Occurring in patients aged over 40, chronic hydrocephalus in adults is one of the treatable dementias thanks to the fitting of a valve. The cause of this phenomenon is rarely identified. Among these patients, hydrocephalus develops insidiously as they retain much of their ability to absorb the fluid. They notably present impaired cognitive functions and difficulties in walking but no signs of intracranial hypertension. The device developed by Neurallys will contribute to a better understanding of the disease and allow better adjustment of drainage in these patients who are often fragile.