Diagnosis of cognitive impairment

PhysicalityThe 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.

Mini-Mental State Examination

The function under study	Exercise	Number of points
Orientation in time	Name the date (day, month, year, day of the week, season)	0-5
Orientation in the place	Where are we (country, region, city, clinic, room)?	0-5
Perception	Repeat three words: lemon, key, ball	O-z
Concentration of attention	Serial counting (for example, subtract 7 from 100) - five times	0-5
Memory	Remember three words (spoken during the perception test)	0-3
Naming objects	What is this? (The patient must name the objects shown to him, for example, a pen and a watch.)	0-2
Repetition	Repeat the phrase: "No ifs, no buts."	0-1
Understanding the team	Take a piece of paper with your right hand, fold it in half and place it on the table	O-z
Reading	Read aloud what is written ("Close your eyes") and do it	0-1
Letter	Think of and write a sentence	0-1
Drawing	Copy this picture	0-1

The total score is 0-30.

Instructions and interpretation

• Orientation in time. Ask the patient to name today's date, month, year, day of the week and season in full. For each correct answer, 1 point is awarded. Thus, the patient can receive from 0 to 5 points.
• Orientation in place. The question is asked: "Where are we?" The patient must name the country, region, city, institution where the examination is taking place, room number (or floor). For each correct answer, the patient receives 1 point. Thus, for this test, the patient can also receive from 0 to 5 points.
• Perception. The patient is given the following instructions: "Repeat and try to remember three words: lemon, key, ball." The words must be pronounced as clearly as possible at a rate of one word per second. The correct repetition of each word by the patient is assessed as 1 point. After this, we ask the patient: "Have you remembered the words? Repeat them again." If the patient has difficulty repeating them, we name the words again until the patient remembers them (but no more than 5 times). Only the result of the first repetition is assessed in points. In this test, the patient can receive from 0 to 3 points.
• Concentration of attention. The following instructions are given: "Please subtract 7 from 100, subtract 7 from the result again, and do this several times." 5 subtractions are used (up to a result of 65). For each correct subtraction, 1 point is awarded. The patient can receive from 0 to 5 points in this test. In case of an error, the doctor must correct the patient by suggesting the correct answer. A point is not awarded for an erroneous action.
• Memory. The patient is asked to recall the words he learned during the perception test. Each correctly named word is assessed at 1 point.
• Naming objects. Show the patient a pen and ask: "What is this?", use a watch in the same way. Each correct answer is worth 1 point.
• Phrase repetition. The patient is asked to repeat the following phrase: "No ifs, no buts." The phrase is pronounced only once. Correct repetition is assessed as 1 point.

• Understanding the command. A command is given orally, which requires the sequential execution of 3 actions. "Take a sheet of paper with your right hand, fold it in half and put it on the table." Each correctly performed action is assessed at 1 point.
• Reading. The patient is given a piece of paper on which is written in large letters: "CLOSE YOUR EYES." The following instructions are given: "Read aloud and do what is written here." The patient receives 1 point if, after reading aloud correctly, he actually closes his eyes.
• Letter. The patient is asked to think of and write a sentence. The patient receives 1 point if the sentence he thinks of is meaningful and grammatically correct.
• Drawing. The patient is given a sample (2 intersecting pentagons with equal angles, a quadrangle is formed at the intersection), which he must redraw on unlined paper. If the patient redraws both figures, each of which contains five angles, the lines of the pentagons are connected, the figures actually intersect, a quadrangle is formed at the intersection, the patient receives 1 point. If at least one of the conditions is not met, no point is awarded.

The overall test result is obtained by summing the results for each item. 24 points and less are typical for dementia.

Clock Drawing Test

Ask the patient to draw a round clock on unlined paper with hands on the dial indicating a certain time (for example, 15 minutes to 2). The patient draws the clock independently (without prompts), from memory (without looking at a real clock). The result is assessed on a 10-point scale.

• 10 points - normal, a circle is drawn, the numbers are in the right places, the arrows show the specified time.
• 9 points - minor inaccuracies in the placement of the hands.
• 8 points - more noticeable errors in the position of the hands (one of the hands deviates from the required time by more than an hour).
• 7 points - both hands show the wrong time.
• 6 points - the hands do not perform their functions (for example, the required time is circled or written in numerical form).
• 5 points - incorrect arrangement of numbers on the dial (they are in reverse order, i.e. counterclockwise, or the distance between the numbers is not the same).
• 4 points - the clock is not intact, some numbers are missing or located outside the circle.
• 3 points - the numbers and the dial are not related to each other.
• 2 points - the patient's activity shows that he is trying to follow the instructions, but unsuccessfully.
• 1 point - the patient makes no attempt to follow the instructions.

Interpretation: less than 9 points is a sign of severe cognitive impairment.

Next, it is also necessary to assess how cognitive impairment affects the patient's daily activities. To do this, it is necessary to obtain information about his professional activities, hobbies and interests, the degree of independence in social communication, household responsibilities, use of household appliances, and self-care. It is advisable to verify the information obtained from the patient with his relatives, friends, or colleagues, since dissimulation is very typical for the early stages of dementia: patients hide their defect or downplay its severity. If there are real difficulties in daily activities, we can talk about dementia itself, otherwise the syndromic diagnosis should be formulated as follows: "mild cognitive impairment" or "moderate cognitive impairment".

The second stage of the diagnostic search is the differential diagnosis of dementia and conditions that mimic dementia, such as pseudodementia and delirium.

By definition, dementia is a severe primary cognitive impairment that is not causally related to emotional disturbances or disturbances in the level of wakefulness or consciousness.

Depressive pseudodementia - cognitive and/or behavioral disorders secondary to depression. Such disorders may lead to difficulties in daily activities and imitate dementia, but they have no organic substrate and regress when mood normalizes.

Signs that a patient has depression:

• a depressed or depressed state that has been present most of the time for the past month or more;
• a feeling of hopelessness, pronounced dissatisfaction with one's life, lack of desire to live, frequent thoughts of death, suicidal statements;
• difficulty falling asleep or early morning awakenings that occur almost every night;
• chronic headaches (>15 days per month) or constant heaviness in the head that prevents concentration;
• strong causeless anxiety, especially in the evenings, restlessness, irritability, leading to frequent conflicts in the family or at work;
• a marked deterioration in appetite, weight loss in the absence of somatic reasons for this;
• expressed concern about memory loss despite normal or near-normal neuropsychological test results.

The presence of clinically significant depression is the basis for consultation and observation by a psychiatrist and appropriate therapy. At the same time, elderly people should avoid drugs with a pronounced anticholinergic effect, such as tricyclic antidepressants. Drugs of this pharmacological group have a negative effect on cognitive functions. Therefore, selective serotonin reuptake inhibitors or serotonin and norepinephrine reuptake inhibitors are more preferable. According to some data, these drugs, on the contrary, contribute to the improvement of cognitive functions.

Regression of cognitive disorders against the background of prescription of antidepressants indicates the secondary nature of disorders of higher brain functions in relation to depression. In these cases, the diagnosis of pseudodementia is correct. If, despite a good antidepressant effect, cognitive disorders persist, we are talking about a combination of true dementia and depression, which is possible with vascular and mixed dementia, Parkinson's disease and other diseases with damage to the subcortical basal ganglia with dementia, in the early stages of Alzheimer's disease, frontotemporal dementia. In these cases, a repeated assessment of disorders, clinical, laboratory and instrumental examination are necessary. Thus, differential diagnostics of pseudodementia and true dementia in combination with depression is carried out ex juvantibus based on the results of the appropriate therapy.

Delirium is an acute state of confusion with pronounced mnestic-intellectual disorders. Delirium should be suspected in all cases of acute or subacute development of cognitive disorders and in the presence of noticeable fluctuations in the severity of disorders, for example, depending on the time of day. Delirium is usually accompanied by disorientation in place and time, psychomotor agitation and psychoproductive symptoms in the form of delirium and hallucinations. However, these signs are not always present. The presence of pronounced cognitive disorders associated with clouding or confusion of consciousness is considered mandatory.

The main causes of delirium in the elderly are as follows.

• Dysmetabolic disorders; dehydration, liver or kidney failure, hypoxia, hypo- or hyperglycemia, acute intoxication.
• Infectious diseases: pneumonia, urinary tract infection, any infection with high fever.
• Trauma: traumatic brain injury, including mild, fractures of the extremities.
• Surgical interventions, especially those using general anesthesia.
• Decompensation of cardiac or respiratory failure.

When the cause of delirium is established and dysmetabolic or other disorders are corrected in a timely manner, the patient's level of consciousness is restored, which is accompanied by a significant improvement in cognitive functions. However, cognitive abilities rarely return to the pre-delirious state. More often, after exiting the state of acute decompensation, patients demonstrate some decrease in cognitive functions compared to the initial level.

The third stage of diagnostic search is establishing a nosological diagnosis of dementia. For this purpose, clinical laboratory and neurovisual examination of patients is carried out.

Nosological diagnostics should begin with the search for so-called potentially reversible dementia. Potentially reversible dementia is a condition when timely diagnosis and proper treatment can lead to complete or almost complete regression of disorders. According to statistics, at least 5% of dementias are potentially reversible. These include the following types:

• dementia secondary to systemic dysmetabolic disorders (dysmetabolic encephalopathy);
• dementia due to brain tumors or other space-occupying processes;
• dementia in normal pressure hydrocephalus.

The main causes of dysmetabolic encephalopathy are:

• hypothyroidism;
• vitamin _B12 or folate deficiency;
• liver failure;
• renal failure;
• chronic hypoxic condition;
• poisoning with heavy metal salts;
• alcoholism and drug addiction;
• drug intoxications (anticholinergic drugs, tricyclic antidepressants, neuroleptics, benzodiazepines, etc.).

The minimum amount of research required to identify these causes consists of the following activities:

• general blood and urine analysis;
• biochemical blood test to determine the concentration of creatinine, urea nitrogen, liver enzyme activity, and, if possible, the content of vitamin B12 _and folic acid, homocysteine;
• laboratory examination of thyroid function (content of triiodothyronine, thyroxine, thyroid-stimulating hormone, antibodies to thyroglobulin).

The use of neuroimaging methods allows the diagnosis of potentially reversible brain lesions such as normal pressure hydrocephalus and brain tumor.

Clinical and imaging features of normal pressure hydrocephalus

Cognitive impairment	Neurological disorders	CT or MRI signs
Disorders of activity regulation	Gait disturbance. Urinary incontinence.	Significant symmetrical expansion of the ventricular system

Clinical and imaging features of brain tumor

Cognitive impairment	Neurological disorders	CT or MRI signs
Varying in severity and qualitative characteristics (depending on the location of the tumor)	Focal symptoms (depending on tumor location). Headache, congestion in the fundus, visual impairment	Focal brain lesion that accumulates contrast medium. Ventricular dilation (occlusive hydrocephalus)

Suspicion of normal pressure hydrocephalus or a brain tumor is a reason to contact a neurosurgeon, who decides on the indications for surgical treatment.

After excluding potentially reversible forms of dementia, the clinical, psychological and instrumental features of the case should be re-examined.

Comparative characteristics of the main nosological forms of dementia

	Alzheimer's disease	Vascular dementia	Dementia with Lewy bodies	Frontotemporal dementia
Start	Always gradual, not before 40 years, more often after 60 years	Acute or gradual, at any age, but more often after 60 years	Gradual, rarely acute, usually after 60 years	Gradual, usually up to 60 years
Family history	Sometimes	Rarely	Sometimes	Often
Major cognitive symptom	Memory impairment	Dysregulatory disorders	Visual-spatial disturbances, fluctuations	Dysregulatory disorders, speech disorders
Neurological disorders	None	Gait disturbances, pseudo-bulbar syndrome	Parkinsonism	"Primitive reflexes" (eg grasping)
Emotional disorders	Anxiety, depression at the onset of the disease	Depression, emotional lability	Depression	Indifference, rarely depression
Changes in MRI	Atrophy of the cortex, hippocampus	Postinfarction cysts, leukoaraiosis	Dilation of the posterior horns of the lateral ventricles	Local atrophy of the frontal and anterior temporal lobes (often asymmetrical)
Behavioral disorders	Delusion of damage (in the stage of moderate dementia)	Irritability	Visual hallucinations	Decreased criticism, disinhibition, apathy

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