The role of cerebrospinal fluid flow study using phase contrast MR imaging in diagnosing idiopathic normal pressure hydrocephalus.

BACKGROUND The purpose of this prospective study was to identify the ability of cerebrospinal fluid flow study using phase contrast MR imaging to replace the invasive methods currently used to establish the diagnosis of idiopathic normal pressure hydrocephalus (iNPH). MATERIALS AND METHODS Between January 2003 and April 2005, 61 patients with clinical symptoms fitting the Hakim triad and a dilated ventricular system on CT underwent a intrathecal infusion test and cerebrospinal tap test. All patients also had a phase contrast MRI to determine the CSF flow rate in the aqueduct. Shunted patients were followed postoperatively up to 12 months. The pre- and postoperative symptomatic condition was evaluated using the clinical Kiefer score. The outcome was calculated by the NPH Recovery Rate. FINDINGS Patients were classified into 41 with iNPH and 20 patients with brain atrophy. Thirty-nine iNPH patients were shunted and two patients refused surgery. The mean Kiefer score of the shunted patients was statistically significantly lower after surgery. In patients screened for clinical symptoms and ventriculomegaly on CT imaging, an aqueduct-CSF flow rate greater than 24.5 ml/min was found to be statistically specific for a diagnosis of iNPH. CONCLUSIONS The measurement of the CSF flow rate in the aqueduct by using the phase contrast MRI technique is a highly specific pre-selective method for diagnosing iNPH.