Mild Cognitive Impairment (MCI): concept, causes and symptoms

March 29, 2024

By Mild Cognitive Impairment (MCI) , according to consensus, we understand that transitory phase between normal aging and dementia characterized by an objective loss of cognitive functions, demonstrated in a neuropsychological evaluation and, on the part of the patient.

Signs and symptoms of Mild Cognitive Impairment

On a subjective level, is accompanied by complaints regarding loss of cognitive abilities . In addition, in order to deal with Mild Cognitive Impairment, these cognitive deficits should not interfere in the independence of the patient and should not be able to relate to other pathologies such as psychiatric and neurological disorders, addictions, etc. Therefore, the main difference with respect to a patient with dementia is the maintenance of independence in the activities of daily life, despite a certain degree of cognitive impairment.

The first diagnostic criteria for MCI were described by Petersen et al (1999), although the concept was born much earlier. Doing a search in Pubmed we can see that in 1990 we already found manuscripts in which we speak of Mild Cognitive Impairment. Initially, DCL was only seen as a diagnosis that led the subject to Alzheimer's disease ; however, in 2003 a team of experts (including Petersen himself) proposed classifying the diagnosis of MCI based on the cognitive domains affected in the neuropsychological evaluation. Later, in a review by Gauthier et al. which took place in 2006, it was proposed for the first time that different types of Mild Cognitive Impairment can lead to different types of dementia. Nowadays, MCI is seen as a state that can lead the subject to some kind of dementia or, simply, it may not evolve.

Clinical Characterization of Mild Cognitive Impairment

Being realistic, A clear, unique and well-established diagnosis for Mild Cognitive Deficit is not yet available .

Different authors apply different criteria to diagnose it, and there is not a total consensus about how to identify it. Even so, the first steps have been taken to generate an agreement and in the manual DSM-V we can already find a diagnosis of "Mild Neurocogntive Disorder", which bears a certain resemblance to the DCL. Due to the lack of consensus, we will briefly mention the two bases on which the diagnosis of MCI is based.

1. Neuropsychological evaluation

Neuropsychological evaluation has become an indispensable tool in the diagnosis of dementias and also of mild cognitive impairment. For the diagnosis of DCL a comprehensive neuropsychological battery should be applied that allows us to evaluate the main cognitive domains (memory, language, visuospatial reasoning, executive functions, psychomotor capacity and speed of processing).

Through the evaluation it must be demonstrated that, at least, there is a neuropsychological domain that is affected. Even so, there is currently no established cut-off point to consider a cognitive domain as affected. In the case of Dementia, 2 negative standard deviations are usually established as a cut-off point (in other words, the performance is below 98% of the population of the patient's age and educational level). In the case of MCI, there is no consensus for the cut-off point, with authors establishing it in 1 negative standard deviation (16th percentile) and others in 1.5 negative standard deviations (7th percentile).

Based on the results obtained in the neuropsychological evaluation, the type of mild cognitive impairment with which the patient is diagnosed is defined. Depending on the domains that are affected, the following categories are established:

Single domain amnesiac DCL : Only the memory is affected.

Multi-domain amnesic DCL : Memory is affected and, at least, another domain.

Single domain non-amnesic DCL : Memory is preserved but there is some domain that is affected.

Non-amnesic multi-domain DCL : Memory is preserved but there is more than one affected domain.

These diagnostic types can be found in the review by Winblad et al. (2004) and are some of the most used in research and clinical. Nowadays, many longitudinal studies try to follow the evolution of the different subtypes of DCL towards dementia. In this way, through the neuropsychological evaluation, a patient's prognosis could be made to perform specific therapeutic actions.

Currently there is no consensus and the research has not yet offered a clear idea to confirm this fact, but, even so, some studies have reported that the DCL of amnesic type of single or multidomain domain would be the one that, with more probabilities, would lead to Alzheimer's dementia , whereas in the case of patients that evolved towards vascular dementia, the neuropsychological profile could be much more varied, and there may or may not be memory impairment. This would be because in this case the cognitive deterioration would be associated with lesions or micro lesions (cortical or subcortical) that could lead to different clinical consequences.

2. Evaluation of the degree of patient independence and other variables

One of the indispensable criteria for the diagnosis of Mild Cognitive Impairment, which is shared by almost the entire scientific community, is that the patient must maintain his independence . If the activities of daily life are affected we will suspect dementia (which would not be confirmatory of anything either). For this, and even more so when the cut points of the neuropsychological evaluation are not clear, the anamnesis of the patient's clinical history will be essential. In order to evaluate these aspects, I suggest different tests and scales that are widely used in the clinic and research:

IDDD (Interview for Deterioration in Daily Living Activities in Dementia): Evaluates the degree of independence in the activities of daily life.

EQ50: Evaluates the quality of life of the patient.

3. Presence or not of complaints

Another aspect that is considered necessary for the diagnosis of Mild Cognitive Impairment is the presence of subjective complaints of cognitive type . Patients with MCI usually report different types of cognitive complaints in the consultation, which are not only related to memory, but also to anomie (difficulty in finding the name of things), disorientation, concentration problems, etc. Considering these complaints as part of the diagnosis is essential, although it should also be borne in mind that in many cases patients suffer anosognosia, that is, they are not aware of their deficits.

In addition, some authors argue that subjective complaints have more to do with the state of mind than with the real cognitive state of the subject and, therefore, we can not leave everything to the profile of subjective complaints, although they should not be ignored. It is very useful to contrast the patient's version with that of a family member in cases of doubt.

4. Disposal of underlying neurological or psychiatric problems

Finally, when reviewing the clinical history, it should be ruled out that poor cognitive performance is the cause of other neurological or psychiatric problems (schizophrenia, bipolar disorder, etc.). It is also necessary to evaluate the degree of anxiety and mood. If we adopted strict diagnostic criteria, the presence of depression or anxiety would rule out the diagnosis of MCI. However, some authors defend the coexistence of Mild Cognitive Impairment with this type of symptomatology and propose diagnostic categories in terms of possible MCI (when there are factors that make the diagnosis of MCI doubtful) and probable MCI (when there are no concomitant factors to MCI). ), similar to how it is done in other disorders.

A final reflection

Nowadays, Mild Cognitive Impairment is one of the main focuses of scientific research in the context of the study of dementias. Why was he going to study? As we know, medical, pharmacological and social advances have led to an increase in life expectancy .

This has been added to a decrease in the birth rate that has resulted in a more aging population. Dementias have been an unappealable imperative for many people who have seen that as they got older they maintained a good level of physical health but suffered memory losses that condemned them to a situation of dependency. Neurodegenerative pathologies are chronic and irreversible.

From a preventive approach, Mild Cognitive Impairment opens a therapeutic window to the treatment of precipitous evolution towards dementia through pharmacological and non-pharmacological approaches. We can not cure a dementia, but the MCI is a state in which the individual, although cognitively impaired, retains its full independence. If we can at least slow the evolution towards dementia, we will be positively influencing the quality of life of many individuals.

Bibliographic references:

Espinosa A, Alegret M, Valero S, Vinyes-Junqué G, Hernández I, Mauleón A, Rosende-Roca M, Ruiz A, López O, Tárraga L, Boada M. (2013) A longitudinal follow-up of 550 Mild Cognitive Impairment Patients: Evidence for large conversion to Dementia rates detection of major risk factors involved. J Alzheimers Dis 34: 769-780

Gauthier S, Reisberg B, Zaudig M, Petersen RC, Ritchie K, Broich K, Belleville S, Brodaty H, Bennett D, Chertkow H, Cummings JL, Leon M, Feldman H, Ganguli M, Hampel H, Scheltens P, Tierney MC, Whitehouse P, Winblad B. (2006) Mild Cognitive Impairment. Lancet 367: 1262-70.

Gorelick PB et al. (2011) Vascular Contributions to Cognitive Impairment and Dementia: A statement for healthcare professionals from the American Heart Association / American Stroke Association. Stroke 42: 2672-713.

Janoutová J, Šerý O, Hosák L, Janout V. (2015) Is Mild Cognitive Impairment a Precursor of Alzheimer's Disease? Short Review.Cent Eur J Public Health 23: 365-7

Knopman DS and Petersen RC (2014) Mild Cognitive Impairment and Mild Dementia: A Clinical Perspective. Mayo Clin Proc 89: 1452-9.

Winblad B et al. (2004) Mild cognitive impairment-beyond controversies, towards a consensus: report of the international working Group on Mild Cognitive Impairment. J Intern Med 256: 240-46.

Petersen RC, Smith GE, Waring SC, Ivnik RJ, Tangalos EG, Kokmen E. (1999) Mild Cognitive Impairment: Clinical characterization and outcome. Arch Neurol 56: 303-8.

Ryu SY, Lee SB, Kim TW, Lee TJ. (2015) Subjective memory complaints, depressive symptoms and instrumental activities of daily living in mild cognitive impairment. Int Psychogeriatr 11: 1-8.