ABSTRACT
Normal pressure hydrocephalus(NPH) is defined as a combination of dementia, gait disturbance and/or urinary incontinence, hydrocephalus on C-T scan, with a normal intracranial pressure. The clinical effect of CSF shunting in patients with this syndrome is sometimes striking but generally only 50-60% of the shunted patients benefit from the treatment. So many pre-operative investigations are performed including clinical examination, computed tomography, R-I cistrnography, T1/2 calculated from ventricular volume pressure curve and lumbar drainage. Among the pre-operative investigations, the effect of preoperative lumbar drainage was the most reliable indicator of NPH. The possible mechanisms of improved case are proposed. The differential diagnosis of primary brain atrophy and NPH can be made by the effect of pre-operative lumbar drainage.