MR cisternography: is it useful in the diagnosis of normal pressure hydrocephalus and the selection of 'good shunt responders'?

PURPOSE The aim of this study was to evaluate the efficiency of MR cisternography (MRC) in the diagnosis of idiopathic normal-pressure hydrocephalus (INPH) and in the prediction of the response to shunt treatment. MATERIALS AND METHODS Thirty-six patients with the diagnosis of "probable INPH" were included in the study group and 15 asymptomatic age-matched individuals were included in the control group. Pre-contrast T1-weighted (T1W) imaging was followed by intrathecal administration of 1 ml gadopentetate dimeglumine. Post-contrast T1W images were taken at the 12(th), 24(th) and 48(th) hours. The presence of contrast material in the lateral ventricles for more than 24 hours was accepted as a positive diagnosis of INPH. Data from both groups were compared statistically. Statistical significance was accepted for P < 0.05. RESULTS All of the INPH patients had remaining contrast material in their lateral ventricles at the 12(th) and 24(th) hours, while only 28 (78%) patients had contrast material remaining at the 48(th) hour after MRC. Only 3 (20%) of the control cases had remaining contrast material in their lateral ventricles at the 24(th) hour. No contrast material was present in the control cases at the 48(th) hour. The contrast material was found to be significantly more prevalent in the INPH patients at the 24(th) and the 48(th) hours compared with the control cases (P < 0.001). Shunt placement was performed in 14 INPH patients, and eight improved after shunt placement. All patients (100%) who improved after shunt placement had remaining contrast material in their lateral ventricles at the 24(th) and at the 48(th) hours. The sensitivity and specificity of MRC in the prediction of the response to shunt treatment were 100% and 17%, respectively. CONCLUSION MRC does not use ionizing radiation and is generally a useful procedure to diagnose NPH and to predict a positive response to shunt treatment; thus, we recommend MRC after routine MRI in patients with the presumed diagnosis of NPH.