Affiliations: [a] Universitá Vita-Salute San Raffaele, Milan, Italy | [b] Clinical Neuroscience Department, San Raffaele Hospital, Milan, Italy | [c] Istituto di Bioimmagini e Fisiologia Molecolare C.N.R., Segrate, Italy | [d] Department of Neurological, Institute of Experimental Neurology–INSPE, San Raffaele Hospital, Milan, Italy | [e] Department of Neuroradiology, CERMAC, San Raffaele Hospital, Milan, Italy | [f] Department of Nuclear Medicine, Division of Neuroscience, San Raffaele Hospital, Milan, Italy | [g] Istituto Universitario di Studi Superiori, Pavia, Italy
Correspondence:
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Correspondence to: Dr. Chiara Cerami, Universitá Vita-Salute San Raffaele and Clinical Neuroscience Dept., San Raffaele Hospital, Via Olgettina 60, 20134 Milan, Italy. Tel.: +39 02 26435760 2713; Fax: +39 02 26435738; E-mail: [email protected].
Abstract: Posterior cortical atrophy (PCA) is characterized by basic visual and high order visual-spatial dysfunctions. In this study, we investigated long-distance deafferentation processes within the frontal-parietal-occipital network in ten PCA patients using a MRI-PET combined approach. Objective voxel-based [18F]FDG-PET imaging measured metabolic changes in single patients. Comprehensive investigation of diffusion tensor imaging (DTI) metrics and grey-matter density with voxel-based morphometry were obtained in a subgroup of 6 patients. Fractional anisotropy in the superior longitudinal fasciculus correlated with the PET metabolic changes within the inferior parietal and frontal eye field regions. [18F]FDG-PET analysis showed in each PCA case the typical bilateral hypometabolic pattern, involving posterior temporal, parietal, and occipital cortex, with additional hypometabolic foci in the frontal eye fields. Voxel-based morphometry showed right-sided atrophy in the parieto-occipital cortex, as well as a limited temporal involvement. DTI revealed extensive degeneration of the major anterior-posterior connecting fiber bundles and of commissural frontal lobe tracts. Microstructural measures in the superior longitudinal fasciculus were correlated with the PET metabolic changes within the inferior parietal and frontal eye field regions. Our results confirmed the predominant occipital-temporal and occipital-parietal degeneration in PCA patients. [18F]FDG-PET and DTI-MRI combined approaches revealed neurodegeneration effects well beyond the classical posterior cortical involvement, most likely as a consequence of deafferentation processes within the occipital-parietal-frontal network that could be at the basis of visuo-perceptual, visuo-spatial integration and attention deficits in PCA.
