Differentiation of subgroups of monosymptomatic enuresis according to prepulse inhibition of the startle reflex.

Aim:  Monosymptomatic enuresis (ME) is a common disorder in children with serious social and psychological consequences. Treatment is usually initiated with desamino-arginine vasopressin (dDAVP) and/or alarm therapy as first-line treatment and imipramine as second-line. All treatments have proven efficacy, but are not successful with all patients. Therefore, a differentiation into subgroups according to treatment efficacy would be beneficial. Methods:  A group of patients resistant to first-line treatment was treated with imipramine and compared with matched controls successfully treated with dDAVP and/or alarm therapy. Prepulse inhibition (PPI) to acoustic startle reflexes was measured in all patients. Results:  In a group of 23 nonresponders, the median PPI was 72% (range 43–94%) compared with the matched dDAVP/alarm – responders with a median PPI of 26% (range 0–61%) (p < 0.0001). The response rate to imipramine was 87%. Conclusion:  The presented data provide evidence that PPI allows to identify two subgroups of ME. The results offer further insight into (at least) two different pathomechanisms involved in ME: (i) a maturational delay of reflex inhibition with reduced PPI and (ii) a normal PPI, possibly with abnormal sleep patterns, that can be influenced by imipramine.