PEDIATRIC UROLOGY

The Impact of Attention Deficit Hyperactivity Disorders on Brainstem Dysfunction in Nocturnal Enuresis
Baeyens D, Roeyers H, Hoebeke P, Antrop I, Mauel R, Walle JV
Department of Psychology, Developmental Disorders, Ghent University, Belgium
J Urol. 2006; 176: 744-8

• Purpose: In a specialized university setting the prevalence of attention deficit hyperactivity disorder in general and particularly the inattentive subtype attention deficit hyperactivity disorder of the predominantly inattentive subtype is highly increased. We replicated previous research findings that enuresis is associated with a brainstem deficit and investigated the impact of attention deficit hyperactivity disorder on this brainstem deficit in enuresis.
• Materials and Methods: Electromyography recorded startle eye blink modification with and without attentional modulation was used to measure brainstem functioning in 158 children between 6 and 12 years old. Performance in 3 enuresis groups, including children with enuresis, enuresis plus attention deficit hyperactivity disorder of the predominantly inattentive subtype and enuresis plus attention deficit hyperactivity disorder combined, respectively, was compared with that in normally developing controls and in children with attention deficit hyperactivity disorder subtypes without enuresis.
• Results: In an automatic attentional task the enuresis groups showed decreased brainstem inhibition compared to that in the control and attention deficit hyperactivity disorder groups (p < 0.006). In a controlled attentional task children with and without enuresis who had attention deficit hyperactivity disorder of the predominantly inattentive subtype were unable to show attentional modulation in all age groups (p < 0.02).
• Conclusions: Startle eye blink modification research reveals a brainstem inhibition deficit in children with enuresis, which could explain why they are unable to remain dry at night. When additional attention is allocated to specific trials in the task, children with attention deficit hyperactivity disorder of the predominantly inattentive subtype fail to optimize sensory gating. With respect to enuresis, this could result in an identification problem of bladder signals, leading to an inadequate or absent arousal effect in attention deficit hyperactivity disorder of the predominantly inattentive subtype.
  
  
• Editorial Comment
  The authors use Startle Eye Blink studies to compare children with enuresis to controls and to compare those with attention deficit disorders to normals. They demonstrated clear differences, with enuretic children (even those with ADHD) having much lower percentage pre-impulse inhibition of startle. In some ways but not all, the response was similar to that seen in patients with ADHD-inattentive subtype who did not have enuresis. Because Startle Eye Blink studies are a measure of brain-stem function, the results indicate that children with enuresis have a clearly documented brain stem dysfunction. In general, this dysfunction over-rides the effects of ADHD as an association with enuresis.
  Nocturnal enuresis is caused by a combination of a large nocturnal urine output, small nocturnal bladder capacity and a failure of arousal. These factors all can be related to central nervous system dysfunction. Hence, it is not surprising that enuretic children might have brainstem dysfunction. This particular study is confounded a bit in that almost 30% of the enuretic group had daytime symptoms also. Since it is generally thought that diurnal enuresis has a different etiology than mono-symptomatic nocturnal enuresis, it would have been nice to have the different groups separated out. Also, the percentage pre-impulse inhibition of startle can be increased by medications, in particular methylphenidate. It would have been fascinating to test the results of methylphenidate treatment in these groups, even though it has not been shown to improve enuresis. Any divergence of effect would be helpful in understanding the pathophysiology of nocturnal enuresis better.
  Studies of this type should be encouraged. The relationship between brain function and voiding function is intuitively clear, but obviously quite complex. Nonetheless, further application of modern neuroscience tools to patients with voiding function should be encouraged as these investigations will be helpful in understanding the conditions and in developing new therapeutic interventions.

Dr. Barry A. Kogan
Chief and Professor of Urology and Pediatrics
Albany Medical College
Albany, New York, USA