Background

Deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) has been reported to improve gait disturbances in Parkinson's disease (PD); however, there are controversies on the radiological and electrophysiological techniques for intraoperative and postoperative confirmation of the target and determination of optimal stimulation parameters.

Objectives

We investigated the correlation between the location of the estimated PPN (ePPN) and neuronal activity collected during intraoperative electrophysiological mapping to evaluate the role of microelectrode recording (MER) in identifying the effective stimulation site in two PD patients.

Materials and Methods

Bilateral PPN DBS was performed in two patients who had suffered from levodopa refractory gait disturbance. They had been implanted previously with DBS in the internal globus pallidus and the subthalamic nucleus, respectively. The PPN was determined on MRI and identified by intraoperative MER. Neuronal activity recorded was analyzed for mean discharge rate, bursting, and oscillatory activity. The effects were assessed by clinical ratings for motor signs before and after surgery.

Results

The PPN location was detected by MER. Groups of neurons characterized by tonic discharges were found 9–10 mm below the thalamus. The mean discharge rate in the ePPN was 19.1 ± 15.1 Hz, and 33% of the neurons of the ePPN responded with increased discharge rate during passive manipulation of the limbs and orofacial structures. PPN DBS with bipolar stimulation at a frequency range 10–30 Hz improved gait disturbances in both patients. Although PPN DBS provided therapeutic effects post-surgery in both cases, the effects waned after a year in case 1 and three years in case 2.

Conclusions

Estimation of stimulation site within the PPN is possible by combining physiological guidance using MER and MRI findings. The PPN is a potential target for gait disturbances, although the efficacy of PPN DBS may depend on the location of the electrode and the stimulation parameters.

中文翻译：

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微电极记录在脑桥脑深部刺激中的作用：两例生理学研究

背景

据报道，桥脑桥核 (PPN) 的深部脑刺激 (DBS) 可改善帕金森病 (PD) 的步态障碍；然而，对于术中和术后确认靶点和确定最佳刺激参数的放射学和电生理学技术存在争议。

目标

我们研究了估计的 PPN (ePPN) 的位置与术中电生理映射期间收集的神经元活动之间的相关性，以评估微电极记录 (MER) 在确定两名 PD 患者有效刺激部位中的作用。

材料和方法

对两名患有左旋多巴难治性步态障碍的患者进行双侧 PPN DBS。它们之前已分别在内部苍白球和丘脑底核中植入 DBS。PPN 在 MRI 上确定并通过术中 MER 确定。分析记录的神经元活动的平均放电率、爆发和振荡活动。通过手术前后运动体征的临床评分来评估效果。

结果

MER 检测到 PPN 位置。在丘脑下方 9-10 毫米处发现了以强直放电为特征的神经元组。ePPN 中的平均放电率为 19.1 ± 15.1 Hz，在被动操作四肢和口面部结构期间，33% 的 ePPN 神经元的放电率增加。频率范围为 10-30 Hz 的双极刺激 PPN DBS 改善了两名患者的步态障碍。尽管 PPN DBS 在这两种情况下都提供了术后治疗效果，但在病例 1 和病例 2 的一年后效果减弱。

结论

通过结合使用 MER 和 MRI 发现的生理指导，可以估计 PPN 内的刺激部位。PPN 是步态障碍的潜在目标，尽管 PPN DBS 的功效可能取决于电极的位置和刺激参数。