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Detecting dysexecutive syndrome in neurodegenerative diseases: are we using an appropriate approach and effective diagnostic tools?
  1. Michele Poletti1,
  2. Marco Cavallo2,3,
  3. Mauro Adenzato4,5
  1. 1Child and Adolescent Psychiatry Unit, Department of Mental Health and Pathological Addiction, Azienda Unità Sanitaria Locale, Reggio Emilia, Italy
  2. 2eCampus University, Novedrate, Italy
  3. 3Azienda Sanitaria Locale Torino 3, Collegno, Italy
  4. 4Department of Psychology, Center for Cognitive Science, University of Turin, Turin, Italy
  5. 5Neuroscience Institute of Turin, Turin, Italy
  1. Correspondence to Mauro Adenzato, Center for Cognitive Science, Department of Psychology, University of Turin, via Po 14, Turin 10123, Italy; mauro.adenzato{at}unito.it

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The term ‘dysexecutive syndrome’ refers to a dysregulation of executive functions and is strictly associated to frontal lobe damage. Dysexecutive syndrome typically encompasses emotional, motivational and behavioural symptoms, as well as cognitive deficits.1 This disabling condition can be observed in various clinical domains, and above all characterises degenerative diseases such as frontotemporal dementia (FTD) and—to a lesser degree—corticobasal degeneration (CBD).

In recent years, neuropsychological tools have been used to investigate dysexecutive syndrome.2 However, to date this field of clinical research suffers from a significant paradox: while clinicians and caregivers perceive with ease the presence of the symptoms that characterise patients' clinical picture, surprisingly it has not yet been possible to promptly and reliably detect this cohort of symptoms with effective diagnostic tools.

The paper by Gansler et al3 has the merit of making a significant step further in this direction, by proposing the distinction, but also the strict synergy, between the realms of ‘executive functions’ (EF) and ‘dysexecutive behaviours’ (DB), and by supporting the utility of integrating EF and DB measures for diagnostic purposes. In detail, Gansler et al included a large cohort of patients (N=243) affected by the behavioural variant of FTD (bvFTD, N=124), primary progressive aphasia (PPA, N=34) or CBD (N=85): for the majority of them, the authors collected patients' performance on an EF neuropsychological battery (the Delis-Kaplan executive function system), and caregivers' report of patients' behaviour through the FrSBe (the frontal behaviour scale). As expected, bvFTD patients got significantly lower scores on EF tests and higher scores on the DB measure, compared to other subgroups. Interestingly, factor analyses showed that EF and DB were distinct but overlapping constructs, and this was corroborated at a neuroimaging level: the EF composite was uniquely associated with left lateral and dorsomedial prefrontal cortex, and with the middle temporal gyrus and temporo-parietal junction, while DB was uniquely associated with cingulate gyrus bilaterally, right subcallosal gyrus, and right frontal anterior pole. The rostral part of the lateral and dorsomedial prefrontal cortex was associated with EF and DB. Finally, the authors' results showed that by considering EF and DB measures jointly, diagnostic precision increased significantly (even if this was more true for PPA and CDB, than for bvFTD cases where DB measures alone already possessed good explanatory power).

In our view, Gansler et al's study takes the need to improve an early and precise detection of neurodegenerative disease symptoms seriously by considering the interplay between neural, cognitive and behavioural levels. To take the next step, we support the position that future studies in this field should also include an assessment of Theory of Mind (ToM) abilities, that is, the capacity to explain and predict other people's behaviour by attributing independent mental states to them. As recently shown,4 ,5 ToM is another domain significantly involved in dementias and CBD partially dissociated from EF impairment, and interestingly ToM tasks typically present a higher degree of ‘ecological’ validity, compared to standard neuropsychological tests. Researchers and clinicians should, therefore, include a careful ToM assessment to improve diagnostic procedures, with the ultimate goal to implement effective management strategies.

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Footnotes

  • Funding MA was supported by an MIUR grant (FIRB 2012–2017, protocol number: RBFR12F0BD_001) and by the University of Torino (Ricerca scientifica finanziata dall'Università ‘Cognizione sociale e attaccamento in popolazioni cliniche e non cliniche)’.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

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