White Matter Lesions May Aid in Differentiating Idiopathic Normal Pressure Hydrocephalus and Alzheimer's Disease

Background: Idiopathic normal pressure hydrocephalus (iNPH) is often misdiagnosed as Alzheimer's disease (AD) due to overlapping pathophysiology and similar imaging characteristics, including ventricular enlargement and increased white matter lesions (WMLs). Objective: To compare the extent and distribution of WMLs directly between iNPH and AD and examine the association with underlying pathophysiology. Methods: Twelve patients with iNPH (mean age: 78.08 years; 5 females), 20 with AD (mean age: 75.40 years; 13 females), and 10 normal cognition (NC) participants (mean age: 76.60 years; 7 females) were recruited. The extent and distribution of WMLs and the lateral ventricular volume (LV-V) were evaluated on MRI using voxel-based morphometry analysis. Concentrations of cerebrospinal fluid biomarkers, such as amyloid-beta protein (A beta)(42), A beta(40), A beta(38), and tau species, were also measured. Risk factors for small vessel disease (SVD) were assessed by blood examination and medical records. Results: The periventricular WML volume (PWML-V) and deep WML volume (DWML-V) were significantly larger in iNPH than in AD and NC. The DWML-V was dominant in iNPH, while the PWML-V was dominant in AD and NC. GM-V was significantly smaller in AD than in iNPH and NC. The LV-V positively correlated with WML-V in all participants. There was a significant negative correlation between LV-V and A beta(38) in iNPH. Furthermore, there was no significant difference in SVD risk factors between the groups. Conclusion: The differences in the extent and distribution of WMLs between iNPH and AD, especially predominance of DWML-V over PWML-V in iNPH, may reflect decreased fluid and A beta clearance.

Automated summary

This study compared the extent and distribution of white matter lesions (WMLs) between idiopathic normal pressure hydrocephalus (iNPH) and Alzheimer's disease (AD), and found that deep WML volume was significantly larger in iNPH than in AD, while periventricular WML volume was dominant in AD. The lateral ventricular volume positively correlated with WML volume in all participants, and there was a significant negative correlation between lateral ventricular volume and Aβ(38) in iNPH.