Subthalamic stimulation benefits are durable in PD patients
MedWire News: Most of the beneficial effects of deep brain stimulation of the subthalamic nucleus (STN-DBS) in patients with Parkinson's disease (PD) are sustained for up to 10 years, report researchers.
Their study shows that motor benefits are maintained throughout follow-up, although axial signs worsen over time, causing an overall slight worsening of patients' PD symptoms.
"Taking into account the significant progressive and parallel loss of the levodopa response on axial scores, the decline in DBS benefit could be due to the natural progression of PD," the team comments in the Archives of Neurology.
Elena Moro (University of Toronto, Ontario, Canada) and colleagues identified 18 patients who were available for follow-up 10 years after bilateral STN-DBS surgery. At this time, the patients had less severe PD symptoms with active stimulation than without, as rated by an assessor blinded to treatment condition.
Specifically, off-medication Unified PD Rating Scale scores were 36.6 under stimulation versus 48.6 without stimulation. On-medication scores were 35.0 with stimulation versus 39.6 without; both of these differences were statistically significant.
Scores for resting tremor, action tremor, rigidity, and bradykinesia were all significantly better when tested under stimulation relative to no stimulation. However, axial signs, speech, arising from chair, posture, gait, and postural stability were no better with than without stimulation.
The patients were also assessed at 1 and 5 years after surgery. This revealed a worsening of UPDRS scores over time under stimulation but off medication, which was due in part to worsening axial signs, with scores increasing from 6.4 at 1 year to 11.4 at 10 years.
However, axial signs also worsened in patients when tested under stimulation and on medication, from 5.6 at 1 year to 10.8 at 10 years.
"Despite the PD progression, STN stimulation allowed a persistent, marked reduction in dopaminergic drug dosages," the researchers note.
The average levodopa equivalent daily dose fell from 1238 mg at baseline to a low of 706 mg at 5 years and remained reduced, at a dose of 789 mg, at the 10-year follow-up.
"These data, together with the minimal changes in stimulation settings in the long-term, further support the sustained benefit of stimulation," say Moro et al.
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By Eleanor McDermid