Alzheimer;'s disease is a common disease in the United States; in fact, it is considered the sixth leading cause of death in the country. It affects more than 5 million Americans. A new research from the Mayo Clinic in Florida reveals that approximately 600,000 Americans may have a subtype of Alzheimer's disease called 'hippocampal sparing Alzheimer's disease'.
The research team was led by Dr. Melissa Murray, an assistant professor of neuroscience at the Mayo clinic. The study was presented at the American Academy of Neurology Annual Meeting in Philadelphia, PA.
The research team studied 1,821 brains that were confirmed to have Alzheimer's disease. Apparently, every subtype of Alzheimer's has two specific hallmarks, plaques and tangles in the brain. Amyloid beta is responsible in the formation of plaques in the brain while tau is the one that produces tangles in the brain.
The team used tangle numbers to create a mathematical algorithm wherein they found out that all Alzheimer's subtypes contain the same amount of amyloid beta while the hippocampal sparing variant has tau tangles in unequal areas of the hippocampus. Hence, they discovered that in patients with this disease, tau damages neurons in brain areas responsible for behaviour, motor recognition, motor awareness and use of speech and vision.
The said subtype was discovered in 11% of the patients. This type of Alzheimer's has low impact on memory but more on behavioural problems. One type of behavioural problem is sudden outburst of anger or emotions. Furthermore, language and visual problems might happen. Also, they are more common in males with onset occurring at a younger age than the traditional Alzheimer's disease wherein it usually happens by 50 years old and above.
Dr. Murray said that since the symptoms and manifestations usually does not include any memory lapses, it is usually misdiagnosed. Some patients can be diagnosed with frontotemporal dementia which is characterized by changes in personality and social behaviour. They may also be diagnosed to have corticobasal syndrome wherein there is cognitive dysfunction and movement problems.
"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, regardless of subtype," Dr. Murray said.