By Andrew Czyzewski
Deep brain stimulation (DBS) for patients with Parkinson's disease (PD) achieves improvements in motor symptoms that are sustained over 3 years, report researchers.
They also found that targeting the globus pallidus interna (GPi) or subthalamic nucleus (STN) gave largely equivalent benefit.
However, all treated patients showed a steady decline in cognitive function and quality of life, after early improvements.
Reporting in Neurology, Frances Weaver (Department of Veterans Affairs, Washington, DC, USA) and colleagues say the findings "likely reflect underlying disease progression and highlight the importance of non-motor symptoms in determining quality of life."
The researchers initiated a multicenter controlled trial of patients with advanced PD who were randomly assigned to receive GPi (n=89) or STN DBS (n =70) and followed up for 36 months. The primary outcome was motor function on stimulation/off medication using the Unified Parkinson's Disease Rating Scale motor subscale.
Weaver et al report that motor function improved between baseline and 36 months for GPi (41.1 to 27.1 points) and STN (42.5 to 29.7 points); improvements were similar between targets and stable over time.
Health-related quality of life improved at 6 months on all subscales (all values significant), but improvement diminished over time.
Despite their broad equivalence in the on stimulation/off medication state, there were some differences between GPi and STN. The GPi group had consistently lower (better) motor scores compared with the STN group in the off medication/off stimulation state, which remained stable throughout the 36-month follow-up period.
Meanwhile, the on medication/on stimulation tests showed that both groups initially benefited from a synergistic effect of DBS plus medications. This was largely maintained in the GPi group during the study period but significantly dropped off in the STN group after 6 months.
In an accompanying editorial, Michele Tagliati (Cedars-Sinai Medical Center, Los Angeles, California) says the study suggests some specific benefits of targeting the GPi. "In the absence of severe resting tremor, which probably remains more sensitive to
STN stimulation, GPi DBS is becoming an increasingly frequent and important option."
She adds: "This study will inject more reliable evidence in delicate long-term decisions, based until now almost exclusively on the preference and personal experience of the DBS provider."
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