• Shigeki Yamada, Hirotaka Ito, Hironori Matsumasa, Motoki Tanikawa, Satoshi Ii, Tomohiro Otani, Shigeo Wada, Marie Oshima, Yoshiyuki Watanabe, and Mitsuhito Mase.
• Department of Neurosurgery, Nagoya City University Graduate School of Medical Science, Aichi, Japan; Interfaculty Initiative in Information Studies/Institute of Industrial Science, The University of Tokyo, Tokyo, Japan; Normal Pressure Hydrocephalus Center, Rakuwakai Otowa Hospital, Kyoto, Japan. Electronic address: shigekiyamada393@gmail.com.
• World Neurosurg. 2023 Aug 1; 176: e427e437e427-e437.

ObjectiveThe presence of tightened sulci in the high-convexities (THC) is a key morphological feature for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH), but the exact localization of THC has yet to be defined. The purpose of this study was to define THC and compare its volume, percentage, and index between iNPH patients and healthy controls.MethodsAccording to the THC definition, the high-convexity part of the subarachnoid space was segmented and measured the volume and percentage from the 3D T1-weighted and T2-weighted magnetic resonance images in 43 patients with iNPH and 138 healthy controls.ResultsTHC was defined as a decrease in the high-convexity part of the subarachnoid space located above the body of the lateral ventricles, with anterior end on the coronal plane perpendicular to the anterior commissure-posterior commissure (AC-PC) line passing through the front edge of the genu of corpus callosum, the posterior end in the bilateral posterior parts of the callosomarginal sulci, and the lateral end at 3 cm from the midline on the coronal plane perpendicular to the AC-PC line passing through the midpoint between AC and PC. Compared to the volume and volume percentage, the high-convexity part of the subarachnoid space volume per ventricular volume ratio < 0.6 was the most detectable index of THC on both 3D T1-weighted and T2-weighted magnetic resonance images.ConclusionsTo improve the diagnostic accuracy of iNPH, the definition of THC was clarified, and high-convexity part of the subarachnoid space volume per ventricular volume ratio <0.6 proposed as the best index for THC detection in this study.Copyright © 2023 Elsevier Inc. All rights reserved.

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