Lobar Degeneration: Diagnosis and Differential Diagnosis Algorithm

Abstract

Frontotemporal Lobar Degeneration: Diagnosis and Differential Diagnosis Algorithm

Frontotemporal lobar degeneration is a heterogeneous clinical syndrome causing prefrontal and anterior temporal lobe degeneration with the core symptoms of progressive behavioral and/or language disorders. The clinical syndromes classified under the Neary criteria made the heterogeneous terminology simpler. According to these criteria, the whole syndrome was named as frontotemporal lobar degeneration and three subtypes were included; a) frontal lobe dementia (FLD), b) progressive non-fluent aphasia (PNFA), and c) semantic dementia/ progressive fluent aphasia (SD). In later version, a fourth clinical subtype of prosopagnosia was added. FLD has core symptoms of behavioral disorder, while PNFA shows nonfluent aphasia with the dominant frontal language areas involvement. Fluent aphasia with the degenerative involvement of dominant anterior and inferior temporal cortex is classified under SD. FTLD differential diagnosis should be made with Alzheimer’s disease at first. Age onset, early clinical symptoms and course of disease can differentiate these two degenerative dementias without great difficulty. In this article, FTLD criteria will be defined and other related diseases will be reviewed with a special emphasis on the differential diagnosis.