The safety of adjustable valves has become a major concern for neurosurgeons because of the growing use of electromagnetic devices in daily life and the development of high power MRI (3 teslas). Indeed, these devices are liable to modify the selected pressure accidentally, with the risk of disrupting CSF drainage and causing serious complications for the patient. The Polaris® valve is a major breakthrough for the safety of patients fitted with adjustable valves. Its exclusive locking mechanism enables it to resist: Direct knocks to the valve; Everyday magnetic fields; Magnetic Resonance Imaging (MRI), up to 3 teslas.