Case Studies Illustrating Focal Alzheimer's, Fluent Aphasia, Late-Onset Memory Loss, and Rapid Dementia

Abstract

Many dementia subtypes have more shared signs and symptoms than defining ones. We review 8 cases with 4 overlapping syndromes and demonstrate how to distinguish the cases. These include focal cortical presentations of Alzheimer's disease (AD; posterior cortical atrophy and corticobasal syndrome [CBS]), fluent aphasia (semantic dementia and logopenic aphasia), late-onset slowly progressive dementia (hippocampal sclerosis and limbic predominant AD) and rapidly progressive dementia (Creutzfeldt-Jakob disease and limbic encephalitis). Recognizing the different syndromes can help the clinician to improve their diagnostic skills, leading to improved patient outcomes by early and accurate diagnosis, prompt treatment, and appropriate counseling and guidance.

Keywords: Atypical Alzheimer’s; Fluent aphasia; Late-onset dementia; Rapid dementia.

Figure 1

MRI brain showing bilateral occipitoparietal atrophy in Posterior Cortical Atrophy (PCA).

Figure 2

Corresponding FDG-PET in PCA revealing severe right more than left occipital hypometabolism.

Figure 3

This patient presented with corticobasal syndrome, but upon autopsy was found to have neuropathologic changes consistent with Alzheimer’s disease. (A) Parasagittal atrophy was noted when examining the fixed tissue. Immunohistochemical evaluation with a tau antibody revealed (B) a paucity of neurofibrillary tangles, (C) relative to the abundance of mature and extracellular tangles noted in the parietal lobe. A 1X magnification of the (D) parietal cortex shows an appreciably higher tau burden compared to the (E) hippocampus. Scale bar at 50 μm for 20x images.

Figure 4

MRI brain showing left temporal lobe atrophy in a patient with Semantic Dementia (SD).

Figure 5

This patient presented with a long-standing amnestic syndrome. Upon autopsy (A) no obvious cortical atrophy was noted when examining the fixed tissue. (B) When the hippocampus was observed, however, focal discoloration of the subiculum was noted in the fixed tissue and (c) upon examination with H&E without observable senile plaques. Immunohistochemical evaluation with a TDP-43 antibody revealed (D) fine neurites consistent with hippocampal sclerosis of a neurodegenerative etiology. (E) By definition, there was insufficient tau pathology to account for the (F) extensive neuronal loss (inset: pyknotic neuron). Scale bar at 100 μm for 20x images and 50 μm for inset.

Figure 6

This patient presented with a long-standing amnestic syndrome. Upon autopsy (A) no obvious cortical atrophy was noted when examining the fixed tissue. (B) The hippocampus, however, was greatly atrophied with extensive tau pathology noted. (C) Frequent neurofibrillary tangles were noted with extensive neuronal loss in CA1 and subiculum of the hippocampus. (D) Consistent with the limbic predominant form of Alzheimer’s disease, sparse neurofibrillary tangles were noted in the neocortex as illustrated by the temporal lobe. Scale bar at 50 μm for 20x images.

Figure 7

Diffusion weighted imaging (DWI) shows cortical ribboning in the occipital and temporal lobes bilaterally, left more than right.

Figure 8

MRI brain can be negative in limbic encephalitis.