Journal of Diseases Disorders & Treatments

Introduction

Cognitive functions carry out a complex process of rational cognition of the world, including memory, attention, intelligence, speech, praxis and gnosis. There are three degrees of severity of cognitive impairment: mild, moderate and severe (dementia).

Cognitive impairments of all degrees of severity, including dementia, are of great interest to the global medical community, the World Health Organization and doctors, due to the growing trend of life expectancy and aging of the world population. Today, there are more than 46 million people worldwide with dementia. According to WHO forecasts, by 2050 this number will increase to 1315 million [1-3]. Today, the scientific community is working to identify the causes of cognitive impairments. However, the greatest interest is in the early diagnosis of mild cognitive impairment (MCI), not dementia. This is due to the possibility of prescribing therapy that allows stopping the progression of impairments while maintaining the patient’s ability to work, social and everyday adaptation, and in some cases even allows achieving regression of cognitive deficit, in contrast to severe cognitive impairments.

The need to search for methods of early diagnosis of MCI in the clinical practice of a neurologist and general practitioner is due to the fact that MCI does not cause maladaptation of the patient, does not affect his autonomy in everyday life and patients do not seek medical help, thereby missing opportunities for effective and early treatment.

Currently, there is a persistent trend towards an increase in the prevalence of cognitive disorders worldwide [4,5]. According to various studies, the prevalence of mild cognitive impairment ranges from 6·7 to 25·2% [6,7]. According to other reviews, the prevalence of this disorder ranges from 1·2 to 87%. Studies on the prevalence of MCI have high heterogeneity of the results obtained due to differences in the composition of cohorts, diagnostic criteria, research methodology, etc [8].

Cognitive impairments, along with high prevalence, are also characterized by a high level of disability, which is estimated at 26·3–30·8% among individuals with subclinical cognitive impairment [9-11]. In addition to neurodegenerative processes, macro- and microvascular processes play an important role in the development of cognitive impairment. Vascular dementia or vascular cognitive impairment developing after a stroke and against the background of cerebrovascular insufficiency are distinguished. Post-COVID syndrome still plays an important role. The incidence of complications, including cognitive impairment, after suffering from the disease caused by the SARS-CoV-2 pathogen in patients treated on an outpatient basis and at home ranges from 10-35%. However, among hospitalized patients, the prevalence can reach 80% [12-14].

An additional factor that exacerbates the situation with the prevalence of cognitive impairment is the aging of the population in developed countries around the world. By 2000, the proportion of the population over 65 years old was 18 percent. In 2020, the number fell slightly to 9·3%, which may be associated with the epidemic of the new coronavirus infection COVID-19. But, according to WHO forecasts, by 2050 the situation will deteriorate sharply, when the proportion of the elderly and old-age population will be 38% (2.1 milliard people) [15,16].

Thus, in connection with the relevance of the problem of cognitive disorders of varying severity, the issue of the earliest possible diagnosis of cognitive disorders becomes the most important in the practical activities of a physician.

One of the main areas of early diagnostics of cognitive disorders is the search for specific clinical markers that can indicate the development of cognitive disorders before the manifestation of all specific signs, or biochemical markers that reflect the launch of the pathogenetic chain of neurodegenerative processes. Some researchers argue that perception should be used as such a marker [17]. This theory is based on the hypothesis that gnosis is the main function, on the state of which all other components of intelligence depend. According to modern research, the disruption of various types of perception is involved in the pathological process of cognitive disorders at early stages [18,19].

In this case, we are talking not only about damage to the brain part of the visual or auditory analyzer, but also about the pathology of the sensory organ itself. Recent studies have confirmed the presence of visual disturbances in dementia with Lewy bodies in the form of contrast and color sensitivity disorders, as well as the presence of abnormalities in the electroretinogram in these patients [20-22].

As for auditory perception, modern studies note the existence of a relationship between cognitive status and some components of auditory gnosis: the level of dichotic sound processing, understanding of noisy speech or in conditions of speech masking [19-24].

Thus, given the relevance of the problem, a study on the level of visual perception as an early marker of neurodegenerative processes was conducted.

The aim of the study is to analyze the role of visual and auditory types of perception for the early diagnosis of cognitive disorders.

Material and Methods

Principles of Cohort Formation and Study Implementation The study was conducted from September 2023 to April 2024 at clinics in Yekaterinburg, Russia: medical rehabilitation departments in Central City Clinical Hospitals No. 3, No. 6, No. 14 The study group included patients of the 24-hour inpatient departments of the specified hospitals using a random sampling method in accordance with the inclusion and exclusion criteria.

Inclusion Criteria

• age over 18 years
• early recovery period (from 29 days to 6 months) of ischemic stroke
• absence of aphasia or presence of mild/moderate motor or semantic aphasia
• signed informed consent to participate in the

Exclusion Criteria

• late recovery period after stroke
• aphasia, apraxia or agnosia of high or moderate severity
• severe visual or auditory disorders
• disorders of consciousness and/or mentality
• epilepsy
• diabetes type II
• occlusive atherosclerosis
• use of drugs that affect higher cortical functions (sedatives, hypnotics, tranquilizers).

The Study was Conducted in Accordance with the Following Regulatory and Legal Acts

• Ethical principles set out in the Declaration of Helsinki [25].
• Joint Guidelines for Good Clinical Practice E6 of the International Conference on Harmonization [26].
• National standard of the Russian Federation “Good Clinical Practice” (GOST R 52379-2005)
• All applicable laws and regulations, including (the list is not exhaustive) the Federal Law “On Personal Data” dated 27.07.2006 No. 152-FZ, the Federal Law “On the Fundamentals of Health Protection of Citizens of Russia” dated November 21, 2011 N 323-FZ and other regulations.

Methods of Data Acquisition and Processing

Registration of the State of Cognitive Abilities was Carried out Using the Main Traditional Neuropsychological Diagnostic Scales

• MiniCoq: the maximum possible number of points is 5, the range of points corresponding to the normal state of cognitive abilities is 5-4
• MoCA: the maximum possible number of points is 30, the range of points corresponding to the normal state of cognitive abilities is 30-26
• MMSE: the maximum possible number of points is 30, the range of points corresponding to the normal state of cognitive functions is 30-28, light cognitive impairment is 27-20, mild cognitive impairment is 19-10, severe cognitive impairment (dementia) is 9-0;
• ACE: the maximum possible number of points is 100, the range of points corresponding to the normal state of cognitive abilities is 100-88.

The study of visual perception was conducted using the methods authored by A.R. Luria, the Gollin figure test and the Poppelreiter test [27]. The list of tests used to determine the state of visual gnosis is presented in the table (Table 1).

Table 1: List of Neuropsychological Tests used to Determine the State of Separated Components of Visual Gnosis

The NEPSY auditory test battery method was used to test auditory perception [28-30]. Statistical analysis of the obtained data was performed using descriptive statistics methods. The hypothesis about the normality of the data distribution was tested using the Kolmogorov-Smirnov goodness-of-fit test. Outliers were identified using the three sigma method. Correlation analysis was performed using the pair correlation method. The tabular value of the Student’s criterion was taken to be 1.98 at a confidence level of p = 0·95. Data collection and storage, as well as subsequent statistical processing, were performed using Microsoft Excel 2016 software.

Results

The study group consisted of 136 patients. There were predominantly women - 94 (69·12%), men - 42 (30·88%). The age distribution was as follows: middle-aged (45-59 years) - 64 (47·06%), elderly (60-74 years) - 51 (37·5%), and senile (75-89 years) - 21 (15·44%). The average age was 62.4 ± 1.99 years. Average cogmnitive indicators: MiniCoq - 2·58 ± 0·18 points, MoCA test - 19·49 ± 0·96 points, MMSE - 22·27 ± 0·94 points, ACE - 68·64 ± 1.88 points.

Thus, according to MiniCoq data, deviations of 40-50% from the norm were revealed. According to the MoCA and MMSE scales, deviations of 65-73% were determined in the study group, and according to the ACE results, of 68%. These differences may be due to different diagnostic capabilities and accuracy of neuropsychological tests. After eliminating outliers, a paired correlation test was conducted for the visual and auditory perception indicators separately with the results of each of the four presented neuropsychological scales. The obtained values are presented in the table (Table 2).

Table 2: Paired Correlation Coefficient Values of Visual and Auditory Gnosis with each type of Cognitive Status Questionnaire

• Montreal Cognitive Assessment
• Mini–mental state examination
• Addenbrooke’s Cognitive Examination
• Confidence level p = 0·95

The highest value was found between the state of visual gnosis and the MMSE scale. Next in descending order are the values of the correlation of the level of perception with the MoCA and ACE tests. The minimum level of correlation was found between visual perception and the MiniCoq scale. As for auditory perception, its correlation dependence repeats the dynamics of visual gnosis, but the correlation values are significantly lower compared to visual perception.

Discussion

According to the neuropsychological diagnostic scales, a high prevalence of cognitive impairment was found in patients undergoing rehabilitation in the early recovery period of ischemic stroke in the left carotid basin – 75 - 90·44%. When studying the correlation coefficients of the level of visual perception with four main diagnostic scales, it was found that visual gnosis demonstrates a strong positive relationship with the MMSE and MoCA scales. A positive moderate correlation was found with the Addenbrooke’s cognitive scale, and a positive weak correlation with the MiniCoq test indicators. At the same time, auditory perception demonstrates moderate and weak correlation with all the cognitive status indicators used.

However, the analysis of individual scale indicators revealed that not all patients have a decrease in mnestic functions that corresponds to the negative dynamics of the level of visual or auditory perception; various values of the studied indicators are noted. The difference in the degree of correlation can be explained by the different structure of tests for assessing cognitive deficit. If MoCA and MMSE are aimed at identifying mild and light cognitive disorders, and ACE, as a large-scale diagnostic tool, is aimed at a detailed study of cognitive functions, then MiniCoq is a quick method for determining cognitive status in emergency situations, as well as in conditions of time constraints during an appointment with a general practitioner.

Thus, according to the results of the study, a high potential for using visual gnosis as an early marker of mild to moderate cognitive impairment was revealed. However, this indicator cannot serve as a tool for determining the dynamics of the level of cognitive deficit in patients during treatment and rehabilitation, as well as for making a final diagnosis. Also, the direction of the cause- and-effect relationship between visual perception and cognitive abilities remains unclear, namely, what suffers first and which component triggers the pathological process. However, given the potential of visual gnosis to assess cognitive status, further more detailed study is advisable, including practical verification of this hypothesis.

The study of auditory perception showed low sensitivity to the assessment of cognitive status. It is important to consider that, unlike visual gnosis, there are no specific validated methods for the analysis of auditory perception, so at the moment, measuring auditory gnosis in an outpatient appointment with a general practitioner or neurologist is a labor-intensive, lengthy and unpromising method.

Conclusion

As a result of the study, it was revealed that there is a direct strong or moderate correlation between visual perception and cognitive abilities. Although the assessment of visual gnosis cannot yet be considered the most sensitive testing for clarifying the level of severity of cognitive impairment, this marker has the potential for early detection of the neurodegenerative process. At the same time, the inclusion of special scales for assessing visual gnosis in neuropsychological testing will help to more fully study the degree of cognitive deficit, since perception processes are important for the quality of life of patients and the development of an individual rehabilitation program.

As a result of the study, a moderate correlation was revealed between auditory perception and cognitive abilities. Given the high labor intensity of measuring the level of this type of perception, the assessment of auditory gnosis using the NEPSY test cannot be considered as an early marker for diagnosing and clarifying the level of severity of cognitive impairment.

Funding

This study was conducted without any fundings either from government or private companies.

Conflict of Interest

The authors declare no obvious or potential conflicts of interest.

Compliance with Ethical Principles

The study was conducted in accordance with the ethical standards prescribed in the legislation of the Russian Federation and the Declaration of Helsinki. Voluntary informed consent was obtained from the patients who became the objects of the study or their legal representatives for the participation in the study and publication of its results in anonymous form.

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