Restoring scents: faulty sniffers may get help

Science News, July 7, 2007 by Janet Raloff

Working the same trick with human olfactory stem cells has proved challenging, however. Recognizing such cells in a donor's nasal tissue is not easy, Schwob says, and the stem cells don't grow well in the lab.

Indeed, Henkin says that there's much to learn about the environment that the cells of faulty sniffers need in order to regenerate. But the payoff for success, he says, is watching patients come alive to the scents around them.

In particular, Betty says, "I've learned how wonderful foods can smell and taste." It's something that her husband no doubt appreciates: He's a chef.

Of course, there can be one weighty side effect of gaining smell. "When I first was beginning to smell things, I became ravenous," Betty says. "I don't know if food tasted better or the new scents just stimulated my appetite. But I [temporarily] gained 30 pounds over the first couple years."

RELATED ARTICLE: Beyond the nose.

Smell studies may offer nonolfactory benefits

Smell loss may be an early diagnostic symptom of Alzheimer's disease, new data indicate. Ten years ago, scientists at Rush University Medical Center in Chicago recruited more than 1,000 area seniors, all about 80 years old, into the hospital's Memory and Aging Project. At enrollment, the volunteers took scratch-and-sniff tests of their ability to recognize such familiar odors as turpentine, soap, and lemon.

After the recruits die, Robert S. Wilson and his colleagues at Rush compare data from those smell-recognition tests with autopsy analyses of cell-fiber tangles in the brain--one hallmark of Alzheimer's disease.

Data from the first 129 individuals show that the more trouble a person had identifying smells accurately, the greater the number of tangles that showed up in the brain's olfactory area. This link was strong even in people "with no cognitive impairment" when the smell testing took place, Wilson told Science News, suggesting "that problems in smell ability may be a very early sign of [Alzheimer's] disease." His team's findings appeared in the January Journal of Neurology, Neurosurgery, and Psychiatry.

In the early stages of Alzheimer's, nerve connections between the nose and brain may work fine, Wilson says. The problem may lie in the inability of brain tissue riddled with tangles to make sense of odor signals.

A new tool developed by Robert A. Frank and his colleagues of the University of Cincinnati may help researchers such as Wilson continue their smell analyses in people with Alzheimer's, other dementias, Parkinson's disease, or olfactory loss alone. Frank's team devised canisters that open when people stick their noses into them and inhale. The more quickly a person notices an odor, the smaller the sniff he or she takes. Computers monitor each inhalation's length and intensity, thereby gauging ability to smell in people who may not be able to speak or even think clearly, says Frank.

Wilson adds that smell testing may one day help identify patients with Alzheimer's and other neurological conditions before dementia or other crippling symptoms set in--a time when therapy can be most effective. --J.R.