Posterior Cortical Atrophy: Does Complaint Match the Impairment? A Neuropsychological and FDG-PET Study

Abstract

Objective: Posterior Cortical Atrophy (PCA) is a neurodegenerative disease characterized predominantly by visual impairment. However, diagnosis of PCA remains complicated with an interval of several years between initial reporting of symptoms and diagnosis. The aim of the present study is to define if patients' visual and gestural complaints are consistent with their clinical profile. Method: An evaluation of daily visual problems as well as a full neuropsychological assessment and FDG-PET were performed in 15 PCA patients. We compared glucose metabolism between these PCA patients and 18 healthy controls. Correlation analyses were conducted in PCA patients between visual and gestural complaint, clinical impairments, and brain glucose metabolism. Results: Major impairment of cognitive functions was detected in PCA patients specifically in visual domains. Positive correlations were found between visual impairments and hypometabolism in the right temporo-parieto-occipital cortices. However, no correlation was found between complaint and visual impairment in PCA patients. Discussion: Our main results suggest a consistent relationship between clinical impairment and brain metabolism. However, the patient's complaint and visual performance are not linked. Combining the literature and our results, it seems that patients are generally aware of difficulties but misinterpret them. This misinterpretation may be responsible for the delayed diagnosis.

Keywords: Alzheimer's disease; FDG-positron emission tomography; neuropsychological assessment; patient's complaint; posterior cortical atrophy; visuospatial and visuoperceptive dysfunction.

Figure 1

Correlation between performance and complaint in visual (A) and gestural (B) modality. The correlation was carried out using Spearman's correlation test with a threshold of p < 0.05.

Figure 2

Brain metabolism in PCA Patients (A), Healthy Controls (B), and comparison between PCA patients and Healthy Controls (C) measured by [18F] FDG PET. “Occipital tunnel sign” is represented by preserved uptake in the medial occipital areas (red arrows) in comparison to lateral occipital (blue arrows). Metabolism asymmetry with right predominance (blue arrows) is also found in PCA patients. (A,B) represent the mean of PCA patients (n = 15) and healthy controls (n = 18), respectively. The statistical threshold for group comparison is pFWE-corr < 0.05 (k > 50 voxels). PCA, posterior cortical atrophy; SUVR, Standard Uptake Value Ratio.

Figure 3

Hemispheric asymmetry index of [18F]FDG uptake in regions of interest in healthy subjects (n = 18) and PCA patients (n = 15). Dot plot representing asymmetry index [%] using the formula: −200 × (R – L)/(R + L). Red dots represent the median for each group. Differences between healthy controls and PCA patients were assessed using the Wilcoxon-Mann-Whitney signed-ranked test. *p < 0.05. R, Right; L, Left; PCA, Posterior Cortical Atrophy.

Figure 4

Areas of the brain where metabolism correlates with primary visual functions (Shape detection Screening Test), visuoperceptive (Silhouettes Test), visuospatial (Dot Counting Test), and gestural functions in PCA patients. The statistical threshold is puncorr < 0.001 (k > 50 voxels). Correlations on the right panel are performed on the whole cluster considered (i.e., the right superior parietal cortex for visual functions and the left supramarginal gyrus for gestural functions).