SYDNEY—Deep brain stimulation (DBS) is a neuromodulatory modality with the potential to effectively treat a number of symptoms and features of movement disorders. This was the message that came from both a plenary session and a teaching course at the 17th International Congress of Parkinson’s Disease and Movement Disorders.
DBS for Tremor Control and Dystonia
Michele Tagliati, MD, Director of the Movement Disorders Program at Cedars-Sinai Medical Center in Los Angeles, reported on the benefits of DBS in the treatment of tremor, which was the first symptom in Parkinson’s disease to be treated. There are two main targets for the control of tremor. The initial research focused on stimulation of the ventral intermediate (VIM) nucleus of the thalamus, which demonstrated very good control, Dr. Tagliati said, but currently the subthalamic nucleus (STN) appears to be a better target for parkinsonian tremor as it can also control the other motor symptoms of the disease (ie, bradykinesia). “Whatever the target, the outcomes of DBS in tremor have been short of exceptional since the very beginning of our experience,” he said.
Dr. Tagliati also referred to “an explosion of peer-reviewed papers on DBS for dystonia,” noting that DBS is indicated mainly for primary generalized dystonia refractory to conventional therapies. Initial results with pallidal dystonia were short of incredible, he reported, leading to a number of seminal papers, the first of which—by Vidailhet et al—showed 55% improvement in motor scores at 12 months postsurgery. Long-term outcomes for DBS in dystonia appear to be very good. “Unlike Parkinson’s disease, the benefits tend to stay,” he concluded.
STN-DBS for Parkinson’s Disease
DBS was introduced for tremor by the Grenoble group in 1987, but the target at that time was the VIM nucleus of the thalamus. STN-DBS was first conducted in 1993 in Grenoble as a treatment for motor fluctuations, dyskinesia, and tremor. Jens Volkmann, MD, PhD, Chairman of the Department of Neurology at the University Clinic of Würzburg, Germany, reported on a systemic review indicating that STN-DBS reduced Unified Parkinson’s Disease Rating Scale (UPDRS) II and III scores by an average of 50% and 52%, respectively, compared with presurgical levels.
The safety of STN-DBS is very good, with generally a lower adverse event profile than drug therapies in similar patients. The main area of concern, Dr. Volkmann noted, was a detrimental effect on cognition, mood, and behavior, which could result from selection of patients too late in the course of their disease to benefit from surgery. “DBS is usually done around age 65, which means we are wasting the opportunity to intervene earlier in some patients,” Dr. Volkman said.
Two large-cohort studies showed that the effects of STN-DBN on motor symptoms of Parkinson’s disease are sustained for up to five years, after which, there is gradual worsening of axial symptoms such as dysarthria, gait freezing, and postural imbalance, Dr. Volkmann explained. Nonmotor signs such as cognitive decline, apathy, and loss of executive function that normally occur with advanced Parkinson’s disease may be worsened by STN-DBS, suggesting that the modality is better suited for younger patients.
PPN-DBS for Parkinson’s Disease
Elena Moro, MD, PhD, Professor of Neurology at the University Hospital Center of Grenoble, France, reviewed clinical research on a new target, pedunculopontine (PPN) DBS, reporting that clinical evidence suggests that PPN works in Parkinson’s disease. Initially, three clinical trials from different centers reported benefits in freezing and falls. Two studies also demonstrated improvements in sleep disorders and three more indicated improved cognition. The first patients were treated nine years ago, and long-term data are initially positive, although there appears to be some loss of benefits over time. Dr. Moro questioned whether studies are looking at the right end points, as patients are generally very happy with outcomes despite lack of measurable improvements. They spend less time on small tasks, and enjoy slightly more control and less fear, she said.
—Linda Peckel
Contributing Writer