Dementia, Animation

(USMLE topics, neurology) Causes (types) of progressive dementias: Alzheimer’s disease, vascular dementia, Lewy body dementia and frontotemporal dementia. Also includes less common causes and reversible dementias.

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Voice by: Ashley Fleming

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Dementia is a general term for a DECLINE in memory and other cognitive abilities. It is NOT a disease on its own but rather a group of symptoms caused by an UNDERLYING condition. Most dementias WORSEN over time and are irreversible, but some types can be reversed with treatment. While the incidence of dementia increases with age, it is NOT a normal part of aging.
The most common cause of dementia, responsible for more than 50% of all cases, is Alzheimer’s disease. In this condition, abnormal toxic deposits of proteins, known as PLAQUES and TANGLES, cause the death of neurons. The damage initially takes place in the hippocampus, the part of the brain that is essential in forming memories. Short-term memory loss is usually one of the earliest symptoms. Most patients show first signs of mental decline after the age of 65, but for a small subset of cases, the disease runs in FAMILIES and strikes EARLIER in life.
Second to Alzheimer’s is VASCULAR dementia, a condition in which POOR blood supply to the brain IMPAIRES normal function of neurons. Symptoms may appear SUDDENLY after a stroke; in a STEP-wise fashion after a series of mini-strokes; or GRADUALLY as a result of age-related vascular wear-and-tear, or any conditions that DAMAGE or NARROW blood vessels over time, such as high blood pressure, high cholesterol, and diabetes. Incidence of vascular dementia increases with age and cardiovascular risk factors.
In the third place is LEWY BODY dementia. Lewy bodies refer to abnormal protein clumps typically found in neurons of these patients. The earliest, and also most PROMINENT feature of this type, is a SLEEP BEHAVIOR disorder in which patients physically, sometimes violently, ACT OUT their dreams. Other early symptoms may include visual hallucinations. Memory loss may NOT be noticeable until LATER stages. Dementia caused by advanced Parkinson's disease belongs to this group.
FRONTOTEMPORAL dementia is another common type of progressive dementia. This group is characterized by neuronal cell death in the FRONTAL and TEMPORAL lobes of the brain - the areas associated with behaviors and language. Common signs and symptoms include changes in behaviors, apathy, blunting of emotions, and language deficits. A significant portion of this type has a STRONG GENETIC component and tends to occur EARLY, in the MIDDLE-AGE population.
More than one type of the above-mentioned dementias may CO-exist in ONE patient.
Less common causes of dementia include Huntington’s disease, Creutzfeldt-Jakob disease, and traumatic brain injuries.
Dementia may also develop as a result of endocrine or metabolic problems, such as thyroid disorders and vitamin deficiencies; or infections such as Lyme disease and neurosyphilis. For these types, symptoms can be reversed with treatment of the underlying condition.