Frontotemporal dementias

Abstract

Abstract Nosological classification of organic dementia is based on current knowledge and theories of aetiology, including genetics, clinical picture, the pathological substrate, and the predominant location of brain damage. This chapter is concerned with dementia syndromes caused by a degenerative disease primarily affecting the frontal and temporal lobes, named frontal-lobe dementia or frontotemporal dementia (FTD). The terminology should be viewed from a historical perspective. The relationship between localized cortical atrophy in dementia and symptoms of aphasia was first reported by Pick in 1892. The pathological account of this lobar degeneration by Alzheimer in 1911 described ‘ballooned’ neurones (Pick cells) and argentophilic globes (Pick bodies), and the clinicopathological entity was named Pick's disease. In the 1980s, attention was drawn to a larger group of frontal-lobe dementias associated with frontotemporal cortical degeneration. The Lund–Manchester consensus of 1994 delineated the prototypical clinical syndrome of FTD with three neuropathological constituents, frontal lobe degeneration of non-Alzheimer type (FLD), (alternatively designated ‘dementia lacking distinctive histology’), Pick's disease, and motor neurone disease (MND) with dementia (FTD-MND). The 1998 consensus on clinical diagnostic criteria for frontotemporal lobar degeneration (FTLD) encompassed two additional dementia syndromes; progressive non-fluent aphasia (PA), and semantic dementia. Corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) have also been associated with FTLD. A changing clinical classification is shown in Fig. 4.1.3.1. The addition of important genetic and histochemical characteristics has further added to the complex classification of FTD and FTLD with a risk of developing numerous and partly competing definitions. FTLD may be further subclassified into forms positive or negative for tau and ubiquitin. The ubiquitinated form will be referred to as FTD-U, which is synonymous to FLTD-U.