The relationship between primary progressive aphasia and neurodegenerative dementia

Objective: To examine the relationship between primary progressive aphasia (PPA) and neurodegenerative dementia. Methods: Subjects were selected from 1723 consecutive patients who had undergone a medical examination at the Kumamoto University Hospital Dementia Clinic, Japan, from April 2007 to October 2012. First, patients with semantic dementia (SD) and patients with progressive non-fluent aphasia were diagnosed by clinical diagnostic criteria for frontotemporal lobar degeneration. Next, in the same cohort, patients with PPA were diagnosed according to the recent international consensus criteria. The relationship and clinical symptoms including language and psychiatric symptoms in each patient group were then compared. Results: In all, 12 of 27 SD patients fulfilled both SD and semantic variant PPA criteria (SD+PPA+ group), whereas the other 15 who met the SD criteria could not be included in the semantic variant PPA group due to prominent behavioural disturbances (SD+PPA- group). No significant differences in clinical characteristics and language functions were found between these 2 groups. Neuropsychiatric symptoms were more severe in the SD+PPA- group. Conclusion: The results suggest the possibility that SD and semantic variant PPA may be identical, regardless of different severities of behavioural disturbance. When considering the language disorder of neurodegenerative dementia, it may be more important to diagnose the subtype of language disorder the patient has than to emphasise isolated language deficits.