The neuropathological profile of mild cognitive impairment (MCI): a systematic review

Abstract

Whether mild cognitive impairment (MCI) has a distinct neuropathological profile that reflects an intermediate state between no cognitive impairment and dementia is not clear. Identifying which biological events occur at the earliest stage of progressive disease and which are secondary to the neuropathological process is important for understating pathological pathways and for targeted disease prevention. Many studies have now reported on the neurobiology of this intermediate stage. In this systematic review, we synthesize current evidence on the neuropathological profile of MCI. A total of 162 studies were identified with varied definition of MCI, settings ranging from population to specialist clinics and a wide range of objectives. From these studies, it is clear that MCI is neuropathologically complex and cannot be understood within a single framework. Pathological changes identified include plaque and tangle formation, vascular pathologies, neurochemical deficits, cellular injury, inflammation, oxidative stress, mitochondrial changes, changes in genomic activity, synaptic dysfunction, disturbed protein metabolism and disrupted metabolic homeostasis. Determining which factors primarily drive neurodegeneration and dementia and which are secondary features of disease progression still requires further research. Standardization of the definition of MCI and reporting of pathology would greatly assist in building an integrated picture of the clinical and neuropathological profile of MCI.

Perception of Biological Motion and Emotion in Mild Cognitive Impairment and Dementia

“…Stephan et al (2011) note that while the latter neural changes are most commonly found in memory-related regions, the hippocampus and the visual association cortex, some studies have also identified neuritic plaques in neocortical regions, and neurofibrillary tangles in the amygdalae. Social cognitive difficulties might therefore not only be a feature of dementia, but also be evident in MCI.…”

“…With respect to MCI, in a recent systematic review of 162 studies, Stephan et al (2011) noted that MCI is associated with numerous neuropathological changes such as neurochemical deficits, cellular injury, and oxidative stress, in addition to the histopathological hallmarks of AD. Stephan et al (2011) note that while the latter neural changes are most commonly found in memory-related regions, the hippocampus and the visual association cortex, some studies have also identified neuritic plaques in neocortical regions, and neurofibrillary tangles in the amygdalae.…”

Mild cognitive impairment: A comprehensive review

“…Available data indicate that individuals with MCI have neuropathologic changes in the brain that are intermediate between normal aging and early dementia [33,34]. These findings suggest a transitional state that is evolving to dementia [35].…”

The Role of Physical Fitness in the Neurocognitive Performance of Task Switching in Older Persons with Mild Cognitive Impairment

“…This condition might be associated with early neuropathological aging [5,6], possibly caused by AD, vascular dementia, traumatic brain injuries, metabolic dysregulation, or psychiatric diseases [7,8]. Although individuals with MCI do not yet fulfill the diagnostic criteria for AD/dementia, the high-risk rate of MCI developing to dementia within one year is estimated at about between 10 to 54% [4,[9][10][11][12][13], and that of developing to AD at about 10-15% per year, representing approximately a 10-fold increased risk of AD relative to individuals without memory impairments [4,12].…”