<qa>  How many patients will be included in the study?A prospective blinded confirmative study of at least 200 consecutively included patients with INPH fulfilling the clinical and radiological inclusion and exclusion criteria. Patients will be included during a period of 2 years by 20 or more centres that will enrol at least 5 patients per year each. All patients in the study will receive a ventriculo-peritoneal shunt, using the Codman Programmable valve. 