Comparing neurocognition in severe chronic schizophrenia and frontotemporal dementia

Abstract

Objective: Previous research has suggested cognitive similarities between schizophrenia and frontotemporal dementia. In the current study, we compared neurocognition in a group of hospitalised patients with chronic schizophrenia, who may have a more severe form of schizophrenia resembling Emil Kraepelin’s dementia praecox, with patients with frontotemporal dementia. We hypothesised minimal group differences in cognitive performance, and a large overlap in between-group score distributions in each cognitive domain. Methods: Retrospective neuropsychological data for 26 patients with severe chronic schizophrenia and 34 patients with frontotemporal dementia (behavioural variant) was collated. Neuropsychological measures were categorised into 16 cognitive domains. Raw scores were converted into standardised z-scores for each measure, which were then averaged across measures within each domain. In addition to difference analysis, equivalence testing was utilised, whereby overlap percentages were computed to reflect the amount of score distribution overlap in each domain between groups. Results: A statistically significant difference was observed only in the executive function sub-domain of Switching. Small-to-moderate and moderate effect sizes were noted in four other domains. Equivalence testing showed more than 85% of overlap in score distribution in most domains. Conclusions: Our findings suggest that some patients with severe chronic schizophrenia have cognitive deficits similar in degree and pattern to patients with frontotemporal dementia. The few differences observed between both groups of patients are important for differential diagnostic purposes. One limitation is the retrospective nature of the study. Suggestions for future research include longitudinal follow-up studies of these two patient populations and studies of aspects beyond neurocognition. An implication of our findings is that the ‘dementia of schizophrenia’ concept may be applicable to patients with severe chronic schizophrenia.

A pilot study of the utility of cerebrospinal fluid neurofilament light chain in differentiating neurodegenerative from psychiatric disorders: A ‘C-reactive protein’ for psychiatrists and neurologists?

“…Cognitive symptoms are often present in psychiatric disorders such as schizophrenia, major depressive disorder and bipolar disorder, while psychiatric symptoms are frequently present in neurodegenerative and neurological disorders. For example, common diagnostic challenges include distinguishing Alzheimer's disease from the 'pseudodementia' associated with major depression, and behavioural variant frontotemporal dementia (bvFTD) from schizophrenia, bipolar disorder or depression (Chan et al, 2014;Galimberti et al, 2015;Velakoulis et al, 2009;Woolley et al, 2011). Early-onset, or younger-onset dementia (defined as age at onset less than 65 years) in particular, can have broader, less 'typical' presenting features and can be more likely to present with psychiatric features, compared to 'typical', lateonset or older-onset (age at onset greater than 65 years) presentations, contributing to higher rates of misdiagnosis and diagnostic delays of over 3 years (Draper et al, 2016;Rossor et al, 2010).…”

Behavioral variant frontotemporal dementia in patients with previous severe mental illness: a systematic and critical review

“…On LILACS, none of the nine retrieved met the requirements. Therefore, 42 articles were selected, of which 10 were cohort studies 15,16,17,18,19,20,21,22,23,24 , three were case-control studies 25,26,27 , 12 were case repo rts 28,29,30,31,32,33,34,35,36,37,38,39 and 17 other studies were cross-sectional surveys 6,7,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54 .…”

Cerebrospinal fluid neurofilament light chain differentiates behavioural variant frontotemporal dementia progressors from ‘phenocopy’ non-progressors

“…Diagnostic delay is greatest in patients with younger onset (symptom onset before 65 years) dementia who frequently present with psychiatric or behavioural symptoms [1][2][3][4]. In particular, the behavioural, personality and executive dysfunction symptoms of behavioural variant frontotemporal dementia (bvFTD) can be difficult to distinguish from primary psychiatric symptoms and other non-neurodegenerative causes of frontal lobe dysfunction [4][5][6][7][8][9][10][11][12].…”