Mild Cognitive Impairment: Evolution of the Clinical Diagnosis

Evolution Of Criteria For Mild Cognitive Impairment

It would be simplistic to assume MCI as a transitional state between normal ageing and dementia. However there appears some overlap between both MCI with normal ageing and MCI with dementia. The original 1999 Mayo criteria assumed MCI to be a precursor state for Alzheimer’s Dementia and emphasized on episodic memory impairment. These were (Petersen et al., 1999):

• 1.

  Memory complaint, preferably corroborated by informant

• 2.

  Memory impairment documented according to appropriate reference values

• 3.

  Essentially normal performance in non-memory cognitive domains

• 4.

  Generally reserved activities of daily living

• 5.

  Absence of dementia

However, since not all MCI progressed to Alzheimer’s dementia, a broader conceptualization of the diagnostic criteria were required. A neuropsychological assessment of a subset of patients with MCI revealed subtle deficits in other cognitive domains like executive functioning, language and visuo-spatial skills (Molano et al., 2010). These patients were at higher risk of converting to Lewy body dementia or fronto-temporal dementia. With the expanding literature on MCI suggesting that it is a heterogenous group and not just a precursor of Alzheimer’s dementia, the revised Mayo criteria were published in 2003 (Petersen, 2004) which expanded to include cognitive deficits in domains other than memory. They divided MCI into amnestic MCI (aMCI) and Non-amnestic MCI (naMCI) based on the type of cognitive deficits present.