Adjustable Gravitational vs. Adjustable Differential Pressure Valves in iNPH

Inclusion Criteria: * Age of patients (between 60 and 85 years old) * Clinically suspected Normal Pressure Hydrocephalus (NPH) with at least gait and one other symptom from Hakim-Adams triad (incontinence or dementia) * maximal initial pressure of 20 cmH2O during lumbar infusion test * Rout during LIT \>9mmHg/ml\*min * at least 15% improvement in Gait scale score after ELD * Conclusion of neuropsychological examination suggestive of iNPH (based on MoCA, Test of phonemic and verbal fluency, RAVLT, ROCFT, TMT A and B, Subtest of WAIS III, GDS) Exclusion Criteria: * Aetiology of hydrocephalus other than idiopathic normal pressure hydrocephalus (secondary normal pressure hydrocephalus - history of meningitis or subarachnoid haemorrhage, obstructive type of hydrocephalus - eg aqueductal stenosis, Blake's pouch cyst) * Intracranial tumor * Other neurodegenerative diseases may be present (AD, Parkinson's disease, Lewy body dementia, Progressive supranuclear palsy and cerebrovascular diseases), however have to be mild and evaluated in neurological, neuropsychological examinations and on MRI