Nocturnal enuresis (NE) is the involuntary loss of urine that occurs only at night in children aged 5 years or more.

NE is a common problem, affecting about 10% of school children. The prevalence declines with each year of maturity but for some it persists in to adolescents and early adulthood. It can lead to bad self-confidence and low self-esteem, which can have psychosocial consequences.

NE is a multifactorial condition. Three central factors have been identified:

A) Many bedwetting children produce large amounts of urine at night due to a deficiency of the antidiuretic hormone vasopressin.

B) Other children have a lack of inhibition of bladder emptying during sleep. C) Almost all children are deep sleepers with high arousal thresholds. They simply don't wake up when the bladder is full or when it contracts.

There are two well established and evidence based treatments today: the bed-wetting alarm and the pharmacologic treatment desmopressin. The alarm emits a sound when the child wets the bed, which conditions the child to wake up or inhibit bladder emptying. This method is curative for about half of the patients who try this, but relapse occurs. Desmopressin is a synthetic analog of arginine vasopressin and works by decreasing the urine volume at night. About half of the patients become dry with this medication but only as long as they take the medicine. To day, at least 25% of all children with NE do not respond to any of the above treatment.

Rapid maxillary expansion (RME) is a common orthodontic technique to treat patients with a narrow upper jaw. The brace is fitted by an orthodontist, and has a jack-screw, which is activated twice every day for 10-14 days. The procedure is neither painful nor harmful and is not very visible at all.

There are a few reports about children who have become dry after RME treatment. None of them have been randomised or placebo controlled but indicates that quite a few children do become dry after this treatment. A recently carried out study in Sweden show that half of the children became dry after RME treatment. These children were all classed as therapy resistant and had already tried the alarm and medication without success.

The reports are intriguing, but invite the question why a brace would help cure NE? It is likely that sleep and respiration is involved. This study will investigate these children's sleep during the treatment. The trial is a randomised, placebo controlled trial.

Inclusion Criteria:

• Patients aged 7-14 years old
• At least 7 wet nights out of 14

Exclusion Criteria:

• Daytime incontinence
• Constipation
• ADHD