ABSTRACT

With 18-month prevalence rates approaching 90%, behavioural and psychological signs and symptoms of dementia (BPSD) are highly prevalent (Steinberg et al., 2003). A major proportion of BPSD consists of frontal lobe symptoms. Frontal lobe symptoms are not confined to dementia disorders with frontal lobe involvement such as frontotemporal dementia (FTD). Indeed, compared with normal, age-matched control subjects, 72% of Alzheimer's disease (AD) patients displayed apathy and 36% displayed disinhibition, both of which are typical frontal lobe symptoms (Mega, Cummings, Fiorello, & Gornbein, 1996). A prospective, longitudinal study showed that 39.8% of patients with mild cognitive impairment (MCI) presented with apathy and that the proportion of conversion from MCI to AD was significantly higher for MCI patients with apathy at baseline (Robert et al., 2006). Studying apathy in AD patients, Kuzis, Sabe, Tiberti, Dorrego, and Starkstein (1999) and Starkstein, Petracca, Chemerinski, and Kremer (2001) found associations with dysthymia and major depression as well as with memory deficits, frontal lobe-related cognitive deficits, and impairment in activities of daily living. There is substantial evidence from observational and neuroimaging studies that agitation, aggressiveness, psychosis, and aberrant motor behaviour are manifestations of frontal lobe dysfunction too (Hirono, Mega, Dinov, Mishkin, & Cummings, 2000; Mega et al., 2000a; Senanarong et al., 2004). A neuropathological study found increased burden of neurofibrillary tangles in several frontal lobe regions of AD patients displaying agitation, apathy, and aberrant motor behaviour compared to AD patients without these symptoms (Tekin et al., 2001). Given the prevalence rates of frequently occurring symptoms of presumably frontal lobe origin such as agitated behaviour (60%) and aberrant motor behaviour (38%) in AD (Mega et al., 1996), the role of frontal lobe dysfunction in the pathophysiology of BPSD might have been systematically underestimated.