What is Dementia?

James M. Ellison, MD, MPH

Swank Center for Memory Care and Geriatric Consultation, ChristianaCare

  • Expert Advice
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An abstract illustration of a human head. The brain region is depicted by a tree with leaves falling off.

This article defines dementia, describes the most common forms of dementia, including Alzheimer’s disease, and outlines the various treatment options.

When Mrs. Pilgrim brought her 74-year-old husband to the Memory Disorders Clinic, she had one burning question on her mind: “Does Richard have Alzheimer’s or dementia?” Like many people who seek advice about memory impairment and other cognitive symptoms, she wasn’t sure about the terms, but she was pretty clear that her husband needed an examination because of changes in his memory, personality, and mood that had developed gradually during the previous year.


Dementia Defined

Cognitive actions of the brain involve the skills we use to get along in the world. Dementia is diagnosed when a cognitive skill becomes impaired so much that a person can no longer get along independently. The cognitive problem or problems in dementia are acquired rather than lifelong, as occurs with an intellectual disability, for example. That means that the person was functioning at a higher level prior to developing dementia. The loss of that higher level of functioning is one of the tragedies of dementia. It may mean having to leave a job or becoming unable to continue activities that previously were enjoyable and meaningful.

Six Checkpoints

Clinicians look, in particular, at six areas of cognition when diagnosing dementia, where one or more of these cognitive skills are very impaired:

  • Complex attention refers to the ability to sustain focus and switch between tasks.

  • Learning and memory, which includes recall of recent and more remote events as well as of how to do things.

  • Executive function refers to skills, for example, which enable people to plan, organize, remember things, prioritize, or pay attention to tasks.

  • Language includes both expression and understanding in spoken and written forms.

  • Perceptual-motor function is the ability to understand such things as shapes, locations, and directions.

  • Social cognition is the ability to recognize the meaning of others’ facial expressions and behavior so that we can interact successfully.

Dementia is a “condition” or “syndrome,” not just a single disease. The current diagnostic term for “dementia” is “major neurocognitive disorder,” but the word “dementia” won’t be going away soon.

Alzheimer’s Disease

There are many causes of dementia, and Alzheimer’s disease is the most common by far in the United States and many other countries. Alzheimer’s disease can be suspected clinically, and certain brain scans can almost make the diagnosis a certainty. However, Alzheimer’s disease is ultimately diagnosed by microscopic examination of brain tissue after death. The typical “plaques” and “tangles” of Alzheimer’s disease, which represent damage outside and inside brain cells, make the diagnosis clear. After Alzheimer’s disease, the next most common dementias are vascular dementia and dementia with Lewy bodies.

Vascular Dementia

Vascular dementia develops when the brain is deprived of oxygen and nutrients by disease of either large or small blood vessels. It can look different from Alzheimer’s disease because failure of large blood vessels may result in strokes, which cause neurological symptoms that are found with destruction of specialized brain areas. Problems with mental slowness and recall along with difficulties affecting language, walking, or urination, for example, may suggest a vascular cause of memory problems. The memory problems themselves are different in vascular dementia because they represent a problem in retrieving information that has been stored in the brain. In Alzheimer’s disease, the actual storage does not work properly so reminders are less helpful than for a person with vascular dementia.

Dementia with Lewy Bodies

Dementia with Lewy bodies looks like a combination of some features of both Alzheimer’s disease and Parkinson’s disease. The cognitive problems begin before or shortly after the muscle symptoms. A person with Lewy body dementia has more emotional and cognitive ups and downs, more falls, more sleep problems, and more visual hallucinations than someone with Alzheimer’s disease.

Frontotemporal Lobar Dementia

Less common, but still important to distinguish, is frontotemporal lobar dementia (FTLD). Diagnosis of this dementia can be confusing because sometimes it appears with changes in language or changes in behavior. These changes, which can be very obvious, can hide a simultaneous memory problem.

Sometimes FTLD is mistaken for depression, mania, personality disorder, or a substance abuse problem because of the behavioral disturbances. Treatment for FTLD is in some ways different from treatment of Alzheimer’s disease, another reason for distinguishing these from each other.

Other Causes of Dementia

There are many other causes of dementia including infections like HIV, prion disease such as Creutzfeldt-Jakob disease, head trauma, Parkinson’s disease, Huntington’s disease, and others. There are also some dementia-like conditions that are treatable or even reversible, including some sleep disorders, some hormonal diseases, depression, and having a bad reaction to medications.


A clinical examination to determine whether dementia is present should include a careful discussion of the patient’s medical history and the development of symptoms, an examination of memory and other cognitive skills, physical examination, blood tests, and neuroimaging. Special additional tests, such as an electroencephalogram to record electrical activity of the brain, may be required when there are indications that one of the more unusual causes of dementia might be present.


Medication treatments for dementia are limited at this time except for those conditions in which a treatable medical condition is identified.

Approved Medications

Different classes of medications are available for treating people with Alzheimer’s disease, but their limited effects relieve symptoms for only a temporary period. For dementia problems that are not cognitive or behavioral, there are limited options. For example, the combination of dextromethorphan and quinidine has been approved in treating “pseudobulbar affect,” an unstable emotional state, which is characterized by uncontrollable episodes of crying and/or laughing. Pimavanserin has been approved for treating psychosis in Parkinson’s disease.

Off Label Medications

For other behaviors such as aggression, depression, anxiety, and insomnia, many medications are used “off label,” which means that the FDA has not determined the medication to be safe and effective for treating dementia, even though some research may suggest that the medication can help, and even though the medication has been proven safe and effective for other uses. Antidepressants or antipsychotics are off-label treatments for depression and psychosis, respectively. Antidepressants sometimes help. Antipsychotic medications are often avoided due to their recognized side effects, risks, and limited effectiveness in this role.

The medications that have been approved by the FDA for Alzheimer's disease are also sometimes used to treat vascular dementia or Lewy body dementia, where they also can have mild benefits. Their effect on FTLD is less predictable.

Many other medications are being testing at present for the treatment of dementia. Perhaps before many years have passed we will have medications to treat, delay, or even cure some of these disorders.

Non-Medication Treatments

Even now, as we wait for more effective medications, we already have non-medication treatments that can be very helpful. Support groups and other forms of education or therapy can help a person adjust to the diagnosis of dementia. Planning ahead is very important and requires discussion of difficult topics such as when to give up driving, how to make the living environment safe and usable, what to do about financial matters, and what treatments are acceptable near the end of life. For people with non-cognitive behavior problems, the “DICE” model (Describe, Investigate, Create a plan, and Examine its effect) and other behavioral interventions have been helpful.

About the author

Headshot of Dr. James Ellison

James M. Ellison, MD, MPH

Swank Center for Memory Care and Geriatric Consultation, ChristianaCare

James Ellison, MD received his medical degree from UCSF in 1978 and trained in psychiatry at the Massachusetts General Hospital (1979-1982).

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