Lewy bodies are round collections of proteins in the brain that are considered the pathological hallmark of Parkinson's disease. Lewy bodies are never found in healthy normal brains. In Parkinson's disease the Lewy bodies are largely localized to an area of the brain stem called the substantia nigra. In DLB, Lewy bodies are also found in brain's cortex.
Although DLB accounts for as much as 20 to 35 percent of the dementia seen in the United States, treatment and diagnosis is often complicated by a lack of information about the disease. In the study, Dr. Ferman and colleagues examined episodes of fluctuation in cognition (problems in thinking or concentration) experienced by individuals with AD or DLB or normal older adults who had no signs of dementia.
"Fluctuating cognition is an important symptom of DLB but has been the center of some controversy because it is comprised of a number of behaviors, some common to all dementias and perhaps even found in normal aging," said Dr. Ferman, assistant professor and clinical neuropsychologist in the department of psychiatry and psychology at the Mayo Clinic in Jacksonville, Fla. "Even though attempts have been made to carefully describe these behaviors, they have not been used reliably as diagnostic tools." Dr. Ferman spoke today at an American Medical Association media briefing on Alzheimer's disease in New York City.
Some of the common behaviors of DLB that comprise fluctuating cognition include episodes of confusion, excessive sleepiness, a waxing and waning of cognition, inattention, incoherent speech and varying ability to perform tasks. When this occurs, family members often describe their loved ones as "zoned out," or "not with us." This collection of behaviors is called fluctuations because these behaviors come and go. In the study, 200 normal older adults, 70 patients with AD and 70 patients with diagnosed DLB were compared on aspects of fluctuating cognition. Spouses, adult children or others involved with the subject on a day-to-day basis provided information.
Four characteristics significantly distinguished patients with DLB from persons with AD and normal elderly controls: daytime drowsiness and lethargy despite getting enough sleep the night before; falling asleep two or more hours during the day; staring into space for long periods and episodes of disorganized speech.
"For the normal elderly control group, one or two of these behaviors was found in only 11 percent of the group," said Dr. Ferman. "For the patients with AD, one or two of these behaviors were not uncommon, but over 63% of the patients with DLB had three or four of these behaviors. This gives us a clear set of behaviors to use to reliably distinguish the fluctuations of Lewy body dementia from Alzheimer's."
"Medications that may be helpful to an Alzheimer's patient may actually aggravate DLB symptoms such as hallucinations and symptoms of parkinsonism. Other medications that are only marginally helpful in AD sometimes have a dramatic impact on Lewy body dementia," said Dr. Ferman. "It's very important to diagnose correctly because proper treatment can help us manage symptoms and help caregivers cope."
Both AD and DLB are dementias, that is, classified by a decline in thinking skills greater than expected by age that interferes with the activities of daily living, explained Dr. Ferman. In AD the first loss in thinking skills is in memory; in DLB the earliest loss appears to be with attention and visual perception. These differences may be related to different patterns of damage to the brain. In addition, patients with DLB may have fully formed hallucinations, Parkinson-like movement problems and/or fluctuating cognition. These symptoms may be present in late-stage AD, but one or all of them are present in early DLB.
"As our understanding and ability to recognize Lewy body dementia has improved, there has been an explosion of research," said Dr. Ferman. "As we develop effective treatments to prevent or delay progression of DLB, early diagnosis will be key."