Clinical applicability of arterial spin labeling magnetic resonance imaging in patients with possible idiopathic normal pressure hydrocephalus: A prospective preliminary study

Purpose: idiopathic Normal Pressure Hydrocephalus (iNPH) patients have a global reduction of cerebral blood flow (CBF) and Arterial Spin Label (ASL) MRI allows a global evaluation of CBF without the injection of contrast agents. This work aims to assess the qualitative evaluation agreement of ASL CBF colored maps between different neuroradiologists and by correlating these data to the Tap Test. Methods: Thirty - seven patients with the diagnosis of possible iNPH were consecutively submitted to a diagnostic MRI on a 1.5 Tesla Magnet before and after the lumbar infusion test and the Tap Test. Twenty - seven patients improved after the Tap Test and were addressed to surgery while 10 patients did not improve. All the MRI examinations included a 3D-Pulsed ASL sequence. Two different neuroradiologists independently reviewed all ASL images. They were asked to give a score (0 not improved; 1 improved) to global perfusion image quality by comparing ASL images obtained after the Tap Test to those obtained before. Comparison between inter- and intra-reader qualitative scores were performed with Cohen's kappa. Results: Inter-reader agreement between the two neuroradiologists showed that qualitative scores were attributed similarly by two readers (k = 0.83). This technique has a good PPV (90.5 %; CI 95 %, 72.7–97.1 %), NPV (50 %; CI 95 %, 34.1–65.6 %), SN (70.37 %; CI 95 %, 49.8–86.2 %) SP (80 %; CI 95 %, 44.4–97.5 %) and accuracy (73 %; CI 95 %, 55.9–86.2 %) when considered in the setting of possible iNPH patients. Conclusion: ASL-MRI seems to be a promising non-invasive technique in the preoperative selection of patients affected by possible iNPH.