Good Correlation between CT-Measured Z-Evans’ Index and CT Volumetric of Ventricular System in Patients with iNPH Treated by Cerebrospinal Fluid Shunting
Pipat Chiewvit¹, Chanon Ngamsombat¹, Theerapol Witthiwej²
Affiliation : ¹ Division of Diagnostic Radiology, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand; ² Division of Neurosurgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background: Patients with idiopathic normal pressure hydrocephalus (iNPH) demonstrated an increase in the volume of lateral ventricles oriented along the Z-axial axis, as opposed to the X-axial axis.
Objective: To determine which computed tomography (CT)-measured X-Evans’ index and Z-Evans’ index, exhibit a stronger correlation with CT-derived ventricular volume both before and after shunting procedures. Additionally, a comparative examination between those with iNPH characterized by disproportionate enlargement of subarachnoid space hydrocephalus (DESH) and those without DESH features.
Materials and Methods: The present study enrolled forty-three iNPH patients who underwent shunting between April 2013 and April 2016. The initial screening involved a thorough review of pre-shunting CT images, leading to the categorization of patients into two distinct groups, those with DESH and without DESH features.
Results: Both the X-Evans’ index and Z-Evans’ index exhibited a noteworthy correlation with ventricular volume, substantiated by correlation coefficients (r) of 0.777 (p<0.001) and 0.876 (p<0.001), respectively. Notably, the correlation between the change in CT ventricular volume and the change in Z-Evans’ index was more conspicuous in the overall patient cohort (r=0.730, p<0.001) than X-Evans’ index change (r=0.599, p<0.001). This tendency was particularly discernible within the DESH group, where the correlation with Z-Evans’ index (r=0.826, p<0.001).
Conclusion: The Z-Evans’ index emerged as a more effective representation of ventricular volume compared to the X-Evans’ index in the entirety of the iNPH patient cohort. In contrast, during the subsequent CT follow-up, the change in X-Evans’ index exhibited superior efficacy in capturing the corresponding alterations in ventricular volume.
Received 18 April 2024 | Revised 3 September 2024 | Accepted 9 September 2024
DOI: 10.35755/jmedassocthai.2024.10.816-826-893
Keywords : CT brain; iNPH; Evans’ index; CT volumetric; DESH
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