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Background Segmented deep brain stimulation (DBS) leads, which are capable of steering current in the direction of any 1 of 3 segments, can result in a wider therapeutic window by directing current away from unintended structures, particularly, the corticospinal tract (CST). It is unclear whether the use of motor evoked potentials (MEPs) is feasible during DBS surgery via stimulation of individual contacts/segments in order to quantify CST activation thresholds and optimal contacts/segments intraoperatively. Objective To assess the feasibility of using MEP to identify CST thresholds for ring and individual segments of the DBS lead under general anesthesia. Methods MEP testing was performed during pulse generator implantation under general anesthesia on subjects who underwent DBS lead implantation into the subthalamic nucleus (STN). Stimulation of each ring and segmented contacts of the directional DBS lead was performed until CST threshold was reached. Stereotactic coordinates and thresholds for each contact/segment were recorded along with the initially activated muscle group. Results A total of 34 hemispheres were included for analysis. MEP thresholds were recorded from 268 total contacts/segments. For segmented contacts (2 and 3, respectively), the mean highest CST thresholds were 2.33 and 2.62 mA, while the mean lowest CST thresholds were 1.7 and 1.89 mA, suggesting differential thresholds in relation to CST. First dorsal interosseous and abductor pollicis brevis (34% each) were the most commonly activated muscle groups. Conclusion MEP threshold recording from segmented DBS leads is feasible. MEP recordings can identify segments with highest CST thresholds and may identify segment orientation in relation to CST.

The goal of glioma surgery is maximal safe resection in order to provide optimal tumor control and survival benefit to the patient. There are multiple imaging modalities beyond traditional contrast-enhanced magnetic resonance imaging (MRI) that have been incorporated into the preoperative workup of patients presenting with gliomas. The aim of these imaging modalities is to identify cortical and subcortical areas of eloquence, and their relationship to the lesion. In this article, multiple modalities are described with an emphasis on the underlying technology, clinical utilization, advantages, and disadvantages of each. functional MRI and its role in identifying hemispheric dominance and areas of language and motor are discussed. The nuances of magnetoencephalography and transcranial magnetic stimulation in localization of eloquent cortex are examined, as well as the role of diffusion tensor imaging in defining normal white matter tracts in glioma surgery. Lastly, we highlight the role of stimulated Raman spectroscopy in intraoperative histopathological diagnosis of tissue to guide tumor resection. Tumors may shift the normal arrangement of functional anatomy in the brain; thus, utilization of multiple modalities may be helpful in operative planning and patient counseling for successful surgery.

The future of psychiatric neurosurgery can be viewed from two separate perspectives: the immediate future and the distant future. Both show promise, but the treatment strategy for mental diseases and the technology utilized during these separate periods will likely differ dramatically. It can be expected that the initial advancements will be built upon progress of neuroimaging and stereotactic targeting while surgical technology becomes adapted to patient-specific symptomatology and structural/functional imaging parameters. This individualized approach has already begun to show significant promise when applied to deep brain stimulation for treatment-resistant depression and obsessive-compulsive disorder. If effectiveness of these strategies is confirmed by well designed, double-blind, placebo-controlled clinical studies, further technological advances will continue into the distant future, and will likely involve precise neuromodulation at the cellular level, perhaps using wireless technology with or without closed-loop design. This approach, being theoretically less invasive and carrying less risk, may ultimately propel psychiatric neurosurgery to the forefront in the treatment algorithm of mental illness. Despite prominent development of non-invasive therapeutic options, such as stereotactic radiosurgery or transcranial magnetic resonance-guided focused ultrasound, chances are there will still be a need in surgical management of patients with most intractable psychiatric conditions.

OBJECTIVE Airway obstruction after postoperative extubation is a dreaded but uncommon complication in patients undergoing circumferential cervical spine surgery (CCSS). The cuff leak test (CLT) has been utilized to assess air leak around the endotracheal tube which may reflect airway swelling. In this prospective observational study, we analyze the temporal evolution of CLT and perioperative factors that may influence it. METHODS Twenty patients undergoing single-stage CCSS were managed according to our extubation protocol. Patients were maintained intubated overnight following surgery. They were extubated if a CLT > 200 mL and both intensive care unit (ICU) and Neurosurgery teams agreed that it was safe. Patients extubated in the first postoperative day (8 of 20) comprised the early group, and the remaining patients (12 of 20) the delayed group. Patient and operative data were analyzed as a single group and comparing both groups. RESULTS The main indication for surgery was cervical deformity. Median number of levels fused was 5 anteriorly (range, 1-6) and 6 (range, 1-13) posteriorly. Patients were kept intubated for an average of 73.6 hours (range, 26-222 hours) and stayed in the ICU for 119.1 hours (range, 36-360 hours). There were 4 failed extubations and 3 patients (15%) required a tracheostomy. Patient profiles between both groups were very similar across most patient variables but differed significantly regarding infraglottic luminal area (p < 0.05). Patients with larger preoperative cuff leak values tended to have a shorter intubation period (p = 0.053). CONCLUSION This study objectively demonstrates the difficulties in airway management following CCSS and provides useful insight for preoperative planning and counseling. Local anatomic factors influence airway outcome more than operative factors. The study format does not allow for testing of interventions but we suggest that patients with favorable anatomy (larger infraglottic luminal area) may benefit from a less strict airway management protocol.

Objective: During deep brain stimulation (DBS) surgery, microelectrode recording (MER) leads to target refinement from the initial plan in 30% to 47% of hemispheres; however, it is unclear whether the DBS lead ultimately resides within the MER-optimized target in relation to initial radiographic target coordinates in these hemispheres. This study aimed to determine the frequency of discordance between radiographic and neurophysiologic nucleus and whether target optimization with MER leads to a significant change in DBS lead location away from initial target. Methods: Consecutive cases of DBS surgery with MER using intraoperative computed tomography were included. Coordinates of initial anatomic target (AT), MER-optimized target (MER-O) and DBS lead were obtained. Hemispheres were categorized as “discordant” (D) if there was a suboptimal neurophysiologic signal despite accurate targeting of AT. Hemispheres where the first MER pass was satisfactory were deemed “concordant” (C). Coordinates and radial distances between 1) AT/MER-O; 2) MER-O/DBS; and 3) AT/DBS were calculated and compared. Results: Of the 273 hemispheres analyzed, 143 (52%) were D, and 130 (48%) were C. In C hemispheres, DBS lead placement error (mean ± standard error of the mean) was 0.88 ± 0.07 mm. In D hemispheres, MER resulted in significant migration of DBS lead (mean AT-DBS error 2.11 ± 0.07 mm), and this distance was significantly greater than the distance between MER-O and DBS (2.11 vs. 1.09 mm, P < 0.05). Directional assessment revealed that the DBS lead migrated in the intended direction as determined by MER-O in D hemispheres, except when the intended direction was anterolateral. Conclusions: Discordance between radiographic and neurophysiologic target was seen in 52% of hemispheres, and MER resulted in appropriate deviation of the DBS lead toward the appropriate target. The actual value of the deviation, when compared with DBS lead placement error in C hemispheres, was, on average, small.

Although peripheral neuromodulation devices have been utilized as far back as the 1960s following the pioneering work of Wall and Sweet, it was not until the late 1990s that less invasive, percutaneous techniques were introduced. These minimally invasive techniques brought forth an expanse of utilization for peripheral nerve stimulation (PNS) as implantation was no longer restricted to peripheral nerve surgeons but could also be performed by anesthesiologists and physiatrists. Given the low invasiveness of these procedures, reliance is placed almost entirely on intraoperative imaging to guide lead placement in real time. Both intraoperative fluoroscopy and ultrasound have proven to be crucial adjuncts in the placement of percutaneous PNS electrodes. In this chapter, we focus on procedural details of PNS lead implantation where intraoperative fluoroscopy is used for surgical targeting while highlighting the specific workflows for the placement of these electrodes.

BackgroundThe Medtronic “Percept” is the first FDA approved deep brain stimulation (DBS) device with sensing capabilities during active stimulation. Its real-world signal recording properties have yet to be fully described.ObjectiveThis study details sources of artifact (and potential mitigations) in local field potential (LFP) signals collected by the Percept, and assesses the potential impact of artifact on the future development of adaptive DBS (aDBS) using this device.MethodsLFP signals were collected from seven subjects in both experimental and clinical settings. The presence of artifacts and their effect on the spectral content of neural signals were evaluated in both the stimulation ON and OFF states using three distinct offline artifact removal techniques.ResultsTemplate subtraction successfully removed multiple sources of artifact, including 1) electrocardiogram (ECG), 2) non-physiologic polyphasic artifacts, and 3) ramping related artifacts seen when changing stimulation amplitudes. ECG removal from stimulation ON (at 0 mA) signals recovered the spectral shape seen when OFF stimulation (averaged difference in normalized power in theta, alpha, and beta bands ≤ 3.5%). ECG removal using singular value decomposition was similarly successful, though required subjective researcher input. QRS interpolation produced similar recovery of beta-band signal, but resulted in residual low-frequency artifact.ConclusionsArtifacts present when stimulation is enabled notably affected the spectral properties of sensed signals using the Percept. Multiple discrete artifacts could be successfully removed offline using an automated template subtraction method. The presence of unrejected artifact likely influences online power estimates, with the potential to affect aDBS algorithm performance.

Background: The Medtronic “Percept” is the first FDA-approved deep brain stimulation (DBS) device with sensing capabilities during active stimulation. Its real-world signal-recording properties have yet to be fully described. Objective: This study details three sources of artifact (and potential mitigations) in local field potential (LFP) signals collected by the Percept and assesses the potential impact of artifact on the future development of adaptive DBS (aDBS) using this device. Methods: LFP signals were collected from 7 subjects in both experimental and clinical settings. The presence of artifacts and their effect on the spectral content of neural signals were evaluated in both the stimulation ON and OFF states using three distinct offline artifact removal techniques. Results: Template subtraction successfully removed multiple sources of artifact, including (1) electrocardiogram (ECG), (2) nonphysiologic polyphasic artifacts, and (3) ramping-related artifacts seen when changing stimulation amplitudes. ECG removal from stimulation ON (at 0 mA) signals resulted in spectral shapes similar to OFF stimulation spectra (averaged difference in normalized power in theta, alpha, and beta bands ≤3.5%). ECG removal using singular value decomposition was similarly successful, though required subjective researcher input. QRS interpolation produced similar recovery of beta-band signal but resulted in residual low-frequency artifact. Conclusions: Artifacts present when stimulation is enabled notably affected the spectral properties of sensed signals using the Percept. Multiple discrete artifacts could be successfully removed offline using an automated template subtraction method. The presence of unrejected artifact likely influences online power estimates, with the potential to affect aDBS algorithm performance.

BackgroundMany adaptative deep brain stimulation (DBS) paradigms rely upon the ability to sense neural signatures of specific clinical signs or symptoms in order to modulate therapeutic stimulation. In first-generation bidirectional neurostimulators, the ability to sense neural signals during active stimulation was often limited by artifact. Newer devices, with improved design specifications for sensing, have recently been developed and are now clinically available.ObjectiveTo compare the sensing capabilities of the first-generation Medtronic PC + S and second-generation Percept PC neurostimulators within a single patient.MethodsA 42-year-old man with Parkinson’s disease was initially implanted with left STN DBS leads connected to a PC + S implantable pulse generator. Four years later, the PC + S was replaced with the Percept PC. Local field potential (LFP) signals were recorded, both with stimulation OFF and ON, at multiple timepoints with each device and compared. Offline processing of time series data included artifact removal using digital filtering and template subtraction, before subsequent spectral analysis. With Percept PC, embedded processing of spectral power within a narrow frequency band was also utilized.ResultsIn the absence of stimulation, both devices demonstrated a peak in the beta range (approximately 20 Hz), which was stable throughout the 4-year period. Similar to previous reports, recordings with the PC + S during active stimulation demonstrated significant stimulation artifact, limiting the ability to recover meaningful LFP signal. In contrast, the Percept PC, using the same electrodes and stimulation settings, produced time series data during stimulation with spectral analysis revealing a peak in the beta-band. Online analysis by the Percept demonstrated a reduction in beta-band activity with increasing stimulation amplitude.ConclusionThis report highlights recent advances in implantable neurostimulator technology for DBS, demonstrating improvements in sensing capabilities during active stimulation between first- and second-generation devices. The ability to reliably sense during stimulation is an important step toward both the clinical implementation of adaptive algorithms and the further investigation into the neurophysiology underlying movement disorders.

BackgroundDomoic acid (DA) is a naturally occurring neurotoxin harmful to marine animals and humans. California sea lions exposed to DA in prey during algal blooms along the Pacific coast exhibit significant neurological symptoms, including epilepsy with hippocampal atrophy.ObservationsHere we describe a xenotransplantation procedure to deliver interneuron progenitor cells into the damaged hippocampus of an epileptic sea lion with suspected DA toxicosis. The sea lion has had no evidence of seizures following the procedure, and clinical measures of well-being including weight and feeding habits have stabilized.LessonsThese preliminary results suggest xenotransplantation has improved the quality-of-life (QOL) for this animal and holds tremendous therapeutic promise.

Image guidance (IG) and robotics systems are becoming more widespread in their utilization and can be invaluable intraoperative adjuncts during spine surgery. Both are highly reliant upon stereotaxy and either pre- or intraoperative radiographic imaging. While user-operated IG systems have been commercially available longer and subsequently are more widely utilized across centers, robotics systems provide unique theoretical advantages over freehand and IG techniques for placing instrumentation within the spine. While there is a growing plethora of data showing that IG and robotic systems decrease the incidence of malpositioned screws, less is known about their impact on clinical outcomes. Both robotics and IG may be of particular value in cases of substantial deformity or complex anatomy. Indications for the use of these systems continue to expand with an increasing body of literature justifying their use in not only guiding thoracolumbar pedicle screw placement, but also in cases of cervical and pelvic instrumentation as well as spinal tumor resection. Both techniques also offer the potential benefit of reducing occupational exposures to ionizing radiation for the operating room staff, the surgeon, and the patient. As the use of IG and robotics in spine surgery continues to expand, these systems' value in improving surgical accuracy and clinical outcomes must be weighed against concerns over cost and workflow. As newer systems incorporating both real-time IG and robotics become more utilized, further research is necessary to better elucidate situations where these systems may be particularly beneficial in spine surgery.

Background and importance Abdominal epilepsy is a rare seizure disorder characterized by episodic gastrointestinal symptoms with electroencephalogram abnormalities. It is typically well treated with anti-epileptic medications; however, little is known about treatment of refractory cases. Clinical presentation The patient is a 16-yr-old male who began experiencing episodic abdominal pain and distension at the age of 2. After undergoing an extensive negative gastrointestinal workup, he was referred for neurological examination. The patient's examination and brain magnetic resonance imaging were normal, but epileptiform discharges were noted on the electroencephalogram. He initially failed treatment with several anti-epileptic medications but achieved seizure control with lamotrigine for 10 yr. However, his seizure frequency increased at age 15 and vagal nerve stimulation (VNS) was proposed for treatment. He underwent VNS placement surgery and experienced significant seizure reduction. By 22 mo postsurgery, he had experienced 11 total seizures compared to his preoperative seizure frequency of 16 seizures per month. Additionally, the patient's neuropsychological testing postsurgery demonstrated improvements in verbal reasoning and reading comprehension in comparison to presurgical testing. Conclusion VNS has been used to treat intractable, nonfocal epilepsy although the therapeutic mechanism remains poorly understood. This case demonstrates utility of VNS for the treatment of abdominal epilepsy that remains refractory to pharmacotherapy.

A significant degree of heterogeneity exists in the way that deep brain stimulation (DBS) surgery is performed. Here we describe our technique of “targeted” microelectrode recording (MER) using intraoperative imaging to confirm the stereotactic position of the microelectrode after neurophysiologic information is recorded. This technique has provided invaluable information in situations where a discordance between radiographic target and optimal neurophysiologic target exist. Despite our perceived value of MER, “asleep” DBS techniques using general anesthesia without MER reliant upon direct, image-based targeting have also been shown to be effective in terms of lead accuracy and short-term outcomes. While we believe that our technique of “targeted” MER is effective, we also believe that DBS surgery should still be performed in a manner that the surgeon and center are most comfortable with, thus providing the patient with the best possible outcome. As technology and techniques evolve, so may the reliance on MER to guide lead placement; nonetheless, the target remains electrophysiological in movement disorders surgery.

Background Temporal bone dehiscence (TBD) often results in leakage of cerebrospinal fluid (CSF) and/or encephalocele. TBD can also occur over the superior semicircular canal, causing debilitating vertigo. Both can be repaired surgically, but traditional treatment is focused only on one pathology, not both. Objective To report our experience in the treatment of TBD via the middle cranial fossa (MCF) approach. Methods A retrospective review was conducted for all patients who underwent MCF approach for surgical repair of any temporal fossa dehiscence. Results A total of 34 patients underwent a total of 37 surgeries. Obesity was prevalent; 21 patients (61.8%) were obese (BMI [body mass index] > 30 kg/m2), and 7 (20.6%) were overweight (BMI 25-30 kg/m2). The most common presenting symptom was hearing disturbance (70.3%), followed by otorrhea (51.4%). Empty sella was noted on computed tomography or magnetic resonance imaging in 15 patients (45.5%). Eight of the 34 patients (23.5%) were found to have superior semicircular canal dehiscence (SCD). Hearing improved with surgical intervention in 25 of 26 patients with hearing loss as a presenting symptom (96%). CSF resolved in 18 of 19 cases (95%). Seventy-three percent of patients reported at least minimal improvement in vertigo. Conclusion TBD may present with symptoms of CSF leak/encephalocele, but may also present with superior SCD. We recommend consistent review of the temporal bone imaging to check for superior SCD, and repair of the SCD first to prevent complications involving the labyrinth and cochlea. MCF approach using a multilayer repair without a lumbar drain is highly effective with minimal risk of complications.

Background The impact of vancomycin powder on reducing postoperative surgical site infections (SSIs) in spine surgery has been studied extensively and is considered standard of care at many institutions. More recently, vancomycin powder has been shown to reduce SSI in cranial neurosurgery; however, limited studies have been performed assessing its impact in reducing SSIs in deep brain stimulation (DBS) surgery. Objective To investigate the use of vancomycin powder as an adjunct to the current antibiotic prophylaxis regimen in DBS surgery in a large cohort of patients. Methods All patients undergoing DBS-lead implantation surgery and chest generator placement or exchange were analyzed prior to and after the implementation of intrawound vancomycin powder, and the impact on infection rate and any complications were subsequently examined. Results From 2015 to 2017, a total of 419 consecutive patients (159 in the pretreatment group, 260 in the post-treatment group) were included in the study. The rate of SSI prior to implementation of intrawound vancomycin was 3.1% (n = 5), which was reduced to 0.38% (n = 1) in the post-treatment group. No complications were noted as a direct result of using vancomycin powder. Conclusion Given its relatively low cost and side effect profile, the use of vancomycin powder may be an effective adjunct in reducing the rate of SSI in DBS surgery.

Microelectrode recording (MER) is used to confirm targeting accuracy during deep brain stimulation (DBS) surgery. We describe a technique using intraoperative computed tomography (CT) extrapolation (iCTE) to predetermine and adjust the trajectory of the guide tube to improve microelectrode targeting accuracy. We hypothesized that this technique would decrease the number of MER tracks and operative time, while increasing the recorded length of the subthalamic nucleus (STN).Thirty-nine patients with Parkinson's disease who underwent STN DBS before the iCTE method were compared with 33 patients undergoing STN DBS using iCTE. Before dural opening, a guide tube was inserted and rested on dura. Intraoperative computed tomography (iCT) was performed, and a trajectory was created along the guide tube and extrapolated to the target using targeting software. If necessary, headstage adjustments were made to correct for error. The guide tube was inserted, and MER was performed. iCT was performed with the microelectrode tip at the target. Coordinates were compared with planned/adjusted track coordinates. Radial error between the MER track and the planned/adjusted track was calculated. Cases before and after implementation of iCTE were compared to determine the impact of iCTE on operative time, number of MER tracks and recorded STN length.The use of iCTE reduced the average radial MER track error from 1.90 ± 0.12 mm (n = 54) to 0.84 ± 0.09 mm (n = 49) (P0.001) while reducing the operative time for bilateral lead placement from 272 ± 9 minutes (n = 30) to 233 ± 10 minutes (n = 24) (P0.001). The average MER tracks per hemisphere was reduced from 2.24 ± 0.13 mm (n = 66) to 1.75 ± 0.09 mm (n = 63) (P 0.001), whereas the percentage of hemispheres requiring a single MER track for localization increased from 29% (n = 66) to 43% (n = 63). The average length of recorded STN increased from 4.01 ± 0.3 mm (n = 64) to 4.75 ± 0.28 mm (n = 56) (P0.05).iCTE improves microelectrode accuracy and increases the first-pass recorded length of STN, while reducing operative time. Further studies are needed to determine whether this technique leads to less morbidity and improved clinical outcomes.

Microelectrode recording (MER) is used to confirm electrophysiological signals within intended anatomic targets during deep brain stimulation (DBS) surgery. We describe a novel technique called intraoperative CT-guided extrapolation (iCTE) to predict the intended microelectrode trajectory and, if necessary, make corrections in real-time before dural opening. Prior to dural opening, a guide tube was inserted through the headstage and rested on dura. Intraoperative CT (iCT) was obtained, and a trajectory was extrapolated along the path of the guide tube to target depth using targeting software. The coordinates were recorded and compared to initial plan coordinates. If needed, adjustments were made using the headstage to correct for error. The guide tube was then inserted and MER ensued. At target, iCT was performed and microelectrode tip coordinates were compared with planned/adjusted track coordinates. Radial error between MER track and planned/adjusted track was calculated. For comparison, MER track error prior to the iCTE technique was assessed retrospectively in patients who underwent MER using iCT, whereby iCT was performed following completion of the first MER track. Forty-seven MER tracks were analyzed prior to iCTE (pre-iCTE), and 90 tracks were performed using the iCTE technique. There was no difference between radial error of pre-iCTE MER track and planned trajectory (2.1±0.12mm) compared to iCTE predicted trajectory and planned trajectory (1.76±0.13mm, p0.05). iCTE was used to make trajectory adjustments which reduced radial error between the newly corrected and final microelectrode tip coordinates to 0.84±0.08mm (p0.001). Inter-rater reliability was also tested using a second blinded measurement reviewer which showed no difference between predicted and planned MER track error (p=0.53). iCTE can predict and reduce trajectory error for microelectrode placement compared with the traditional use of iCT post MER.

Objectives Intraoperative computed tomography (iCT) is currently used to confirm the target location of the microelectrode (ME) during microelectrode recording (MER) and ultimate location of deep brain stimulation (DBS) leads at our institution. We evaluated whether iCT can be used to predict the trajectory and accuracy of the ME track. Patients and methods Intraoperative imaging profiles of ten consecutive patients who had undergone DBS surgery were retrospectively reviewed. We found that cranial iCT, in addition to visualizing the target, also visualizes the extra-cranial segment of the guide tube (ECGT) used to insert the ME. We propose a hypothetical technique that extrapolates the trajectory of only the ECGT down to target depth using planning software. In order to provide a proof of concept analysis of this hypothetical technique, we retrospectively assessed post MER placement iCT studies and used planning software to visualize only the ECGT. An extrapolated vector was drawn along the long axis of the ECGT down to the same depth ( z ) as the ME. The obtained x and y coordinates were subsequently recorded and compared to the x and y coordinates of the ME tip to validate this technique. Results The average radial error between ECGT trajectory coordinates and final ME tip coordinates was 0.93±0.1mm (mean±SEM). Conclusion The use of iCT to predict accuracy of microelectrode location is feasible. In the future, performing iCT before guide tube penetration of dura can allow for trajectory prediction and if needed, correction of the ME, thereby potentially improving accuracy and reducing the number of MER tracks.

PURPOSE Local field potential recordings from deep brain stimulation (DBS) leads provide insight into the pathophysiology of Parkinson disease (PD). We recorded local field potential activity from DBS leads within the subthalamic nucleus in patients with PD undergoing DBS surgery to identify reproducible pathophysiological signatures of the disease. METHODS Local field potentials were recorded in 11 hemispheres from patients with PD undergoing subthalamic nucleus-DBS. Bipolar recordings were performed off medication for 2 minutes at rest and another 2 minutes with continuous repetitive opening-closing of the contralateral hand. Spectral analysis and bicoherence were performed and compared between the two testing conditions. RESULTS In all hemispheres, predominance of the beta band frequency (13-30 Hz) was observed at rest and during movement. Beta peak energy was significantly (P < 0.05) increased during movement compared with rest in 6 of 10 hemispheres. Significant beta bicoherence was observed at rest and during movement in 5 of 10 hemispheres. The most robust local field potential recordings were observed at the DBS contact(s) independently chosen for programming in 9 of the 10 hemispheres. CONCLUSIONS In patients with PD, beta activity that increases with repetitive movement may be a signature of the "off" medication state. These findings provide new data on beta oscillatory activity during the Parkinsonian "off" state that may help further define the local field potential signatures of PD.

Image guidance (IG) can serve as a very important adjunct to the surgeon during minimally invasive spine surgery (MISS). There is robust data showing that IG decreases the incidence of suboptimal screw placement and more recent data that IG may decrease the incidence of neurological complications and need for reoperations following thoracolumbar instrumentation while improving workflow. IG is invaluable in cases of severe deformity or other altered anatomy as well as for the intraoperative training of residents and fellows. Indications for its use continue to expand with a growing body of literature justifying its use in not only guiding thoracolumbar pedicle screw placement but also cervical and pelvic instrumentation as well as spinal tumor resection. IG offers the further benefit of minimizing occupational exposures to ionizing radiation for the surgeon and OR staff. Future studies will help to modify imaging protocols in IG to also minimize patients’ radiation exposure.

Background Deep brain stimulation (DBS) via anatomical targeting of white matter tracts defined by diffusion tensor imaging (DTI) may be a useful tool in the treatment of pathologic neurophysiologic circuits implicated in certain disease states like treatment resistant depression (TRD). We sought to determine if DTI could be used to define the stria medullaris thalami (SM), the major afferent white matter pathway to the lateral habenula (LHb), a thalamic nucleus implicated in the pathophysiology of TRD. Methods Probabilistic DTI was performed on ten cerebral hemispheres in five patients who underwent preoperative MRI for DBS surgery. Manual identification of the LHb on axial T1 weighted MRI was used for the initial seed region for tractography. Variations in tractography depending on chosen axial slice of the LHb and chosen voxel within the LHb were also assessed. Results In all hemispheres the SM was reliably visualized. Variations in chosen axial seed slice as well as variations in single seed placement did not lead to significant changes in SM tractography. Conclusions Probabilistic DTI can be used to visualize the SM which may ultimately provide utility for direct anatomic targeting in DBS surgery., Highlights • Diffusion tensor imaging based probabilistic fiber tracking can reliably identify the stria medullaris fiber bundles. • The seeding of habenula reliably and consistently identifies the stria medullaris fiber tracks. • Identification of the stria medullaris is useful in deep brain stimulation surgery.

Approximately 10%-13% of the population is left-handed (LH), and certain professions have varied representation of LH individuals. LH surgeons must overcome unique difficulties owing to the right-handed (RH) operative environment. This study assesses prevalence and impact of left-handedness on training and operative experience of neurosurgeons.An e-mail survey was designed and sent to 5109 U.S. neurosurgeons and neurosurgical trainees. The survey was completed by 1482 responders (29.0% response rate).Of respondents, 252 (17.0%) reported being LH. LH neurosurgeons were more likely than RH neurosurgeons to report ambidexterity in the operating room (36.5% vs. 13.3%, P0.001). During neurosurgical training, 23.5% of RH trainers addressed LH-specific issues compared with 44.7% of LH trainers. LH trainers were more likely to describe LH trainees as having greater technical ability (18.9%). Most trainers reported equal comfort teaching LH and RH trainees. LH trainees reported difficulties with RH surgical tools (42.7%) and a tendency to alter handedness for surgery (62.7%). The impact of these areas lessens in LH attendings (27.8% and 39.9%, respectively). Most LH neurosurgeons denied specific training for left-handedness and access to LH-specific tools, and 24.0% of LH trainees reported feeling disadvantaged owing to their handedness.LH neurosurgeons may be overrepresented in neurosurgery, yet handedness is rarely addressed in neurosurgical training. Despite this, there is evidence of some degree of adaptation through training. There may be some benefit from recognizing differences in handedness in the operating room and attempting to give access for LH-specific mentorship during training.

Advancements in neuroimaging have led to a trend toward direct, image-based targeting under general anesthesia without the use of microelectrode recording (MER) or intraoperative test stimulation, also referred to as “asleep” deep brain stimulation (DBS) surgery. Asleep DBS, utilizing imaging in the form of intraoperative computed tomography (iCT) or magnetic resonance imaging (iMRI), has demonstrated reliable targeting accuracy of DBS leads implanted within the globus pallidus and subthalamic nucleus while also improving clinical outcomes in patients with Parkinson’s disease. In lieu, of randomized control trials, retrospective comparisons between asleep and awake DBS with MER have shown similar short-term efficacy with the potential for decreased complications in asleep cohorts. In lieu of long-term outcome data, awake DBS using MER must demonstrate more durable outcomes with fewer stimulation-induced side effects and lead revisions in order for its use to remain justifiable; although patient-specific factors may also be used to guide the decision regarding which technique may be most appropriate and tolerable to the patient.

Background The massa intermedia (MI) or interthalamic adhesion is an inconsistent band spanning between bilateral medial thalami that is absent in up to 20%–30% of individuals. Little is known of its significance, especially in regard to functional pathways. Probabilistic diffusion tensor imaging (DTI) has recently been used to seed the lateral habenula and define its afferent white matter pathway, the stria medullaris thalami (SM). We sought to determine whether the MI serves as a conduit for crossing of limbic fibers such as the SM. Methods Probabilistic DTI was performed on 10 subjects who had presence of a MI as visualized on magnetic resonance imaging. Tractography was also performed on 2 subjects without MI. Manual identification of the lateral habenula on axial T1-weighted magnetic resonance imaging was used for the initial seed region for tractography. Results In all subjects, the SM was reliably visualized. In 7 of the 10 subjects with MI, there was evidence of SM fibers that crossed to the ipsilateral hemisphere. Three subjects with small diameter MI did not have tractographic evidence of crossing SM fibers. Of the 7 subjects with crossing SM fibers within the MI, 5 showed predilection toward the right orbitofrontal cortex from both the left and right seed regions. Conclusions Probabilistic DTI provides evidence of SM fibers within the MI. Given its anatomic location as a bridging pathway between thalami, further studies are necessary to assess its role within the limbic functional network.

Bilateral thalamic dysfunction secondary to venous congestion may result from either venous sinus thrombosis or high flow arteriovenous malformations or a combination of both. We present a case of bilateral thalamic edema resulting from concomitant choroid plexus arteriovenous malformation (AVM) and straight sinus thrombosis and describe our treatment approach. The patient presented with several weeks of progressive confusion and memory deficits. Magnetic resonance imaging and venography (MRI/ MRV) showed bilateral thalamic T2 hyperintensities and straight sinus thrombosis. Subsequent cerebral angiography revealed a choroid plexus AVM within the right lateral ventricle. The patient underwent surgical resection of the AVM resulting in postoperative resolution of bilateral thalamic edema on MRI and improvement of his confusion and memory deficits. This case demonstrates a rare example of reversible bilateral thalamic edema secondary to venous hypertension from both an AVM and sinus occlusion after appropriate treatment of the AVM.

Microelectrode recording (MER) provides vital neurophysiological information about target nuclei during deep brain stimulation (DBS). There have been extensive studies looking at the accuracy of DBS lead placement; however, to date, no large series have assessed the accuracy of the microelectrode. In this study, we report the accuracy of microelectrode tip placement in comparison to preoperatively planned radiographic target. Patients who underwent DBS with MER from 2014 to 2016 were included in the study. At the authors’ institution, intra-operative CT (iCT) is routinely performed after the first microelectrode track to confirm tip accuracy. Retrospective analysis of microelectrode track error was calculated between the planned trajectory and the microelectrode tip. The radial error was calculated on the same axial plane using the Euclidian distance formula, and multivariate analysis was performed to ascertain any directional bias of error. A total of 227 microelectrode tracks were analyzed, (150 STN, 50 ViM, 27 GPi) yielding a total radial error of 1.2 mm ± 0.2 SEM across all targets. Analysis of vector error distribution revealed lack of directional bias. MER is an accurate electrophysiological representation of the planned target.

Introduction Implantation of responsive neurostimulation (RNS) system has been previously discussed in the literature but there is a paucity of data on target accuracy and the use of intraoperative imaging. We describe our experience with 8 patients using intraoperative computed tomography (iCT) during implantation of the NeuroPace RNS system. Methods A frame-based system was used. CT images were obtained and merged with preoperative magnetic resonance imaging and metabolic imaging studies to calculate target coordinates. An occipital entry point with a trajectory parallel to the hippocampus was planned. The leads were placed in the parahippocampal white matter circuitry. iCT images were obtained for immediate confirmation of lead accuracy. Images were computationally merged and superimposed on the magnetic resonance images and final coordinates of the distal contact were compared with the intended target. Targeting error was calculated in each axis as well as Euclidean distance. Preoperative and postoperative seizure frequency per month was used to evaluate outcomes. Results Fifteen occipitotemporal leads were placed in 8 patients. The vector error means in the x, y, and z planes were 0.57 mm ± 0.44 mm, 0.71 mm ± 0.84 mm, and 2.23 mm ± 1.43 mm, respectively. The mean Euclidean distance error was 2.63 mm ± 1.32 mm. The z axis was found to have a significantly higher error [F2,42 = 12.955; P = 0.001] when compared with the x or y axes. The median preoperative and postoperative seizure frequency per month was 3.4 and 0.78 seizures, respectively. Conclusions Frame-based stereotactic implantation of the NeuroPace RNS system using iCT is feasible and allows for intraoperative target accuracy confirmation and correction.

Introduction Local field potential (LFP) recordings from implanted deep brain stimulator (DBS) leads can provide insight into the pathogenesis of the Parkinson’s disease (PD) specifically by looking at some of the local network properties at the location of the electrode. We recorded LFP activity from DBE leads implanted in the subthalamic nucleus (STN) and performed subsequent data analysis on PD patients undergoing DBS surgery in the off state both at rest and during continuous movement of the contralateral hand in order to identify any reproducible pathophysiological signatures of the disease. Methods LFPs were recorded in 8 patients with PD who underwent bilateral DBS lead implantation within the STN. Following DBS lead placement, bipolar (0–1, 1–2, 2–3) recordings were performed for 2 min at rest and another 2 min with contralateral repetitive hand grasp movements. All recordings were performed in the off state with at least 12 h of since their last medication and prior to macrostimulation testing in the nucleus. The raw LFP recordings were transformed to the frequency domain via the fast fourier transform and then a power spectral was generated from that data with a frequency resolution of 1.3 Hz. Beta-band spectral peaks were located and compared between the two testing states. Results In all patients, predominance of both low and high beta band frequencies (13–20 and 20–35 Hz respectively) were observed both at rest and during movement at the DBS contact where stimulation was deemed to be most therapeutic. Paradoxically, stronger beta peak energy was noted during movement as opposed to the rest state in all patients. Conclusion In patients with PD, excess beta band coupling that paradoxically synchronizes with movement may be a signature of the off state. This excess beta band activity appears to also correlate with the most active DBS lead contact. This increase in energy, or synchronization, during the movement phase is in contrast to what happens in the cortex during similar EEG analysis. This increase in the abnormal beta energy, in PD patients, may help explain the abnormal movements, such as rigidity and bradykinesia, seen in these patients. Further investigations may to help to identify and provide stimulation in situations where excess beta band activity is prevalent at the active contact.

In light of failed medical therapy for movement disorders, the use of deep brain stimulation (DBS) has increased the last two decades. Many complications may transpire; however, to our knowledge, the literature does not mention the phenomena of brain shift from a second unrelated neurosurgical procedure and its theoretical effect on lead displacement and lead function. We present a patient with a left sided DBS for essential tremor and subsequent left amygdalohippocampectomy for temporal lobe epilepsy with minimal radiographic distortion of the DBS lead and without clinical or functional complications. A 47-year-old woman presented with bitemporal epilepsy secondary to a brain injury acquired in childhood in addition to a comorbid bilateral essential tremor, both refractory to medical intervention. A successful left-sided DBS placement was performed with satisfactory resolution of her essential tremor. The patient subsequently developed deterioration of seizure control, becoming refractory to anti-epileptic medications, requiring surgical intervention. A left-sided selective amygdalohippocampectomy and techniques to minimize brain shift were performed without complications. Postoperative imaging suggested minimal distortion of the DBS lead. This did not correspond with reemergence of her essential tremor, implying that the lead maintained functional utility. Brain shift secondary to a craniotomy may cause DBS lead displacement. This phenomenon should be considered when planning operative approaches and can be limited by selective resections. With the growing propensity for placement of DBS leads and the risk of lead displacement, it is important to consider operative approaches to minimize brain shift.