Mahlon DeLong, a globally revered neurologist who spearheaded treatment and research for Parkinson’s disease and other movement disorders, died peacefully at home on May 17 at the age of 86.

DeLong joined the Johns Hopkins University School of Medicine faculty after completing a residency in neurology in 1976, and then became a full professor of neurology and neuroscience in 1986. During his time at the institution, he spearheaded research into the basal ganglia and associated brain circuits involved in movement, emotions and cognition.

His work at Johns Hopkins and elsewhere laid the groundwork for focal neurosurgical approaches, including deep-brain stimulation, in treating Parkinson’s, dystonia and tremor. Other studies he conducted while at Johns Hopkins paved the way for the use of acetylcholinesterase inhibitors in patients with Alzheimer’s.

“Mahlon Delong was a pioneering neurologist whose work at Johns Hopkins revolutionized the treatment of Parkinson’s disease and other neurological disorders,” says Ted Dawson, the Leonard and Madlyn Abramson Professor of Neurogenerative Diseases and director of the Johns Hopkins Institute for Cell Engineering. “His groundbreaking work has given hope and relief to countless patients around the world, transforming lives through the power of science and innovation.”

DeLong graduated from Stanford University in 1961 and Harvard Medical School in 1966. Prior to Johns Hopkins, he completed an internship and one year of residency at Boston City Hospital, then worked as a research associate at the National Institutes of Health.

In 1990, DeLong was recruited to the Emory University School of Medicine, where he served as chair of the neurology department until 2003. He helped grow the department, both in size and prominence, and performed internationally renowned work in the use of pallidotomy procedures to relieve symptoms of Parkinson’s.

He remained a researcher and physician at Emory until 2019. A mentor to many, DeLong served in leadership positions for many foundations and associations, published hundreds of papers, lectured to national and international audiences, and was awarded prominent prizes in neurology.