Participants were excluded if they showed a history of, or unmanaged, neurological or psychiatric impairment. The design of this study was an analysis of existing data from participants enrolled in the Clinical Core of the Northwestern Alzheimer’s Disease Center, 1 of 32 such centers funded by the National Institute on Aging/NIH. The goal was to determine whether the use of MoCA Index scores could help differentiate the salient deficits unique to amnestic versus aphasic dementia syndromes in early stages. The current study compared MoCA Index scores between cognitively normal controls, patients in mild stages of DAT with an amnestic syndrome, and patients in mild stages of PPA with an aphasic syndrome. Items in each domain yield individual index scores, providing an opportunity to make use of domain-specific test items in characterizing different dementia syndromes. The MoCA total score is comprised of 30 points for items categorized into six domains: (1) Memory (2) Executive Functioning (3) Attention (4) Language (5) Visuospatial and (6) Orientation. The MoCA has been validated in typical amnestic DAT ( Nasreddine et al., 2005), but it remains unclear whether the MoCA can be used to differentiate between distinctive clinical dementia syndromes in which episodic memory loss is not a primary symptom. It was originally used to detect MCI in patients who performed in the “normal range” on the MMSE. The Montreal Cognitive Assessment (MoCA) was published in 2005 as a brief cognitive screening tool with high sensitivity and specificity ( Nasreddine et al., 2005). In fact, a common instrument, the Mini-Mental State Examination (MMSE), has been shown to penalize individuals with PPA since the performance is heavily dependent on language ( Osher, Wicklund, Rademaker, Johnson, & Weintraub, 2007). Most screening instruments were not developed to differentiate among distinct clinical dementia syndromes such as DAT versus PPA. Indeed, PPA can be caused by frontotemporal lobar degeneration or AD, the latter of which has been shown to be atypically distributed in left-hemisphere language regions as opposed to memory-related limbic regions ( Gefen et al., 2012). Primary progressive aphasia (PPA) is diagnosed when language impairment arises as the most salient symptom and progresses to affect daily functioning. Within the last few decades, it has become clear that AD does not exclusively manifest as an amnestic syndrome, and that, although less common than amnesia, progressive visuospatial, language (i.e., aphasic), or behavioral deficits may also appear early in disease course ( Dickerson et al., 2017 Rogalski et al., 2016). Studies have shown memory to be the first cognitive domain to decline in patients who progress to DAT ( Petersen et al., 2009) as such, research on screening tools has typically focused on the amnestic phenotype of dementia. In particular, individuals with mild cognitive impairment (MCI) (a prodromal state in which there is cognitive impairment with minimal impact in activities of daily living Petersen et al., 2018) have become increasingly important to research as they are at high risk for progression to DAT ( Gauthier et al., 2006). Several screening instruments have been developed to identify differences between normal age-related changes in cognition and mild stages of DAT. Dementia of the Alzheimer’s type (DAT) is typically characterized by episodic memory deficits, or amnesia, in early stages ( Weintraub, Wicklund, & Salmon, 2012). Alzheimer’s disease (AD) is the most common neurodegenerative disease causing dementia among individuals over 65 ( Hebert, Weuve, Scherr, & Evans, 2013). In primary care settings, screening tools for the early detection of cognitive impairment that are simple to administer, short, and well validated are particularly valuable. Early detection is critical for accurate and timely diagnosis and is important for facilitating entry into clinical trials, once available. Neurodegenerative disorders associated with aging are a rapidly growing public health crisis.
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