While conducting experiments in mice, researchers stumbled upon a correlation between Alzheimer’s disease plaques and hearing loss. In one transgenic mouse model of Alzheimer’s, older mice exhibited hearing changes akin to those observed in humans with Alzheimer’s.

The critical factor appeared to be the location of amyloid beta protein plaques, with hearing impairment linked to plaques on the auditory brainstem.

This finding could offer a new approach to tracking Alzheimer’s disease progression and inform diagnostic practices.

Key Facts:

The research involved two different transgenic mouse models of Alzheimer’s disease, both of which were designed to produce amyloid beta protein, the main component of the plaques associated with Alzheimer’s.
The study revealed that plaques in certain parts of the brain, such as the hippocampus and auditory cortex, didn’t appear to have a substantial impact on hearing loss. The crucial factor seemed to be the presence of plaques in the auditory brainstem.
Researchers found that the plaques on the auditory brainstem impeded the area’s ability to coordinate responses to sound, potentially explaining why some Alzheimer’s patients experience auditory symptoms.

Na was conducting hearing tests on mice with amyloid beta, the main component of protein plaques and tangles found in Alzheimer’s. While looking at two different transgenic mouse models of the disease, he found for one model, called 5xFAD, the older mice had hearing changes similar to what is found in people with Alzheimer’s disease. The other model did not demonstrate these hearing changes, nor did younger mice in the 5xFAD group.

Researchers found that the brains of older mice from both models had plaques in the hippocampus and auditory cortex. Credit: Neuroscience News

“It was a chance observation,” said Na, who is first author of a paper with these findings in Frontiers in Neuroscience.

“Both mouse models had amyloid beta protein, but where we found the plaque varied, and that may be why hearing loss varied across the groups.”

Researchers found that the brains of older mice from both models had plaques in the hippocampus and auditory cortex. But the brain of mice with hearing changes also had a small amount of plaque on the auditory brainstem, suggesting this area may be sensitive to disruption from plaque found in Alzheimer’s. Researchers discovered that the plaque reduced the brainstem’s ability to coordinate responses to sound.

“This may explain why Alzheimer’s patients have auditory symptoms,” said Patricia White, PhD, professor of Neuroscience and senior author of the study.

“We think the location of plaques may be more important to hearing decline. It could be a potential biomarker to track disease progression because it could be assessed with amyloid PET imaging.

“Our data also suggest that regular auditory Brainstem Response assessments could help with diagnosis.”

Article originally appeared on NeuroScience News