Salivary Gland Test Can Spot Early Parkinson’s Disease, Mayo Team Says

No accurate diagnostic tests are available

Researchers at the Mayo Clinic in Arizona and at Banner Sun Health Research Institute have determined that testing a portion of a person’s submandibular gland may be a way to diagnose early Parkinson’s disease (PD). The study was published in Movement Disorders.

Currently, no accurate diagnostic tests are available for PD. The researchers believe that transcutaneous submandibular-gland biopsy may provide the needed accuracy. The test involves inserting a needle into the submandibular gland and withdrawing the needle to obtain the core of gland tissue within. The researchers looked for an abnormal protein in the cells from patients with early PD and compared it with proteins from subjects without the disease.

“This is the first study demonstrating the value of testing a portion of the submandibular gland to diagnose a living person with early Parkinson’s disease. Making a better diagnosis in living patients is a big step forward in our effort to understand and better treat patients,” said study co-author Charles Adler, MD, PhD, a professor of neurology at the Mayo Clinic in Arizona.

The study involved 25 patients who had PD for less than five years and 10 control subjects without PD. Biopsies were taken from one submandibular salivary gland. The biopsies were done as an office procedure. The biopsied tissues were tested for evidence of the abnormal PD by study co-author Thomas Beach, MD, PhD, a neuropathologist at the Banner Sun Health Research Institute.

“This procedure will provide a much more accurate diagnosis of Parkinson's disease than what is now available,” Beach said. “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 PD protein was detected in 14 of the 19 patients who had enough tissue to study, providing positive results that need further investigation. The research team previously had shown that the biopsy could detect the protein in 9 of 12 patients with advanced disease.

PD is a progressive disorder of the nervous system that affects movement as well as sleep, walking, balance, blood pressure, and smell. The disorder develops gradually, sometimes starting with a barely noticeable tremor in one hand. But while tremor may be the best-known sign of PD, the disorder also commonly causes stiffness or slowing of movement. Currently, a diagnosis is based on the patient’s medical history, on a review of signs and symptoms, on a neurological examination, and by ruling out other conditions. In a previous study, Adler and Beach found that up to 45% of PD patients may be misdiagnosed early in the disease. Although PD can’t be cured, medications may improve symptoms.

Source: Mayo Clinic; February 1, 2016.