A 58-year-old female with blurred vision and apraxia

Abstract

A 58-year-old right handed woman, with 12 years of formal education, had a five-year history of slowly progressive blurred vision and apraxia. Five years before the examination she gradually became blurred vision and had difficulties identifying static objects within the visual field. Then she went to an ophthalmologist and received cataract surgery. However, the symptoms were not improved after surgery. Two years later, she had difficulty doing household chores and was unable to dress herself. She developed an anxiety disorder in the absence of prominent language or memory deficits. Five years after onset, she showed global cognitive decline and abilities of daily life decline. On neurological examination she was alert. Neuropsychological testing revealed a mini-mental state examination (MMSE) score of 20/30 with anomia, agraphia, alexia and partial impairment on time orientation. Biochemical investigations for disorders involving thyroid function, vitamin B₁₂, and folate were unremarkable. A brain MRI showed diffuse cortical atrophy and hippocampus atrophy. An ¹⁸F-FDG PET scan showed bilateral hypometabolism at the frontal lobes, tempoparietooccipital adjunction, posterior cingulate cortices and precuneus, insular lobes, caudate nuclei and right thalamus. An ¹¹C-PIB PET scan showed bilateral amyloid deposits at bilateral frontal lobes and occipital lobes, left temporal lobe and insular, basal ganglia, bilateral cingulate cortices and precuneus. No PSEN1, PSEN2 or APP mutations were identified. This early-onset patient had an unusual cognitive complaint, including visual agnosia and apraxia. The clinical features, structural and functional imaging findings of this case were compatible with the diagnosis of Posterior Cortical Atrophy (PCA). PCA is a neurodegenerative condition characterized by a progressive, often dramatic and relatively selective decline in visual processing skills and other functions subserved by parietal, occipital and occipito-temporal regions, relatively intact memory and language in the early stages, and atrophy of posterior brain regions. Often considered as an atypical or variant form of Alzheimer’s disease (AD), PCA typically presents in the mid-50s or early 60s with a variety of unusual symptoms, such as difficulty in interpreting, locating, or reaching for objects under visual guidance or difficulty in navigating. Understanding numbers and reading and writing or spelling may also be affected and, as the disease progresses, patients often develop a more diffuse pattern of cognitive dysfunction, ultimately leading to dementia. The vast majority (>80%) of PCA patients are found to have AD pathology as the cause of dementia at autopsy. Both PCA and AD patients show a similar pattern of high cortical binding on amyloid positron emission tomography (PET) imaging, and analogous changes in cerebrospinal fluid (CSF) level of Aβ42, total tau, and phosphorylated tau. PCA and AD show overlapping atrophy and hypometabolism/hypoperfusion in temporoparietal regions, suggesting a common anatomic focus of neurodegeneration. Structural neuroimaging with either MRI or CT initially shows greater atrophy of visual processing areas in parietotemporo-occipital cortex and relative sparing of critical memory regions in the medial temporal lobe. Over time, the neuroimaging profile of PCA may also merge with that of typical AD. This patient has five-year history of blurred vision and apraxia. At the time of examination, she has been in the stage of global cognitive declining. Diffuse cortical atrophy and hippocampus atrophy in MRI is very difficult to distinguish from typical AD. Hypometabolism and amyloid deposits from PET scan also showed overlapping with typical AD.

doi: 10.3969/j.issn.1672-6731.2014.07.018