Deep brain stimulation of the subthalamic nucleus for control of extrapyramidal features in advanced idiopathic Parkinson's disease: one year follow-up

Summary. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) with a quadripolar electrode was carried out in 9 patients with advanced idiopathic Parkinson's disease (PD) affected with severe diurnal motor fluctuations. The effect of bilateral STN stimulation was evaluated by clinical methods in all patients after 3 and 12 months. Assessment was based on the Unified Parkinson's Disease Rating Scale (UPDRS), timed motor tests, the Schwab and England Activities of Daily Living and a diary chart to document motor fluctuations. Alterations in parkinsonian signs, motor performance and functional outcome were recorded postoperatively (1) under temporary complete withdrawal of both STN stimulation and medication; (2) in the presence of STN stimulation only; and (3) in the presence of both STN stimulation and medication. The results were compared with the preoperative data assessed in defined on-phase and defined off-phase. STN stimulation on (compared to STN stimulation off) results in a significant improvement in UPDRS motor scores: after 3 months from 50.5 ± 14.3 to 27.8 ± 5.8, and after 12 months from 49.4 ± 14.1 to 27.1 ± 7.1 (p < 0.01). There was a significant decrease in the average duration of off-periods from 8.82 ± 2.47 hours to 1.00 ± 1.06 hours (p < 0.001), a marked increase in on-periods without dyskinesia from 4.62 ± 2.72 to 14.62 ± 1.51 hours (p < 0.01), and a sharp drop in on-periods with dyskinesia from 2.87 (± 4.18) to 0.25 (± 0.97) hours (p < 0.05), which remained stable up to 12 months (off-periods: 1.25 ± 1.58 hours, p < 0.001; on-periods without: 13.87 ± 1.95 hours, p < 0.001; and on-periods wth dyskinesia: 0.37 ± 1.06 hours, p < 0.05). However, our first PD patient with an implanted DBS electrode within the STN died from cardiac infarction two days after surgery. This sudden death was not linked either to surgery nor to stimulation – and happened by chance. Our findings confirm that STN stimulation is a suitable functional neurosurgical procedure for the modulation and control of PD signs associated with severe motor fluctuations, in that they demonstrate a beneficial effect which was fully sustained over a one year follow-up period. Received June 25, 1998; accepted February 3, 1999