Les démences frontotemporales (DFT) se caractérisent par l’existence de troubles du comportement d’apparition progressive associés à une dégénérescence frontale et temporale antérieure. Elles comportent des caractéristiques cliniques parfois trompeuses qui en font un diagnostic différentiel fréquent en psychiatrie. Nous exposons les critères consensuels qui ont été proposés pour ce diagnostic et les situations qui, en pratique clinique, doivent le faire suspecter. L’apparition progressive d’un changement de personnalité ou d’un trouble des conduites sociales chez un sujet d’âge moyen, le plus souvent rapporté par l’entourage, doit conduire à un examen des fonctions supérieures et à une imagerie cérébrale. Des tests cliniques simples dans le contexte de la consultation peuvent faire évoquer le diagnostic et indiqueront des tests neuropsychologiques plus approfondis. L’identification précoce des patients présentant une DFT permet une prise en charge adaptée à ce type de démence. En effet, si les essais thérapeutiques sont peu nombreux dans cette pathologie, certains antidépresseurs ont prouvé leur efficacité et doivent être proposés plutôt que les anticholinestérasiques. Enfin, la prise en charge globale de ces patients doit tenir compte, d’une part des répercussions dans la vie quotidienne différentes de celles d’autres démences comme la maladie d’Alzheimer (MA), et d’autre part, de son évolution souvent plus rapide.

Frontotemporal dementia (FTD) is a neurological disorder characterised by the progressive degeneration of the frontal and anterior temporal cortex. FTD, as well as nonfluent progressive aphasia and semantic dementia, belongs to the more generic entity of frontotemporal lobe degeneration. Considering the involvement of the frontal lobe, the initial clinical presentation of FTD may be psychiatric, such as changes in personality or behavioural disorders. Psychiatrists, therefore, have to establish the differential diagnosis with late-onset schizophrenia or affective disorders. An accurate history of the onset of symptoms, thanks to the patient and especially to his/her family, is essential to recognize this dementia. In addition to behavioural changes, memory impairment, and speech disturbances are often present from the beginning. Consensus criteria have been proposed in 1998 that help to bring this diagnosis to mind in clinical practice. The progressive occurrence of personality changes or inappropriate social conducts in the fifth or sixth decade must prompt cognitive evaluation.

A brief cognitive evaluation, such as the frontal assessment battery (FAB) may help to identify a dysexecutive syndrome and to prompt a thorough neuropsychological evaluation. The pattern of neuropsychological impairment reflects the involvement of the frontal lobe and appears different from that of other degenerative diseases, such as Alzheimer’s dementia, which involves hippocampal damage. Additional investigations should however be made to detect a potentially curable dementia. Cerebral imaging is essential to the differential diagnosis and also shows evidence for the positive diagnosis of FTD. Structural MRI may initially not show the bilateral atrophy of the frontal lobe, but functional imaging may be helpful in the early stages of the illness by showing evidence of abnormalities in the anterior cerebral hemisphere.

In recent years, significant advances in the understanding of the pathological characteristics of FTD were made with genetic contribution, especially the discovery of the tau protein involvement. In fact, neuropathological examination with immunohistochemical analysis defines Pick’s disease with Pick bodies that belong to tauopathies. Ubiquitinated intraneuronal inclusions may also be found, and some types of FTD have no distinctive pathological feature. However, although a definite diagnosis would only be established after postmortem pathological examination, the clinical, neuropsychological and imaging data enable the early identification of patients with FTD and, subsequently, the appropriate management.

Although the prevalence of FTD reaches 1 Alzheimer’s disease (AD) to 1.6 FTD in the general population between 45- and 64-year old, only few studies have focused on the treatment of FTD. Some evidence supports the positive effect of serotonergic agents, especially with regard to behavioural symptoms. Selective serotonin reuptake inhibitors or trazodone should therefore be prescribed in preference to acetylcholinesterase medications as in AD. However, no drug yet has the ability to stop or slow down the degenerative process. The management of daily life also bears specificities related to the younger age of these patients and to their behavioural disorders. Caregivers should receive some education about the characteristics of this dementia and should be helped in social management. As concerns aggressive behaviour, neuroleptics should generally be avoided because of poor tolerance. Finally, the outcome is characterized by a rapid loss of autonomy and sometimes by a premature institutionalisation.