I receive a lot of questions about dementia. Often people use the diagnosis of Alzheimer’s disease as though it describes all types of dementias but this is not the case. Alzheimer’s disease is only one of many conditions which are all variations of dementing illnesses. In this column I’ll describe some of the more common subtypes of dementias and some of their distinguishing characteristics.
Let’s start with a definition: Dementia is a syndrome of progressive cognitive decline, often accompanied by additional symptoms in behavior and movements. The specific areas or domains of cognitive functioning that are most often affected are: memory, learning, and executive functioning (this includes things such as organization and planning, staying on task, and problem solving). Other cognitive domains which are frequently affected include language, visuospacial processing, and mood/emotion.
More technically, the DSM (this is the guidebook for diagnosing mental disorders) requires the following elements to establish a diagnosis of dementia:
- Impairment of recent memory and at least one other cognitive domain
- Represents a decline from previous level of function and be severe enough to interfere with daily function and independence
- Occur in the absence of other psychiatric, neurologic, or systemic disease
- Does not occur only with delirium (delirium is caused by other processes)
This is the most common form of dementia and accounts for anywhere between 60–80%. Typically, this presents as a progressive decline in many areas of intellectual functioning. Recent memory is often severely affected, personality less so. As the disease progresses it usually follows a path of retrogenesis, which literally means back to the beginning. Skills and memories regress almost like reverse aging. In the final stages, adults with Alzheimer’s type dementia require total care, much like an infant.
Vascular refers to blood vessels. When blood vessels are diseased, the tissues supplied by these blood vessels may suffer from reduced blood flow and be damaged as a result. When the blood vessels are those in the brain or supplying the brain, the result may be a stroke if the territory of brain is large, or they be relatively small portions of brain tissue. These small areas of damage may not be large enough to cause a stroke, but when there are many small areas, the cumulative affect may be vascular dementia. This typically occurs in individuals with risk factors for vascular disease: diabetes, hypertension, smoking, and/or high cholesterol. Vascular dementia is the second most common type of dementia and may coexist with other dementing processes such as Alzheimer’s disease (mixed dementia).
Dementia with Lewy bodies
Lewy bodies describe a characteristic pathologic finding seen by pathologists examining brain tissue. There is almost always a motor component to Lewy body dementia, i.e. muscles and therefore movement is affected. Most often the motor symptoms are increased rigidity and stiffness as is also seen with Parkinson’s disease (described below). The cardinal features of Lewy body dementia are fluctuating cognitive impairment, hallucinations, along with the motor symptoms. A particular sleep disorder called REM sleep behavior disorder, in which people physically act out their dreams is sometimes present. Men are more often affected than women. Some of the medications use to treat hallucinations and/or Parkinsonian features may actually worsen symptoms. Although relatively common (over a million affected individuals in the United States), Lewy body dementia is often under diagnosed.
Parkinson’s disease with dementia
Many experts consider Parkinson’s disease with dementia and Lewy body dementia to be clinical variations of the same disease process. As a result of a specific neurodegenerative process in the motor cortex area of the brain which depletes the production of a neurotransmitter, Parkinsonism manifests with a variety of motor symptoms. These include rigidity, reduced facial expression described as masked facies, slowing of movement, tremor, and difficulty initiating movement. As the disease progresses, swallowing difficulties frequently occur which significantly increase the chance for aspiration pneumonia. Depression often accompanies Parkinson’s disease. While the motor symptoms predominate, over time, this degenerative process involves other areas of the brain and causes cognitive decline.
There are several disorders with a variety of symptoms which may result in Frontotemporal dementia. As suggested by the name, the areas of brain involved are in the frontal and temporal cortex. Because some of these parts of the brain are involved in regulating emotional response, the most common manifestations include changes in personality and behavior. This type of dementia can be especially challenging as the behaviors might be very inappropriate. Poor personal hygiene, sexually inappropriate behaviors, compulsions, or apathy might occur. Typically, the individual affected is unaware of the behaviors or unable to recognize them as inappropriate. Sometimes language, speech, or movement may be affected.
I have tried to cover some of the more common forms of dementia, but briefly want to include a few others. Certain neurotoxic substances can damage the brain and cause dementia. Alcohol is the most common of these toxic substances. There are different infectious agents which can damage the brain and lead to dementia. Some of the more common of these include syphilis, HIV, and Creutzfeld-Jacob disease (similar to mad cow disease). Two metabolic disorders which may lead to dementia include hypothyroidism (low thyroid hormone) and vitamin B12 deficiency. Fortunately, both of these types of dementia are reversible with proper treatment. Finally, severe depression can sometime mimic the signs and symptoms of dementia. Doctors sometimes refer to this as pseudo-dementia.
As you can see, there are many differences which characterize many types of dementias. Any of these types can be difficult to deal with both for the individuals affected and their families. It is especially difficult to witness the cognitive changes, behavioral disturbances, and functional decline which accompany dementia. The Alzheimer’s Association, your health care provider, and local community resources are good places to turn for help.