Lafreniere-Roula Myriam, Hutchison William D, Lozano Andres M, Hodaie Mojgan, Dostrovsky Jonathan O
Department of Physiology, University of Toronto, Ontario, Canada.
J Neurosurg. 2009 Oct;111(4):724-8. doi: 10.3171/2009.3.JNS09111.
The aim of the current study was to examine and compare the aftereffects of local high-frequency microstimulation through the recording electrode on the firing of neurons in the subthalamic nucleus (STN) and the substantia nigra pars reticulata (SNr) in patients undergoing surgery for deep brain stimulation. Deep brain stimulation has been playing an increasing role in the treatment of Parkinson disease, with the subthalamic nucleus (STN) being the preferred implantation target. Changes in cellular activity indicative of the borders of the STN are typically used during surgery to determine the extent of the STN and locate the optimal target, but in some cases borders may be difficult to identify. In this study the authors compared the effects of microstimulation in the SNr and STN. In previous studies they have shown that microstimulation in the internal globus pallidus, which is functionally similar to the SNr, inhibits firing, whereas similar microstimulation in the STN has minimal effect. The presence of inhibition in the SNr but not in the STN could be used as an additional criterion to help identify the location of the border between the STN and SNr.
Dual microelectrode recordings were performed during stereotactic surgery in 4 patients. Well-isolated high-amplitude units were stimulated extracellularly through the recording microelectrode with 0.5-second trains of high frequency (200 Hz) and low current (<or= 5 microA).
In the majority (92%) of SNr neurons, this type of stimulation led to a period of inhibition lasting several hundreds of milliseconds following the end of the train. In contrast, only 1 neuron of 70 judged to be in the STN by other criteria was inhibited by this type of microstimulation, and this neuron was located at the ventral border of the STN.
These findings indicate that prolonged inhibition of firing following low-amplitude high-frequency microstimulation via the recording electrode is a consistent feature of almost all SNr neurons and rarely if ever occurs in STN neurons. This feature therefore provides a useful additional finding that can be used to help identify the border between the STN and SNr.
本研究旨在通过记录电极对接受脑深部刺激手术患者的丘脑底核（STN）和黑质网状部（SNr）神经元放电进行局部高频微刺激，并比较其后续效应。脑深部刺激在帕金森病治疗中发挥着越来越重要的作用，丘脑底核（STN）是首选的植入靶点。手术过程中，通常利用指示STN边界的细胞活动变化来确定STN范围并定位最佳靶点，但在某些情况下，边界可能难以识别。在本研究中，作者比较了SNr和STN中微刺激的效应。他们在之前的研究中表明，在功能上与SNr相似的苍白球内侧部进行微刺激会抑制放电，而在STN中进行类似的微刺激则作用极小。SNr中存在抑制作用而STN中没有，这一现象可作为一项额外标准，用于辅助确定STN与SNr之间的边界位置。
对4例患者在立体定向手术期间进行双微电极记录。通过记录微电极以0.5秒的高频（200赫兹）和低电流（≤5微安）对分离良好的高振幅单位进行细胞外刺激。
在大多数（92%）SNr神经元中，这种类型的刺激在一串刺激结束后会导致持续数百毫秒的抑制期。相比之下，根据其他标准判断位于STN中的70个神经元中，只有1个神经元受到这种微刺激的抑制，且该神经元位于STN的腹侧边界。
这些发现表明，通过记录电极进行低振幅高频微刺激后，放电的长时间抑制是几乎所有SNr神经元的一个一致特征，而在STN神经元中极少出现。因此，这一特征为辅助识别STN与SNr之间的边界提供了一项有用的额外依据。
