Dementia with Lewy bodies affects more than 1 million Americans.
DLB accounts for around 10-15 percent of all dementia cases.
Some of these symptoms are shared with Alzheimer's and Parkinson's diseases; however, the treatments for DLB and Alzheimer's differ, and the earlier a diagnosis is reached, the more effective the treatment will be.
Identifying patients with mild cognitive impairments who are at risk of developing DLB is vital for effective early interventions.
Difficulties diagnosing dementia with Lewy bodies
DLB is characterized by a buildup of Lewy bodies - protein deposits - in the brain. Lewy bodies also appear in other diseases, including Parkinson's disease. Depending on where the Lewy bodies appear, symptoms vary.
If they arise in the base of the brain, they can create motor symptoms similar to Parkinson's. When they appear in the outer layers of the brain, they produce cognitive symptoms, similar to Alzheimer's. Diagnosing DLB is primarily a case of watching symptoms develop and gradually ruling out other, similar conditions; there are no reliable diagnostic tests.
Researchers from the Mayo Clinic in Rochester, MN, set out to investigate whether brain volume could be useful in diagnosing DLB at an earlier stage. Their findings are published this week in the journal Neurology.
"Being able to identify people who are at risk for dementia with Lewy bodies is important so they can receive the correct treatments early on. Early diagnosis also helps doctors know what drugs to avoid - up to 50 percent of people with dementia with Lewy bodies have severe reactions to antipsychotic drugs."
Study author Dr. Kejal Kantarci
The research utilized 160 participants from the Mayo Clinic Alzheimer's Disease Research Center. All of the individuals had mild cognitive impairments - a slight but measurable reduction in cognitive abilities. People with mild cognitive impairments are known to be at a greater risk of developing Alzheimer's or other types of dementia.
Individuals with other neurological conditions, epilepsy, brain tumors, and substance abuse were excluded.
Charting changes in hippocampus volume
Each participant received an MRI scan at the start of the study and an average of two more annual scans. During the trial, 61 participants (38 percent) developed Alzheimer's disease and 20 people (13 percent) progressed to probable DLB. It is referred to as "probable" because DLB can only be definitively diagnosed by an autopsy.
Specifically, the team examined the volume of the hippocampus, an area known to shrink in the lead up to Alzheimer's.
Once the data were analyzed, patients with no measurable shrinkage were 5.8 times more likely to develop DLB when compared with those who did display hippocampal shrinkage.
Seventeen out of the 20 participants (85 percent) who developed DLB had normal hippocampus volumes. Conversely, 37 out of the 61 individuals (61 percent) who went on to develop Alzheimer's disease did show shrinkage.
DLB does not always affect memory, so when the researchers only looked at the data from those whose cognitive deficits did not include memory problems, the results were even more pronounced. As the authors explain, "we demonstrated that those with preserved hippocampal volumes are at an increased risk for probable DLB."
Although the study is on a relatively small scale, the results are encouraging. Dr. Kantarci hopes that the research will be duplicated and followed up with studies that include a postmortem autopsy to confirm DLB diagnoses.