ABSTRACT
Dementia was initially thought of as a unitary behavioural syndrome, characterised by a homogeneous decline in intellectual functions, regardless of aetiology. Subsequently, clinical studies of cognition in dementias suggested that the pattern of dysfunction in dementia was heterogeneous, depending largely on whether the pathological process affected predominantly cortical or subcortical structures. Dementia is defined as decline of memory and other cognitive functions in comparison with the patient’s previous level of function, implying a change between two or more assessment points (McKhann et al., 1984). Evaluation of dynamic change over time, by accounting for potential confounders, is clinically more meaningful than a single assessment. There are many kinds of dementia documented, with the traditional breakdown being 70% AD, 20% vascular disease, and 10% other (made of uncommon conditions and the so-called reversible dementias). Fronto-temporal dementia (FTD) is the second cause of primary degenerative dementia, after AD
with or without Lewy bodies (Neary et al., 1998). FTD was often confused with AD and rarely diagnosed during life, although differentiating FTD from AD is feasible even on the basis of retrospective historical information obtained from relatives of patients (Barber et al., 2002). Dementia of the Alzheimer’s type and multi-infarct dementia (MID) are usually considered to be the two most frequent forms of dementia, even if recent anatomoclinical an neuropathological studies have shown that vascular lesions alone are probably unable to provoke a clear clinical syndrome of dementia (Nolan et al., 1998; Ott et al., 1998; Snowdon et al., 1997). As a consequence of the different locations of neurofibrillary tangles and senile plaques, and of lacunar infarcts, AD and MID patients have different neuropsychological profiles. Poorer performance is usually found in AD patients on episodic memory tasks and to a lesser extent, on tasks of language, on tasks of constructional apraxia, and on tasks requiring visuospatial abilities (Gainotti et al., 1989, 1992; Kertesz & Clydesdale, 1994; Looi & Sachdev, 1999). Inferior performance is observed in MID patients on tasks involving executive functions,
attention, and psychomotor speed (Almkvist et al., 1993; Gainotti et al., 1992; Villardita, 1993). A recent study confirmed that while psychomotor speed and the lower (sensorimotor) levels of attention are preferentially impaired in subcortical forms of dementia such as MID, the higher levels of selective and divided attention are more markedly disrupted in the Alzheimer type of dementia (Gainotti et al., 2001).
