Troubles du comportement aux urgences, ou démence fronto-temporale? Un défi pour les psychiatres

Introduction. The diagnosis of fronto-temporal dementia (FTD) represents a challenge for the psychiatrist, especially since this insidious pathology partly mimics other psychiatric diseases. Case-report. We present a clinical case that illustrates the difficulty of FTD diagnosis particularly well. A 32 year-old woman without previous medical history presented with psychomotor agitation, logorrhea and flight of ideas. The criteria for bipolar disorder according to DSM IV were met and the patient was referred to an outpatient clinic where a mood stabilizer was initiated (lithium, 400 mg/day). An in-depth interview with her husband revealed mild but progressive modification of her personality and behavior over the course of two years. She showed signs of mild fatigue and irritability that evolved into a loss of interest for both leisure and domestic activities. In addition, she showed increasing erratic behavior and emergence of frequent episodes of verbal abuse. After the birth of her second child, the patient's clinical state worsened with the appearance of uninhibited behavior, loss of personal hygiene, sleep disturbances and nightmares. The patient was forced to stop her work as a cleaner, a steady employment that she had maintained for 10 years. The hypomanic state worsened and psychotic symptoms such as delusions and echolalia appeared within a few weeks. These events culminated in a first hospitalization in a psychiatric unit. We evoked both diagnoses of schizoaffective disorder and psychotic disorder not otherwise specified. In the following months, we conducted neurological examinations on account of the progressive deterioration of her cognitive functions. Neuroradiological results (CT scan with contrast agents, MRI, cerebral scintigraphy) coupled with her clinical evolution (neurological examination and neuropsychological testing) permitted diagnosis of fronto-temporal dementia. Discussion. Fronto-temporal dementia usually presents itself as an autosomal dominant disease in 89% of reported cases, with an insidious onset associated with thymic symptoms and behavioral disturbances. The first consultation often concludes with a suspicion of a psychiatric disorder in 33% of the cases (unipolar and bipolar depressive disorders, psychotic disorders, alcohol dependence). The clinical description of such a heterogenic and neuropsychiatric disorder should be widely disseminated, so that psychiatrists can distinguish early symptoms and diminish the risk of misdiagnosis of FDT. Conclusion. Such case reports emphasize the importance for psychiatrists to be aware of the clinical prodromal FDT symptoms, particularly since the neuro-imaging data of dementia are often delayed.