What are the different types of dementia?
Alzheimer�s dementia/Alzheimer�s disease (AD) is the most common form of dementia. The cause has not yet been identified. While patients with AD have amyloid plaques (an accumulation of an abnormal protein) identified in certain areas of their brain, it is unclear if these plaques are the cause of the disease or a result of the disease. Although most cases of Alzheimer's disease begin after the age of 65, in some cases symptoms begin when someone is in their 40s or 50s. This early onset Alzheimer's disease can progress more rapidly than later onset AD.
Vascular dementia is the second most common cause of dementia, and is due to multiple strokes occuring within the brain. Often, these strokes may have been unnoticed and patients may not have any associated symptoms such as weakness, visual loss, or numbness. Patients with untreated high blood pressure or heart disease may be at risk of developing vascular dementia.
Frontotemporal dementia is associated with pronounced atrophy or shrinkage of the frontal and temporal lobes in the brain. In addition to forgetfulness and word finding problems, patients may have marked personality changes, impulsivity, or poor judgment. Some patients with frontotemporal dementia can develop incoordination or stiffness of their muscles.
Lewy body dementia/Lewy body disease is caused by Lewy bodies, which are abnormal clumps of certain proteins, accumulating inside of neurons. Forgetfulness and other signs of cognitive decline are the primary features of this condition, but patients can also develop prominent hallucinations which seem very real to them. Some patients with Lewy body disease develop symptoms which look like Parkinson's disease, such as tremor and slowness.
Creutzfeldt-Jakob disease is a rare condition where an abnormal protein leads to destruction of brain cells and dementia. While most cases occur without an underlying cause, in some patients there is a family history of this disorder. Even less often, patients might be exposed to the abnormal protein. Mad cow disease is one example of external exposure. This condition tends to progress rapidly, over only a few years, and is often associated with abnormal muscle movements.
Mixed dementia refers to patients who have evidence of two (or more) types of dementia. They are often described as having mixed dementia. Alzheimer's disease and vascular dementia are the most common causes of mixed dementia.
Normal pressure hydrocephalus is an abnormal enlargement of the ventricles, or fluid filled spaces within the brain, that causes pressure on areas of the brain. This leads to problems with walking, memory, and ability to control urine flow (incontinence). Although this can be identified with imaging of the brain (MRI or CT scan), further testing may be required to confirm the diagnosis. If diagnosed, this condition can be treated with placement of a shunt to drain the extra fluid.
Huntington�s disease causes characteristic abnormal movements, called chorea, in affected individuals. The movements are the hallmark of the diagnosis. However, in some cases, problems with memory can precede the development of the chorea by many years.
Alcoholic dementia is caused when patients drink heavily and develop deficiency in one of the B vitamins. When this happens, brain cells are unable to function normally and memory loss can occur. This is called Korsakoff syndrome. Although it is most commonly seen in alcoholics, patients who are malnourished from other causes are also at risk of developing this disorder.
Traumatic brain injury (concussion)/dementia pugilistica can lead to memory problems, as we have learned in recent years. In some cases, recurrent brain injuries or repeated concussions can contribute to the underlying changes identified in Alzheimer's disease.
Dementias caused by other conditions can lead to changes within the brain and associated cognitive decline. These include Parkinson's disease, HIV (AIDS), multiple sclerosis, Wilson's disease, meningitis (infection of the brain coverings), blood clots in the brain, and heart attacks. Some patients with brain tumors may develop memory problems which resemble dementia. Different medications can lead to some memory problems. Additionally, some patients with memory loss may take their medications incorrectly. It is important to note that not everyone that has been diagnosed with one of these conditions will develop dementia.
Delirium is a condition associated with confusion which comes on very rapidly and is associated with underlying illness or toxicity from alcohol or drugs. Withdrawal from certain medications or alcohol can also cause delirium. While in many cases delirium can be reversed, it's important to recognize the condition and obtain prompt treatment.
Dementia is rare in children, but individuals with Down Syndrome are at risk of developing dementia at an early age. Metabolic diseases such as Niemann-Pick disease, Lafora disease, or Batten disease can lead to dementia in children, but are typically associated with many other symptoms prior to the development of the memory problems.