Alzheimer's isn't the only explanation for dementia. Other causes include vascular dementia caused by strokes, Lewy body disease, Parkinson's disease, frontotemporal dementia, and other disorders. Proper diagnosis can influence treatment.
Is it Alzheimer's or some other form of dementia?
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Dementia isn't a disease; it's a symptom. The term refers to a loss of brain function, as evidenced by memory loss, impaired judgment, behavior changes, learning difficulties, and communication problems. One in seven Americans over age 70 has some form of dementia, according to 2007 data from the nationally representative Health and Retirement Study -- but not all dementia is alike. It's caused by a variety of illnesses, some of which can be treated.
The number-one thing to do when someone exhibits memory loss or other mental or behavioral changes is to make sure the person gets a thorough medical evaluation.
Alzheimer's disease accounts for most cases of dementia -- 69.9 percent. In fact, the older the person, the more likely that the problem is due to Alzheimer's disease: Alzheimer's accounts for almost 80 percent of dementia in people age 90 or older, compared with just 46.7 percent among people in their 70s.
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But other diseases, disorders, and medical conditions share similar symptoms and may be managed in different ways. Unlike Alzheimer's, some of these other dementias can be reversible.
Note: Early memory problems aren't always considered dementia. When they show up on memory tests but don't significantly affect daily living, mental impairments may reflect a lesser condition known as mild cognitive impairment (MCI).
How Vascular Dementia Can Cause Symptoms of Dementia
1. Vascular dementia
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What it is: Vascular dementia accounts for 17.4 percent of all cases of dementia. It happens when a stroke interferes with blood flow to the brain. Usually the culprit is multiple small strokes (infarcts) caused by blood clots or thickened or ruptured small arteries that connect to the center of the brain. (This is called multi-infarct dementia.) It may also be caused by one big stroke (which would be referred to as post- stroke dementia).
How the symptoms compare to Alzheimer's: Vascular dementia may appear to be Alzheimer's because it, too, involves memory problems, confusion, disorientation, and trouble following directions. In this condition, however, recall of day-to-day events (episodic memory) becomes impaired, but recognition -- of people, for example -- doesn't. Alzheimer's generally affects both.
Unlike Alzheimer's, vascular dementia often begins abruptly. Memory loss may progress to hallucinations, agitation, or withdrawal. Symptoms may clearly worsen after each successive stroke.
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Other signs of possible stroke may be observed, such as garbled speech, dizziness or loss of coordination, or weakness on one side of the body (face or limbs). These signs may not be apparent in very small strokes. Some people have both Alzheimer's and vascular dementia.
How it's diagnosed and treated: It's relatively easy for a physician to determine whether dementia has a cerebrovascular cause. An MRI or CT scan will show evidence of a stroke. A history of stroke or cardiovascular problems, as well as smoking, high cholesterol, high blood pressure, and diabetes are major risk factors. Treating these factors can slow the progress of dementia symptoms.
There are no medications approved for vascular dementia, although those used for Alzheimer's are sometimes prescribed to help cognitive symptoms, with mixed results. In 2006, donepezil (Aricept) was linked to 11 deaths in a clinical trial evaluating its use for vascular dementia, compared with none in the control group.
How Lewy Body Disease Can Cause Dementia
2. Dementia with Lewy bodies (DLB)
What it is: Lewy body disease occurs when protein deposits in the brain called Lewy bodies (named for Friederich Lewy, who discovered them in the early 1900s) impede normal cognitive function. Some researchers consider DLB the second most common form of dementia, accounting for up to 20 percent of cases. Others believe DLB may be a subtype of Alzheimer's disease rather than a separate disease.
How the symptoms compare to Alzheimer's: Symptoms of both can include confusion, problems with concentration, and some memory impairment. Hallucinations tend to be more common. Like Alzheimer's, DLB is progressive. People with Alzheimer's have good days and bad days, but people with DLB may experience changes more frequently (even from one hour to the next -- and these changes may seem quite extreme.
REM sleep behavior disorder, which causes movements, gesturing, and speaking during sleep and confusion upon awakening, is often considered an early sign of DLB.
People with DLB also experience problems with mobility, similar to those of Parkinson's disease. These include movements that are slow, stiff, or shaky, trouble balancing, and a shuffling walk.
How it's diagnosed and treated: A complete medical workup can help identify symptoms of DLB and rule out other possible causes. As with Alzheimer's, the presence of dementia with Lewy bodies can only be confirmed with an autopsy.
There are no drugs approved for DLB. Alzheimer's medications are sometimes given or, in the case of movement problems, drugs used to treat Parkinson's disease. Other treatment is similar to that for Alzheimer's.
How Parkinson's Disease Can Cause Dementia
3. Dementia caused by Parkinson's disease
What it is: About 1 in 5 people with Parkinson's disease develop dementia due to Lewy bodies in the brain and brain stem. The onset of Parkinson's disease itself involves damage to nerve cells that control muscle movement.
How the symptoms compare to Alzheimer's: The symptoms of Parkinson's are usually diagnosed first because the dementia develops in the disease's later stages. Parkinson's dementia does not typically involve problems with language.
How it's diagnosed and treated: When dementia occurs in someone with Parkinson's, a medical hist ory, physical exam, and neurological exam are used to rule out other possible causes. There are no approved medications for treatment of dementia with Parkinson's disease, although symptoms can be managed as part of the overall therapy to manage the effects of the disease.
How Frontotemporal Dementia Can Cause Dementia
4. Frontotemporal dementia
What it is: Frontotemporal dementia is associated with rare diseases or disorders that affect the frontal lobe or front of the temporal lobes of the brain. Pick's disease is one example. Pick's involves abnormal deposits of the tau protein in the brain (called Pick bodies). Damage to the frontal and temporal lobes affects personality, memory, and behavior.
How the symptoms compare to Alzheimer's: Frontotemporal dementia is associated with impaired judgment, changes in personality, mood swings, problems with language, and a decreased interest in activities that were once enjoyed. Symptoms can occur suddenly.
Though frontotemporal dementia is a progressive disease, personality and behavioral symptoms tend to occur early on, whereas disorientation (getting lost) tends to occur late. (It's typically reversed in Alzheimer's.) Semantic memory (memory of the meaning of words and objects) is more affected than episodic (time related) memory.
Uninhibited or inappropriate behavior is common in people with frontotemporal dementia. They may demonstrate a marked lack of empathy, acting without regard to what other people think or feel.
How it's diagnosed and treated: In addition to the findings of a full medical exam, a brain scan may show evidence of atrophy (deterioration) of the frontal or temporal lobes. There are no medical treatments available, so the emphasis is on managing symptoms for better quality of life.
How Huntington's Disease Can Cause Dementia
5. Dementia caused by Huntington's disease (HD)
What it is: This fatal disease is caused by a genetic abnormality that destroys certain nerve cells in the brain and lowers leve ls of neurotransmitters. Mental, emotional, and behavioral declines follow.
Although HD victims are born with the defective gene, they don't usually experience symptoms until middle age. If a parent has the defective gene, there's a 50 percent chance that a child will have inherited the gene. Some 30,000 Americans have HD.
How the symptoms compare to Alzheimer's: Common symptoms include personality changes, mood swings, and disorientation. Attention and judgment can be impaired early in the disease, while memory loss occurs later.
As with Parkinson's, someone with Huntington's disease has involuntary movements that appear jerky, clumsy, or irregular. They may appear to fidget. Eventually they lose the ability to walk, talk, and swallow.
How it's diagnosed and treated: Huntington's disease can be diagnosed by a blood test to look for the genetic defect. There's no cure or medical treatment, so treatment focuses on improving quality of life.
How Infectious Disease Can Cause Dementia
6. Dementia caused by an infectious disease
Sometimes a bacterial or viral infection that enters the brain can cause dementia. For example, when HIV develops into AIDS, it may cause a person to experience problems with memory and concentration, a loss of motivation, and decreased interest in things that were previously enjoyed. The presence of other AIDS symptoms, along with an HIV (blood) test, will help a physician determine whether the dementia is HIV related.
Creutzfeldt-Jakob disease is another example. It's very rare -- one case per million people per year. ("Mad cow disease" is one form.) Creutzfeldt-Jakob disease is caused by transmission of a prion (an infectious protein). The prions infect and subsequently destroy the brain's nerve cells. Unlike dementia caused by Alzheimer's, memory problems and behavioral changes caused by Creutzfeldt-Jakob disease progress very quickly.
A physician may diagnose Creutzfeldt-Jakob disease through a medical history, a neurological exam, an electroencephalogram (or EEG, which tracks the electrical activity in the brain), a brain scan (an MRI may be especially useful), and a cerebral spinal fluid analysis (spinal tap). Only an autopsy can definitively confirm the diagnosis; the destruction of brain cells is apparent by holes in the brain tissue.
5 Conditions That Can Cause Dementia
7. Other possible causes of dementia
Rarely, certain conditions cause dementia that is partially or completely reversible. These include:
- A brain tumor
- Normal pressure hydrocephalus (an irregular accumulation of cerebrospinal fluid in the brain). This type of hydrocephalus usually affects people over 65.
- A head injury that causes hydrocephalus or a subdural hematoma, which is an accumulation of blood underneath the brain's covering
- A thyroid or other metabolic or endocrine disorder
How they're diagnosed and treated: Tumors, hydrocephalus, and subdural hematomas can be identified through a medical history and a brain scan. Thyroid or other endocrine or metabolic disorders can be identified through laboratory tests of the blood and urine. About 1 in 10 dementia cases have an unknown cause.