It also appears that patients with single-domain cognitive decline have less progression to dementia, followed by those who are multi-domain amnestic or non-amnestic, causing the use of electrophysiology to deteriorate.29,47,48 As MCI atrophy sets in and advances to dementia, positive hypometabolic FDG PET scans are helpful indicators. Brain metabolism then creates a cognitive tipping point that is indicative of dementia or AD.31 Our subjects, although incompletely characterized, had MCI by a series of neuropsychological measures. Current characterizations suggest that MCI needs greater stratification considering the many patients who already have features of dementia. Most patients with hypometabolic FDG PET scans do have early dementia, even if their current symptoms resemble only MCI.15
MCI is heterogeneous, with electrophysiological decline, memory and attention failure, multiple domains of cognitive deterioration with and without losses of hippocampal volume, and cortical atrophy steering patients from MCI into dementia. There are numerous clinical variants of MCI that are antecedents to dementia, where progression is altered dependent on different cognitive phenotypes (e.g., individuals who emphasize working memory vs. auditory memory, abstract IQ vs. emotional IQ).49 A similar progression occurs in heart disease based on risk factors (e.g., cholesterol [HDL/LDL], electrophysiological dysfunction, valve and coronary artery disease, hormonal and vascular factors) which may occur in any combination dependent on genetic predispositions or environmental factors. Although no one system is perfectly predictive, an in-office model has been implemented, where electrophysiological decline, particularly, delays of processing speeds when moving from thought to action (e.g., TOVA and P300) seem to be validating PET hypometabolism.
CONCLUDING REMARKS
A significant rise in AD is expected with a continuing demographic shift to a more elderly population. AD is predicted to increase from 4.5 million in 2000 to 13.2 million in 2050 as Baby Boomers age and life expectancy increases.50 If primary care practices implement proper MCI checklists, P300, and TOVA testing done within an hour’s time, physicians will be able to diagnose early MCI antecedents.51-55 Sustaining our intellectual faculties with age may be possible with early diagnosis and treatment. These practices may also have economic advantages as a patient can receive the MCI domain assessment, electrophysiological markers and brain testing at a cost-effective price of $500, while PET scans still remain at an expensive price of $3000-6000 per patient. This proposal may aid in lessening the United States’ $200 billion dementia burden by identifying high-risk patients through multiple domains (e.g., P300 low voltage and slow speed and temporal differences between thought and action).56 These clinical implications may potentially impact the epidemic of dementia at a primary care level, similar to the ways an electrocardiography (ECG), cholesterol testing (HDL/LDL), and the echocardiogram lessened the cardiac burden worldwide.
Future work confirming this clinically relevant research may indeed provide sufficient evidence to suggest the incorporation of impaired electrophysiological and neuropsychological determinants as an efficient means for identifying and validating reduced brain metabolism and cognitive impairment in MCI care settings leading to an early hallmark identifier of patient progression to dementia. We must await further studies before any real interpretation can be garnished from this important preliminary study.
ACKNOWLEDGEMENTS
The following individuals researched relevant literature, conducted statistical analysis, and/or assisted with manuscript revisions: Kenneth R. Perrine, Ph.D. (Weill Cornell Medical College), Vivian Lau, Mona Li, Raquel Lohmann, Pooja Reddy, Pavan Reddy, and Swetha Yeldandi.
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