Takashi Morishita, Kelly D. Foote, Samuel S. Wu, Charles E. Jacobson IV, Ramon L. Rodriguez, Ihtsham U. Haq, Mustafa S. Siddiqui, Irene A. Malaty, Christopher J. Hass and Michael S. Okun
Microelectrode recording (MER) and macrostimulation (test stimulation) are used to refine the optimal deep brain stimulation (DBS) lead placement within the operative setting. It is well known that there can be a microlesion effect with microelectrode trajectories and DBS insertion. The aim of this study was to determine the impact of intraoperative MER and lead placement on tremor severity in a cohort of patients with essential tremor.
Consecutive patients with essential tremor undergoing unilateral DBS (ventral intermediate nucleus stimulation) for medication-refractory tremor were evaluated. Tremor severity was measured at 5 time points utilizing a modified Tremor Rating Scale: 1) immediately before MER; 2) immediately after MER; 3) immediately after lead implantation; 4) 6 months after DBS implantation in the off-DBS condition; and 5) 6 months after implantation in the on-DBS condition. To investigate the impact of the MER and DBS lead placement, Wilcoxon signed-rank tests were applied to test changes in tremor severity scores over the surgical course. In addition, a generalized linear mixed model including factors that potentially influenced the impact of the microlesion was also used for analysis.
Nineteen patients were evaluated. Improvement was noted in the total modified Tremor Rating Scale, postural, and action tremor scores (p < 0.05) as a result of MER and DBS lead placement. The improvements observed following lead placement were similar in magnitude to what was observed in the chronically programmed clinic setting parameters at 6 months after lead implantation. Improvement in tremor severity was maintained over time even in the off-DBS condition at 6 months, which was supportive of a prolonged microlesion effect. The number of macrostimulation passes, the number of MER passes, and disease duration were not related to the change in tremor severity score over time.
Immediate improvement in postural and intention tremors may result from MER and DBS lead placement in patients undergoing DBS for essential tremor. This improvement could be a predictor of successful DBS lead placement at 6 months. Clinicians rating patients in the operating room should be aware of these effects and should consider using rating scales before and after lead placement to take these effects into account when evaluating outcome in and out of the operating room.
Houtan A. Taba, Samuel S. Wu, Kelly D. Foote, Chris J. Hass, Hubert H. Fernandez, Irene A. Malaty, Ramon L. Rodriguez, Yunfeng Dai, Pamela R. Zeilman, Charles E. Jacobson IV and Michael S. Okun
In this paper, the authors' aim was to examine reasons underpinning decisions to undergo, or alternatively forgo, a second-sided deep brain stimulation (DBS) implantation in patients with Parkinson disease (PD).
Fifty-two patients with Parkinson disease (PD) were randomized to receive DBS to the subthalamic nucleus or globus pallidus internus (GPi) as part of the COMPARE trial. Forty-four patients had complete data sets. All patients were offered a choice at 6 months after unilateral implantation whether to receive a contralateral DBS implant. All patients had advanced PD. The mean patient age was 59.8 years (range 43–76 years), and the mean duration of disease was 12.2 years (range 5–21 years). The mean baseline Unified Parkinson's Disease Rating Scale (UPDRS)–III motor score was 42.7. The main outcome measures used in this study were the UPDRS-III Motor Scale and the UPDRS-IV Dyskinesia Scale.
Twenty-one (48%) of the 44 patients in the cohort did not undergo bilateral implantation and have been successfully treated for an average of 3.5 years; of these, 14 (67%) had a GPi target. The most common reason for adding a second side was inadequacy to address motor symptoms. Patient satisfaction with motor outcomes after unilateral DBS implantation was the most common reason for not undergoing bilateral implantation. Those who chose a second DBS procedure had significantly higher baseline UPDRS-III motor and ipsilateral UPDRS-III scores, and a significantly lower asymmetrical index. The logistic regression analysis revealed that the odds of proceeding to bilateral DBS was 5.2 times higher for STN than for GPi DBS. For every 1% increase in asymmetry, the odds of bilateral DBS decreased by 0.96.
Unilateral DBS is an effective treatment for a subset of patients with PD. Baseline asymmetry is an important factor in the effectiveness and decision-making process between unilateral and bilateral DBS. Patients with GPi DBS in this cohort were more likely to choose to remain with unilateral implantation.