BackgroundPrader-Willi syndrome (PWS) is a complex neurodevelopmental genetic disorder with hypothalamic dysfunction, early morbid obesity with hyperphagia, and specific psychiatric phenotypes including cognitive and behavioural problems, particularly disruptive behaviours and frequent temper outbursts that preclude socialization. A deficit in oxytocin (OT)-producing neurons of the hypothalamic paraventricular nucleus has been reported in these patients.MethodsIn a double-blind, randomised, placebo-controlled study, 24 adult patients with PWS received a single intranasal administration of 24 IU of OT or placebo and were tested 45 min later on social skills. Behaviours were carefully monitored and scored using an in-house grid as follows: over the two days before drug administration, on the half-day following administration, and over the subsequent two days. All patients were in a dedicated PWS centre with more than ten years of experience. Patients are regularly admitted to this controlled environment.ResultsPatients with PWS who received a single intranasal administration of OT displayed significantly increased trust in others (P = 0.02) and decreased sadness tendencies (P = 0.02) with less disruptive behaviour (P = 0.03) in the two days following administration than did patients who received placebo. In the half-day following administration, we observed a trend towards less conflict with others (p = 0.07) in the OT group compared with the placebo group. Scores in tests assessing social skills were not significantly different between the two groups.ConclusionsThis study needs to be reproduced and adapted. It nevertheless opens new perspectives for patients with PWS and perhaps other syndromes with behavioural disturbances and obesity.Trial registration numberClinicalTrials.gov: NCT01038570

The Prader-Willi syndrome (PWS), a rare multisystem genetic disease, leads to severe disabilities, such as morbid obesity, endocrine dysfunctions, psychiatric disorders, and social disturbances. We explored the whole brain of patients with PWS to detect abnormalities that might explain the behavioral and social disturbances, as well as the psychiatric disorders of these patients. Nine patients with PWS (six males, three females; mean age 16.4 years) underwent a positron emission tomography (PET) scan with H 2 15 O as a tracer to measure regional cerebral blood flow (rCBF). The images were compared with those acquired from nine controls (six males, three females; mean age 21.2 years). A morphologic magnetic resonance imaging (MRI) was also performed in PWS patients, and their cognitive and behavioral skills were assessed with Wechsler Intelligence Scale for Children III and the Child Behavior Check List (CBCL). The MRI images showed no evident anatomic abnormalities, whereas PET scans revealed hypoperfused brain regions in PWS patients compared with controls, particularly in the anterior cingulum and superior temporal regions. We observed a significant relationship (P < 0.05) between rCBF in the hypoperfused regions and CBCL scores. The functional consequences of these perfusion abnormalities in specific brain regions might explain the behavioral and social problems observed in these individuals.