Not All Alzheimer's Patients Have Memory Loss

Hippocampal sparing Alzheimer disease variant was characterized by protein tangle count and location

(RxWiki News) Alzheimer’s disease typically affects the area of the brain involved in memory. However, there’s a less common type of Alzheimer’s in which memory loss is not the main symptom.

In one variation of Alzheimer’s disease, called hippocampal sparing Alzheimer's disease (HpSp AD), patients have personality and behavioral changes. They may have abnormal movements and difficulty reasoning. Most patients have near normal memory, but may have language and speaking problems.

Through examining brains of patients diagnosed with any type of Alzheimer's, a research team found that HpSp AD affected different areas of the brain than the more common type of Alzheimer’s disease.

These researchers found that HpSp AD was more common in males than females. The study also found that patients were affected at a much younger age and died sooner after showing HpSp AD symptoms than typical Alzheimer's disease patients.

"Discuss memory or behavior concerns with your doctor."

Melissa E. Murray, PhD, from the Mayo Clinic in Jacksonville, Florida, led the team of researchers who conducted this study.

For their study, Dr. Murray and her team analyzed brain tissue stored in a tissue bank.

Two proteins are commonly found in the brains of Alzheimer's patients with typical Alzheimer's disease. These proteins are called beta-amyloid, which produces plaques or clumps, and tau proteins that can become tangles, or misshapen proteins in the brain. In the common form of Alzheimer's, beta-amyloid and tau proteins are most often found in the hippocampus, the area of the brain involved in memory.

Among the 1,821 brains of people who had Alzheimer’s disease, the researchers identified 187 brains with tau protein tangles in areas other than the hippocampus.

The brain areas where the researchers found Alzheimer's tau protein tangles were the temporal region (the brain region near the temples), the frontal region (the area behind the forehead) and the parietal region (the region on the top of the head over the ears).

The research team categorized where the proteins were found and how many tangles of tau proteins they found. Based on the number and location of tangles, they created a formula to characterize Alzheimer's not involving the hippocampus. They called it hippocampal sparing Alzheimer's disease (HpSp AD). This variation of Alzheimer's disease, HpSp AD, was found in 11 percent of the brains the researchers analyzed.

Protein patterns of HpSp AD were found in the same approximate numbers in the frontal, parietal and temporal regions of the brains analyzed. Between 59 and 63 percent of the HpSp AD cases were found in males.

Age when symptoms appeared differed depending on where the HpSp AD was found. Symptoms of this Alzheimer's variation found in the frontal lobe started when patients were an average of 59 years old. Symptoms started at an average age of 61 years for patients with HpSp AD in the parietal region and at age 61 for HpSp AD in the temporal area.

Symptoms of patients with HpSp AD got worse faster than those with typical Alzheimer's disease.

The age at death varied depending on where the HpSp AD proteins were found.

The average age at death was 70 years old among patients with involvement in the frontal region, 69 years old for those with HpSp AD proteins in the parietal region and 78 years for patients with temporal HpSp AD.

"What is tragic is that these patients are commonly misdiagnosed and we have new evidence that suggests drugs now on the market for [Alzheimer's disease] could work best in these hippocampal sparing patients — possibly better than they work in the common form of the disease," Dr. Murray said in a press release.

"Our studies support the notion that dementia related to [Alzheimer's disease] does not necessarily equate to a loss of memory, and points to the need for more research in amyloid and tau imaging biomarkers to help clinicians accurately diagnose [Alzheimer's disease] — regardless of subtype," Dr. Murray said.

Dr. Murray presented this research at the Annual Meeting of the American Academy of Neurology in Philadelphia on May 1, 2014.

Funding for this study was provided by the Robert H. and Clarice Smith and Abigail Van Buren Alzheimer’s Disease Research Program.

Review Date: 
May 5, 2014