Behavioural variant frontotemporal dementia - selected diagnostic dilemmas in neuropsychiatry

Introduction: Differential diagnosis of behavioural variant frontotemporal dementia remains a challenge for neurologists and psychiatrists as some behavioural symptoms of this illness and psychiatric disorders, such as apathy, are not specific. Aim: The paper aims at presenting the differential diagnosis of behavioural variant frontotemporal dementia and primary psychiatric disorders. Discussion: Behavioural symptoms of behavioural variant frontotemporal dementia overlap with symptoms typical for primary psychiatric disorders. Psychotic symptoms, apathy and inappropriate behaviour are prominent in schizophrenia. Repetitive behaviours are typical for obsessive-compulsive disorders. Inattention and impulsivity are common in attention deficit and hyperactivity disorder. Disinhibition is typical of mania in the context of bipolar disorder. Thus, all these psychiatric diagnoses need to be considered in the differential diagnosis of behavioural variant frontotemporal dementia. This condition is associated with language deficits and more widespread executive and social cognition deficits. Also, the presence of neurological symptoms, such as oculomotor dysfunction, upper/lower motor neuron dysfunction or bradykinesia, may facilitate the diagnosis. Functional decline is observed during follow-up in behavioural variant frontotemporal dementia, but not in phenocopy syndrome. Conclusions: Differential diagnosis requires integration of behavioural and neuropsychological data with the results of neurological assessment and neuroimaging work-up. In ambiguous cases, if genetic testing is negative, only longitudinal observation can confirm the diagnosis of behavioural variant frontotemporal dementia or phenocopy syndrome.