Mild cognitive impairment

Within the cognitive functioning continuum from normal ageing to dementia three broad states can be distinguished: normal functioning for age, clear-cut impairment meeting diagnostic criteria for dementia, and mild cognitive impairment (MCI), which falls below normal but short of dementia in severity (Fig. 8.5.1.1.1). There is active debate over what MCI is, how to define and classify this state, and where to set its borders on the described continuum. Some definitions depict MCI as the tail-end of normal cognitive ageing whereas in other definitions MCI embodies the early clinical manifestation of Alzheimer Disease (AD) and other dementias. In 2003, the key elements of different MCI definitions were integrated into a consensus diagnostic and classification framework, thus establishing some common ground in a field that is still evolving. MCI has also been positioned as a potentially important target for early treatment interventions to delay progression to dementia. Nosologically, MCI is not currently included as a diagnostic entity in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) and the International Classification of Diseases, 10th revision. The diagnostic categories of Mild Neurocognitive Disorder (DSM-IV-TR) and Mild Cognitive Disorder (ICD-10) are similar to MCI because they require the presence of cognitive impairment but these categories can only be assigned if a specific neurological or general medical condition can be identified to account for the cognitive symptoms. Much of the current condition of MCI does not fit as it has no aetiologic specification. Nevertheless, MCI is increasingly a presenting condition in primary and specialized settings of care. Medical practice guidelines have recognized MCI as a risk state for dementia and recommend careful clinical evaluation and monitoring of individuals with this diagnosis.