Short Lesson On Dementias

Hey team,

Recently been reading and learning from Stahl's Essential Psychopharmacology 5th edition, which I excitingly received for Christmas. So far in my learning I've mostly focused on affective disorders like depression but I decided to dive into learning about dementia as it seems to be a popular topic that I am not too informed on. 

Dementia is a progressive neurologic/ psychiatric disorder that arrises in later life. Its signature symptoms are significant cognitive problems such as poor memory, poor problem solving, communication issues and often behavioral and psychotic symptoms which seem to be the hardest on the people surrounding the person with dementia. Of course, as we age in our later years things do slow down and we're not where we might of been in our youth, however dementia involves incredible and rapid slowing down of brain capacity/ function which is almost always debilitating and is by all means a disorder (cluster of symptoms that impair quality of life).

The first symptom to pop up in dementia is mild cognitive impairment (MCI), which is almost always a precursor to further worsening of condition and likely alzheimers disease (a type of dementia). The different types of dementia include Alzheimers disease (AD), which has signature accumulation of  beta amyloid plaques (specific type of abnormal proteins) along with hyperphosphorylated tau proteins which tangle up microtubules that typically serve a healthy role of transporting synaptic vesicles along with providing structure to neurons and more. As chains of amyloid beta buildup, they bind one another forming larger and larger units forming toxic plaques (that can trigger inflammation via immune response)  along with tangle build up in different areas of the brain, we see symptoms corresponding to the area of the brain that is no longer working up to code. For example, Alzheimers is very well known to effect memory, and this is a result of damage (from plaques and tangles) to the basal forebrain which connects to the PFC and hippocampus and encompass the neural networks responsible for memory. Early on in the disease, the damage is presynaptically and there is no problem with the parts post synoptically, hence why medication can still help resolve issues that are partially reserved from extensive damage elsewhere. However once damage occurs in pre and post synaptic areas of the brain, medication can't do much because there is nowhere for the drug to effect (it's all damaged). This is the result of a progressive illness, one that gets worse over time. 

Vascular dementia is a dementia characterized by damage to the vasculature of the brain. Just as people develop heart disease as a result of poorer and poorer circulation to their heart (via the coronary arteries), people develop vascular dementia as a result of poorer and poorer circulation to their brains. Like essentially all cells in the body, neurons need oxygen and nutrients supplied from the blood, so as this blood supply is cut off by thickened arteries, blood clots, endothelial plaques and other gunk, neurons die off or become greatly and irreversibly impaired, leading to dementia. vascular dementia occurs within several months of a stroke (clot gets logged in a cerebral vessel).

Lewy body dementia is a comparable to AD in my opinion as it also involves accumulation of toxic proteins. However instead of amyloid beta plaques of tau tangles, it involves accumulation of several units of a protein called alpha synuclein into toxic units deemed "lewy bodies" and "lewy neurites". These lewy bodies build up and lead to loss of brain tissue and cause symptoms of dementia, often alongside symptoms parkinsons disease (PD). Parkinsons disease also has hallmark lewy bodies that effect key dopamine neurons in the brain that are required for movement. These two disorders don't alway overlap, but there is a strong correlate of cognitive/ behavioral and movement symptoms given the presence of lewy bodies. In addition, buildup of toxic tau and beta amyloid proteins is not uncommon to in lewy body dementia / parkinsons disease dementia. The key point is that disorders are by nature, discrete categories of symptoms and clinical features/ markers, however individuals are not and hence don't always fit into the box of "this dementia" or "that dementia" with only specific proteins buildup and subsequent symptoms. Everyone is a unique case with unique features. 

This has been a brief overview on some different types of dementia, though not all inclusive (another major category is frontotemporal dementia, but thats explanatory from the name ). Hope you enjoy.