<unk>  <unk>  is a gradually worsening disorder of speech with an insidious onset. It was first described by Marsel Mesulam in 1982.
There is considerable controversy over the nosology of this disorder. Clinical and pathological overlap have led it to being considered as part of the frontotemporal lobar degeneration (FTLD) spectrum of disorders. In the classical Mesulam criteria for<unk>  there are 2 variants: a non-fluent type (progressive non-fluent aphasia or PNFA) and a fluent aphasia. However, recent work has suggested that the underlying cognitive impairment in patients with progressive fluent aphasias is loss of semantic knowledge (semantic dementia or SD).  In the consensus criteria for FTLD described by Neary et al in 1989, PNFA and SD are the two classifications used.
The San Francisco group have recently suggested that there is a third variant of<unk>  (so-called logopaenic<unk>  - Gorno-Tempini et al, 2004). However, there are limited descriptions of this disorder in the medical literature and early reports suggest that it is an atypical form of Alzheimer's disease rather than a disease falling into the frontotemporal lobar degeneration spectrum.
There are no known risk factors for the progressive aphasias. However, one observational study has recently suggested that vasectomy could be a risk factor for<unk>  in men. These results have yet to be replicated elsewhere.
Primary progressive aphasia
Logopenic progressive aphasia
Multiple system atrophy
Akinetic-rigid syndromes
Progressive supranuclear palsy
Semantic dementia
Spinocerebellar ataxia
Essential tremor