Safety issues during surgical monitoring.

While intra-operative neuro-physiologic assessment and monitoring improve the safety of patients, its use may also introduce new risks of injuries. This chapter looks at the electric safety of equipment and the potential hazards during the set-up of the monitoring. The physical and functional physiologic effects of electric shocks and stimulation currents, standards for safety limits, and conditions for tissue damage are described from basic physical principles.

Neurophysiology during movement disorder surgery.

During stereotactic procedures for treating medically refractory movement disorders, intraoperative neurophysiology shifts its focus from simply monitoring the effects of surgery to an integral part of the surgical procedure. The small size, poor visualization, and physiologic nature of these deep brain targets compel the surgeon to rely on some form of physiologic for confirmation of proper anatomic targeting. Even given the newer reliance on imaging and asleep deep brain stimulator electrode placement, it is still a physiologic target and thus some form of intraoperative physiology is necessary.

Intraoperative Neuromonitoring.

Intraoperative neuromonitoring encompasses a variety of different modalities in which different neuropathways are monitored either continuously or at defined time points throughout a neurosurgical procedure. Surgical morbidity can be mitigated with careful patient selection and thoughtful implementation of the appropriate neuromonitoring modalities through the identification of eloquent areas or early detection of iatrogenic pathway disruption. Modalities covered in this article include somatosensory and motor evoked potentials, electromyography, electroencephalography, brainstem auditory evoked responses, and direct cortical stimulation.

Subthalamic Peak Beta Ratio Is Asymmetric in Glucocerebrosidase Mutation Carriers With Parkinson's Disease: A Pilot Study.

Up to 27% of individuals undergoing subthalamic nucleus deep brain stimulation (STN-DBS) have a genetic form of Parkinson's disease (PD). G () mutation carriers, compared to sporadic PD, present with a more aggressive disease, less asymmetry, and fare worse on cognitive outcomes with STN-DBS. Evaluating STN intra-operative local field potentials provide the opportunity to assess and compare symmetry between and non- mutation carriers with PD; thus, providing insight into genotype and STN physiology, and eligibility for and programming of STN-DBS.

Dynamic Computational Model of the Human Spinal Cord Connectome.

Connectomes abound, but few for the human spinal cord. Using anatomical data in the literature, we constructed a draft connectivity map of the human spinal cord connectome, providing a template for the many calibrations of specialized behavior to be overlaid on it and the basis for an initial computational model. A thorough literature review gleaned cell types, connectivity, and connection strength indications.

Practice guidelines for the supervising professional: intraoperative neurophysiological monitoring.

The American Society of Neurophysiological Monitoring (ASNM) was founded in 1989 as the American Society of Evoked Potential Monitoring. From the beginning, the Society has been made up of physicians, doctoral degree holders, Technologists, and all those interested in furthering the profession. The Society changed its name to the ASNM and held its first Annual Meeting in 1990.

Neuromonitoring for Spinal Cord Stimulation Lead Placement Under General Anesthesia.

Spinal cord stimulation (SCS) is a common therapeutic technique for treating medically refractory neuropathic back and other limb pain syndromes. SCS has historically been performed using a sedative anesthetic technique where the patient is awakened at various times during a surgical procedure to evaluate the location of the stimulator lead. This technique has potential complications, and thus other methods that allow the use of a general anesthetic have been developed.

Theoretical Effect of DBS on Axonal Fibers of Passage: Firing Rates, Entropy, and Information Content.

Background: Deep brain stimulation (DBS) has effects on axons that originate and terminate outside the DBS target area.

Objective: We hypothesized that DBS generates action potentials (APs) in both directions in "axons of passage," altering their information content and that of all downstream cells and circuits, and sought to quantify the change in fiber information content.

Methods: We incorporated DBS parameters (fiber firing frequency and refractory time, and AP initiation location along the fiber and propagation velocity) in a filtering function determining the AP frequency reaching the postsynaptic cell.

High-Frequency Stimulation of Dorsal Column Axons: Potential Underlying Mechanism of Paresthesia-Free Neuropathic Pain Relief.

Objective: Spinal cord stimulation (SCS) treats neuropathic pain through retrograde stimulation of dorsal column axons and their inhibitory effects on wide dynamic range (WDR) neurons. Typical SCS uses frequencies from 50-100 Hz. Newer stimulation paradigms use high-frequency stimulation (HFS) up to 10 kHz and produce pain relief but without paresthesia.

Mechanism of dorsal column stimulation to treat neuropathic but not nociceptive pain: analysis with a computational model.

Objective: Stimulation of axons within the dorsal columns of the human spinal cord has become a widely used therapy to treat refractory neuropathic pain. The mechanisms have yet to be fully elucidated and may even be contrary to standard "gate control theory." Our hypothesis is that a computational model provides a plausible description of the mechanism by which dorsal column stimulation (DCS) inhibits wide dynamic range (WDR) cell output in a neuropathic model but not in a nociceptive pain model.

Modeling effects of scar on patterns of dorsal column stimulation.

Objective: The purpose of this study was to examine how scar formation may affect electrical current distribution in the spinal cord when using paddle leads placed in the epidural space during treatment with spinal cord stimulation.

Materials And Methods: A finite element model of the spinal cord was used to examine changes in stimulation using a guarded cathode configuration with and without scar. Additionally, two potential "compensatory" programming patterns were examined in order to understand how the three-dimensional electrical field may be affected by scar.

Localized stimulation and recording in the spinal cord with microelectrode arrays.

The use of microelectrodes for both recording and stimulation of cortical tissue is a well-established technique in neuroscience. We demonstrate that the use of existing microelectrode arrays and instrumentation can be extended to studying the spinal cord. We show that microelectrode arrays can be used to perform stimulation and recording in the corticospinal tract of an animal model commonly used in spinal cord injury (SCI) research.

Intraoperative neurophysiologic methods for spinal cord stimulator placement under general anesthesia.

Objectives:   To demonstrate that spinal cord stimulators (SCSs) may be placed safely and accurately under general anesthesia (GA) and that the proposed evaluation method activates structures predominantly in the dorsal columns.

Materials And Methods:   Data were retrospectively analyzed from 172 electrodes implanted with spinal cord SCSs at the Lahey Clinic between September 2008 and July 2011. All patients had their SCS placed under GA.

Heuristic map of myotomal innervation in humans using direct intraoperative nerve root stimulation.

Objective: Considerable overlap exists in nerve root innervation of various muscles. Knowledge of myotomal innervation is essential for the interpretation of neurological examination findings and neurosurgical decision-making. Previous studies relied on cadaveric dissections, animal studies, and cases with anomalous anatomy.

Successful bilateral deep brain stimulation of the globus pallidus internus for persistent status dystonicus and generalized chorea.

The authors report the cases of 2 young male patients (aged 16 and 26 years) with dystonic cerebral palsy of unknown origin, who developed status dystonicus, an acute and persistent combination of generalized dystonia and chorea. Both patients developed status dystonicus after undergoing general anesthesia, and in 1 case, after administration of metoclopramide. In attempting to control this acute hyperkinetic movement disorder, multiple medication trials failed in both cases and patients required prolonged intubation and sedation with propofol.

Motor cortex stimulation in patients with Parkinson disease: 12-month follow-up in 4 patients.

Object: Since the initial 1991 report by Tsubokawa et al., stimulation of the M1 region of cortex has been used to treat chronic pain conditions and a variety of movement disorders.

Methods: A Medline search of the literature published between 1991 and the beginning of 2007 revealed 459 cases in which motor cortex stimulation (MCS) was used.

Motor cortex stimulation for pain and movement disorders.

Since initial reports in the early 1990s, stimulation of the M1 region of the cortex (MCS) has been used to treat chronic refractory pain conditions and a variety of movement disorders. A Medline search of literature between 1991 and 2007 revealed 512 cases using MCS. Although most of these relate to the treatment of pain (422), 84 of them involve movement disorders.

Neurosurgical decision-making with IOM: DBS surgery.

Intraoperative monitoring (IOM) adds new information to intraoperative surgical decision-making. When presented clearly and accurately, it can help guide decision processes during the procedure, but can be a detriment overall if the information is inaccurate or misleading. Troubleshooting abilities and vigilance of the IOM staff play a large role in bolstering the level of trust a surgeon develops in IOM.