Cognitive impairment

Impaired cognitive function

Dementia (from Latin de - "loss", mentos - "mind"; synonym - feeblemindedness) - acquired stable multifunctional cognitive impairment (deterioration of memory, intelligence, mental performance, etc.), expressed to a significant degree, determined against the background of clear consciousness, caused by organic damage to the brain.

The acquired nature of cognitive impairment in dementia indicates that this condition develops as a result of some brain damage that occurred during life. Dementia is a decrease in intelligence compared to an initially higher level. This distinguishes dementia from the initial underdevelopment of cognitive functions (oligophrenia).

The stability of disorders implies that they are present for a certain long period of time. Thus, in accordance with the recommendations of the International Classification of Diseases, Tenth Revision (ICD-10), the diagnosis of "dementia" is valid if the duration of cognitive disorders is at least 6 months. Before this period, the diagnosis can be formulated tentatively.

The polyfunctional nature of the disorders implies the simultaneous impairment of several cognitive functions, for example, memory and speech, memory and intellect, or memory, intellect and speech, etc. In this case, the impairment of each cognitive function is expressed to a significant degree.

A significant degree of impairment implies the fact that it has a negative impact on everyday life, i.e. causes difficulties in at least one of the following areas: professional activity, hobbies and interests, interaction with other people, everyday life, self-care. In the absence of such difficulties, one should not talk about dementia, but about non-dementia (mild or moderate) cognitive impairment.

Cognitive impairments in dementia are revealed against the background of clear consciousness, i.e. they are not associated with clouding of consciousness. A patient with dementia demonstrates memory and attention disorders while in a state of active wakefulness. This is how dementia differs from delirium.

By definition, dementia is always based on organic damage to the brain. It is important to note that it is not always primary, i.e. not always associated with direct anatomical damage to cerebral structures. The brain may suffer secondary to somatic pathology. The pathogenetic mechanism of damage in such cases is systemic dysmetabolic disorders (the so-called dysmetabolic encephalopathy, for example, in hypothyroidism).

It should be noted that severe depression sometimes leads to pronounced cognitive disorders in the absence of organic brain damage. The terms "pseudo-dementia" and "depressive pseudo-dementia" are used to describe such conditions.

Epidemiology of cognitive impairment

The prevalence of dementia is at least 5% among people over 65 years of age and increases many times in older age groups. In total, 21 million patients with dementia were officially registered worldwide in 2006.

Classification of cognitive impairments

According to their severity, cognitive impairments are divided into mild, moderate and severe. Dementia is one of the types of severe cognitive impairments.

• Severe disorders of cognitive functions are those that limit daily activities and lead to partial or complete loss of independence and autonomy of the patient. In addition to dementia, severe cognitive disorders are observed in delirium (often transient) and depressive pseudo-dementia. Severe cognitive disorders should also include pronounced monofunctional disorders, such as gross aphasia, apraxia and others that limit daily activities.
• Moderate cognitive impairment is a mono- or polyfunctional defect that is subjectively recognized and attracts the attention of others, but does not cause maladaptation of the patient, i.e. loss of independence and autonomy. At the same time, the patient may experience difficulties in complex and unusual activities. In more than half of the cases, moderate cognitive impairment eventually transforms into dementia. Thus, this syndrome is usually noted in pre-dementia stages of progressive brain diseases.
• Mild cognitive impairment is a subjective and/or objective decrease in cognitive abilities compared to the individual baseline level, which does not cause any difficulties in everyday activities, including the most complex types. Mild cognitive impairment is not always a pathological symptom. In some cases, it may be a consequence of natural age-related involutional changes in the brain (the so-called age-related memory impairment, or age-related cognitive impairment).

Symptoms of cognitive impairment

The clinical picture of dementia consists of cognitive, behavioral, emotional disorders and disturbances in daily activities.

Cognitive impairment is the clinical core of any dementia. Cognitive impairment is the main symptom of this condition, so its presence is mandatory for diagnosis.

Symptoms of cognitive impairment

Causes of cognitive impairment

Dementia is a polyetiological syndrome that develops with various diseases of the brain. There are several dozen nosological forms within which dementia syndrome can develop. The most common of them are Alzheimer's disease, dementia with Lewy bodies, cerebrovascular insufficiency, frontotemporal degeneration, diseases with predominant damage to the subcortical basal ganglia ("subcortical dementia"). The specified nosological forms are responsible for at least 80% of dementia in old age.

Causes of cognitive impairment

Diagnosis of cognitive impairment

The first stage of dementia diagnostics is to identify cognitive impairments and assess their severity (syndromic diagnosis). Clinical methods (collection of complaints, patient history) and neuropsychological tests are used to study cognitive functions. Ideally, each patient with cognitive complaints should undergo a detailed neuropsychological examination, but in practice this is hardly possible. Therefore, neurologists, psychiatrists and doctors of other specialties are recommended to independently use so-called dementia screening scales during a conversation with a patient, which take a relatively short time and are quite simple to conduct and interpret. The most commonly used are the Mini-Mental Status Examination and the Clock Drawing Test.

Diagnosis of cognitive impairment

Treatment of dementia and other cognitive impairments

The choice of therapeutic tactics depends on the cause (nosological diagnosis) and severity of cognitive impairment. In the stage of mild and moderate dementia associated with Alzheimer's disease, vascular and mixed (vascular-degenerative) dementia, dementia with Lewy bodies and Parkinson's disease with dementia, acetylcholinergic and glutamatergic drugs have proven themselves well.

Currently, 4 drugs from the acetylcholinesterase inhibitor group are used in the treatment of dementia: donepezil, rivastigmine, galantamine and ipidacrine. The use of these drugs helps to reduce the severity of cognitive impairment, normalize behavior, improve adaptation in everyday life, which ultimately leads to an improvement in the quality of life of patients and their immediate environment.

Another approach to pathogenetic therapy of dementia is the use of memantine, a reversible non-competitive blocker of N-methyl-O-aspartate receptors to glutamate. It is used in the same diseases as acetylcholinesterase inhibitors. In severe dementia, memantine is the drug of first choice, since the effectiveness of acetylcholinergic drugs at this stage has not been sufficiently studied. Contraindications to the use of memantine are epilepsy and renal failure. Side effects are extremely rare.

Treatment of dementia and cognitive impairment

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