladder sensation concomitant with UDC may be used for spinal cord injury (SCI) patients to trigger neurostimulation in daily life.

Nineteen male and 7 female SCI patients suspected of detrusor overactivity (DO) underwent conventional and 6-hr ambulatory urodynamics. Patients were instructed to do normal daily activities and to activate event buttons of the ambulatory recorder to mark events: physical activity, bladder sensation, micturition or intermittent catheterization, and urinary incontinence. Detection rate was defined as the number of recorded bladder sensation divided by the total number of recorded UDC during ambulatory urodynamics.

Bladder sensation was reported by 73% of patients in daily life. Only 41% of patients had analyzable bladder sensation concomitant with UDC during ambulatory urodynamics. For ambulatory and conventional urodynamics, mean detection rates were 23% and 72%, respectively, with mean recording delays of 57 and 16 sec after UDC onset, respectively.

Bladder sensation only occurs in a small group of SCI patients combined with a rather low detection rate and long reaction time. Therefore, bladder sensation as a trigger for conditional stimulation does not seem to be suitable for SCI patients with DO. Reliable techniques for chronic bladder activity monitoring are a prerequisite for successful clinical application of conditional stimulation.