Neurological Disorders

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Mild cognitive impairment is a relatively new diagnosis that has been around for ten years.  Alzheimer’s disease and other progressive degenerative diseases tend to develop long before they present clinically.  Some early signs might have differential diagnostic value.  Hippocampal atrophy and memory decline are usually prominent early on with Alzheimer’s disease. According to the DSM an Alzheimers disease diagnosis requires (1) memory impairment, (2) impairments in other areas, (3) functional impairment and (4) a progressive onset. 

Mild cognitive impairment (MCI) means mildly abnormal cognitive decline that falls short of dementia.  MCI requires memory complaint, impaired memory on testing, normal general intellectual functioning and activities of daily living.  Points of controversy inclue the subjectiveness of some memory complaints.  There is also controversy about what constitutes a “normal” activity of daily living.  Dr. Farias (2006) found that MCI is associated with deficits in everyday functioning. 

Now we have revised subtypes named amnestic (memory plus or minus another domain) and non-amnestic (executive plus or minus language). 

The crux of MCI is prognosis.  There is a lot of research on the rate of conversion from MCI to Alzheimer’s disease.  Fifteen percent a year convert over from MCI to Alzheimer’s in a memory disorders center.  Seven and a half in a community sample and one or two percent of normal controls convert to Alzheimer’s disease.  One of the reasons for this high rate of conversion in the clinical population is that they are more functionally impaired.  Clinic vs. community effects on conversion are not significant after controlling for functional impairment. 

Highest conversion rate to AD is the amnestic group.  Having additional deficits increases the likelihood of developing AD.  Other predictors include neuropsychologialc test scores and hippocampal volume, white matter hyperintensity volume.

Eight to twenty five percent of those diagnosed with MCI improve or revert to normal.  Rate of improvement is much less in clinical samples.  Not all decliners are MCI.  Intervening after MCI is diagnosed may be too late.  MCI can be caused by AD, other degenerative diseases, static brain injury, developmental disorders, experience or other conditions. 

In conclusion, mild MCI may be closer to normal than it is to severe MCI.

MCI diagnosis facilitates communication by providing a convenient label for a complex set of clinical findings.  It is also useful in the identification of progressive dementing disease as early as possible is important.  It can also provide standardization for studies.  The clinical implications are that patients should be characterized along multiple dimensions and careful clinical evaluations can identify at risk patients early in the course.

Mild Cognitive Impairment