First symptoms--frontotemporal dementia versus Alzheimer's disease

Frontotemporal dementia (FTD) is often misdiagnosed as Alzheimer's disease (AD). We hypothesized that the first symptoms associated with FTD would be different from those seen in AD and that the first symptoms in FTD would reflect loss of function in the frontal region with the greatest degree of degeneration. The objective of the study was to compare the earliest symptoms in patients with FTD and AD, and to delineate the symptoms that were associated with right, left or bilateral frontotemporal degeneration in FTD. The first symptoms in 52 FTD and 101 AD patients were determined in retrospect. Based on functional imaging studies, the FTD patients were divided into those with predominantly bilateral (n = 15), left-sided (n = 19) and right-sided (n = 18) patterns of atrophy. The results showed that disinhibition, social awkwardness, passivity and loss of executive function were more common in FTD, while memory loss was more common in AD. Disinhibition was greatest in the asymmetric right-sided group, language dysfunction was commonest in the asymmetric left-sided group and loss of executive function was most frequent in the bilateral group. In summary, different first symptoms appeared in FTD and AD, which may help distinguish between the diseases. The anatomic site for FTD largely determined the kind of first symptoms.