Mild Cognitive Impairment (MCI): causes and symptoms

For 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

On a subjective level, it is accompanied by complaints about loss of cognitive abilities. In addition, for it to be Mild Cognitive Impairment, these cognitive deficits should not interfere with independence of the patient and must not be related to other pathologies such as psychiatric and neurological disorders, addictions, etc. Therefore, the main difference compared to a patient with dementia is the maintenance of independence in the 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. Doing a search in Pubmed we can see that in 1990 we already found manuscripts that speak of Mild Cognitive Impairment. Initially,

MCI was only seen as a diagnosis that led to Alzheimer's disease; however, in 2003 a team of experts (including Petersen himself) proposed to classify 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 first proposed that different types of Mild Cognitive Impairment can lead to different types of dementia.

Today, MCI is viewed as a state that can lead to some type of dementia or, simply, 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 no total consensus about how to identify it. Even so, the first steps have been taken to generate an agreement and in the DSM-V manual we can already find a diagnosis of "Mild Neurocogntive Disorder", which has a certain resemblance to MCI. Due to the lack of consensus, we are going to briefly cite 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 MCI an exhaustive neuropsychological battery must be applied that allows us to evaluate the main cognitive domains (memory, language, visuospatial reasoning, executive functions, psychomotor ability and processing speed).

Through the evaluation, it must be demonstrated that, at least, there is one 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 the cut-off point (or whatever is the same, that the performance is below 98% of the population of the age group and educational level of the patient). In the case of MCI, there is no consensus for the cut-off point, with authors who establish it at 1 negative standard deviation (16th percentile) and others by 1.5 negative standard deviations (16th percentile) 7).

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:

• Single domain amnesic MCI: Only memory is affected.

• Multi-domain amnesic MCI: Memory is affected and, at least, one more domain.

• Non-amnesic single domain MCI: The memory is preserved but there is some domain that is affected.

• Non-amnesic multi-domain MCI: 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 they are one of the most used in research and clinics. Today, many longitudinal studies attempt to follow the evolution of the different subtypes of MCI towards dementia. In this way, through neuropsychological evaluation, a prognosis of the patient could be made to carry out specific therapeutic actions.

There is currently no consensus and research has not yet offered a clear idea to confirm this fact, but even so, some studies have reported that single-domain or multi-domain amnesic-type MCI would be the one 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, 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 injuries or micro-injuries (cortical or subcortical) that could lead to different clinical consequences.

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

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

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

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 cognitive complaints. Patients with MCI usually refer different types of cognitive complaints in the consultation, which are not only related to memory, but to anomia (difficulty in finding the name of things), disorientation, problems with concentration, etc. Considering these complaints as part of the diagnosis is essential, 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.

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

4. Rule out underlying neurological or psychiatric problems

Finally, when reviewing the medical 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 carry out an evaluation of the degree of anxiety and the mood. If we 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 key of possible MCI (when there are factors that make the diagnosis of MCI doubtful) and probable MCI (when there are no factors concomitant to MCI), similarly to how it is performed in others disorders.

A final thought

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

This has been coupled with a decline in the birth rate that has resulted in an older population. Dementias have been an unappealable imperative for many people who have seen that as they aged 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 for us by treatment of the precipitous course to dementia using pharmacological approaches and not pharmacological. 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 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, 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.