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So what is mild cognitive impairment? This earliest form of cognitive dysfunction
associated with dementia. Well, in terms of a definition, mild cognitive impairment
or MCI is an early stage of memory loss or other cognitive abilities such as language
or visual-spatial perception in individuals who maintain the ability to independently
perform most of their activities of daily living. Most of these patients are working,
they are socially engaged, they have cognitive dysfunction but it has not impaired
their daily function. Mild cognitive impairment is an intermediate category in which
the severity of the cognitive change appears worse than expected for normal aging,
so it's not normal aging but does not meet the criteria for dementia. So when we
think about MCI, we divide it into 3 categories. There's amnestic MCI, non-amnestic
MCI, and multi-domain MCI. And this is important because the risk of developing
subsequent dementia varies for these 3 domains and the type of dementia the patients
may develop is different. So let's walk through the steps we take when evaluating
a patient with MCI and understanding their risk of subsequent dementia and type of
dementia. MCI is a disorder characterized by cognitive complaints. So we see that
cognitive complaints are out of proportion to age, the patients are not frankly
demented, there is non-impairment of their daily function. We can see cognitive
decline that fits those 4 A's; amnesia, agnosia, apraxia, and aphasias. Those are
the complaints we hear from patients. And the patient otherwise has essentially
normal function. When we're evaluating a patient for these complaints, our first
question is "Is the MCI impairing memory? Is there memory impairment?" In patients
that do have prominent memory impairment, short-term memory loss, difficulty
remembering dates or appointments or names or where their keys are or those sorts
of things, that fits a category of amnestic MCI. Here, memory is impaired only,
there are not other cognitive domains that are affected and in patients where
there is memory-only impairment, this is amnestic MCI, the single domain where
there are other cognitive impairments that is termed amnestic MCI multi-domain,
really describing the number of cognitive domains that are affected. In patients that do
not have memory impairment related to their MCI, that's non-amnestic MCI. And
again, we can categorize that as a single non-memory domain that's affected or
multi-domain. Categorizing those into non-amnestic MCI of single domain and
non-amnestic MCI multi-domain type. So how is this important? Why do we
categorize MCI in this way? Well, it can help us to break the risk of advanced
dementia and the type of dementia the patient may develop. For patients with
amnestic MCI with only memory impairments, single memory domain type, memory
is the main modality that is affected and those patients are at high risk of subsequent
development of Alzheimer's disease. We counsel those patients, we want to treat
those patients, and prevent progression to Alzheimer's disease. In patients with
amnestic MCI of the multi-domain type, memory is affected as well as other cognitive
dysfunction; apraxia, agnosia, aphasia, other cognitive dysfunction. And those
patients are at risk for Alzheimer's disease as well as vascular dementia, we need
to think about risk of advanced vascular dementia in those patients and modify risk
accordingly. In patients with the non-amnestic MCI either single or multi-domain,
we worry about progression to alternative forms of dementia; Frontotemporal
dementia, Lewy body dementia, Parkinson's disease dementia, as well as Alzheimer's
dementia and we look for other findings that may support those diagnoses.