The purpose of this study is to investigate the safety and efficacy of deep brain stimulation in obese patients with Prader Willi syndrome refractory to conventional treatment.

The purpose of this study is to investigate the safety and efficacy of deep brain stimulation in obese patients with Prader Willi syndrome refractory to conventional treatment. Patients will be implanted with hypothalamic DBS electrodes. Calorimetric and anthropometric measures, body mass index, side effects, neuropsychiatric evaluations will be carried out at 6 months for measuring primary and secondary outcome. Side effects will be monitored at 1, 3, 6 and 12 months following surgery.

Inclusion Criteria:

• 15 years or older
• Parents able to give informed consent
• Diagnosis of Prader-Willi syndrome confirmed by genetic analysis
• Refractoriness to medical treatment, defined as a weight loss lower than 10% of the body weight with nutritional, pharmacological or surgical interventions
• Severe or morbid obesity
• No contra-indications to the surgical procedure

Exclusion Criteria:

• Cardiovascular disease that might significantly increase the surgical risk
• Brain lesions detected clinically or during MRI
• Use of cardiac pacemakers/ defibrillators
• Clinical conditions that may require the use of MRI in the post-operative period
• Patients undergoing chemotherapy or immunosuppressive treatments
• Patients unable to return to the hospital at the required intervals
• Previous neurosurgical treatments that may increase the risk of DBS surgery
• Active medical conditions that may require in-hospital treatment in the nearby future
• Previous diagnosis of epilepsy or status epilepticus
• Chronic infection
• Plan to use diathermy
• Metallic implants that might preclude MRI imaging of the brain
• Active participation in other experimental studies