[Mild Cognitive Impairment or pre-demential Alzheimer's disease?]

Abstract

The concept of Mild Cognitive Impairment (MCI) is proposed to define a state of cognition where the deficiency is greater than expected for a subject's age and socio-cultural background, but not sufficiently severe to satisfy the criteria of nosographic classifications of dementia. The concept of MCI cannot provide an etiological diagnosis but can be useful for recognizing and following patients with mild impairment. It raises the question of early diagnosis of Alzheimer's disease. The risk of progression to dementia is greater in patients with MCI, particularly those whose memory is the only domain involved - "amnesic MCI". Patients with amnesic MCI can be distinguished from those with MCI with multiple domains slightly impaired or non-amnesic MCI where only one domain (language, visual-spatial.) other than memory is involved. Depending on the type of deficiency, amnesic MCI may progress to different types of disease states. At the early stage of pure memory impairment, a distinction should be made between Alzheimer-related memory disorders and those related to another neurological conditions or the brain aging process. The question is whether the diagnosis of Alzheimer's disease can be made at this stage. Biological markers and brain imaging provide useful information, but these diagnostic tools remain imprecise and have not been validated for routine use. The process of diagnosis must therefore focus on an analysis of the cognitive impairment. The predementia phase of Alzheimer's disease is characterized by a progressive "hippocampal" decline in memory, sometimes associated with impaired execution. A careful analysis of the cognitive impairment helps identify "hippocampal amnesia syndrome" suggestive of the diagnosis of Alzheimer's disease.