In a new study, researchers examined a key region of the brain and found that patterns of Alzheimer’s-related damage differed by subtype and age of onset.
These observations could have important treatment implications.
The research was conducted by a team from Mayo Clinic in Florida.
Despite decades of scientific scrutiny, Alzheimer’s disease researchers have yet to work out its cause or treatment.
Understanding what underlies its three distinct subtypes is thought to be a promising new research avenue.
In the study, the team examined brain tissue donated by over 1,000 deceased Alzheimer’s patients.
They focused on an area referred to as the cholinergic hub, which is the target of the only therapies known to effectively manage symptoms in some Alzheimer’s patients.
They looked at a main feature of the disease: neurofibrillary tangles, abnormal protein accumulations that disrupt a neuron’s transport system.
They observed two interesting patterns.
First, they saw more severe signs of disease in patients with the “hippocampal-sparing” subtype of Alzheimer’s.
Whereas the typical Alzheimer’s subtype affects the hippocampus — the brain’s memory center — the hippocampal-sparing subtype mainly affects the cortex, an area of the brain responsible for thoughts and actions.
Thus, Alzheimer’s patients with this subtype may have symptoms related to behavior, language or visual disturbances rather than memory loss.
Second, the team observed more Alzheimer’s-related damage in patients with young-onset Alzheimer’s — presenting with symptoms prior to age 65 — compared to those whose symptoms arose later in life.
Based on these observations, the researchers believe that available therapies will be most effective for people with this Alzheimer’s subtype and in patients with a young-onset form of the disease.
As a next step, the researchers hope to test this hypothesis on living patients. Meanwhile, the team emphasizes the importance of striving for diagnostic accuracy.
The hippocampal-sparing subtype is thought to account for over 10% of Alzheimer’s cases, but it’s often misdiagnosed due to its younger-onset and atypical symptoms.
Cognitive decline can happen quickly for these patients, making a correct initial diagnosis especially important.
The lead author of the study is Melissa Murray, Ph.D.
The study is published in JAMA Neurology.
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