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New research may aid in diagnosing Parkinson's disease

The key to diagnosing Parkinson's disease may be found within your mouth -- in saliva to be exact.

Researchers from Mayo Clinic in Arizona and Banner Sun Health Research Institute have determined that testing a portion of a person's saliva gland may be a way to diagnose Parkinson’s disease.

Parkinson's disease is a progressive disorder of the nervous system that affects movement. It develops gradually, sometimes starting with a barely noticeable tremor in just one hand. But while tremor may be the best-known sign of Parkinson's, the disorder also commonly causes stiffness or slowing of movement. Currently, diagnosis is made based on medical history, a review of signs and symptoms, a neurological and physical examination, and by ruling out other conditions. Up to 30 percent of patients may be misdiagnosed early in the disease. Although Parkinson's disease can't be cured, medications may markedly improve symptoms. This study was funded by the Michael J. Fox Foundation for Parkinson's Research.

Previously there was no accurate diagnostic test for Parkinson’s disease. The researchers state that a procedure termed transcutaneous submandibular gland biopsy may prove to provide the needed accuracy. The test involves inserting a needle into the submandibular gland, located under the jaw, and then withdrawing the needle to obtain the core of gland tissue within. The researchers looked for a protein in the cells from patients who have Parkinson’s disease and compare this to subjects without the disease.

“This is the first study demonstrating the value of testing a portion of the saliva gland to diagnose a living person with Parkinson's disease. Making a diagnosis in living patients is a big step forward in our effort to understand and better treat patients," says study author Charles Adler, M.D., Ph.D., a neurologist with Mayo Clinic in Arizona.

The study involved 15 people with an average age of 68 who had Parkinson's disease for an average of 12 years, responded to Parkinson's medication and did not have known saliva gland disorders. Biopsies were taken of two different saliva glands: the submandibular gland and the minor saliva glands in the lower lip. The surgical team was led by Michael Hinni, M.D., and David Lott, M.D., at Mayo Clinic in Arizona, and the biopsied tissues were tested for evidence of the abnormal Parkinson's protein by study co-author Thomas Beach, M.D., Ph.D., a neuropathologist with Banner Sun Health Research Institute.

"This procedure will provide a much more accurate diagnosis of Parkinson's disease than what is now available," Dr. Beach says. "One of the greatest potential impacts of this finding is on clinical trials, as at the present time some patients entered into Parkinson's clinical trials do not necessarily have Parkinson's disease and this is a big impediment to testing new therapies."

The abnormal Parkinson's protein was detected in nine of the 12 patients who had enough tissue to study providing very positive results that need further studies.

"This study provides the first direct evidence for the use of submandibular gland biopsies as a diagnostic test for living patients with Parkinson's disease," Dr. Adler. "This finding may be of great use when needing definitive proof of Parkinson's disease, especially when considering performing invasive procedures such as deep brain stimulation surgery or gene therapy."