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Título

Interleaved stimulation for refractory tremor in PD: a series case

Resumo

Introduction: Interleaved stimulation (IS) in DBS provides individualized energy for two contacts alternately. Most documented indication concerns the management for levodopa induced dyskinesias. On the other hand, it is well acknowledged that refractory PD tremor responds better to high frequency DBS, although with adverse events on balance and speach. Animal studies demonstrate that coordinated reset stimulation of the subthalamic nucleus presents short and long-term improvement in the parkinsonian motor condition, with lower energy expenditure and lower incidence of complications. We hypothesized if IS, as a quasi-coordinated reset mode, would control tremor and avoid complications. Objective: To test IS would improve tremor without causing adverse effects. Methods: We evaluated 5 tremor-dominant Parkinson's disease patients, on medication and previously stimulated in a basic pattern, all at high voltage and frequency. All had DBS complication due to high total energy delivered, like balance and dysarthrophonia, and pain. We modified the stimulation to the interleaved pattern, using the contacts that the patients already had before. Data analyzed included Unified PD Rating Scale III and tremor score. Results: There were 4 male and 1 female, with mean age of 59. Mean baseline UPDRS was 60,6 and mean tremor score was 3,5. All 5 patients showed satisfactory improvement in parkinsonian symptoms and relief from stimulation-induced side effects after interleaved stimulation, established by a large effect size (Cohen d) in UPDRS III (d=3,71285) and tremor score (d=1,543766). All patients were free of complications after changing the stimulation mode to IS. Discussion: The use of the interleaved mode is known to improve dyskinesias, through stimulating pallid-fugal fibers in the Zona Incerta, and sensory-motor fibers in the laterodorsal zone of the subthalamic nucleus. Requires frequency reduction, so it would be a bad alternative for the tremor-dominant patient, as they tend respond to high frequencies. On the other hand, the high frequency leads to adverse effects such as hypophonia, dysarthrophonia and worsening of balance. Conclusion: With this study, we demonstrated a substantial improvement in the motor condition of these patients, in addition to an improvement in side effects.