ABSTRACT
A striking feature of degenerative diseases of the brain, which affect people in middle and old age, is that they can be remarkably circumscribed both in terms of the distribution of brain atrophy and the resulting changes in mental function. As a consequence of this selectivity, degenerative disorders can represent a natural model for assisting understanding of brain function. Frontotemporal dementia (FTD) is the prototypical and most common ‘‘focal’’
dementia syndrome. It is characterized by profound character change and alteration
in a person’s social conduct and is associated with a range of executive impairments. In keeping with the clinical picture, the degenerative process preferentially involves the frontal lobes and anterior parts of the temporal lobes, more posterior parts of the brain remaining relatively unaffected even in advanced disease. The precise distribution of pathology within the anterior hemispheres differs across individual patients and reflects phenotypic variations within FTD. This chapter describes the characteristics of this intriguing and challenging disorder and examines the relationship of behavioral and cognitive features to the underlying structural changes in the brain.
FTD is an early onset dementia, affecting people most commonly in middle age. Symptoms typically begin between the ages of 45 and 65, although there are exceptions. The youngest recorded onset in a pathologically confirmed case is 21 years (Snowden, Neary, & Mann, 2004). Occasionally, initial symptoms may present in the elderly. The onset and progression of illness is insidious, with death occurring between 2 and 20 years following onset of symptoms. The high variability in duration of disease is influenced by patients’ physical well-being. Many patients with FTD remain physically well, with few neurological signs. However, Parkinsonian features of akinesia and rigidity may develop particularly in the later stages. Moreover, a minority of patients with established FTD develops the physical signs of motor neuron disease=amyotrophic lateral sclerosis (MND=ALS) (Neary et al., 1990). Patients who remain physically well typically have a prolonged course, whereas those who develop neurological abnormalities, which compromise their level of physical activity, have an attenuated course. A short course is particularly evident in the minority of FTD patients with MND=ALS (Hodges, Davies, Xuereb, Kril, & Halliday, 2003; Neary et al.). FTD is strongly a familial disorder. A positive family history of a similar dementing illness in a first-degree relative is recorded in about 40% of cases. There are no obvious environmental determinants and patients come from a wide variety of cultural, socioeconomic, and geographic backgrounds. Men and women are affected with comparable frequency (Rosso et al., 2003). In people presenting with a dementing illness before the age of 65, the frequency of occurrence of FTD compared to Alzheimer’s disease is about 1:3.
