Frontotemporal dementia (FTD), also known as frontotemporal degeneration, and historically as Pick's disease, is a family of neurodegenerative disorders, caused by frontotemporal lobar degeneration that affects the frontal and temporal lobes. The FTD family includes behavioral variant FTD, primary progressive aphasia (PPA) and its semantic and nonfluent/agrammatic variants. primary progressive apraxia of speech (PPAOS), progressive supranuclear palsy, and corticobasal syndrome. Through a mutual risk gene, FTD and amyotrophic lateral sclerosis (ALS) share a clinical spectrum, where symptoms of both disorders can co-occur. Symptoms of FTD will typically match a specific disorder at first, though symptoms of other disorders will begin to show as the disease progresses to different areas of the brain. FTD disorders are a common young-onset dementia occurring under the age of 60. Approximately 60% of people diagnosed with FTD have no known cause and no family history of FTD or related conditions; this is known as sporadic FTD. While environmental causes and unidentified gene variants are suspected causes of sporadic FTD, research in this area is still ongoing. When people have a family history of FTD, other dementias, or conditions like depression and anxiety, it is referred to as familial FTD, and roughly 20% have an underlying genetic basis. Variants in three genes are responsible for most genetic FTD. Notably, in about 10% of people with seemingly sporadic FTD, a genetic variant is identified. FTD diagnosis currently relies on clinical examination based on the signs and symptoms experienced and imaging of the brain through magnetic resonance imaging or positron emission tomography. FTD disorders have heterogeneous symptoms and pathological features, which contribute to a lengthy differential diagnostic process and high rates of misdiagnosis. A neuropathological examination after death usually provides a definitive diagnosis by identifying the specific features of FTD subtypes. There is no cure for FTD, nor are any disease-modifying treatments approved that could slow disease progression. The aim of treatment is to manage symptoms, which is primarily accomplished through non-pharmacological interventions such as person-centric care strategies or physical and occupational therapy. Medication can be used to address symptoms like depression or anxiety, but some drugs, like sleep or antipsychotic medicines, carry a considerable risk of side effects for people with FTD. Death is usually the result of complications of FTD, such as pneumonia or fall-related injuries. The average life expectancy after symptoms start is 7 to 13 years, but varies significantly by individual and FTD subtype. The clinical features of FTD were first described by Czech-German psychiatrist Arnold Pick between 1892 and 1906. Pick's observations were followed by Alois Alzheimer's first description of tau aggregations in neurons (called "Pick bodies") in 1911. The disorder described by Pick was named "Pick's disease" in 1922. The first research criteria were created in 1994, and the publication was the first to use the term "frontotemporal dementia".
Signs and symptoms Frontotemporal dementia is an early onset disorder that mostly occurs between the ages of 45 and 65, but can begin earlier, and in 20–25% of cases onset is later. Men and women appear to be equally affected. It is the most common early presenting dementia. FTD is the second most prevalent type of early onset dementia after Alzheimer's disease. The International Classification of Diseases recognizes the disease as causative to disorders affecting mental and behavioral aspects. Dissociation from family, compulsive buying disorder (oniomania), vulgar speech characteristics, screaming, and inability to control emotions, behavior, personality, or temperament are characteristic social display patterns. The gradual onset and progression of subtle changes in behavior or language deficits commonly leads to a long delay between the onset of symptoms and time of presentation to a neurologist.
Subtypes and related disorders The main subtypes of frontotemporal dementia are behavioral variant FTD (bvFTD), two variants of primary progressive aphasia – semantic dementia and progressive nonfluent aphasia, as well as FTD associated with amyotrophic lateral sclerosis (FTD–ALS). Two distinct rare subtypes are neuronal intermediate filament inclusion disease, and basophilic inclusion body disease. Related disorders are corticobasal syndrome, and progressive supranuclear palsy.
Behavioral variant frontotemporal dementia
Behavioral variant frontotemporal dementia was previously known as Pick's disease, and is the most common of the FTD types. Behavior can change in behavioral variant FTD in either of two ways—it can change to being impulsive and disinhibited, acting in socially unacceptable ways; or it can change to being listless and apathetic. About 12–13% of people with bvFTD develop motor neuron disease. The Pick bodies which are present in behavioral variant FTD are spherical inclusion bodies found in the cytoplasm of affected cells. They consist of tau fibrils as a major component together with a number of other protein products including ubiquitin and tubulin.
Semantic dementia Semantic dementia is characterized by the loss of semantic understanding, resulting in impaired word comprehension. However, speech remains fluent and grammatical.
Progressive nonfluent aphasia Progressive nonfluent aphasia is characterized by progressive difficulties in speech production.
Neuronal intermediate filament inclusion disease Neuronal intermediate filament inclusion disease is a rare distinct variant, having inclusion bodies that are cytoplasmic and made up of type IV intermediate filaments. Neuronal intermediate filament inclusion disease has an early age of onset between 23 and 56. Symptoms can include behavioral and personality changes, memory and cognitive impairments, language difficulties, motor weakness, and extrapyramidal symptoms. It is one of the frontotemporal lobar degeneration–FUS proteopathies. Imaging commonly shows atrophy in the frontotemporal region, and in part of the striatum in the basal ganglia. Post-mortem studies show a marked reduction in the caudate nucleus of the striatum; frontotemporal gyri are narrowed, with widened intervening sulci, and the lateral ventricles are enlarged.
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