Abstract
Primary progressive aphasia (PPA) is a neurodegenerative disorder with language impairment as the primary feature. Different subtypes have been described and the 3 best characterized are progressive nonfluent aphasia (PNFA), semantic dementia (SD) and logopenic/phonological aphasia (LPA). Of these subtypes, LPA is most commonly associated with Alzheimer's disease (AD) pathology. However, the features of PPA associated with AD have not been fully defined. Here we retrospectively identified 14 patients with PPA and either pathologically confirmed AD or cerebrospinal fluid (CSF) biomarkers consistent with AD. Analysis of neurological and neuropsychological features revealed that all patients had a syndrome of LPA with relatively nonfluent spontaneous speech, phonemic errors, and reduced digit span; most patients also had impaired verbal episodic memory. Analysis of the pattern of cortical thinning in these patients revealed left posterior superior temporal, inferior parietal, medial temporal, and posterior cingulate involvement and in patients with more severe disease, increasing involvement of left anterior temporal and frontal cortices and right hemisphere areas in the temporo-parietal junction, posterior cingulate, and medial temporal lobe. We propose that LPA may be a “unihemispheric” presentation of AD, and discuss this concept in relation to accumulating evidence concerning language dysfunction in AD.
Highlights
Primary progressive aphasia (PPA) refers to a group of neurodegenerative disorders with language impairment as the initial symptom (Mesulam, 1982, 2001, 2003)
Recent evidence has suggested that logopenic/ phonological aphasia (LPA) is underpinned by Alzheimer’s disease (AD) pathology in a high proportion of cases and may be the most common aphasia phenotype of AD (Gorno-Tempini et al, 2008; Mesulam et al, 2008; Rabinovici et al, 2008)
Both progressive nonfluent aphasia (PNFA) and semantic dementia (SD) have been reported with AD pathology, as have syndromes that do not fit clearly into a single category, so-called “mixed” aphasia (Alladi et al, 2007; Knibb et al, 2006)
Summary
Primary progressive aphasia (PPA) refers to a group of neurodegenerative disorders with language impairment as the initial symptom (Mesulam, 1982, 2001, 2003). Recent evidence has suggested that LPA is underpinned by AD pathology in a high proportion of cases and may be the most common aphasia phenotype of AD (Gorno-Tempini et al, 2008; Mesulam et al, 2008; Rabinovici et al, 2008) Both PNFA and SD have been reported with AD pathology, as have syndromes that do not fit clearly into a single category, so-called “mixed” aphasia (Alladi et al, 2007; Knibb et al, 2006). We review the clinical, neuropsychological and cross-sectional neuroimaging features of a retrospective series of patients with a clinical diagnosis of PPA and AD pathology either demonstrated directly or presumed on the basis of cerebrospinal fluid (CSF) biomarker profiles. We consider these cases in relation to previously published series of PPA patients with either pathologically confirmed AD or a positive Pittsburgh compound B (PIB)-positron emission tomography (PET) scan suggestive of AD
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