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aPercentage improvement from baseline medication off state to medication off/stimulation on at follow-up. bPercentage reduction in dyskinesia.

Abbreviations: ADL, activities of daily living; DBSPDSG, Deep Brain Stimulation for Parkinson's Disease Study Group; UPDRS, Unified Parkinson's Disease Rating Scale.

aPercentage improvement from baseline medication off state to medication off/stimulation on at follow-up. bPercentage reduction in dyskinesia.

Abbreviations: ADL, activities of daily living; DBSPDSG, Deep Brain Stimulation for Parkinson's Disease Study Group; UPDRS, Unified Parkinson's Disease Rating Scale.

In the medication off state they showed an 18% improvement in UPDRS ADL scores and a 39% improvement in UPDRS motor scores with stimulation compared to baseline medication off scores. There was also an 89% reduction in dyskinesia and a 3% reduction in antiparkinsonian medications. Lyons et al. (22) reported nine patients (three unilateral and six bilateral) with a mean follow-up of 48.5 months (range 25-81 months) after GPi DBS. There was a significant improvement in UPDRS ADL scores of 21% and a 37% improvement in UPDRS motor scores. Dyskinesia was reduced by 64% and there were no reductions in antiparkinsonian medications. Rodriguez-Oroz et al. (23) reported results of a multicenter study of 20 PD patients who received bilateral GPi DBS. After three to four years of follow-up, significant improvements in UPDRS ADL and motor scores in the medication off/stimulation on condition compared with the baseline medication off state were maintained. More specifically, at the three-to-four-year visit, there were significant improvements in tremor, rigidity, bradykinesia, gait, and dyskinesia compared to baseline and there was no significant worsening compared to the one-year visit.

In contrast, some studies have shown a loss of effect of GPi DBS over time (18,20). Ghika et al. (18) reported six PD patients with a minimum follow-up of 24 months after GPi DBS. The mean improvement in UPDRS motor scores in the medication off/stimulation on state compared to the baseline medication off condition was 50% and for UPDRS ADL scores it was 68%. Mean daily off time decreased from 40% to 10% and dyskinesia was reduced by 65%. Although the improvements persisted beyond two years after surgery, signs of decreased efficacy were seen after 12 months. Volkmann et al. (20) reported long-term outcomes of bilateral GPi DBS 12, 36, and 60 months after surgery (Table 1). UPDRS motor scores were significantly improved in the medication off/stimulation on condition compared to baseline by 56% at 12 months and 43% at 36 months. However, at 60 months there was a nonsignificant improvement of 24% compared to baseline. Similarly, for UPDRS ADL scores, at 12 months, there was a significant improvement of 49% compared to baseline; however, a 26% improvement at 36 months was not significantly different from baseline and at 60 months there was a worsening of 1.5%. More specifically, at 12 months, there was a significant improvement in bradykinesia, rigidity, tremor, and postural instability/gait, at 36 months there were significant improvements only in bradykinesia and postural instability/gait, and by 60 months, there was a significant improvement only in rigidity. In contrast, dyskinesia continued to be significantly improved throughout the five-year follow-up.

In summary, multiple studies have demonstrated the short-term benefits of GPi DBS in controlling the cardinal symptoms of PD and reducing dyskinesia. Results have been inconsistent regarding the long-term benefits in the cardinal symptoms of PD with GPi DBS; however, there is consensus regarding a significant and sustained reduction in levodopa-induced dyskinesia despite minimal if any reductions in antiparkinsonian medications. Further research is necessary to confirm the long-term benefits of GPi DBS.

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Brain Blaster

Brain Blaster

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