Smell Loss in Neurologic Disorders
Researchers are discovering that a loss of smell can be a hallmark symptom in the earliest stages of many diseases.
In the 1970s, researchers learned that smell is compromised in neurodegenerative conditions like Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis (MS). Now, they are discovering that loss of smell can be a hallmark symptom in the earliest stages of many diseases.
"Recent studies of brains from Alzheimer's and Parkinson's disease patients reveal structural and biochemical alterations in regions associated with the sense of smell," says Richard Doty, Ph.D., professor and director of the Smell & Taste Center at the University of Pennsylvania. Loss of smell occurs 90 percent of the time in Parkinson's disease. This is greater than the prevalence of tremor, a cardinal sign of the disorder.
Yet in one study of Parkinson's patients, 72 percent were unaware they had a smell disorder before undergoing standardized testing. Only two out of 34 Alzheimer's disease patients reported suffering from smell and/or taste problems-even though 90 percent of the patients scored lower on standardized smell tests than healthy subjects. https://www.brainandlife.org/articles/what-the-nose-knows