As outlined in Chapter 1, three major clinical presentations of frontotemporal dementia are commonly described: a behavioural form (bv-FTD), and two language variants, semantic dementia (SD) and progressive non-fluent aphasia (PNFA). The clinical symptoms derive from the distribution of the underlying pathology which is predominantly in the frontal and temporal lobes. The FTD variants overlap, however, on a number of levels: clinical, anatomical and pathological. Despite the increasing availability of various diagnostic investigations, good clinical acumen remains crucial in both the diagnosis and management of these syndromes. Careful clinical assessment helps to appropriately weight the presence or absence of symptoms, and assess the significance of their emergence over the course of the disease. The following descriptions are based, very largely, upon our experience of around 300 patients seen in Cambridge over the past 15 years.
Behavioural or frontal variant FTD (bv-FTD)
The overriding presenting feature in bv-FTD is an alteration in the patient's social conduct and personality which becomes gradually evident to family, friends and colleagues. A cluster of symptoms comprising apathy, disinhibition, aberrant social conduct, a distinct lack of empathy, alterations in eating behaviour and the development of motor and verbal stereotypies was reported in key papers by Arnold Pick and other early authors as detailed in Chapter 1, and has been formalised to form the basis of the clinical and research diagnostic criteria for the disease (Brun et al., 1994; Gregory et al., 1997; McKhann et al., 2001; Neary et al., 1998). The most widely used Neary et al. (1998) consensus criteria are shown in Table 3.1. Although bv-FTD is defined by its behavioural presentation, patients with language variants of FTD often have marked behavioural disturbance. Conversely, a variable degree of language impairment frequently accompanies the behavioural syndrome.
Symptom onset is gradual and insidious, and represents a change from premorbid functioning. It is typically difficult, if not impossible to accurately date the onset of symptoms which in many cases represent an exaggeration of premorbid personality traits rather than a distinct change. Only a minority of patients will display all of the core features of the consensus criteria on initial presentation (Mendez and Perryman, 2002). Diagnosis is easy when many of these features are present, but is challenging in the early stages of disease. The most common symptoms are listed in Table 3.2.