Lewy bodies are abnormal clumps or aggregates of the protein alpha-synuclein that build up inside nerve cells in the brain. They are considered a pathological hallmark of Parkinson’s disease and are believed to accumulate throughout the brain as the disease progresses. The absence of this pathology, particularly among patients presumed to be in later stages of disease progression, was therefore unexpected.

Previous studies—largely in postmortem tissue—have consistently found widespread Lewy pathology in patients with advanced Parkinson’s disease. However, little was previously known about how this hallmark of disease appears in individuals, especially at the time of DBS surgery.