Frontotemporal dementia

Frontotemporal dementia refers to sporadic inherited disorders that affect the frontal and temporal lobes, including Pick's disease.

Frontotemporal dementia (FTD) accounts for up to 10% of all dementias. The onset of this neurological disease is at a younger age (55 to 65 years) than the onset of Alzheimer's disease. Frontotemporal dementia affects men and women equally often. Pick's disease, as one of the variants of frontotemporal dementia, is pathomorphologically characterized by pronounced atrophy of the brain tissue, loss of neurons, gliosis, and the appearance of abnormal neurons (Pick cells) containing inclusions (Pick bodies).

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Causes of frontotemporal dementia

Approximately 1/2 of frontotemporal dementia cases are hereditary, the most significant mutations occur in chromosome 17q21-22, which leads to disturbances in the structure of tauprotein, so frontotemporal dementia is called a tauopathy. Some experts classify progressive supranuclear palsy and corticobasal degeneration as frontotemporal dementia, since they are based on similar pathological changes and genetic mutations that damage tauprotein. Symptoms may not always correspond to genetic mutations and pathological manifestations of the disease, and vice versa. For example, similar mutations cause manifestations of frontotemporal dementia in one family, and in members of another family - symptoms of corticobasal degeneration, Pick cells may be absent in patients with typical manifestations of Pick disease.

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Symptoms of frontotemporal dementia

In general, frontotemporal dementia affects personality, behavior, and language functions (syntax and fluency) to a greater extent, and memory to a lesser extent, compared with Alzheimer's disease. Abstract thinking and attention (maintenance and switching) are lost, and responses are disorganized. Orientation is preserved, but retrieval of information may be impaired. Locomotor skills are usually preserved. Patients have difficulty sequencing tasks, although visual-spatial and constructive tasks are less affected.

Signs of frontal cortex disinhibition (grasp phenomena, sucking, proboscis reflexes, brow (glabellar), palmomental (palmar) reflexes) appear in later stages of the disease, but may also be present in other types of dementia. Some patients develop a clinical picture of motor neuron disease with generalized muscle atrophy, weakness, fasciculations, bulbar symptoms (including dysphagia, dysphonia, difficulty chewing), which increases the risk of aspiration pneumonia and early death.

Frontal variant of frontotemporal dementia

Due to damage to the structures of the base of the frontal lobe, the patient's social behavior and personality traits are affected. Patients become impulsive and lose control over social inhibitions (including theft), and neglect personal hygiene. Some have manifestations of Kluver-Bucy syndrome, including emotional dullness, hypersexuality, hyperorality (including bulimia, sucking and lip smacking), and visual agnosia. There is a decrease in the ability to concentrate, inactivity, and mental rigidity. Behavior becomes stereotyped (the patient may go to the same place every day). Patients may collect and manipulate random objects (utilization behavior). Verbal production decreases, echolalia, perseveration (inappropriate repetition of answers to questions) appear, and mutism eventually develops.

Primary progressive aphasia

Speech functions are lost due to asymmetric (more left-sided) anterolateral temporal atrophy; the hippocampus and memory are moderately affected. Most patients have difficulty finding words. Attention (including sequential digital counting) can be significantly impaired. Many patients have aphasia with decreased fluency of speech and difficulty understanding speech structures; uncertainty in speech production and dysarthria are also common. In some patients, aphasia as a monosymptom develops 10 or more years after the onset of the disease, while in others, global deficits occur over several years.

Semantic dementia is a type of primary progressive aphasia. When the left hemisphere of the brain is damaged to a greater extent, the ability to understand words is progressively lost. Speech remains fluent, but lacks meaning (for example, similar or related terms are used despite the presence of specific names for objects). When the right hemisphere is damaged to a greater extent, patients develop progressive anomia (inability to name objects) and prosopagnosia (inability to recognize familiar faces). They cannot remember topographic relationships. Some patients with semantic dementia have Alzheimer's disease.

Diagnosis of frontotemporal dementia

Diagnosis is based on establishing typical clinical signs of the disease. As with other types of dementia, cognitive deficits are assessed in patients. CG and MRI are performed to determine the location and extent of brain atrophy and to exclude other possible causes (including brain tumors, abscesses, stroke). Frontotemporal dementia is characterized by severe brain atrophy, sometimes with a degree of thinning of the temporal and frontal sulci reaching the thickness of a sheet of paper. Since MRI and CT may not reveal areas of predominant cortical atrophy until late stages of frontotemporal dementia, neuroimaging may be less useful in excluding Alzheimer's disease (in which the hippocampus and parietal lobes are predominantly damaged in the early stages), but clinical differences between these diseases allow them to be distinguished. For example, primary progressive aphasia differs from Alzheimer's disease by the preservation of memory and spatial-visual function with the loss of the syntactic component of speech and its fluency.

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Treatment of frontotemporal dementia

There is no specific treatment for Pick's disease. Supportive care is usually given.

Prognosis of frontotemporal dementia

Frontotemporal dementia usually progresses gradually, but the rate of progression can vary; if symptoms are limited to speech and language dysfunction, progression to global dementia may be slower.

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