The idiopathic normal pressure hydrocephalus is a syndrome, characterized by gait impairment, cognitive decline and urinary incontinence, and associated with ventriculomegaly in the absence of elevated CSF pressure. Pathogenesis is not understood; intermittent intracranial hypertension, decreased CSF absorption and cerebral ischemia have been blamed. Hallmark of neuroimaging in NPH is ventriculomegaly out of proportion with sulcal atrophy, MRI is the choice of imaging; CSF flow in NPH is hyperdynamic, with an increase in the amount and velocity of CSF passing rostrally, then caudally, through the cerebral aqueduct with each cardiac cycle. Clinical improvement after CSF drainage implies good response to shunting. The best results are found in the subjects treated with low-pressure valves. Increased use of adjustable valve seems to be beneficial. Gait is most likely to improve. Postoperative reduction in ventriculomegaly is not always seen or proportionate to the clinical improvement.