In all published series of adult chronic hydrocephalus, there is a percentage between twenty and twenty-five percent of patients who present poor results after implantation of a cerebrospinal fluid shunt,1-11 usually ventriculoperitoneal. The lumboperitoneal shunt is also used but much more rarely. The diagnosis of this pathology is based on the clinical picture, neuroimaging studies (Evans index and corpus callosum angle), cerebrospinal fluid dynamics tests (Katzman test), and invasive intracranial pressure measurements. Despite all this diagnostic arsenal, there is a high percentage of patients (mentioned above) in which treatment by diversion of cerebrospinal fluid does not offer the expected results. Traditionally, this has been attributed to chronic adult hydrocephalus being associated with other types of dementia. This may be the case in some patients, and it would be important to predict which patients will not improve or who will improve poorly in the case of insertion of a cerebrospinal fluid shunt.