Neuropsychological methods in mild cognitive impairment

Mild cognitive impairment (MCI) is a concept that was introduced by Flicker et al 1 and the Mayo Clinic group 2,3 to fill the gap between cognitive changes associated with normal aging and those associated with dementia. The concept of MCI draws attention to cognitive disturbances that occur before the clinical diagnosis of demen-tia. The cognitive changes, measured by neuropsycho-logical test scores, indicate deviation from normal aging and do not involve loss of autonomy. Nevertheless, these MCI criteria are not fully specified or generally agreed upon. As a consequence, studies of MCI conducted by different research groups have divergent results (eg, the number of patients with MCI who develop frank demen-tia of the Alzheimer's type in follow-up studies). In 2001, an international group of experts suggested the subdivision of MCI into three subcategories 6 : • Amnestic MCI, characterized by memory complaint, preservation of activities of daily living, and objective and isolated memory impairment (compared with age and education norms). • Multiple cognitive domain MCI, characterized by multiple areas of cognitive impairment (without associated memory deficit) not sufficiently severe to constitute dementia. • Single cognitive domain (other than memory) MCI, characterized by a deficit of a specific domain as apha-sia or executive dysfunction reflecting prodromal primary progressive aphasia or frontotemporal dementia. In order to limit the heterogeneity of the population concerned by MCI, it will soon be possible to identify the underlying pathological disorders before the affected patients meet the criteria of dementia (Table I), using specific neuropsychological assessments and, in some cases, neuroimaging. This is the case, for example, for the following: • Frontotemporal degeneration can be identified well before the stage of clinical dementia in the presence of apathy and/or behavioral disinhibition coupled with a progressive disturbance in executive functions. • Primary progressive aphasia can be identified early on the basis of anomia with speech apraxia and phonetic disintegration associated with limited atrophy of left perisylvian region. The concept of mild cognitive impairment (MCI) was introduced to fill the gap between cogni-tive changes associated with normal aging and those associated with dementia. Such cognitive changes indicate a deviation from normal aging, but are insufficient to evoke dementia and do not indicate loss of autonomy. MCI is thus a transitional state before dementia. MCI covers a range of disorders and raises the question of population heterogeneity; three MCI subcategories have been defined to reduce this heterogeneity. Recognizing MCI is …