Can Medial Temporal Impairment Be an Imaging Red Flag for Neurodegeneration in Disproportionately Enlarged Subarachnoid Space Hydrocephalus?

Background: The differentiation of idiopathic normal pressure hydrocephalus (iNPH) from neurodegenerative diseases such as Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) is often challenging because of their non-specific symptoms. Therefore, various neuroradiological markers other than ventriculomegaly have been proposed. Despite the utility of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) for the appropriate selection of shunt surgery candidates, the specificity and neuropathology of this finding have not been sufficiently evaluated.

Objective: Investigation of the clinicopathological features and comparison of the neuroradiological findings between DESH with postmortem neuropathological diagnoses (pDESH) and clinically-diagnosed iNPH (ciNPH) patients are the main purposes of this study.

Method: In addition to the retrospective evaluation of clinicopathological information, quantitative, semiquantitative, and qualitative magnetic resonance imaging (MRI) indices were compared between pathologically-investigated 10 patients with pDESH and 10 patients with ciNPHResults:Excluding one patient with multiple cerebral infarctions, the postmortem neuropathological diagnoses of the pathologically-investigated patients were mainly neurodegenerative diseases (five AD, one DLB with AD pathologies, one DLB, one argyrophilic grain disease, and one Huntington's disease). In addition to the common neuroradiological featuresConclusion:Hippocampal atrophy and deformation with temporal horn enlargement seem to be characteristic neuroradiological findings of long-standing severely demented patients with DESH and neurodegenerative diseases, mainly advanced-stage AD.