The diagnosis of any form of dementia is most often made based on:
- the type of symptoms that a person displays
- how long the person had the symptoms
- the way the symptoms developed (suddenly or slowly)
- the results of different types of clinical and behavioral tests.
At the time of this writing, there are no medical tests that can absolutely identify most of the major forms of dementia, except for an examination of the person's brain tissue after they have died.
The DSM-5 requires that before any type of dementia can be identified, the person is first diagnosed with either a Minor Neurocognitive Disorder or a Major Neurocognitive Disorder. The major difference between a Minor or a Major Neurocognitive disorder is the level of impairment that the person displays. People who are diagnosed with Minor Neurocognitive Disorders often do not experience significant problems in their daily functioning because of issues with memory, judgment, movement, etc. Those diagnosed with Major Neurocognitive Disorders do experience significant problems and need assistance.
After the diagnosis of a Minor or Major Neurocognitive Disorder is made the person could be diagnosed with some specific form of dementia. To be diagnosed with a Minor or a Major Neurocognitive Disorder with Lewy Bodies (Lewy Body Dementia) the core features as specified in the DSM-5 are:
- The development of the person's problems with memory and other issues must be gradual. This means that it starts slow and gets worse over time.
- The person must have periods of changes in their thinking, especially with their attention and concentration. These changes mean that the person sometimes has significant problems, but other times does not.
- The person has visual hallucinations (seeing things that aren't there).
- The person has movement problems that look like those that happen in Parkinson's disease. Movement problems happen at the same time or after the development of problems with thinking.
According to the DSM-5 suggestive symptoms are:
- The person has a rapid eye movement sleep disorder. This means that they physically act out their dreams when asleep.
- The person is extremely sensitive to the effects of antipsychotic drugs. These are drugs used to control hallucinations. When the person takes these drugs, it often makes their movement problems more severe.
For all diagnoses in the DSM-5 the person's symptoms cannot be better explained by some other mental disorder, the use of drugs or medications, or some other medical condition. Major or Minor Neurocognitive Disorder can be identified as being:
- Probable: When the person has at least two of the core features listed above or at least one core feature and one suggestive feature.
- Possible: When the person has only one core feature or one or more of the suggestive symptoms.
The diagnosis of any form of dementia is based on the best guess of the doctor. Doctors use many different sources to assist them in making their diagnosis. In some cases, the diagnosis may change when new evidence is presented. The sources that doctors may use to make a diagnosis of Lewy body dementia include:
- Brain imaging tests such as MRI, CT scans, PET scans, and even EEG tests.
- A full medical examination: The doctor performs a full medical evaluation of the person despite what other evaluations have been performed. Then the doctor will rely on some of the sources of information used below to help them in their decision.
- The reports of other doctors such as neurologists, psychiatrists, psychologists, etc. These reports often include:
- Neurological evaluations: Neurologists are doctors who specialize in diagnosing brain disorders.
- Neuropsychological testing results: Neuropsychological tests are tests of thinking and emotional functions. These include tests of memory, reasoning, language, and tests of the person's emotional functioning such as depression, the presence of hallucinations, etc.
- Reports from the patient and family: Doctors will rely heavily on the reports of the patient and the patient's family to determine how the person's symptoms started, developed, and the level of impairment that they produce.
- Other laboratory tests: Other laboratory tests such as blood tests, urinalysis, etc. can be used to rule out other conditions that may be contributing to the patient's problems. However, these tests cannot diagnose dementia in anybody.
When all the test results and observations have been completed, the main rule that is used to determine if the person's problems represent Lewy body dementia as opposed to other conditions is most often the observation that the person's movement problems developed at the same time or within a year after the person began to show signs of dementia (e.g., memory loss or other signs). Most often people with Parkinson's disease develop movement problems first, and then much later may develop signs of dementia. People with Alzheimer's disease most often develop signs of dementia, but do not develop movement problems if they have them until very late in the development of their dementia.
Lewy body dementia is a progressive form of dementia that will continue to worsen over time. Medications, the use of behavioral interventions (e.g., memory aids or other non-medical treatments), and any other forms of treatment may slow down the development of the symptoms. However, over time the person will eventually get worse. In Lewy body dementia, people often vary from day to day, and even during the day, in how severe their problems are. Sometimes they appear to be relatively normal, and other times they can appear to be very impaired. However, over time the person continues to get worse and the "good times" become more and more rare. In some cases, treatment can slow down the overall decline with the person's problems. In other cases, it may not help very much at all.
The progression of Lewy body dementia can be relatively quick or relatively long depending on the person. Different cases develop at different rates. Overall, the average length of progressive dementias is about eight years. However, the range for the development of these dementias can be 1-20 years when all cases are considered. Progressive forms of dementia are eventually fatal, and at the time of this writing, there is no cure for Lewy body dementia.