Perception of emotion on faces in frontotemporal dementia and Alzheimer's disease: a longitudinal study

Frontotemporal dementia (FTD) is a neurodegenerative disease characterised by behavioural disorders that suggest abnormalities of emotional processing. In a previous study, we showed that patients with Alzheimer's disease (AD) and with FTD were equally able to distinguish a face displaying affect from one not displaying affect. However, recognition of emotion was worse in patients with FTD than in patients with AD who did not differ significantly from controls. The aim of this study was to follow up the perception of emotions on faces in these patients. The poor perception of emotion could worsen differently in AD and in FTD, with the progression of atrophy of the amygdala, the anterior temporal cortex and the orbital frontal cortex, structures that are components of the brain's emotional processing systems.

Methods: Patients with AD or with FTD had to recognise and point out the name of one of seven basic emotions (anger, disgust, happiness, fear, sadness, surprise and contempt) on a set of 28 faces presented on slides at the first visit and 3 years later.

Results: Thirty-seven patients (AD = 19, FTD = 18) performed the tests initially. The two patient groups did not differ for age, sex and duration of the disease. During the follow-up, 12 patients died, 4 patients refused to perform the tests and 8 could not be tested because of the severity of the disease. Finally, 7 patients with AD and 6 patients with FTD performed the two tests at a mean delay of 40 months. All patients with AD had worse results at follow-up on the perception of emotion despite the prescription of inhibitors of cholinesterase in all patients and of selective serotonin reuptake inhibitors (SSRIs) in 4 patients. As a whole, patients with FTD had better results in the second than in the first assessment (however, 3 of them had worse results) independently of the prescription of trazodone (n = 2), other SSRIs (n = 2), or the absence of treatment (n = 2), and of possible cognitive change.

Conclusions: Recognition of emotion on faces in AD decreases with the progression of dementia and could be related to the progression of the degeneration of the structures implicated in emotional processing systems. Inconsistency of the results in FTD may be related to impulsiveness, lack of consistency of the patients and to heterogeneity of the progression of the lesions.