Combined Flow and Pressure Study of Craniospinal Dynamic

Normal pressure hydrocephalus (NPH) can cause a type of dementia. However, this type of dementia is the only one that is reversible. To treat this dementia it is necessary to evacuate the accumulation of CSF from the brain to another body cavity using a device called a shunt. But the implantation of this shunt is only effective when the cause of the pathology is an alteration of the normal circulation of the CSF. To diagnose these patients, morphological MRI and lumbar puncture are standard approaches used but remain perfectible in diagnostic terms. The main objective is to build a new model of the interaction of intracranial pressures and fluids in order to obtain a new parameter allowing to obtain information on the cerebral biomechanics.

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