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Alzheimer's update: New way to distinguish Alzheimer's from Lewy body dementia

Looking at specific changes in alertness and cognition may be a reliable way to distinguish Alzheimer's disease (AD) from dementia with Lewy bodies (DLB) and normal aging, according a study by a Mayo Clinic neuropsychologist.

Lewy bodies are round collections of proteins in the brain that are considered the pathological hallmark of Parkinson's disease. Lewy bodies are not typically found in healthy brains. In Parkinson's disease, they are located in the brainstem, particularly in an area called the substantia nigra. In DLB, Lewy bodies also are found in the brain's cortex.

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," Ferman says. "For the patients with AD, one or two of these behaviors were not uncommon."

"But over 63 percent of the patients with DLB had three or four of these behaviors,"Ferman says. "This gives us a clear set of behaviors to use to reliably distinguish the luctuations of Lewy body dementia from Alzheimer's."

The distinctions are important, because medications that may help Alzheimer's patients may aggravate DLB symptoms of dementia, parkinsonism or hallucinations. Moreover, some medicines that are only marginally helpful in AD may have a dramatic impact on DLB.

"It's very important to diagnose correctly," Ferman says, "because proper treatment can help us manage symptoms and help the patient and their caregivers cope with the challenges of this disease."