• Ryusuke Irie, Kohei Tsuruta, Masaaki Hori, Michimasa Suzuki, Koji Kamagata, Atsushi Nakanishi, Kouhei Kamiya, Madoka Nakajima, Masakazu Miyajima, Hajime Arai, and Shigeki Aoki.
• Department of Radiology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan. ririe@juntendo.ac.jp.
• Jpn J Radiol. 2017 Jan 1; 35 (1): 25-30.

PurposeTo evaluate diffusional changes of the corticospinal tract (CST) in patients with idiopathic normal pressure hydrocephalus (iNPH) by neurite orientation dispersion and density imaging (NODDI).Materials And MethodsNineteen patients with iNPH and 12 healthy controls were included. Diffusion MRI data for NODDI were acquired with a 3-T system, using 32 motion-probing gradient directions with six b-values (from 0 to 2500 s/mm2). The orientation dispersion index (ODI), intra-cellular volume fraction (Vic), and isotropic volume fraction (Viso) of the CST were calculated by tract-specific analysis in patients and controls. We also measured the fractional anisotropy (FA) and apparent diffusion coefficient (ADC).ResultsThe ODI of the CST (0.087 ± 0.024 vs. 0.183 ± 0.051, P < 0.01, Mann-Whitney U test) and Vic of the CST (0.551 ± 0.061 vs. 0.628 ± 0.038, P < 0.01, Mann-Whitney U test) were significantly lower in iNPH patients than in healthy controls. In receiver-operating characteristic analysis, the area under the curve (AUC) of the ODI and FA were not significantly different (Fig. 4a, 0.987 vs. 0.904, P = 0.061), and the AUC of the Vic and ADC also showed no significant difference (Fig. 4b, 0.864 vs. 0.912, P = 0.194).ConclusionThe NODDI can effectively evaluate the condition of neurites in the CST of iNPH patients, and the ODI could be clinically useful in the diagnosis of iNPH.

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