Today we are on to Part 3 of our 15-part journey on Dementia. As you can see in the headline chart, there are many different diseases/disorders that fall under the category of Dementias, right? So, would it surprise you to find out that there are over 50 different diseases, disorders, and conditions that are considered as being under the umbrella of Dementia? Yep!
One of the challenges in classification--much like many other medical and life items--is how classification is laid out. In the above example, classification rests on whether or not the condition is progressive (gets worse overtime), non-progressive (relatively constant state), or the effects are able to be reversed by current medical, psychological, and/or technological means. Another way to categorize dementia is to examine the affected area of the brain, whether it is a primary or derivative condition, and then whether it may be reversible or curable.
Cortical and Subcortical Dementia
Cortical dementia refers to those conditions that affect the cortex--the outer layer of the brain--or what we call the grey matter. The parts of the brain that provide for much of our normal functioning and interaction with others is in this area, including:
Information processing
Language and memory processes
Reasoning and Problem-solving
Subcortical dementia affects the area of the brain beneath the cortex--the white matter. When dementia affects this area of the brain, it is most often manifested in outward behaviors, including:
Motivation, emotions, attention span
Depression, apathy, irritability
This category, while appearing rather clean-cut, is somewhat misleading. Perhaps a more accurate description would be to indicate cortical or subcortical as being the primary area. This is because a disease or condition that begins in one region can--and often does--cause damage to the other region as a secondary attack. Once the condition progresses into both regions, symptoms may eventually coincide...which can make diagnosis more difficult if the patient is not evaluated until this cross-over happens.
Primary and Secondary Dementia
This is, perhaps, the simplest area within which to make distinctions. Simply put, primary refers to the dementia condition as being the first--or causative--factor in the observed symptoms and behaviors. Secondary refers to the instance where dementia develops as a result of another disease, disorder, or condition. In the preceding illustration, one may observe examples of primary dementia, while comparing them to conditions that may bring on dementia as a secondary condition.
Reversible vs. Irreversible Dementia
Not all forms of dementia are a foregone degenerative death sentence. In most cases, this applies to secondary dementia--those caused by other conditions, including medication, alcohol, malnutrition, trauma, depression, or other catalysts that restrict oxygen flow to the brain. Hey, don't worry...that one weekend when you got so drunk that you cannot remember anything about it is not going to cause you to die from a progressive dementia (well, probably not, anyway) but if you make it a habit, become an alcoholic, or abuse substances on a regular/continuing basis, the likelihood of a secondary dementia affecting you increases...exponentially with time. You've heard that whole moderation in all things talk before, right? Well, you should listen...seriously.
Irreversible dementia has four fundamental characteristics the define it:
Progressive
Incurable
Irreversible
Causes permanent brain damage
Irreversible dementia is most likely to occur from primary dementia; however, it is possible for the result of a secondary dementia to also transform into an irreversible state. Cases of irreversible dementia--usually primary--include Alzheimer's, vascular dementia, Parkinson's, Huntington's, Creutzfeldt-Jakob Disease, AIDS, and Down's Syndrome, to name a few.
In Closing...
And so one may see that, even with a categorization system in place, no clear, inviolate lines separating different conditions and symptoms exist. This is a challenge for the physician, especially when seeing the patient after he or she has advanced beyond the initial stage of a disease. Dementia is being researched globally--it is considered the next great global health crisis as life expectancy grows longer and aging populations comprise half or more of the total population of the planet.
Tomorrow will be Part 4 of this series: Exploring Alzheimer's Disease--the most common dementia.
Reference:
Earlstein, F. (2016). Dementia Facts & Information. NRB Publishing: Nevada.