Although subthalamic nucleus deep brain stimulation appears to improve or eliminate pain for years in Parkinson’s patients, the majority of patients develop new sources of pain.
Researchers from the Seoul National University Hospital in Korea studied the long-term effects of subthalamic nucleus deep brain stimulation (STN DBS) on pain over eight years in 24 patients with Parkinson’s disease. Of the 67% of patients who experienced pain at baseline, all saw pain either improve or disappear altogether eight years after surgery.
However, 18 of the 24 patients (75%) developed new pain, primarily musculoskeletal, over the eight-year follow-up.
Motor symptoms were assessed using the Unified Parkinson’s Disease Rating Scale and Hoehn and Yahr staging scale. Pain severity was scored based on an ordinal scale ranging from 0 (absent) to 10 (maximum pain) in seven areas of the body: head, neck, trunk, and upper and lower extremities on both sides of the body. Pain was characterized in four ways: dystonic, musculoskeletal, radiculoneuritic, and central.
The number of body parts with pain was 21 at baseline and decreased to 11 at eight years after the surgery, with mean (SD) and median scores of the off-state pain at 6.2 (2.5) and 7.0 at baseline, improving to 3.5 (2.2) and 2.5 at eight years after surgery, respectively. New pain developed in 18 of 24 patients (75%) during the follow-up period, with number of body parts affected reaching 47, and mean (SD) and median scores for new pain reaching 4.4 (3.0) and 3.0, respectively. The types of new pain were musculoskeletal in 11 patients, central in 4 patients, radiculoneuritic in 3 patients, and dystonic in 1 patient.
The researchers pointed out the long-term effectiveness of STN DBS for pain relief in Parkinson’s, but recognized that the therapy does not seem to affect the onset of new pain, particularly musculoskeletal, which may need to be addressed independently.
“Although there is growing consensus that STN DBS decreases the level of pain in people with PD, the literature is mixed on the subtypes of pain that are responsive to DBS, and the study by Jung and colleagues shows that new pain arising years after the procedure is common. This underscores the importance of performing future trials with larger cohorts, longer observational periods and standard methods to enable effective interpretation of outcomes,” wrote Richard B. Dewey, Jr., MD, and Pravin Khemani, MD, of the University of Texas Southwestern Medical Center, in an accompanying editorial.