Frontotemporal dementia and Alzheimer's disease: Differential diagnosis

This report addresses the clinical differentiation of Alzheimer's disease ( AD) from frontotemporal dementia (FTD), including Pick's disease. The accur acy of a clinical diagnosis of a dementing disorder is determined in part b y the prior probability (base rates) of the disorder, which predicts an ove rwhelming likelihood of a diagnosis of AD, because the prevalence of AD is much greater than FTD, The clinical features of the disorder also determine the accuracy of diagnosis. Recent studies have reported an improvement in the differential diagnosis of FTD, utilizing the Lund-Manchester criteria. Patients with FTD typically have early noncognitive behavioral changes with relatively spared cognition, frontal atrophy and enlargement of the Sylvia n fissures on CT and MRI scans, and frontal-temporal deficits on SPECT or P ET scans. In contrast, AD patients have early cognitive changes with relati vely preserved personality and behavior, hippocampal and medial-temporal ro be atrophy on CT or MRI scans, and parietotemporal SPECT or PET deficits.