Effects of polarity of bipolar sensorimotor direct cortical stimulation on intraoperative motor evoked potentials.

OBJECTIVE: The present study investigated the effects of the stimulus polarity and location of motor evoked potential (MEP) to establish a stimulation protocol. METHODS: Nineteen patients who intraoperatively underwent MEP in bipolar direct cortical stimulation were enrolled in the present study. Somatosensory evoked potentials (SEP) of the contralateral median nerve stimulation were recorded to determine stimulation sites. MEP was performed under two settings in all patients: 1. Anodal bipolar stimulation: an anode on the precentral gyrus and a cathode on the postcentral gyrus, 2. Cathodal bipolar stimulation: a cathode on the precentral gyrus and an anode on the postcentral gyrus. MEP amplitudes and the coefficient of variation (CV) at a stimulation intensity of 25 mA and the thresholds of induced MEP were compared between the two settings. RESULTS: An electrical stimulation at 25 mA induced a significantly higher amplitude in cathodal bipolar stimulation than in anodal bipolar stimulation. Cathodal bipolar stimulation also showed significantly lower thresholds than anodal stimulation. CV did not significantly differ between the two groups. CONCLUSIONS: These results indicate that cathodal bipolar stimulation is superior to anodal bipolar stimulation for intraoperative MEP monitoring. SIGNIFICANCE: MEP in cathodal bipolar cortical stimulation may be used in a safe and useful evaluation method of motor fiber damage that combines sensitivity and specificity.

Intraoperative lateral rectus electromyographic recordings optimized by deep intraorbital needle electrodes.

OBJECTIVE: We demonstrate the advantages and safety of long, intraorbitally-placed needle electrodes, compared to standard-length subdermal electrodes, when recording lateral rectus electromyography (EMG) during intracranial surgeries. METHODS: Insulated 25 mm and uninsulated 13 mm needle electrodes, aimed at the lateral rectus muscle, were placed in parallel during 10 intracranial surgeries, examining spontaneous and stimulation-induced EMG activities. Postoperative complications in these patients were reviewed, alongside additional patients who underwent long electrode placement in the lateral rectus. RESULTS: In 40 stimulation-induced recordings from 10 patients, the 25 mm electrodes recorded 6- to 26-fold greater amplitude EMG waveforms than the 13 mm electrodes. The 13 mm electrodes detected greater unwanted volume conduction upon facial nerve stimulation, typically exceeding the amplitude of abducens nerve stimulation. Except for one case with lateral canthus ecchymosis, no clinical or radiographic complications occurred in 36 patients (41 lateral rectus muscles) following needle placement. CONCLUSIONS: Intramuscular recordings from long electrode in the lateral rectus offers more reliable EMG monitoring than 13 mm needles, with excellent discrimination between abducens and facial nerve stimulations, and without significant complications from needle placement. SIGNIFICANCE: Long intramuscular electrode within the orbit for lateral rectus EMG recording is practical and reliable for abducens nerve monitoring.

Microscale dynamics of electrophysiological markers of epilepsy.

OBJECTIVE: Interictal discharges (IIDs) and high frequency oscillations (HFOs) are established neurophysiologic biomarkers of epilepsy, while microseizures are less well studied. We used custom poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) microelectrodes to better understand these markers' microscale spatial dynamics. METHODS: Electrodes with spatial resolution down to 50 µm were used to record intraoperatively in 30 subjects. IIDs' degree of spread and spatiotemporal paths were generated by peak-tracking followed by clustering. Repeating HFO patterns were delineated by clustering similar time windows. Multi-unit activity (MUA) was analyzed in relation to IID and HFO timing. RESULTS: We detected IIDs encompassing the entire array in 93% of subjects, while localized IIDs, observed across < 50% of channels, were seen in 53%. IIDs traveled along specific paths. HFOs appeared in small, repeated spatiotemporal patterns. Finally, we identified microseizure events that spanned 50-100 µm. HFOs covaried with MUA, but not with IIDs. CONCLUSIONS: Overall, these data suggest that irritable cortex micro-domains may form part of an underlying pathologic architecture which could contribute to the seizure network. SIGNIFICANCE: These results, supporting the possibility that epileptogenic cortex comprises a mosaic of irritable domains, suggests that microscale approaches might be an important perspective in devising novel seizure control therapies.

Effect of electroencephalogram-guided anaesthesia administration on 1-yr mortality: follow-up of a randomised clinical trial.

BACKGROUND: Intraoperative EEG suppression duration has been associated with postoperative delirium and mortality. In a clinical trial testing anaesthesia titration to avoid EEG suppression, the intervention did not decrease the incidence of postoperative delirium, but was associated with reduced 30-day mortality. The present study evaluated whether the EEG-guided anaesthesia intervention was also associated with reduced 1-yr mortality. METHODS: This manuscript reports 1 yr follow-up of subjects from a single-centre RCT, including a post hoc secondary outcome (1-yr mortality) in addition to pre-specified secondary outcomes. The trial included subjects aged 60 yr or older undergoing surgery with general anaesthesia between January 2015 and May 2018. Patients were randomised to receive EEG-guided anaesthesia or usual care. The previously reported primary outcome was postoperative delirium. The outcome of the current study was all-cause 1-yr mortality. RESULTS: Of the 1232 subjects enrolled, 614 subjects were randomised to EEG-guided anaesthesia and 618 subjects to usual care. One-year mortality was 57/591 (9.6%) in the guided group and 62/601 (10.3%) in the usual-care group. No significant difference in mortality was observed (adjusted absolute risk difference, -0.7%; 99.5% confidence interval, -5.8% to 4.3%; P=0.68). CONCLUSIONS: An EEG-guided anaesthesia intervention aiming to decrease duration of EEG suppression during surgery did not significantly decrease 1-yr mortality. These findings, in the context of other studies, do not provide supportive evidence for EEG-guided anaesthesia to prevent intermediate term postoperative death. CLINICAL TRIAL REGISTRATION: NCT02241655.

First-in-Human Clinical Experience Using High-Definition Exoscope with Intraoperative Indocyanine Green for Clip Reconstruction of Unruptured Large Pediatric Aneurysm.

The operative exoscope is a novel tool that combines the benefits of surgical microscopes and endoscopes to yield excellent magnification and illumination while maintaining a comparatively small footprint and superior ergonomic features. Until recently, current exoscopes have been limited by 2-dimensional viewing; however, recently a 3-dimensional (3D), high-definition (4K-HD) exoscope has been developed (Sony-Olympus, Tokyo, Japan).1 Our group had previously described the first in-human experiences with this novel tool including microsurgical clipping of intracranial aneurysms. We have highlighted the benefits of the exoscope, which include providing an immersive experience for surgeons and trainees, as well as superior ergonomics as compared with traditional microsurgery.2 To date, exoscopic 3D high-definition indocyanine green (ICG) video angiography (ICG-VA) has not been described. ICG-VA, now a mainstay of vascular microsurgery, uses intravenously injected dye to visualize intravascular fluorescence in real time to assess the patency of arteries and assess clip occlusion of aneurysms.3,4 The ability to safely couple this tool with the novel exoscope has the potential to advance cerebrovascular microsurgery. Here, we present a case of a 11-year-old male with Alagille syndrome, pancytopenia, and peripheral pulmonary stenosis found to have a 12 × 13 × 7 mm distal left M1 aneurysm arising from the inferior M1/M2 junction. The patient was neurologically intact without evidence of rupture. In order to prevent catastrophic rupture, the decision was made to treat the lesion. Due to the patients underlying medical conditions including baseline coagulopathy, surgical management was felt to be superior to an endovascular reconstruction, which would require long-term antiplatelet therapy. Thus the patient underwent a left-sided pterional craniotomy with exoscopic 3D ICG-VA. As demonstrated in Video 1, ICG-VA was performed before definitive clip placement in order to understand flow dynamics with particular emphasis on understanding the middle cerebral artery outflow. Postoperatively, the patient remained at his neurologic baseline and subsequent imaging demonstrated complete obliteration of the aneurysm without any neck remnant. The patient continues to follow and remains asymptomatic and neurologically intact without radiographic evidence of residual or recurrence.

Simultaneous comparison of depth of sedation performance between SedLine and BIS during general anesthesia using custom passive interface hardware: study protocol for a prospective, non-blinded, non-randomized trial.

BACKGROUND: Intraoperative brain function monitoring with processed electroencephalogram (EEG) indices, such as the bispectral index (BIS) and patient state index (PSI), may improve characterization of the depth of sedation or anesthesia when compared to conventional physiologic monitors, such as heart rate and blood pressure. However, the clinical assessment of anesthetic depth may not always agree with available processed EEG indices. To concurrently compare the performance of BIS and SedLine monitors, we present a data collection system using shared individual generic sensors connected to a custom-built passive interface box. METHODS: This prospective, non-blinded, non-randomized study will enroll 100 adult American Society of Anesthesiologists (ASA) class I-III patients presenting for elective procedures requiring general anesthesia. BIS and SedLine electrodes will be placed preoperatively according to manufacturer recommendations and their respective indices tracked throughout anesthesia induction, maintenance and emergence. The concordance between processed EEG indices and clinical assessments of anesthesia depth will be analyzed with chi-square and kappa statistic. DISCUSSION: Prior studies comparing brain function monitoring devices have applied both sensors on the forehead of study subjects simultaneously. With limited space and common sensor locations between devices, it is not possible to place both commercial sensor arrays according to the manufacturer's recommendations, thus compromising the validity of these comparisons. This trial utilizes a custom interface allowing signals from sensors to be shared between BIS and SedLine monitors to provide an accurate comparison. Our results will also characterize the degree of agreement between processed EEG indices and clinical assessments of anesthetic depth as determined by the anesthesiologists' interpretations of acute changes in blood pressure and heart rate as well as the administration, or change to the continuous delivery, of medications at these timepoints. Patient factors (such as burst suppression state or low power EEG conditions from aging brain), surgical conditions (such as use of electrocautery), artifacts (such as electromyography), and anesthesia medications and doses (such as end-tidal concentration of volatile anesthetic or hypnotic infusion dose) that lead to lack of agreement will be explored as well. TRIAL REGISTRATION: Clinical Trials ( ClinicalTrials.gov ), NCT03865316 . Registered on 4 February 2019 - retrospectively registered. SPONSOR: Masimo Corporation.

Direct Cortical Stimulation in Neurosurgical Emergencies: Single-Center Experience in 2 Patients.

BACKGROUND: Intraoperative neuromonitoring (IONM) is widely used for elective resection of eloquently located brain tumors to increase safety and extent of resection. Owing to the need for specially trained personnel for IONM and the sophisticated, time-consuming technical setup, standard IONM is usually not suitable for emergency situations. We report the use of a device that can be operated by the neurosurgeon autonomously for monopolar brain mapping in 2 emergency cases. METHODS: Both patients were initially scheduled for elective neurosurgery under IONM. Acute neurological deterioration in both cases led to emergency surgery. For monopolar cortical/subcortical stimulation, a standard monopolar probe was connected to a new device enabling electromyography real-time tracking of 8 muscles. Preoperative application of subdermal electromyography needles and intraoperative handling of the device were performed by the neurosurgeons independently. RESULTS: Cortical mapping of the motor cortex was performed in both patients with a threshold of 4 mA in case 1 and 14 mA in case 2. Gross total resection with residual tumor volume of <2 mL in case 1 and subtotal resection with residual tumor volume of 4.2 mL in case 2 were achieved under use of the new device without any new neurological deficit. Grade IV glioblastoma was diagnosed in both patients. CONCLUSIONS: We demonstrate the feasibility of monopolar stimulation in 2 patients undergoing emergency neurosurgery using a device autonomously operated by the surgeon. Owing to fast setup and nondemanding handling, monopolar stimulation could be used during emergency neurosurgery to extend resection with preservation of neurological function in both cases.

Facial Nerve EMG: Low-Tech Monitoring with a Stopwatch.

OBJECTIVE: The quantity of A-trains, a high-frequency pattern of free-running facial nerve electromyography, is correlated with the risk for postoperative high-grade facial nerve paresis. This correlation has been confirmed by automated analysis with dedicated algorithms and by visual offline analysis but not by audiovisual real-time analysis. METHODS: An investigator was presented with 29 complete data sets measured during actual surgeries in real time and without breaks in a random order. Data were presented either strictly via loudspeaker (audio) or simultaneously by loudspeaker and computer screen (audiovisual). Visible and/or audible A-train activity was then quantified by the investigator with the computerized equivalent of a stopwatch. The same data were also analyzed with quantification of A-trains by automated algorithms. RESULTS: Automated (auto) traintime (TT), known to be a small, yet highly representative fraction of overall A-train activity, ranged from 0.01 to 10.86 s (median: 0.58 s). In contrast, audio-TT ranged from 0 to 1,357.44 s (median: 29.69 s), and audiovisual-TT ranged from 0 to 786.57 s (median: 46.19 s). All three modalities were correlated to each other in a highly significant way. Likewise, all three modalities correlated significantly with the extent of postoperative facial paresis. As a rule of thumb, patients with visible/audible A-train activity < 1 minute presented with a more favorable clinical outcome than patients with > 1 minute of A-train activity. CONCLUSION: Detection and even quantification of A-trains is technically possible not only with intraoperative automated real-time calculation or postoperative visual offline analysis, but also with very basic monitoring equipment and real-time good quality audiovisual analysis. However, the investigator found audiovisual real-time-analysis to be very demanding; thus tools for automated quantification can be very helpful in this respect.

Intraoperative Neuromonitoring Using a Single Transcartilage Needle Electrode During Thyroidectomy.

OBJECTIVES: Application of transcartilage needle electrode for intraoperative neuromonitoring (IONM) during thyroidectomy has been considered an alternative method of electromyography (EMG) tube recording. However, needle electrodes must be inserted into both sides of the thyroid cartilage with exposure of the cartilage lamina. We sought to evaluate the feasibility of applying a single ipsilateral transcartilage needle electrode for IONM during unilateral hemithyroidectomy. METHODS: Thirty-four patients underwent IONM during unilateral thyroidectomy. A dual disposable needle electrode was inserted obliquely into the inferior lower third of the ipsilateral lamina of the thyroid cartilage. Patients were classified as deep (≥ 5 mm) or superficial (< 5 mm) by the depth of the needle electrode inserted into the thyroid cartilage. Without using an EMG tube, IONM was done according to the standardized procedure using a single needle electrode only. RESULTS: IONM was successful in all nerves at risk. Amplitude of the EMG signal was stable during the surgery, with no cases presenting loss of signal. Amplitude of the signal from vagal and recurrent laryngeal nerve stimulation was significantly lower when needle insertion was superficial (< 5 mm). None of the patients showed postoperative vocal cord paralysis, and complications related to needle electrode were not identified. CONCLUSION: IONM using a single ipsilateral transcartilage needle electrode during unilateral hemithyroidectomy was feasible with no significant complications. It may serve as an alternative method of IONM with the advantage of minimal exposure of the thyroid cartilage lamina. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:448-452, 2021.

Flexible endoscopic assistance in the surgical management of vestibular schwannomas.

Endoscopic-assisted techniques have extensively been applied to vestibular schwannoma (VS) surgery allowing to increase the extent of resection, minimize complications, and preserve facial nerve and auditory functions. In this paper, we retrospectively analyze the effectiveness of flexible endoscope in the endoscopic-assisted retrosigmoid approach for the surgical management of VS of various sizes. The authors conducted a retrospective analysis on 32 patients who underwent combined microscopic and flexible endoscopic resection of VS of various sizes over a period of 16 months. Flexible endoscopic-assisted retrosigmoid approach was performed in all cases, and in 6 cases, flexible and rigid endoscopic control were used in combination to evaluate the differences between the two surgical instruments. The surgical results were additionally compared with a previous case series of 141 patients operated for VS of various sizes without endoscopic assistance. Gross-total resection was achieved in 84% of the cases and near-total resection was accomplished in the rest of them. Excellent or good facial nerve function was observed in all except one case with a preoperative severe facial palsy. Hearing preservation surgery (HPS) was attempted in 11 cases and accomplished in 9 (81.8%). A tumor remnant was endoscopically identified in the fundus of the IAC in all cases (100%). Endoscopic assistance increased the rate of total removal and no intrameatal residual tumor was seen at radiological follow-up. Comparative analysis with a surgical cohort of patients operated with the sole microsurgical technique showed a significative association between endoscopic assistance and intracanalicular extent of resection. Combined microsurgical and flexible endoscopic assistance provides remarkable advantages in the pursuit of maximal safe resection of VS and preservation of facial nerve and auditory functions, minimizing the risk of post-operative complications.

Relationship Between Propofol Target Concentrations, Bispectral Index, and Patient Covariates During Anesthesia.

BACKGROUND: Internationally, propofol is commonly titrated by target-controlled infusion (TCI) to maintain a processed electroencephalographic (EEG) parameter (eg, bispectral index [BIS]) within a specified range. The overall variability in propofol target effect-site concentrations (CeT) necessary to maintain adequate anesthesia in real-world conditions is poorly characterized, as are the patient demographic factors that contribute to this variability. This study explored these issues, hypothesizing that the variability in covariate-adjusted propofol target concentrations during BIS-controlled anesthesia would be substantial and that most of the remaining interpatient variability in drug response would be due to random effects, thus suggesting that the opportunity to improve on the Schnider model with further demographic data is limited. METHODS: With ethics committee approval and a waiver of informed consent, a deidentified, high-resolution, intraoperative database consisting of propofol target concentrations, BIS values, and vital signs from 13,239 patients was mined to identify patients who underwent general endotracheal anesthesia using propofol (titrated to BIS), fentanyl, remifentanil, and rocuronium that lasted at least 1 hour. The propofol target concentrations and BIS values 30 minutes after incision (CeT30 and BIS30) were considered representative of stable intraoperative conditions. The data were plotted and analyzed by descriptive statistics. Confidence intervals were computed using a bootstrap method. A linear model was fit to the data to test for correlation with factors of interest (eg, age and weight). RESULTS: A total of 4584 patients met inclusion criteria and were entered into the analysis. Of the propofol target concentrations, 95% were between 1.5 and 3.5 µg·mL-1. Higher BIS30 values were correlated with higher propofol concentrations. Except for age, all the patient-related variables analyzed entered the regression model linearly. Only 10.2% of the variability in CeT30 was explained by the patient factors of age and weight combined. CONCLUSIONS: Our hypothesis was confirmed. The variability in covariate-adjusted propofol CeT30 titrated to BIS in real-world conditions is considerable, and only a small portion of the remaining variability in drug response is explained by patient demographic factors. This finding may have important implications for the development of new pharmacokinetic (PK) models for propofol TCI.

A Real-Time Depth of Anesthesia Monitoring System Based on Deep Neural Network With Large EDO Tolerant EEG Analog Front-End.

In this article, we present a real-time electroencephalogram (EEG) based depth of anesthesia (DoA) monitoring system in conjunction with a deep learning framework, AnesNET. An EEG analog front-end (AFE) that can compensate ±380-mV electrode DC offset using a coarse digital DC servo loop is implemented in the proposed system. The EEG-based MAC, EEGMAC, is introduced as a novel index to accurately predict the DoA, which is designed for applying to patients anesthetized by both volatile and intravenous agents. The proposed deep learning protocol consists of four layers of convolutional neural network and two dense layers. In addition, we optimize the complexity of the deep neural network (DNN) to operate on a microcomputer such as the Raspberry Pi 3, realizing a cost-effective small-size DoA monitoring system. Fabricated in 110-nm CMOS, the prototype AFE consumes 4.33 µW per channel and has the input-referred noise of 0.29 µVrms from 0.5 to 100 Hz with the noise efficiency factor of 2.2. The proposed DNN was evaluated with pre-recorded EEG data from 374 subjects administrated by inhalational anesthetics under surgery, achieving an average squared and absolute errors of 0.048 and 0.05, respectively. The EEGMAC with subjects anesthetized by an intravenous agent also showed a good agreement with the bispectral index value, confirming the proposed DoA index is applicable to both anesthetics. The implemented monitoring system with the Raspberry Pi 3 estimates the EEGMAC within 20 ms, which is about thousand-fold faster than the BIS estimation in literature.

Retrospective analysis of pedicle screw accuracy for patients undergoing spinal surgery assisted by intraoperative computed tomography (CT) scanner AIRO® and BrainLab© navigation.

Minimally invasive spine surgery techniques for pedicle screw instrumentation are being more frequently used. They offer shorter operative times, shorter hospital stays for patients, faster recovery, less blood loss, and less damage to surrounding tissues. However, they may rely heavily on fluoroscopic imaging, and confer radiation exposure to the surgeon and team members. Use of the AIRO Mobile Intraoperative CT by Brainlab during surgery is a way to eliminate radiation exposure to staff and may improve accuracy rates for pedicle screw instrumentation. We designed a retrospective analysis of our first 12 patients who had a total of 59 pedicle screws inserted when we began to incorporate the AIRO iCT scanner to our surgical workflow. During pedicle screw insertion, projection images were saved, and compared to CT scans gone at the end of the case. We measured the distances between the projected and postprocedural screw locations, at both the screw tips and tulip heads. We observed a mean of 2.8 mm difference between the projection and postprocedural images. None of the screws inserted had any clinically significant complications, and no patient required revision surgery. Overall, iCT guided navigation with the AIRO system is a safe adjunct to spinal surgery. It decreased operator and staff radiation exposure, and helped facilitate successful MIS surgery without fluoroscopic imaging. Additional studies and research can be done to further improve accuracy and reliability.

Difficult extubation of a damaged neural integrity monitor electromyogram tracheal tube: A case report.

INTRODUCTION: The purpose of a neural integrity monitor electromyogram (EMG) tracheal tube is to reduce the risk of damage to the recurrent laryngeal nerves. Complications associated with the use of EMG tube are ventilatory failure, tracheal injury, and difficult extubation. PATIENT CONCERNS: We encountered a case of difficult extubation of an EMG tube after thyroidectomy and partial tracheal resection in a 73-year-old woman. DIAGNOSES: The cuff was torn intraoperatively; but, it was kept inflated to maintain the integrity of the ventilatory circuit. During extubation, the vocal cord blocked the torn hole on the shoulder of the cuff, which subsequently was filled with air, complicating the extubation. INTERVENTIONS: We extubated the EMG tube slowly with the help of videolaryngoscopy with a moderate amount of force and re-intubated with a 6.0-mm ID endotracheal tube. OUTCOMES: We examined the airway during and after re-intubation using videolaryngoscopy. The findings were normal and no bleeding or laceration was observed. The subsequent recovery and extubation occurred smoothly. CONCLUSIONS: Awareness of the characteristics and types of damage that can occur in an EMG tube is essential. Because it can be difficult to ascertain the type of damage before extubation, communication between the surgeon and anesthesiologist, along with the preparation for emergency airway management are necessary for cases of difficult extubation.

Assessing the surgical outcome of the "chopsticks" technique in endoscopic transsphenoidal adenoma surgery.

OBJECTIVE: The "chopsticks" technique is a 3-instrument, 2-hand mononostril technique that has been recently introduced in endoscopic neurosurgery. It allows a dynamic surgical view controlled by one surgeon only while keeping bimanual dissection. Being a mononostril approach, it requires manipulation of the mucosa of one nasal cavity only. The rationale of the technique is to reduce nasal morbidity without compromising surgical results and complication rates. There are, however, no data available on its results in endoscopic surgery (transsphenoidal surgery [TSS]) for pituitary adenoma. METHODS: The authors performed a cohort analysis of prospectively collected data on 144 patients (156 operations) undergoing TSS using the chopsticks technique with 3T intraoperative MRI. All patients had at least 3 months of postoperative neurosurgical, endocrinological, and rhinological follow-up (Sino-Nasal Outcome Test-20 [SNOT-20] and Sniffin' Sticks). The surgical technique is described, and the achieved gross-total resection (GTR) and extent of resection (EOR) together with patients' clinical outcomes and complications are descriptively reported. RESULTS: On 3-month postoperative MRI, GTR was achieved in 71.2% of patients with a mean EOR of 96.7%. GTR was the surgical goal in 122 of 156 cases and was achieved in 106 of 122 (86.9%), with a mean EOR of 98.7% (median 100%, range 49%-100%). There was no surgical mortality. At a median follow-up of 15 months (range 3-70 months), there was 1 permanent neurological deficit. As of the last available follow-up, 11.5% of patients had a new pituitary single-axis deficit, whereas 26.3% had improvement in endocrinological function. Three patients had new postoperative hyposmia. One patient had severe impairment of sinonasal function (SNOT-20 score > 40). The operation resulted in endocrine remission in 81.1% of patients with secreting adenomas. CONCLUSIONS: This study shows that the chopsticks technique confers resection and morbidity results that compare favorably with literature reports of TSS. This technique permits a single surgeon to perform effective endoscopic bimanual dissection through a single nostril, reducing manipulation of healthy tissue and thereby possibly minimizing surgical morbidity.

Role of Robotics in Improving Surgical Outcome in Spinal Pathologies.

BACKGROUND: The desire to improve accuracy and safety and to favor minimally invasive techniques has given rise to spinal robotic surgery, which has seen a steady increase in utilization in the past 2 decades. However, spinal surgery encompasses a large spectrum of operative techniques, and robotic surgery currently remains confined to assistance with the trajectory of pedicle screw insertion, which has been shown to be accurate and safe based on class II and III evidence. The role of robotics in improving surgical outcomes in spinal pathologies is less clear, however. METHODS: This comprehensive review of the literature addresses the role of robotics in surgical outcomes in spinal pathologies with a focus on the various meta-analysis and prospective randomized trials published within the past 10 years in the field. RESULTS: It appears that robotic spinal surgery might be useful for increasing accuracy and safety in spinal instrumentation and allows for a reduction in surgical time and radiation exposure for the patient, medical staff, and operator. CONCLUSION: Robotic assisted surgery may thus open the door to minimally invasive surgery with greater security and confidence. In addition, the use of robotics facilitates tireless repeated movements with higher precision compared with humans. Nevertheless, it is clear that further studies are now necessary to demonstrate the role of this modern tool in cost-effectiveness and in improving clinical outcomes, such as reoperation rates for screw malpositioning.

Relative Contribution of Magnetic Resonance Imaging, Microelectrode Recordings, and Awake Test Stimulation in Final Lead Placement during Deep Brain Stimulation Surgery of the Subthalamic Nucleus in Parkinson's Disease.

INTRODUCTION: For deep brain stimulation (DBS) surgery of the subthalamic nucleus (STN) in Parkinson's disease (PD), many centers employ visualization of the nucleus on magnetic resonance imaging (MRI), intraoperative microelectrode recordings (MER), and test stimulation in awake patients. The value of these steps is a subject for ongoing debate. In the current study, we determined the relative contribution of MRI targeting, multitrack MER, and awake test stimulation in final lead placement during STN DBS surgery for PD. METHODS: Data on PD patients undergoing MRI-targeted STN DBS surgery with three-channel MER and awake test stimulation between February 2010 and January 2014 were analyzed to determine in which MER trajectory final leads were implanted and why this tract was chosen. RESULTS: Seventy-six patients underwent implantation of 146 DBS leads. In 92% of the STN, the final leads were implanted in one of the three planned channels. In 6%, additional channels were needed. In 2%, surgery was aborted before final lead implantation due to anxiety or fatigue. The final leads were implanted in the channels with the longest STN MER signal trajectory in 60% of the STN (38% of the bilaterally implanted patients). This was the central channel containing the MRI target in 39% of the STN (18% bilaterally). The most frequently noted reasons why another channel than the central channel was chosen for final lead placement were (1) a lower threshold for side effects (54%) and (2) no or a too short trajectory of the STN MER signal (40%) in the central channel. The latter reason correlated with larger 2D (x and y) errors in our stereotactic method. CONCLUSIONS: STN DBS leads were often not implanted in the MRI-planned trajectory or in the trajectory with the longest STN MER signal. Thresholds for side effects during awake test stimulation were decisive for final target selection in the majority of patients.

A Novel Passive Method for the Assessment of Skin-Electrode Contact Impedance in Intraoperative Neurophysiological Monitoring Systems.

Intraoperative Neurophysiological Monitoring is a set of monitoring techniques consisting of reading electrical activity generated by the nervous system structures during surgeries. In order to guarantee signal quality, contact impedance between the sensing electrodes and the patient's skin needs to be as low as possible. Hence, monitoring this impedance while signals are measured is an important feature of current medical devices. The most commonly used technique involves injection of a known current and measurement of the voltage drop in the contact interface. This method poses several problems, such as power consumption (critical in battery-powered systems), frequency dependency and regulation issues, which are overcome by using a passive method. The fundamentals of the method proposed in this paper are based on the utilization of the variation suffered by the input random signal when a known resistance is connected in parallel to the input terminals of the low-noise amplifier (LNA) of the analog front-end of the acquisition system. Controlling the connection of the resistors and computing the root mean square of the LNA output voltage has been proved to be a useful tool to assess that the contact impedance is suitably low, allowing the user to know if the neural measurements obtained are valid.