Accurate diagnosis of Parkinson's disease, and the related disease "dementia with Lewy bodies," can be difficult in the early stages of both conditions. While brain biopsies can be more accurate, the risk of complications has been considered too high. New research indicates that a biopsy of the submandibular gland can help identify the same pathology that is seen in the brain, providing some of the increased accuracy of brain biopsy, but not the increased risk.