Most of the symptoms of dementia include cognitive changes or loss of thought processes. In addition to loss of memory, confusion, difficulty with communication and organizational processes, a person with dementia may exhibit changes with the senses, particularly vision and perception. One major troubling symptom of dementia can be the development of hallucinations.
Hallucinations occur when a person senses something that is not really there. Hallucinations can occur with any of the senses including sight, hearing, touch, smell and taste but visual hallucinations are most common in dementia.
Normal Visual Changes of Aging
The process of vision is a complex process that involves transferring information from the eyes, to the brain where it can be interpreted and understood. What we understand from the visual images that we see are also influenced by information coming from other sources – hearing, thoughts, and memories.
Normal processes of aging can contribute to visual difficulties. Vision becomes less focused, it is harder to adjust from lightness to dark, a person may have “floaters” and there may be problems with depth perception. Age-related visual changes do not cause hallucinations or visual disturbances in dementia but they can contribute to them.
Additional Visual Changes Important in Dementia
In addition to normal age-related visual changes, dementia patients have changes in the brain which affect how vision process works. Cognitive losses can change the way a patient understands what is seen. If memories are lost and thoughts are disorganized, visual images can be difficult to understand.
Dementia patients may have additional visual challenges like decreased ability to see contrasting colors or patterns, detect movement, or recognize and identify colors, objects or people. The patient may also have difficulty with double vision or a reduced visual field and may have trouble with balance or hearing as well.
These changes, combined with the cognitive changes of dementia, leave the brain to interpret images with less information. This may result in misperceptions and misidentifications of two types: Illusions (seeing one thing and believing it is another) and hallucinations (seeing something that is not there).
Dementia and Hallucinations
In some cases, people with dementia are thought to be experiencing hallucinations when they are actually misinterpreting what they have seen or having an illusion. An example would be a dementia patient who “sees” a person in the kitchen, when it is really an apron hanging on a hook.
In other cases, actual hallucinations may be occurring. Dementia with “Lewy bodies” (DLB) causes protein formations in the brain may cause hallucination. It is associated with Parkinson’s disease and may occur alongside Alzheimer’s disease or it may occur alone. Patients with DLB often have hallucinations of brightly colored objects, people or animals. They may also experience hallucinations with other senses – including sounds, smells or perceptions of touch.
There are other medical conditions which may cause hallucinations such as schizophrenia, medication reactions, dehydration, intense pain or infections. These causes should be investigated and eliminated as a medical cause but if a patient is in advanced stages of dementia, there is probably no other cause.
Supportive care, reassurance and distraction may be the only treatments for dementia-related hallucinations. If a particular object, such as a mirror, continues to cause a disturbance, it should be removed from the environment. The main goal is to help the dementia patient remain calm and feeling safe.