Hippocampus Shrinkage Absence May Predict Dementia With Lewy Bodies

A lack of shrinkage in the area of the brain called the hippocampus may be a sign that people with thinking and memory problems may develop dementia with Lewy bodies rather than Alzheimer’s disease, a new study suggests.

Atrophy of the hippocampus, the area of the brain responsible for thinking and memory, is an early sign of Alzheimer’s disease.

Lead author Kejal Kantarci, M.D., a Mayo Clinic radiologist, says:

“Identifying people with mild cognitive impairment at risk for dementia with Lewy bodies is critical for early interventions. Early diagnosis helps target appropriate treatments, including what medications not to give. For example, as many as 50 percent of people with Lewy body disease have severe reactions to antipsychotic drugs.”

Correct Diagnosis Difficult

Dementia with Lewy bodies is a progressive disease that causes hallucinations, decline in mental abilities, rigid muscles, slow movement and tremors. With symptoms similar to Alzheimer’s disease and Parkinson’s disease, a correct diagnosis can be difficult.

Comedian Robin Williams, who died by suicide in 2014, was found to have diffuse dementia with Lewy Bodies in an autopsy.

In the study, 160 people with mild cognitive impairment had brain MRI scans to measure hippocampus size. They also had yearly tests for an average of two years. During that time, 61 people, or 38 percent, developed Alzheimer’s disease, and 20 people, or 13 percent, progressed to probable dementia with Lewy bodies.

Because Lewy body disease can be diagnosed only by an autopsy after death, it is called probable dementia with Lewy bodies. The researchers note that their results should be confirmed with studies that use autopsies for final diagnoses.

Hippocampus Shrinkage

The people who had no shrinkage in the hippocampus were 5.8 times more likely to develop probable dementia with Lewy bodies than those who had hippocampal atrophy. Seventeen of 20, or 85 percent, of people who developed dementia with Lewy bodies had a normal hippocampus volume; whereas, 37 of the 61, or 61 percent, of people who developed Alzheimer’s disease had hippocampus atrophy.

The relationship of hippocampus volume and disease was stronger among people without memory issues. Dementia with Lewy bodies does not always affect memory. Affected thinking skills usually include attention, problem-solving and interpreting visual information.

Lewy bodies appear as spherical masses that displace other cell components. Lewy bodies may be found in the brainstem (within the Substantia Nigra) or within the cortex.

A classical Lewy body is an eosinophilic cytoplasmic inclusion consisting of a dense core surrounded by a halo of 10-nm-wide radiating fibrils, the primary structural component of which is alpha-synuclein.

The condition is named for the American neurologist Frederic Henry Lewey (born Friedrich Heinrich Lewy).

He was the first doctor who noticed that there are some unusual proteins in the brain that make some people act and think differently. But, as of that time, scientists hadn’t been able to figure out what the exact purpose of this protein actually is to the brain. The finding was published in the Handbook of Neurology in 1912.

Ronald L. Walton, et al.
TREM2 p.R47H substitution is not associated with dementia with Lewy bodies
Neurology, November 2016 DOI: 10.%u200B1212/%u200BNXG.%u200B0000000000000085

Image: alpha-synuclein intraneuronal inclusions aggregated to form Lewy bodies. Suraj Rajan, CC BY-SA 3.0