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 by the patient.

Signs and Symptoms of Mild Cognitive Impairment

At a subjective level, is accompanied by complaints referring to the loss of cognitive abilities . Furthermore, for it to be a case of Mild Cognitive Impairment, these cognitive deficits must not interfere with the patient’s independence and must not be able to be related 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 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 we found manuscripts that mention Mild Cognitive Impairment. Initially, MCI was only seen as a diagnosis leading to Alzheimer’s disease ; however, in 2003 a team of experts (including Petersen himself) proposed classifying the diagnosis of MCI according to the cognitive domains affected in the neuropsychological assessment. Later, in a 2006 review by Gauthier et al., it was first proposed that different types of MCI can lead to different types of dementia. Today, MCI is viewed as a state that may lead to some form of dementia or may simply not evolve.

Clinical Characterization of Mild Cognitive Impairment

Realistically, there is not yet a clear, unique and well-established diagnosis for Mild Cognitive Deficit .

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 taken to generate agreement and in the DSM-V manual we can already find a diagnosis of “Mild Neurocogntive Disorder”, which bears some resemblance to MCI. Due to the lack of consensus, we will briefly mention the two bases on which the diagnosis of MCD is based.

1. Neuropsychological evaluation

Neuropsychological assessment has become an indispensable tool in the diagnosis of dementias and also of Mild Cognitive Impairment. For the diagnosis of MCI , a comprehensive neuropsychological battery must be applied that allows us to evaluate the main cognitive domains (memory, language, visuospatial reasoning, executive functions, psychomotor capacity and processing speed).

The evaluation must show 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, the cut-off point is usually set at 2 negative standard deviations (in other words, performance is below 98% of the population in the patient’s age group and educational level). In the case of MCI, there is no consensus on the cut-off point, with authors setting it at 1 negative standard deviation (16th percentile) and others at 1.5 negative standard deviations (7th percentile).

From 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:

  • DCL single domain amnesic : Only memory is affected.
  • Multi-domain amnesic MCI : Memory and at least one other domain are affected.
  • Non-amnestic single domain DCL : Memory is preserved but some domain is affected.
  • Non-amnestic multi-domain DCL : Memory 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 some of the most widely used in research and clinical practice. Today, many longitudinal studies attempt to follow the evolution of different subtypes of MCI towards dementia. Thus, through neuropsychological assessment, a prognosis of the patient could be made for specific therapeutic actions.

There is currently no consensus and research has not yet provided a clear idea to confirm this fact, but even so, some studies have reported that single or multi-domain amnesic MCI would be the most likely to lead to Alzheimer’s dementia , while in the case of patients who evolve towards vascular dementia the neuropsychological profile could be much more varied, with or without memory impairment. This would be due to the fact that in this case the cognitive deterioration would be associated with lesions or microinjuries (cortical or subcortical) that could have different clinical consequences.

2. Evaluation 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 independence . If the activities of daily living are affected, this will make us suspect dementia (which would also 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. To be able to evaluate these aspects, I recommend below different tests and scales that are widely used in clinical and research settings:

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

EQ50: Evaluates the degree of 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 a cognitive type . MCI patients often report different types of cognitive complaints in the office, 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 indispensable, although it should also be taken into account that on many occasions patients suffer from anosognosia, that is, they are not aware of their deficits.

Furthermore, 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 the cause of other neurological or psychiatric problems (schizophrenia, bipolar disorder, etc.). An assessment of the degree of anxiety and mood is also necessary. If we were to adopt strict diagnostic criteria, the presence of depression or anxiety would rule out a diagnosis of MCI. However, some authors advocate for the coexistence of Mild Cognitive Impairment with this type of symptomatology and propose diagnostic categories in terms of possible MCI (when there is a factor that makes a diagnosis of MCI doubtful) and probable MCI (when there are no concomitant factors to MCI), similar to other disorders.

A Final Reflection

Today, 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 .

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

From a preventive approach, Mild Cognitive Impairment opens a therapeutic window to the treatment of the precipitated 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 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, 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.
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