Understanding detrusor sphincter dyssynergia--significance of chronology

To evaluate in patients with spinal cord injury (SCI) and detrusor sphincter dyssynergia (DSD) whether the onset of external urethral sphincter (EUS) contractions precedes or follows the onset of bladder contractions and to address the issue of potential therapeutic approaches based on the understanding of DSD chronology.

A retrospective review of video-urodynamic recordings of patients with SCI that demonstrated both untreated neurogenic overactive bladder and DSD, from January 2002 to December 2003, was performed. Delay A was defined as the period between the onset of an EUS pressure increase and the onset of a bladder pressure increase and delay B as the period between the onset of a urethral sphincter pressure increase and the moment at which the bladder pressure increase reached 10 cm H2O greater than the baseline value.

Twenty patients with traumatic SCI matched all inclusion criteria. Delay A was positive (EUS contracted first) in 16 (80%) of 20 patients. The mean time for delay A was 2.2 seconds. A positive association was found among a positive delay A, the completeness of the spinal lesion, and continuous DSD type. Delay B was positive in all 20 patients (100%). The mean time for delay B was 7.6 seconds.

In most patients with SCI and DSD, the EUS contraction started before the onset of the bladder contraction. Additionally, in all patients with SCI, the EUS contraction started before the critical part of the bladder contraction. A pathophysiologic hypothesis for such chronology is discussed. A potential therapeutic application would be to use urethral sphincter activity to trigger inhibition of bladder contractions (conditional neuromodulation) and treat the neurogenic overactive bladder.