Alzheimer's Disease Alzheimer's Disease is the most common form of dementia accounting for 50% of all cases. The onset of the disease is brought about by gradual degeneration in the neurons (nerve cells) on the top layer of the brain. This in turn causes a breakdown in the signals brain cells send to each other.
Click the icon below for a visual look at neuron degeneration common with Alzheimer's disease.
We do not yet know what causes Alzheimer's disease, although there are many promising leads into such potential causes as genetic, environmental and/or viral factors. Research is also exploring treatments for the symptoms.
Dementia is classified into cortical (outer brain) or subcortical (inner brain) depending on the area of the brain affected
Cortical Dementia Cortical dementia causes problems in memory, thinking and language. Alzheimer's Disease is a disorder that causes cortical dementia.
Subcortical Dementia Subcortical dementia affects parts of the brain below the cortex and is characterized by slowing, difficulty in retrieving information from memory, and altered mood. Parkinson's disease and multiple sclerosis are examples of diseases that can result in a subcortical dementia. Language is usually normal, although speech is dysfunctional and the motor system may result in stooped or extended posture, increased muscle tone and tremors. Memory problems are due to a difficulty in retrieving information that is in fact learned. The person's mood may be either apathetic or depressed, and insight into the condition is usually present.
Click the icon below to view a video comparing Alzheimer's disease and Parkinson's disease.
Comparison between Alzheimer's and Parkinson's disease
Transcript Dementia is not a normal process. It is a disease process. It happens to only 7.8 percent of the population who are 65 and over. What is very dramatic is that after age 85, this statistic jumps to 35-38 percent of the population.
50 percent of dementias are Alzheimer-type dementias, and the rest are a variety of different types. For example, 20-30 percent could be various types of vascular diseases, like multiple strokes. Another 10 percent could be multiple different diseases like Parkinson's disease, Pick's disease, Luey Body disease, and Huntington disease. "Dementia" could mean a lot of different things.
Now, because 50 percent is a lot, let me give you a quick difference between a cortical type of dementia, such as Alzheimer's which affects association areas of the brain, versus one that affects other regions, like Parkinson's disease which affects the lower parts of the brain. The major difference between the two is that people with the Parkinson's types of diseases are very, very slow - slow at processing information, and slow at initiating activity. Alzheimer's patients may look good physically. They can walk very well because the motor sensory areas are well preserved until very late in the disease process. So the two patients will look very, very different because different parts of the brain are affected.
Not only are different parts of the brain affected, but also different cognitive functions. If you ask an Alzheimer's patient and a Parkinson's patient to remember three things, after five minutes, both of them will be able to recall the information. But there is an important difference. The Parkinson's patient was probably able to register this information because when offered a series of choices, they are often able to give you the right one. So the information is in there, they are just very slow at recovering it. With Alzheimer's disease, if you ask the patient after five minutes if they remember those three words, they will probably respond, "Three words? How about a thousand words, and how old are you young man asking me do I remember three words? I remember millions of words." They go on and on, and have no clue about being asked to remember three words. If you gave them a whole series of cues or choices, they would never respond with the correct answer.
The point is different diseases affect the brain in different ways. Different brain dysfunctions will affect cognitive functions in different ways. If you understand that, you are able to develop strategies to minimize and compensate for those problems.