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

We explain this neurological disorder from clinical psychology.

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

Signs and Symptoms of Mild Cognitive Impairment

At the subjective level, it is accompanied by complaints of a loss of cognitive abilities.. In addition, for it to be Mild Cognitive Impairment, these cognitive deficits should not interfere with the patient's independence and should not be related to other pathologies such as psychiatric and neurological disorders, addictions, etc. Thus, the main difference from a patient with dementia is the maintenance of independence in activities of daily living, 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. A search in Pubmed shows that in 1990 manuscripts already referred to Mild Cognitive Impairment. Initially, MCI was only contemplated as a diagnosis leading to Alzheimer's diseaseHowever, in 2003 a team of experts (including Petersen himself) proposed to classify the diagnosis of MCI according to the cognitive domains affected in the neuropsychological assessment. Later, in a review by Gauthier et al. which took place in 2006, it was first proposed that different types of Mild Cognitive Impairment can lead to different types of dementia.

Today, MCI is seen as a state that may lead to some form of dementia or may simply not progress.

Clinical Characterization of Mild Cognitive Impairment

Realistically, there is still no clear, single, well-established diagnosis for Mild Cognitive Impairment (MCI)..

Different authors apply different criteria to diagnose it, and there is no total consensus on how to identify it. Even so, the first steps have been made to generate an agreement and in the DSM-V manual we can already find a diagnosis of "Mild Neurocognitive Disorder", which has a certain resemblance to MCI. 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 assessment has become an indispensable tool in the diagnosis of dementias and Mild Cognitive Impairment. For the diagnosis of MCI a comprehensive neuropsychological battery should be applied that allows us to evaluate the main cognitive domains (memory, language, visuospatial reasoning, visual-spatial reasoning, etc.). (memory, language, visuospatial reasoning, executive functions, psychomotor capacity and processing speed).

The assessment must demonstrate that at least one neuropsychological domain is affected. Even so, there is currently no established cut-off point for considering a cognitive domain as affected. In the case of dementia, 2 negative standard deviations are usually established as the cut-off point (or, in other words, that performance is below 98% of the population of the patient's age group and educational level). In the case of MCI there is no consensus for the cut-off point, with some authors establishing it at 1 negative standard deviation (16th percentile) and others at 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 affected, the following categories are established:

• Single domain amnestic MCIOnly memory is affected.

• Multi-domain amnestic MCIMemory and at least one other domain are affected.

• Single-domain non-amnestic MCIMemory is preserved but some domain is affected.

• Non-amnestic MCI multi-domainMemory is preserved but more than one domain is affected.

These diagnostic types can be found in the review by Winblad et al. (2004) and are among the most widely used in research and clinical practice. Nowadays, many longitudinal studies try to follow the evolution of the different subtypes of MCI towards dementia. In this way, through neuropsychological assessment, a prognosis of the patient could be made in order to carry out specific therapeutic actions.

Currently there is no consensus and research has not yet offered a clear idea to confirm this fact, but, even so, some studies have reported that single or multi-domain amnestic type of MCI would be the most likely to lead to Alzheimer's dementia, while in the case of patients with Alzheimer's dementia, the most likely to lead to Alzheimer's dementia would be the single or multi-domain amnestic type of MCI.whereas in the case of patients progressing to vascular dementia, the neuropsychological profile could be much more varied and there may or may not be memory impairment. This would be due to the fact that in this case the cognitive impairment would be associated with lesions or microlesions (cortical or subcortical) that could entail different clinical consequences.

2. Assessment of the patient's degree of 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 or her independence. If the activities of daily living are affected, dementia will be suspected (which would not be confirmatory of anything). For this, and even more so when the cut-off points of the neuropsychological evaluation are not clear, the anamnesis of the patient's clinical history will be essential. In order to assess these aspects I advise below different tests and scales that are widely used in clinical and research settings:

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

EQ50: Evaluates the degree of quality of life of the patient.

3. Presence or absence of complaints

Another aspect that is considered necessary for the diagnosis of Mild Cognitive Impairment is the presence of subjective cognitive complaints.. MCI patients usually refer different types of cognitive complaints in the consultation, which are not only related to memory, but also to anomia (difficulty in finding the name of things), disorientation, concentration problems, etc. It is essential to consider these complaints as part of the diagnosis, although it should also be taken into account that patients often suffer from anosognosia, i.e., they are unaware of their deficits.

Moreover, some authors argue that subjective complaints have more to do with mood than with the actual cognitive state of the subject and, therefore, we cannot leave everything to the profile of subjective complaints, although they should not be ignored. It is usually very useful to contrast the patient's version with that of a relative in cases of doubt.

4. Rule out underlying neurological or psychiatric problems.

Finally, a review of the clinical history should rule out that poor cognitive performance is caused by other neurological or psychiatric problems (schizophrenia, bipolar disorder, etc.). It is also necessary to evaluate the degree of anxiety and mood. If we were to adopt 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 the way it is done in other disorders.

A final thought

Nowadays, Mild Cognitive Impairment is one of the main focuses of scientific research in the context of the study of dementias. Why would it be studied? As we know, medical, pharmacological and social advances have led to an increase in life expectancy and a decrease in the number of people with dementia..

This has been coupled with a declining birth rate resulting in an aging population. Dementias have been an unavoidable imperative for many people who have seen that as they have aged, they have maintained a good level of physical health but suffered memory loss that condemned them to a situation of dependence. Neurodegenerative pathologies are chronic and irreversible.

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