It all started back in 1817 when Dr. Parkinson described “shaking palsy.” Eventually, the disease was named after him. Fast forward almost a hundred years: In 1912, Dr. Lewy was searching for the cause of PD in the autopsied brains of Parkinson’s patients. He found that the microscopic round bodies of protein that were eventually named for him were always present in the area of the brain where movement is controlled. Thus, since 1912, it has been known that Lewy bodies and Parkinson’s occur together, although, until the last decade, they weren’t sure which caused which.
Fast forward again, to the 1980’s. Dr. Kosaka found these same Lewy bodies in the cerebral cortex, or the thinking center, of the brains of people who had displayed the symptoms we now relate with Lewy body dementia.
However, even though researchers knew the same “Lewy bodies” were present in both Parkinson’s and in that dementia Dr. Kosaka had found, dementia was not considered a symptom of PD until the early 1990’s. They were thought to be two separate diseases that often occurred together: PD and ‘dementia,’ usually Alzheimer’s. Then, in 1994, Parkinson’s disease with dementia (PDD) was recognized as part of the Parkinson’s picture and given its own insurance code.
Two years later, in 1996, a world-wide group of dementia specialists convened and developed clinical criteria for Dementia with Lewy Bodies (DLB). At that time, the terms ‘dementia with Lewy bodies’ and ‘Lewy body dementia’ were used synonymously. However, it was not yet associated, at least formally, with PD. Dementia specialists treated LBD and movement specialists treated PDD, as a symptom which could occasionally show up in late stage PD.
By the early 2000’s specialists were beginning to recognize the similarities between PDD and LBD/DLB. Finally, in 2005, a group of movement and dementia specialists met together and agreed that Lewy bodies caused both types of dementia and that their cognitive symptoms were similar. At that time, they determined that ‘DLB’ described the type of dementia that started prior to any motor symptoms and that ‘LBD’ was an umbrella term for both ‘DLB’ and ‘PDD’.
Notice that the experts were now saying that Lewy bodies caused these disorders (and PD as well)--not the other way around. And that’s why we now say that the Lewy body family has at least three members: PD, DLB and PDD. They are all related. PD occurs when the Lewy bodies reside in the midbrain where motor functions are controlled. DLB occurs when Lewy bodies reside in the cerebral cortex where cognitive abilities are controlled. And PDD occurs when the Lewy Bodies migrate from the midbrain to the cortex and both motor and cognitive functions are compromised.
As to what causes the damage that results in Lewy bodies, that’s still up for grabs. However, the evidence is becoming stronger and stronger that it is a combination of genetics and toxins.
Next week’s blog presents a more scientific vies of the Lewy body family.