Clinical And Neuroimaging Differences Between Posterior Cortical Atrophy And Typical Amnestic Alzheimer’s Disease Patients At An Early Disease Stage

Objective:To identify clinical and neuroimaging characteristics between posterior cortical atrophy(PCA)and typical amnestic Alzheimer’s disease(tAD)patients at an early disease stageMethods:16 PC A and 13 age-matched tAD patients were enrolled.And fifteen healthy,age-,education-,and sex-matched control subjects(Clinical Dementia Rating[CDR]of 0)were also recruited.All patients underwent a detailed clinical history interview and physical examination,neuropsychological assessment,and a T1-3D MRI scan.The majority(23/29)of patients underwent 18F-FDG-PET scanning.Nine subjects(including five PCA and four tAD patients)underwent lumbar punctures.Phosphorylated tau(p-tau),total tau(t-tau),and Aβ 1-42 concentrations were analyzed by ELISA.Differences in clinical manifestations,biomarker levels,regional atrophy,and glucose metabolism between the groups were compared,with the possible relationship between neuropsychological tests performance and neuroimaging characteristics in PCA patients further analyzed.Results:All the 16 PCA patients had a different range of visuoperceptual and/or visuospatial impairments.PCA patients showed higher mean recognition and recall test scores,and lower mean calculation,spatial attention,shape discrimination,and writing test scores.Mean right hippocampal volume was larger in PCA patients compared with tAD patients,while cortical gray matter(GM)volume of bilateral parietal and occipital lobes was smaller in PCA patients.Further,when compared with tAD patients,significant hypometabolism was observed in bilateral parietal and occipital lobes,particularly the right occipitotemporal junction in PCA patients.Therefore,PCA patients display better recognition and recall scores,which are associated with larger hippocampal volumes and poorer performance in visual spatial tasks because of marked GM atrophy and hypometabolism of parietal and occipital lobes.Conclusion:Compared with tAD patients,PCA patients show more symptoms related to the visual cortex,and exhibit marked impairments in visuospatial-related cognitive function.These changes in neuropsychological performances are likely associated with specific cortical GM volume loss and Glucose metabolism in the parietal and occipital lobes.Furthermore,we found no differences in APOE4 allele frequency and Aβ levels in CSF and serum between PC A and tAD patients.