Affiliations: [a] Neuroimaging Laboratory, Santa Lucia Foundation, IRCCS, Rome, Italy | [b] Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, Falmer, UK | [c] Institute of Neurology, Università Cattolica, Rome, Italy | [d] Department of Clinical and Behavioural Neurology, Santa Lucia Foundation, IRCCS, Rome, Italy | [e] Department of Neuroscience, University of Rome ‘Tor Vergata’, Rome, Italy
Correspondence:
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Correspondence to: Dr. Marco Bozzali, Neuroimaging Laboratory, Santa Lucia Foundation, IRCCS, Via Ardeatina 306, 00179 Rome, Italy. Tel.: +39 06 5150 1324; Fax: +39 06 5150 1213; E-mail: m.bozzali@hsantalucia.it.
Abstract: This study investigates whether different patterns of grey matter (GM) loss may account for the different neuropsychological profiles observed in patients with amnestic (a-) and non-amnestic (na-) mild cognitive impairment (MCI), and may predict patients' clinical evolution. Fifty-five consecutive individuals complaining of cognitive dysfunction (referred to specialist dementia clinics) were screened and included in the study if they met the diagnostic criteria for MCI on a neurodegenerative basis. After an extensive neuropsychological assessment, patients were classified as suffering from a-MCI or na-MCI. Twenty-eight healthy individuals were also recruited and served as controls. All participants underwent magnetic resonance imaging at 3T, including conventional images and volumetric scans. Volumetric data were processed using voxel-based morphometry to assess between-group differences in regional GM volumes and correlations with neuropsychological performances. When compared to controls, a-MCI patients showed prominent GM volume reductions in the medial temporal lobes, while those with na-MCI showed reduced GM volumes in the orbito-frontal cortex and basal ganglia. In a-MCI patients, significant associations were found between verbal long-term memory performance and GM volumes in the hippocampus. Conversely, in na-MCI patients, associations were found between scores at tests exploring executive functions and GM volumes in the orbito-frontal cortex. At one-year follow-up, conversions were recorded exclusively toward Alzheimer's disease (AD) in the a-MCI group, and toward non-AD dementia in the na-MCI group. This study confirms that MCI is a heterogeneous clinical identity including different neurodegenerative entities; specific patterns of regional GM loss appear to account for specific neuropsychological features and are likely to predict patients' clinical evolution.
