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INTRODUCTION

Professor Arnold Pick first reported, in 1892, a 71-year-old patient with progressive language and cognitive decline, and grossly visible anterior temporal lobe atrophy post-mortem.1 This is thought to be the first report of a patient with what was later called semantic dementia by Professors John Hodges and Julie Snowden. Professor Alois Alzheimer subsequently described the microscopic histologic abnormalities that were later called “Pick’s disease” by Drs. Onari and Spatz. Professor Schneider published a detailed report on clinical course of the disease, highlighting the insidious early changes in behavior and personality and—in contrast with Alzheimer’s disease (AD)—the typical relative preservation of memory and orientation.2 Through most of the rest of the century, patients with behavioral-comportmental dementias were usually diagnosed as having “Pick’s disease.” In the 1980s and 1990s, Professors Marsel Mesulam, Sandra Weintraub, John Hodges, Julie Snowden, Andrew Kertesz, and others reignited the interest of the behavioral neurology and neuropsychiatry field in progressive aphasias.3–5 In the 1980s, the Lund6 and Manchester7 groups reported important early studies generating renewed interest in the behavioral phenotype of frontotemporal dementia (FTD), soon thereafter proposing clinical and pathological diagnostic criteria.8 In the late 1990s, formal international consensus diagnostic criteria9 were developed for three major clinical phenotypes: “frontotemporal dementia,” “progressive nonfluent aphasia,” and “semantic dementia.” In the early 2000s, interest in the syndromes we now call FTDs surged, leading to the development and evolution of clinical and pathological criteria for the diagnosis and, more recently, an explosion in scientific understanding of this family of diseases, as well as a robust international clinical-scientific organization devoted to the diseases (http://www.isftd.org) with biannual international conferences sparking tremendous collaborative energy.10 Important advances were formalized in 2011 when new consensus diagnostic criteria were published for primary progressive aphasia (PPA)11 and the behavioral variant of FTD (bvFTD).12 These criteria were then largely incorporated with some simplification into the fifth edition of the American Psychiatric Association Diagnostic and Statistical Manual in 2013.

Although terminology remains confusing in this family of diseases, we continue to recognize the syndromes of bvFTD, semantic variant PPA (svPPA), and nonfluent or agrammatic variant PPA (nfvPPA) to present in the context of a neuropathological family of diseases termed frontotemporal lobar degeneration (FTLD). The third major subtype of PPA, the “logopenic” variant, is usually associated with AD pathology. FTLD is a loosely knit group of neurodegenerative diseases that preferentially affect the frontal and anterior temporal lobes, with relative sparing of other cortical regions in many cases, and often affecting basal ganglia and in some cases basal forebrain and brainstem nuclei. Largely for reasons of pathological overlap, several other diseases have also now been included in this clinical and pathological spectrum, including progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and FTD with motor neuron disease or amyotrophic lateral sclerosis (FTD-MND or FTD-ALS).

EPIDEMIOLOGY

FTLD is thought to be the third ...

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