Introduction

In discussing the neuropsychological profile of frontotemporal dementia (FTD) there are a number of particular problems. Firstly, there is the problem of the “gold standard” for diagnosis. Very few neuropsychological studies have included cases with a pathological verification of the diagnosis and, as there is inexact correspondence between the clinical and pathological diagnosis of FTD (see Chapter 7), there are problems of contamination by cases with underlying Alzheimer's disease (AD) pathology (Forman et al., 2006). A brief summary, based upon current clinico-pathological studies, suggests that this is not such a great problem in the case of either behavioural variant frontotemporal dementia (bv-FTD) or semantic dementia (SD), both of which seem rarely to be secondary to AD pathology; but in progressive non-fluent aphasia (PNFA) up to a third of cases have AD, at least in the Cambridge series (Knibb et al., 2006). Some groups have attempted to circumvent this problem by using the pattern of brain atrophy, or hypometabolism on single-photon emission computed tomography (SPECT), as the defining feature and have compared cases classified on this basis (Miller et al., 1991), although again the correspondence between these patterns and pathology is uncertain.

Secondly, there is the somewhat artificial division between the variants of FTD. For instance, many patients with SD have prominent behavioural features, and at least mild semantic deficits are sometimes present in bv-FTD. Thirdly, the problem of the boundary between psychiatric disease, personality disorders and earlystage bv-FTD is a major issue when discussing tests sensitive to bv-FTD. As outlined in Chapter 3, some patients diagnosed as suffering from bv-FTD show no progression over a number of years and there is growing evidence that they may have a behavioural phenocopy of bv-FTD which represents either a functional disruption of frontotemporal networks or a long-standing personality disorder with a degree of late-life decompensation. Thus, unless there is independent evidence of frontal abnormality on imaging or of clear-cut progression, the insensitivity of some tests of frontal lobe function might reflect the fact that groups of FTD patients are contaminated by patients with non-organic disorders.

With these provisos in mind we will discuss neuropsychological findings in FTD and attempt to cover both clinically and theoretically orientated studies.