Inclusion Criteria:  age > 55 years Patients with suspected active hydrocephalus (HA) known as "normal pressure": Ventricular dilatation: Evans index > 0.3 Patients with cognitive impairment, and/or gait disorders and/or urinary incontinence or a combination of these three symptoms. Absence of other neurological diseases that could cause ventriculomegaly. Information and collection of the patient's non opposition  Exclusion Criteria:  All patients with neurological disease other than active hydrocephalus will be excluded. Individuals who cannot tolerate an MRI examination All individuals with implants, pacemakers, prostheses and ferromagnetic objects Patients under guardianship, curators or safeguard of justice