Altered cerebellar morphological similarity network correlates with cognitive decline and cerebrospinal fluid biomarkers in mild Alzheimer’s disease: a 7 T MRI study

BACKGROUD: Recent neuroimaging research emphasized cerebellar atrophy and alternation of functional connections in Alzheimer's disease (AD), fewer studies have focus on the cerebellar subfield and its structural network reorganization. This study aimed to explore the utility of 7 T MRI in assessing cerebellar subfield volumes, morphological similarity network (MSN) and their correlation with cognitive decline and cerebrospinal fluid (CSF) biomarkers in mild AD. METHODS: Cerebellar subfield segmentation and individual level MSNs construction were performed using high-resolution structural 7 T MRI data in 30 AD of mild stage and 30 healthy normal controls (NCs). Subfield volumes and topological parameters of the resulting graphs were compared between groups. Correlations between altered MSN metrics and cognitive measurement, CSF biomarkers were further analyzed in AD group. RESULTS: Compared to NCs, AD patients exhibited salient vermis VIIb and vermis VIIIa atrophy and significantly large-scale topological alterations of nodal properties of cerebellar MSN, predominantly in the posterior lobes (lobe VI-IX). The global network metrics were relatively preserved, despite the increased global assortativity. Altered structural network properties of lobule VIII, vermis IX and crus II were significantly associated with cognitive decline and CSF Aβ42 and p-tau181 levels in AD. CONCLUSIONS: Our study emphasizes the crucial role of alterations in morphological connectivity beyond cerebellar atrophy in early AD using 7 T MRI. Structural network alterations in lobule VIII, vermis IX and crus II demonstrated significantly correlation with clinical variables, indicating their potential as sensitive imaging markers and therapeutic targets for AD.