Dementia Overview

This woman would likely want to keep the picture and memory of her wedding day. See more pictures of healthy aging.
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What would you save if there was a­ chance your house might be destroyed? Whether it's a fire that starts in the middle of the night or a hurricane headed right for your hometown, what one thing would you grab as you ran out the door? Many of us would head straight for the family photo albums or to an item with sentimental value, such as grandpa's old six-string or a child's baby blanket. While electronics, clothing and other belongings could eventually be replaced, we know that some souvenirs are special. Our tendency to pick items such as these is an acknowledgment that the experiences in our past in large part determine who we are. We are committed to preserving the physical evidence of our memory.

But it's not so simple when your brain faces destruction or natural disaster. You can't just grab your favorite memories before it shuts down, because different kinds of memories are stored in different parts of the brain. Your episodic memory, or your depository of recent events and new information, is located in the temporal lobe and the prefrontal cortex. The storage space for general knowledge and facts, or semantic memory, is in the temporal lobe and the cortex. Procedural memory, or skills that have become secondhand, like typing or walking, is kept in the cerebellum. Lastly, working memory, which includes the phone number you need to make a call or your ability to recall how to drive to your child's school, is kept in the prefrontal cortex.


Now imagine that a disorder heads for your brain in the same way that a fire heads for a house. First, it might take your episodic memory, making it difficult to remember what you did yesterday, though you can recall perfectly what you did 50 years ago. It's challenging to keep track of the time or remember the names of all the grandchildren. It's harder to find just the right word when speaking, and this makes you irritable and embarrassed. You may snap at people who try to help you, but eventually you withdraw from everyone. You lose the ability to speak altogether, and after a few years, your brain is totally destroyed, so that you can't even take care of basic needs such as swallowing. Unlike when a fire threatens a home, there's not much you can do to save the parts of the brain you care about.

That's the process of dementia, a collection of symptoms caused by brain disorders. To learn more about these disorders and how they affect the brain, go to the next page.


Causes of Dementia: Alzheimer's Disease and Vascular Dementia

This man with Alzheimer's disease has forgotten how to get around his home.
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While it's been held that elephants never forget, humans aren't so lucky. As we age, the neurons in our brains shrink, and the chemicals that transmit messages between these neurons are emitted in lesser quantities. As a result, everyone will likely experience the momentary panic of not knowing where the car keys are or realizing that an important appointment was missed. This is known as age-associated memory impairment.

When this cognitive decline begins, many may start to worry that they have Alzheimer's or some other dementia. But dementia is a significant mental decline that persists over time, and while memory loss is the most distinctive symptom, several other parts of the brain are affected as well. Dementia isn't diagnosed until memory loss is present in conjunction with one or more of these limited brain functions:


  • Aphasia, or loss of the ability to produce or understand language
  • Apraxia, or the inability to make certain movements despite a healthy body
  • Agnosia, or problems recognizing familiar persons and objects, even though the senses are functioning
  • Executive dysfunction, or is an inability to plan, organize or reason

These symptoms were often thought to be the effects of mental illness and carried a shameful stigma. The effects can be off-putting and uncomfortable for those around the person exhibiting them. But these symptoms are caused by a variety of disorders plaguing the brain. The most common disorder that leads to dementia is Alzheimer's disease, which accounts for approximately 50 to 70 percent of all dementia diagnoses [source: Agronin].

As with other dementias, Alzheimer's disease causes the brain to degenerate as nerve cells are destroyed and the connections between them reduced. It strikes first in the hippocampus, where recent memories are stored, and progresses through the brain until it affects judgment, speech patterns and eventually, all forms of memory. Alzheimer's is distinguished by the presence of neurofibrillary tangles and amyloid plaques in the brain, but doctors aren't sure if these abnormalities are the cause or a byproduct of the disease. Doctors also aren't completely sure what causes Alzheimer's, though genetics likely plays a role, particularly abnormalities in a protein called apolipoprotein E. After receiving a diagnosis of Alzheimer's disease, the patient could continue to live for up to 10 years, though 3 to 5 years is more common [source: Beers]. You can read more about Alzheimer's in How Alzheimer's Disease Works.

About 30 percent of patients with Alzheimer's disease also have vascular dementia. Vascular dementia is the second most common cause of dementia, accounting for slightly more than 20 percent of dementia cases [source: Judd]. Vascular dementia is usually the result of damage done to the brain by a stroke, which occurs when a blood clot or a hemorrhage cuts off the brain's blood supply. Sometimes just one stroke is enough to cause damage, which is known as single-infarct dementia. More commonly, however, each small stroke isn't damaging, but the cumulative effect destroys so much brain tissue that memory, language and other cognitive functions are affected. This is known as multi-infarct dementia.

Not every stroke results in dementia, but when one does, the symptoms of dementia appear soon afterwards. Patients with vascular dementia may improve a bit between strokes, but worsen suddenly if another one occurs. Vascular dementia is similar to Alzheimer's in that memory loss and the ability to complete basic tasks are compromised, but factors such as judgment and personality aren't as affected. Vascular dementia also includes a few non-cognitive symptoms, including loss of bladder or bowel control and weakness or paralysis in the face or on one side of the body.

Unfortunately, we're not done with the causes of dementia yet, so turn the page to find out what other disorders can plague the brain.


Lewy Body Dementia, Frontotemporal Dementia and Other Causes of Dementia

Socially inappropriate behavior may be a sign of frontotemporal dementia.
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Lewy body dementia is named for the deposits of a protein called alpha-synuclein that appear in the brain. Lewy bodies are also present in Parkinson's disease, but with Parkinson's disease, the bodies are present in only one part of the brain, whereas they're present throughout the brain in this type of dementia. Lewy body dementia is very similar to Alzheimer's, except, as you might guess, some of the symptoms of Parkinson's disease are also present. This means that in addition to memory loss, the patient may exhibit tremors, a shuffling gait and poor balance. People with this type of dementia also may have intense visual hallucinations. Lewy body dementia accounts for about 5 to 15 percent of dementia cases [source: Rabins].

Frontotemporal dementia makes up approximately 5 percent of dementia cases [source: Rabins]. This type of dementia is caused by damage to neurons in the frontal and temporal lobes of the brain. Neurofibrillary tangles of the tau protein are present, as they are in Alzheimer's disease, but the amyloid plaques that also characterize Alzheimer's are not. Because the frontal and temporal lobes control judgment and recognize social norms, the first symptoms may involve the person engaging in bizarre and socially inappropriate behavior. For example, if a person starts recklessly spending or gambling, making inappropriate comments or crude actions in public, or shoplifting, then it may be a sign of frontotemporal dementia. One type of frontotemporal dementia is Pick's disease, which is distinguished by apathy, carelessness and poor personal hygiene.


In Huntington's disease, the dementia is accompanied by changes in personality and uncontrollable movements. These movements, which include jerking and fidgeting, may be mild for several years, but as the disease progresses, the movements spread to the entire body. The brain can't control coordination anymore. Huntington's is caused by an abnormal gene, so the children of people with Huntington's disease have a 50 percent chance of inheriting the gene [source: Judd]. People can live with the disease for 15 to 20 years after diagnosis [sources: Rabins, Judd].

Creutzfeldt-Jakob disease affects one in every million people each year [source: Rabins]. Doctors have traced this dementia to a prion infection, prion being an abnormal protein. In some cases this abnormality may be genetic, while it may also appear due to infected tissue used in organ or tissue transplants. In some cases, doctors just don't know why it occurs. This dementia accelerates particularly rapidly, with death usually occurring within just a few months of diagnosis. A variation of Creutzfeldt-Jakob disease occurs after eating beef contaminated with mad cow disease.

While there are many other rarer forms of dementia, we'll mention just two more. Some dementias may occur as the result of disease, one example being HIV-associated dementia. This dementia includes slowed thinking, difficulty concentrating, muscle weakness and difficulty moving. Other dementias may occur as the result of a brain trauma; for example, dementia pugilistica affects boxers who receive repeated blows to the head.

How do doctors determine which type of dementia, if any, the patient is suffering from? We'll take a look at the diagnosing process on the next page.


Dementia Diagnosis

A doctor can help you determine if that string around your finger is the onset of dementia.
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Dementia usually begins slowly and worsens over time, so it may be difficult to pick up on the earliest symptoms. As we mentioned earlier, some memory loss is to be expected as a person ages, so diagnosing dementia requires that doctors distinguish between normal age-related forgetfulness, mild cognitive impairment (an intermediate stage of cognitive decline not quite severe enough to be classified as dementia) and dementia.

To think about the difference between these stages, consider the task of remembering that the garbage is picked up on Tuesdays, and all trash and recycling needs to be put on the curb by then. A person exhibiting memory impairment typical of advancing age may occasionally forget to do this. A person exhibiting mild cognitive impairment may not only forget to take out the trash, but also may forget that a doctor's appointment and a grandchild's birthday are on Tuesday. A person with dementia may not even realize that it is Tuesday.


Another distinction between these levels of memory decline is that those with more severe cases usually don't realize there's a problem. If you're aware that you're forgetting things, that's something of a good sign. In the case of dementia, then, it may take someone close to the person exhibiting symptoms to get him or her to the doctor for an official diagnosis.

With so many types of dementia, a proper diagnosis may seem like a game of elimination. Doctors begin evaluating patients from the moment they walk in the door, looking for clues from the patients' appearance, behavior, speech, mood, motor skills and thought processes. The appointment usually starts with an interview; it's especially helpful if someone who has witnessed the cognitive decline is present to provide examples. Understanding a patient's history will provide some context to the symptoms; for example, if the patient has trouble reading and comprehending but is a former English teacher, that's particularly telling, as is a person who was once meticulous in appearance refusing to take a shower or change clothes.

Doctors will also, of course, try to determine exactly what parts of the brain are affected. One of the most common ways to do so is by administering brief cognitive tests. One example is the Mini-Mental State Examination (MMSE). In conducting the MMSE, the doctor will ask the patient some basic questions and to perform several mental tasks, such as counting backward or repeating words in order. To score the MMSE, the doctor assigns points for correct answers and adjusts for education level. Scores in certain ranges on a pre-set scale indicate dementia.

Doctors may administer another quick exam known as the clock drawing test. The patient is asked to draw a clock so that it says a certain time. Although the task might sound easy, it draws upon many areas of the brain to complete correctly. Based on how the final drawing looks, doctors may be able to sense exactly which areas are compromised. Doctors will also use brain imaging scans to look for signs of a stroke or a brain tumor; in the case of vascular dementia, the lesions left by the stroke will be seen on the brain.

Throughout the exam, doctors will be looking for conditions that affect the mind that may be reversible. Memory loss can occur as a side effect of some medications, and it's also associated with depression and medical conditions such as brain tumors and vitamin deficiencies. In these cases, correcting the cause will usually address the symptoms of dementia.

Do doctors have any treatment options when irreversible dementia is diagnosed? Find out on the next page.


Dementia Treatment and Prevention

The task of caring for a person with dementia usually falls to a close relative.
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The progression of some types of dementia can be slowed with drugs, but dementia usually can't be reversed or completely stopped. Currently, the FDA has approved four drugs for persons with some forms of mild to moderate dementia; these drugs are known as cholinesterase inhibitors and consist of the drugs donepezil, galantamine, rivastigmine and tacrine.

These drugs work by suppressing cholinesterase, an enzyme which leads to the breakdown of acetylcholine. Acetylcholine helps transmit messages between neurons, an activity that is vital to learning new things and retaining memories. Memantine, a drug that works differently, was ecently approved by the FDA. Rather than inhibiting cholinesterase, memantine inhibits glutamate, which can cause neuron death when its receptors are overstimulated [source: Whitehouse].


Cholinesterase inhibitors aren't generally used, however, in treating vascular dementia. There is no drug treatment for vascular dementia, though some symptoms can be controlled. The progression of the disease can usually be slowed by treating some of the underlying risk factors for stroke. This means the patient may take medications to control high blood pressure or diabetes, as well as anticoagulants such as aspirin or warfarin. Lewy body dementia is usually treated with cholinesterase inhibitors in combination with Parkinson's medications and antipsychotic medications.

Since little can be done with drugs, the initial diagnosis of dementia may feel like a death sentence, one that's particularly slow and painful for the person involved and everyone around him or her. But it doesn't have to be. Patients with dementia should be encouraged to live normal lives and find ways to feel useful. However, because of the memory loss, these activities may have to be slightly amended. In the book "When a Family Member Has Dementia," author Susan McCurry describes a woman who realized that her mother didn't like sitting around being taken care of. Since her mother used to iron for hours, the woman provided her mother with an old iron with the cord cut off, so that the woman could "iron" without hurting herself [source: McCurry].

This example shows what a delicate dance caregiving for someone with dementia can be. In the early stages of dementia, the patient may be able to stay at home in familiar surroundings, with some safety modifications. As the dementia progresses, however, things may become more challenging for the caregiver. No two people with dementia are exactly alike, so there's no one book with all the answers. The patient may become more unpredictable and challenging, changing from one day to the next so that what worked yesterday won't work tomorrow. It may be a challenge for caregivers to remain resilient rather than resentful.

The physical, emotional and financial toll that caregiving can take is referred to as the caregiver burden. In some cases, the physical toll can be very real; a study found that the risk of death for a woman whose husband has dementia increases 28 percent in the first year after diagnosis, while it increases 22 percent for a husband with a diagnosed spouse [source: Britt]. About 90 percent of caregivers are wives, daughters and daughters-in-law, with spouses alone making up about half of all caregivers [source: Agronin]. It's important that these caregivers ask for help when needed and take care of themselves before trying to take care of others. One study showed that when people with dementia are cared for by people who feel stressed or burdened, then the patients exhibit more behavioral problems [source: Nagourney]. At some point, a nursing home may have to be considered.

Because there is no cure for dementia, the best thing to do is to try to prevent or delay it. While no one can stop the tides of aging or change the course of genetics, many of the risk factors are modifiable, including quitting smoking, maintaining a healthy weight and lowering cholesterol and blood pressure. Additionally, keeping the mind in fighting shape with mental challenges such as crosswords may also have an effect. To learn more tips, see the article "Can you delay dementia?" Additionally, there are several more articles and links for you to read on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Agronin, Marc E. "Dementia: A Practical Guide." Lippincott Williams & Wilkins. 2004.
  • Beers, Mark H., ed. "The Merck Manual of Medical Information. Second Home Edition." Merck Research Laboratories. 2003.
  • Britt, Robert Roy. "Risk of Death Can Soar When Spouse is Sick." Live Science. Feb. 15, 2006. (Sept. 3, 2008)
  • Judd, Sandra J., ed. "Brain Disorders Sourcebook, Second Edition." Health Reference Series. Omnigraphics. 2005.
  • McCurry, Susan M. "When a Family Member Has Dementia." Praeger. 2006.
  • Nagourney, Eric. "Troubled Helpers May Set Back Dementia Patients." New York Times. May 30, 2006. (Sept. 3, 2008)
  • Rabins, Peter V. "The Johns Hopkins White Papers: Memory." Johns Hopkins Medicine. 2007.
  • Rose, Steven. "The Future of the Brain: The Promise and Perils of Tomorrow's Neuroscience." Oxford University Press. 2005.
  • ¬≠Whitehouse, Peter J. and Daniel George. "The Myth of Alzheimer's." St. Martin's Press. 2008.