Many people still believe dementia is a disease. It isn’t.
Dementia is a general term that describes a group of diseases that affect areas of the brain that control memory, language, attention and problem solving. To be considered dementia, the problems must be severe enough to interfere with daily life. Memory loss is an example.
There are at least 50 different types of dementia, the most common of which is Alzheimer’s disease, accounting for about 60% of all dementia cases. Even though the symptoms of the various dementias are similar, their underlying causes define their differences.
This is the diagnosis in about 15% of dementia cases. It is the result of brain damage due to reduced or blocked blood flow in blood vessels leading to your brain. This damage can be caused by stroke, infection of a heart valve (endocarditis) or other blood vessel conditions that deprive brain tissue of oxygen and nutrients. Within minutes, brain cells begin to die.
A major cause of vascular dementia is multiple TIAs (transient ischemic attacks), sometimes called mini-strokes or silent strokes. Each one is like a stroke, producing similar symptoms, but usually lasting only a few minutes or less. A TIA may or may not produce visible symptoms, and may or may not be noticed by the person having it. Once someone has a TIA, they are at an increased risk of having more in the future. And, left untreated, about 1 in 3 people who have a TIA will eventually have a stroke.
Multiple TIAs leave scars in the brain, often called small vessel disease, that can be seen with an MRI exam. These scars may be concentrated in one area of the brain, causing a gradual loss of function in that area. Or, they may be spread throughout the brain, causing a gradual deterioration of mental capabilities.
About 10% of dementias are of the mixed variety, usually a mixture of Alzheimer’s and Vascular Dementia.
Dementia With Lewy Bodies
This dementia is responsible for about 4% of dementias. Lewy bodies are abnormal clumps of the alpha-synuclein protein. Many people with this dementia also have plaques and tangles like those found in Alzheimer’s and Parkinson’s.
Lewy body dementia symptoms are similar to those of Alzheimer’s disease. It is unique, however, because its symptoms include fluctuations between confusion and clear thinking, visual hallucinations, tremors and muscle rigidity. Patients also often have a condition called rapid eye movement (REM) sleep behavior disorder that involves acting out dreams.
2% to 5% of dementias are caused by this progressive cell degeneration in the brain’s frontal lobes (the areas behind your forehead), the temporal lobes (the regions behind your ears) or both. These critical areas control planning and judgment, emotions, speaking and understanding speech, and certain types of movement. Symptoms can include inappropriate behaviors, language problems, difficulty with thinking and concentration, and movement problems.
Parkinson’s Disease Dementia
Many people with Parkinson’s disease eventually develop dementia symptoms. Parkinson’s disease dementia accounts for about 2% of dementias.
Other Types of Dementia
Huntington’s Disease is an inherited disease that causes certain nerve cells in the brain and spinal cord to waste away. The condition causes a severe decline in thinking skills over time. It also causes weakness and difficulty with walking and movement.
Creutzfeldt-Jakob Disease destroys brain cells and gets worse unusually fast. The resulting damage leads to rapid decline in thinking and reasoning as well as involuntary muscle movements, confusion, difficulty walking and mood changes. It affects about one person in a million each year.
Normal Pressure Hydrocephalus is caused by the buildup of fluid in the brain. Symptoms include difficulty walking (shuffling one’s feet), memory loss and inability to control urine. It can often be corrected with surgery to install a shunt in the brain to drain excess fluid.
Wernicke-Korsakoff Syndrome (Alcoholic Dementia) is caused by a severe deficiency of thiamine (vitamin B-1), most commonly the result of alcohol abuse.
- What is Dementia? — Alzheimer’s Association
- Diseases and Conditions: Dementia — Mayo Clinic
- Alzheimer’s Disease & Related Dementias — Alzheimers.gov