Saliva glands may diagnose Parkinson’s disease

New research from Mayo Clinic in Arizona and Banner Sun Health Research Institute suggests that testing a portion of a person’s saliva gland may be a way to diagnose the degenerative disorder Parkinson’s disease. The study will be presented at the American Academy of Neurology’s annual meeting in San Diego in March.

“There is currently no diagnostic test for Parkinson’s disease in living individuals,” said study author and Mayo Clinic neurologist Dr Charles Adler. “It’s critical to make the diagnosis when we are sending Parkinson’s disease patients for invasive procedures like deep brain stimulation surgery, when we do gene therapy … and in other research studies in which we are looking for better treatments and better diagnosis of patients.”

Parkinson’s disease is a progressive disorder of the nervous system that affects movement. It develops gradually, sometimes starting with a tremor in one hand, and commonly causes stiffness or slowing of movement.

Although Parkinson’s disease can’t be cured, medications may markedly improve symptoms, hence the importance of diagnosis. This is currently 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% of patients may be misdiagnosed early in the disease.

Dr Adler explained that there are abnormal proteins in the brains of Parkinson’s disease patients; the presence of the disease could, until now, only be confirmed by finding these proteins in a biopsy of the brain. However, a previous study of Dr Adler’s showed that the proteins have also been discovered in the submandibular saliva gland, found under the lower jaw, during autopsies of Parkinson’s patients.

“We looked at 28 patients with Parkinson’s, and all 28 patients who’d died had the proteins in the submandibular gland,” he said.

The goal of the latest study was to use this method to find these proteins in living patients. Using 15 people who had advanced Parkinson’s disease (over five years), responded to Parkinson’s medication and did not have known saliva gland disorders, biopsies were taken of their submandibular glands. Four of the cases did not have enough tissue to study.

“Of the 11 Parkinson’s patients that we did have enough tissue to look at, nine of those cases had the abnormal protein that we also see in the brain of Parkinson’s patients,” said Dr Adler. “Thus, we believe that we can make a diagnosis of Parkinson’s disease in these living individuals.”

Biopsies were also taken of the minor salivary glands in the lower lip, but only one of the 15 cases had the protein there. “So the minor salivary gland would not be a good biopsy location,” said Dr Adler.

Dr Adler says that making a diagnosis in living patients is “a big step forward in our effort to understand and better treat patients.” In future, he hopes to be able to reproduce his results in patients who have had Parkinson’s disease for less than five years.

The surgical team was led by Dr Michael Hinni and Dr David Lott at Mayo Clinic in Arizona, and the biopsied tissues were tested for evidence of the abnormal Parkinson’s protein by study co-author Dr Thomas Beach with Banner Sun Health Research Institute. The study was funded by the Michael J Fox Foundation for Parkinson’s Research.