Primary bladder neck dysfunction in children and adolescents I: pelvic floor electromyography lag time--a new noninvasive method to screen for and monitor therapeutic response.

Objective: One of the key findings for making the diagnosis of primary bladder neck dysfunction (PBND) on videourodynamics (VUDS) is prolongation of the time between the start of a voluntary detrusor contraction and the start of urine flow (opening time). Since normally this dynamic event is immediately preceded by pelvic floor relaxation, we determined if the interval between pelvic floor relaxation on pelvic floor electromyography (EMG) and the start of flow (pelvic floor EMG lag time), approximated opening time.

Methods: Opening time measured on VUDS and pelvic floor EMG lag time measured on noninvasive uroflowmetry/EMG were compared in 22 consecutive patients with a mean age of 13.8 years diagnosed with PBND and a control group of 17 normal children. In addition, 19 patients with PBND were placed on alpha-blocker therapy, and pretreatment and on treatment uroflowmetry and pelvic floor EMG lag time values were compared.

Results: Mean opening time and mean pelvic floor EMG lag time were statistically indistinguishable from each other in the PBND and normal groups (27.4 vs 23.9 and 1.1 vs 1.3 seconds, respectively, p >0.550), but they differed significantly between the normal and PBND groups (p <0.001). On alpha-blocker therapy a decrease in mean pelvic floor EMG lag time from 24.47 to 6.67 seconds (p <0.001) corresponded with improved flow parameters, while no improvement was noted in untreated patients.

Conclusions: Pelvic floor EMG lag time directly correlates with opening time and, when prolonged and associated with abnormal uroflowmetry, it is highly suggestive of PBND, thereby, justifying more invasive evaluation with VUDS or the initiation of empirical drug therapy. Most importantly, it provides an objective means of monitoring treatment response in a disorder that often has lingering symptoms.