Lewy body dementia is the third most common type of dementia that affects older populations, after Alzheimer’s and vascular disease. Named after the doctor who first identified it, Lewy bodies are tiny deposits of protein or alpha-synuclein that damage nerve cells over a period of time.
While having a close relative or parent with Lewy body dementia increases the risk of developing the disease, it is still very rare as LBD is not considered a genetic disease.
Research has also shown that people with an unrelated Gaucher’s disease gene may also have a higher chance of developing Lewy body dementias.
Lewy bodies are also the underlying cause of several other progressive diseases that affect the brain and the nervous system, notably Alzheimer’s disease and Parkinson’s disease dementia. Together, these are sometimes called Lewy body disorders. Therefore the symptoms in all three of these diseases are common.
Researchers are still trying to understand how Lewy bodies appear in the brain, and how they contribute to dementia. However, it is understood that their presence leads to a loss of connection between nerve cells, and the lack of two important chemical messengers; acetylcholine and dopamine.
The physical symptoms that manifest as a result of Lewy bodies dementia may be different for different people, and depend on the way these Lewy bodies are scattered in the brain.
Lewy bodies at the base of the brain correlates with difficulties in motor abilities, while their presence in the outer surface of the brain adversely affects cognitive abilities.
Why do people develop Lewy body dementia?
The exact reasons why some people develop this disease are unknown.
Usually people who develop Lewy body dementias are 50 years old, or above. However, in exceptional cases, patients can be younger.
The disease usually lasts for an average of five to seven years from diagnosis to death, but it can even last for two to 20 years depending on individual cases.
What happens as the disease progresses?
Dementia with Lewy body causes fluctuations in alertness or attention, depression, muscular rigidity, slow movements, tremors and changes in gait. Some strange behaviors may also develop with disease progression. For example; a patient may suffer from very vivid and detailed hallucinations – seeing objects, animals and people where there are none – he may be found talking to a deceased loved one or acting out on dreams, sometimes making violent movements while asleep.
As patient ages, the risk factors associated with the disease also increase and the symptoms either worsen, or become more pronounced. The motor and psychological changes that are accompanied by the disease may also differ for people, and show at different times.
Brain areas that are affected by the disease
The following areas of the brain are affected by LBD.
1) The cerebral cortex which controls several functions, including perception, thought, information processing and language.
2) The limbic cortex which controls emotions and behavior.
3) The hippocampus – essential for forming new memories.
4) The midbrain, including the substantia nigra, involved in movement.
5) Areas of the brain stem that are important in regulating sleep and maintaining alertness.
6) Brain regions that are important in recognizing smells (olfactory pathways).
It is important to know the type of Lewy body disorder early on so that a treatment can be tailored accordingly, and doctors can have a clearer understanding of how the disease is likely to progress. Researchers and clinicians have developed the ‘1-year rule’ which has proved to be quite accurate in diagnosis.
If cognitive impairments surface less than one year after the changes in motor movements, then it is Lewy body dementia, while if cognitive impairments take more than a year to appear then it is Parkinson’s disease dementia.
Difficult as it may be to diagnose this type of dementia due to the overlapping symptoms and changes with other degenerative brain diseases, it is important to diagnose Lewy body dementia as early as possible so patients can receive the treatment that is best for their condition, have the time to plan financial and legal matters, and are able to build a support system to stay independent and live a full life.
It is also important to remember that not every medical healthcare professional will be able to help with the diagnosis. Only neurologists, as they specialize in the brain and nervous system, have the expertise required for correct diagnosis.