Lably
Skip to content

Frontotemporal dementia

Dementia involving the frontal or temporal lobes

  • 27 min read
  • 8 chapters

Related on Lably

Through Mutation, Brain and Heritability

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 or 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".

Classification

FTD refers to a diverse group of neurodegenerative diseases whose pathology initially affects neurons in the brain's frontal and temporal lobes. These brain regions control functions such as goal-directed behavior, communication, movement, and muscle control.

FTD subtypes are classified based on the signs and symptoms experienced by the person diagnosed, but the classification criteria do not entirely reflect the deeply heterogeneous pathological underpinnings and clinical phenotypes of FTD. Even among people with the same subtype of FTD, symptoms and pathology are diverse, contributing significantly to an already challenging diagnostic process.

Behavioral Variant FTD (bvFTD)

The most common type of FTD, bvFTD, is characterized by personality changes, apathy, hyperorality, and a progressive decline in self-control, empathy, and recognition of social norms. Cognition is also commonly affected in bvFTD, with diagnosed people experiencing difficulties with planning and problem-solving. Over time, behavioral and cognitive impairments will affect a person's ability to perform basic activities such as eating and bathing.

Symptoms of bvFTD can overlap with motor-dominant FTD disorders such as PSP, CBS, and ALS-FTD. BvFTD can at first be misdiagnosed as a psychiatric disorder due to overlapping symptoms.

Primary Progressive Aphasia (PPA)

PPA refers to a family of disorders characterized by language impairment, with a person's diagnosis reflecting the specific language skills affected at symptom onset. Two variants of PPA are more commonly associated with brain pathology seen in FTD: semantic (svPPA) and nonfluent/agrammatic (nfvPPA). In svPPA, people are progressively diagnosed with a loss of word meaning and difficulty recalling object names, making it increasingly difficult to communicate fluently. In nfvPPA, the apraxia of speech makes an affected person's speech gradually slower and more effortful, with aphasia leading to word omission in sentences and a reduced ability to comprehend long sentences.

The logopenic variant (lvPPA), which is associated with difficulty finding words while speaking, is more commonly associated with brain pathology seen in Alzheimer's disease.

Primary Progressive Apraxia of Speech (PPAOS)

PPAOS is a disorder associated with the progressive loss of the brain's ability to control muscle movements that allow for speech, without loss of the meanings of words or object names. People diagnosed with PPAOS experience features such as slowed speech, increased speech distortions, and longer pauses between words.

As the pathology progresses, people with PPAOS may begin to experience additional motor/movement symptoms and may later receive an additional diagnosis of PSP or CBS.

Progressive Supranuclear Palsy (PSP)

PSP is a disorder considered by some to be under the FTD umbrella. The disorder is traditionally associated with motor-based symptoms that are commonly referred to as "atypical Parkinsonism." However, emerging research has found that cognitive, behavioral, and communication symptoms are more common in PSP than previously established, heightening the chance for misdiagnosis. PSP with "classic" movement symptoms is classified as PSP Richardson Syndrome or Richardson-Steele variant (PSP-RS) and makes up between 24-46% of cases. PSP-RS symptoms include gaze palsies, postural instability, and akinesia.

The PSP Speech and Language variant (PSP-SL) features language-based symptoms like non-fluent/agrammatic aphasia and primary progressive apraxia of speech, demonstrating the variable presentation of the disorder.

Corticobasal Syndrome (CBS)

CBS, like PSP, is a traditionally movement-associated disorder considered by some to be under the FTD umbrella, though, like PSP, research is increasingly finding evidence of behavioral, cognitive, and communication symptoms. Typical symptoms of CBS include limb rigidity, bradykinesia, and tremors. A hallmark symptom of CBS is alien limb syndrome, which results in people diagnosed with the disorder experiencing involuntary limb movements and a sense of a limb not belonging to them or feeling "foreign". CBS is the most common cause of alien limb syndrome, comprising at least two-thirds of documented cases.

While accurate estimates for the occurrence of neuropsychiatric symptoms in CBS are lacking, depression, apathy, anxiety, and agitation are commonly documented symptoms experienced by people diagnosed.

FTD-ALS Spectrum Disorders

FTD and ALS caused by pathogenic variants in specific genes share a clinical spectrum, with it possible for symptoms of either or both disorders to develop in carriers of the gene. In addition to the hallmark motor symptoms of ALS, spectrum disorders can cause behavioral changes like apathy or disinhibition. Language difficulties may also develop, including difficulty recalling correct words in a sentence or omitting words. Not all manifestations of behavioral or language in ALS qualify as FTD-ALS according to diagnostic criteria, nor do all incidents of muscle weakness symptoms in FTD.

Due to the overlap of two challenging symptomologies, FTD-ALS can be an exceptionally difficult disease for people diagnosed and their families. Life expectancy after symptoms start for people diagnosed with FTD-ALS is also shorter than that of other FTD disorders, averaging between 2.7-4.4 years.

Sign in to keep reading

7 more chapters are free with a Lably account.

More in Human body