Aphasia with left occipitotemporal hypometabolism: A novel presentation of posterior cortical atrophy?

Abstract

Alzheimer’s disease is a common neurodegenerative disease often characterized by initial episodic memory loss. Atypical focal cortical presentations have been described, including the logopenic variant of primary progressive aphasia (lvPPA) which presents with language impairment, and posterior cortical atrophy (PCA) which presents with prominent visuospatial deficits. Both lvPPA and PCA are characterized by specific patterns of hypometabolism: left temporoparietal in lvPPA and bilateral parietoccipital in PCA. However, not every patient fits neatly into these categories. We retrospectively identified two patients with progressive aphasia and visuospatial deficits from a speech and language based disorders study. The patients were further characterized by MRI, fluorodeoxyglucose F18 and Pittsburgh Compound B (PiB) positron emission tomography. Two women, ages 62 and 69, presented with a history of a few years of progressive aphasia characterized by fluent output with normal grammar and syntax, anomia without loss of word meaning, and relatively spared repetition. They demonstrated striking deficits in visuospatial function for which they were lacking insight. Prominent hypometabolism was noted in the left occipitotemporal region and diffuse retention of PiB was noted. Posterior cortical atrophy may present focally with left occipitotemporal metabolism characterized clinically with a progressive fluent aphasia and prominent ventral visuospatial deficits with loss of insight.

Progressive transcortical sensory aphasia and progressive ideational apraxia owing to temporoparietal cortical atrophy

“…A slight difference in the main affected areas may reflect differences in linguistic features. These linguistic characteristics resemble those of Wicklund’s patients with posterior cortical atrophy [ 10 ] in whom aphasia was characterized by fluent output with normal grammar and syntax, anomia without loss of word meaning, and relatively spared repetition. The characteristics of our cases and previous studies [ 10 , 11 ], in particular transcortical sensory aphasia along with some forms of posterior symptoms (agraphia, acalculia, and visuospatial deficits), may reflect the spectrum between lvPPA and posterior cortical atrophy.…”

“…These linguistic characteristics resemble those of Wicklund’s patients with posterior cortical atrophy [ 10 ] in whom aphasia was characterized by fluent output with normal grammar and syntax, anomia without loss of word meaning, and relatively spared repetition. The characteristics of our cases and previous studies [ 10 , 11 ], in particular transcortical sensory aphasia along with some forms of posterior symptoms (agraphia, acalculia, and visuospatial deficits), may reflect the spectrum between lvPPA and posterior cortical atrophy. In fact, the first five described cases of posterior cortical atrophy [ 20 ] with higher visual dysfunction were reported to have developed transcortical sensory aphasia in later stages.…”

“…Although our cases lack in CSF findings and PIB scan, these two cases and the other reported cases [ 10 , 11 ] might suggest the existence of a subgroup of patients presenting with transcortical sensory aphasia, apraxia, and posterior symptoms (acalculia, agraphia, and visuospatial deficits) in the setting of Alzheimer’s disease. This subgroup may reflect the spectrum of clinical manifestations between lvPPA and posterior cortical atrophy.…”

“…However, not every patient clearly fits into one of these categories. In 2013, Wicklund et al [ 10 ] described two patients with Alzheimer’s disease who showed not only progressive aphasia but also progressive visuospatial deficits with prominent hypometabolism in the left occipitotemporal region. Likewise, Garcia-Azorin et al [ 11 ] described two patients with Alzheimer’s disease who showed progressive aphasia with left parieto-temporo-occipital hypometabolism, suggestive of an overlapping entity between PPA and posterior cortical atrophy.…”

Sample size calculations for clinical trials targeting tauopathies: a new potential disease target

“…In fact, progressive apraxia of speech patients often eventually progress into a PSP-like syndrome [15]; hence little surprise that tau is the underlying pathology. No studies have assessed the prevalence of progressive apraxia of speech or PPAOS, although prevalence can be estimated to be approximately 4.4 per 100,000 persons based on the prevalence of progressive apraxia of speech compared to other speech and language disorders in our cohort [16], and previous prevalence studies of speech and language disorders [17, 18]. The typical age at onset of progressive apraxia of speech is also relatively young [11] which will limit the presence of age-related co morbid pathologies that could confound progression.…”