Frontotemporal degenerative dementias

Abstract

Frontotemporal dementia (FTD) is a clinical term now used for a group of dementing neurodegenerative disorders marked clinically by general predominance of symptoms referable to the frontal lobes. Symptoms may include changes in language ability with expressive or receptive aphasia, and changes in personality, including disinhibited, obsessive, hyperoral, hypersexual, repetitive, and perseverative behaviors. Memory is often affected, but is usually not a primary symptom. Characteristically, analytic, navigational, and other visuospatial abilities may be quite preserved. The clinical symptomatology of FTD contrasts with the general predominance of temporal and parietal symptoms in the most common neurodegenerative disorder, Alzheimer's disease (AD). FTD symptoms also differ from those seen with the second most common neurodegenerative disorder, Lewy Body Dementia (LBD), which while having substantial clinical and pathological overlap with AD, often shows additional clinical visuospatial (occipital) and parkinsonian symptomatology. FTD likely constitutes the third most-common cause of degenerative dementia. Clinical overlap can sometimes make it difficult to distinguish individual cases from AD. Genetic studies have shown that FTD, like AD, occurs in both familial and nonfamilial types, and a proportion of FTD cases arise from autosomal dominant genetic disorders due to mutations in the tau gene. Some recent formulations include in the family of frontal degenerative disorders other dementias with frontal symptomatology such as progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Lending support to such a grouping, neuropathological studies show a group of histologies, sometimes including PSP and CBD, to be the substrates for clinical FTD.