Neurosurg Focus
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Over the last decade, the analysis of genetic defects in primary tumors has been central to the identification of molecular events and biological pathways involved in the pathogenesis of medulloblastoma, the most common malignant brain tumor of childhood. Despite this, understanding of the molecular basis of the majority of cases remains poor. In recent years, the emerging field of epigenetics, which describes heritable alterations in gene expression that occur in the absence of DNA sequence changes, has forced a revision of the understanding of the mechanisms of gene disruption in cancer. ⋯ These findings shed new light on medulloblastoma and offer great potential for an improved understanding of its molecular pathology. The authors review the current understanding of epigenetic events in cancer and their contribution to medulloblastoma development. Their nature, origins, and functional role(s) in tumorigenesis are considered, and the authors assess the potential utility of these events as a basis for novel diagnostic and therapeutic approaches.
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Comparative Study
Subthalamic stimulation for Parkinson disease: determination of electrode location necessary for clinical efficacy.
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) performed using intraoperative microelectrode recording (MER) to adjust electrode placement has become a widely used treatment for patients with advanced Parkinson disease (PD). Few studies have been conducted to examine the location of implanted electrodes relative to the intended target, and even fewer have been undertaken to investigate the degree to which variations in the location of these electrodes impacts their clinical efficacy. This study was performed to examine these issues. ⋯ The findings in this study lead the authors to suggest that a DBS electrode placed anywhere within a 6-mm-diameter cylinder centered at the presumed middle of the STN (based on stereotactic atlas coordinates) provides similar clinical efficacy. Future studies may be warranted to evaluate prospectively the degree to which MER modification of the anatomically and/or image-determined target improves clinical efficacy of DBS electrodes.
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Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects. ⋯ Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.