Research Links Odor Channels to Brain, Onset of Alzheimer’s

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United Press International

A team of British researchers has new evidence supporting the theory that some type of virus or environmental toxin enters the brain through the odor pathway to trigger Alzheimer’s disease.

Scientists at the University of Manchester and the Radcliffe Infirmary in England examined the brains of nine people who had suffered from Down’s syndrome.

They studied those brains because Down’s syndrome victims develop plaques in their brains similar to those found in the brains of Alzheimer’s patients.


Based on the age and the extent of plaques, the researchers said the plaque appeared to originate in parts of the brain known as the amygdala and hippocampus.

“Why areas such as the amygdala and hippocampus should be preferentially or primarily involved is unclear, although their connection with the outside world through the olfactory bulbs and tracts suggests that this latter pathway may provide a possible point of entry to the brain of the Alzheimer’s disease ‘pathogen,’ ” the researchers said.

They reported their findings recently in a letter published in the New England Journal of Medicine.

Nose Could Be Entry Route

“The changes described here as seen in patients with Down’s syndrome, coupled with recent reports pointing to defects in odor identification . . . early in the course of the illness in patients with . . . Alzheimer’s disease, are consistent with the theory of initial damage to associated higher ‘cortical’ centers,” they said.

They added that the observation points to the possibility that the nose or olfactory nerve is the route of entry for some unknown agent that could cause or aggravate the pathological changes that occur in both Down’s syndrome and Alzheimer’s patients.

David Mann, a neuropathologist at the University of Manchester who co-authored the letter, said in a telephone interview that the findings are still far from confirming that this is how Alzheimer’s disease is caused. But they support this hypothesis.


“If one injects things like viruses into the nasal (membranes) they will travel into the brain and spread there. There are clear precedents for agents like viruses accessing the olfactory system and the brain,” he said.