Robotic-Assisted Navigation for Stereotactic Neurosurgery: A Cadaveric Investigation of Accuracy, Time, and Radiation.

BACKGROUND AND OBJECTIVES: Despite frequent use, stereotactic head frames require manual coordinate calculations and manual frame settings that are associated with human error. This study examines freestanding robot-assisted navigation (RAN) as a means to reduce the drawbacks of traditional cranial stereotaxy and improve targeting accuracy. METHODS: Seven cadaveric human torsos with heads were tested with 8 anatomic coordinates selected for lead placement mirrored in each hemisphere. Right and left hemispheres of the brain were randomly assigned to either the traditional stereotactic arc-based (ARC) group or the RAN group. Both target accuracy and trajectory accuracy were measured. Procedural time and the radiation required for registration were also measured. RESULTS: The accuracy of the RAN group was significantly greater than that of the ARC group in both target (1.2 ± 0.5 mm vs 1.7 ± 1.2 mm, P = .005) and trajectory (0.9 ± 0.6 mm vs 1.3 ± 0.9 mm, P = .004) measurements. Total procedural time was also significantly faster for the RAN group than for the ARC group (44.6 ± 7.7 minutes vs 86.0 ± 12.5 minutes, P < .001). The RAN group had significantly reduced time per electrode placement (2.9 ± 0.9 minutes vs 5.8 ± 2.0 minutes, P < .001) and significantly reduced radiation during registration (1.9 ± 1.1 mGy vs 76.2 ± 5.0 mGy, P < .001) compared with the ARC group. CONCLUSION: In this cadaveric study, cranial leads were placed faster and with greater accuracy using RAN than those placed with conventional stereotactic arc-based technique. RAN also required significantly less radiation to register the specimen's coordinate system to the planned trajectories. Clinical testing should be performed to further investigate RAN for stereotactic cranial surgery.

Using pre-surgical suspicion to guide insula implantation strategy.

Rationale: Insular epilepsy can be a challenging diagnosis due to overlapping semiology and scalp EEG findings with frontal, temporal, and parietal lobe epilepsies. Stereotactic electroencephalography (sEEG) provides an opportunity to better localize seizure onset. The possibility of improved localization is balanced by implantation risk in this vascularly rich anatomic region. We review both safety and pre-implantation factors involved in insular electrode placement across four years at an academic medical center. Methods: Presurgical data, operative reports, and invasive EEG summaries were retrospectively reviewed for patients undergoing invasive epilepsy monitoring on the insula from 2016 through 2019. EEG reports were reviewed to record the presence of insula ictal and interictal involvement. We recorded which presurgical findings suggested insular involvement (insula lesion on MRI, insula changes on PET/SPECT/scalp EEG, characteristic semiology, or history of failed anterior temporal lobectomy). The likelihood of pre-sEEG insular onset was categorized as low suspicion if no presurgical findings were present ("rule out"), moderate suspicion if one finding was present, and high suspicion if two or more findings were present. Results: 76 patients received 189 insular electrodes as part of their implantation strategy for 79 surgical cases. Seven patients (8.9%) had insular ictal onset. One clinically significant complication (left hemiparesis) occurred in a patient with moderate suspicion for insular onset. There were 38 low suspicion cases, 36 moderate suspicion cases, and 5 high suspicion cases for pre-sEEG insula ictal onset. Two low suspicion (5.3%), three moderate suspicion (8.6%), and two high suspicion (40%) cases had insular ictal onset. Conclusions: The insula can safely receive sEEG. Having two or more presurgical factors indicating insular onset is a strong, albeit incomplete, predictor of insular seizure onset. Using pre-implantation clinical findings can offer clinicians predictive value for targeting the insula during invasive EEG monitoring.

Infraclavicular de novo placement of a responsive neurostimulator for a patient with eloquent glioma-associated epilepsy: illustrative case.

BACKGROUND: The authors present a 50-year-old female with high-grade glioma involving the motor cortex as the cause of her drug-resistant epilepsy (DRE). Responsive neurostimulation (RNS) was chosen for epilepsy treatment. Due to concerns regarding the generator impeding the regular imaging surveillance required for treatment and monitoring of her glioma, surgeons placed the internal pulse generator (IPG) within an infraclavicular chest pocket. OBSERVATIONS: Implantation of the RNS device and IPG within the infraclavicular pocket was uneventful. However, both subdural and depth electrodes were used and connected to the IPG, and subdural electrodes are considerably shorter than depth electrodes (37 vs 44 cm). The shorter strip leads presumably generated significant tension, leading to fracture of the leads. Therefore, surgery was repeated using only depth electrodes for more length and less tension. The device has good-quality electrocorticography signals that continue to be used for device programming. The seizure burden was reduced, and quality of life improved for the patient. LESSONS: The RNS system with infraclavicular IPG placement reduced the seizure burden and improved the quality of life of a patient with glioma-associated epilepsy. Surgeons may consider the infraclavicular location as an alternative site for implantation for RNS candidates who require recurrent intracranial magnetic resonance imaging.

Deep Brain Stimulation for the Treatment of Hemichorea: Case Series and Literature Review.

Background: Hemichorea (HC) and its severe form hemiballismus (HB) are rare movement disorders which can be medically refractory to treatments and may need surgical intervention. Case Report: We report 3 patients with HC-HB who had meaningful clinical improvement with unilateral deep brain stimulation (DBS) of the globus pallidus interna (GPi). We identified 8 prior cases of HC-HB treated with GPi-DBS, and a majority of these patients experienced significant improvement in their symptoms. Discussion: GPi-DBS can be considered in medically refractory HC-HB in carefully selected patients. However, data is limited to small case series and further studies are needed.

Source-sink connectivity: a novel interictal EEG marker for seizure localization.

Over 15 million epilepsy patients worldwide have drug-resistant epilepsy. Successful surgery is a standard of care treatment but can only be achieved through complete resection or disconnection of the epileptogenic zone, the brain region(s) where seizures originate. Surgical success rates vary between 20% and 80%, because no clinically validated biological markers of the epileptogenic zone exist. Localizing the epileptogenic zone is a costly and time-consuming process, which often requires days to weeks of intracranial EEG (iEEG) monitoring. Clinicians visually inspect iEEG data to identify abnormal activity on individual channels occurring immediately before seizures or spikes that occur interictally (i.e. between seizures). In the end, the clinical standard mainly relies on a small proportion of the iEEG data captured to assist in epileptogenic zone localization (minutes of seizure data versus days of recordings), missing opportunities to leverage these largely ignored interictal data to better diagnose and treat patients. IEEG offers a unique opportunity to observe epileptic cortical network dynamics but waiting for seizures increases patient risks associated with invasive monitoring. In this study, we aimed to leverage interictal iEEG data by developing a new network-based interictal iEEG marker of the epileptogenic zone. We hypothesized that when a patient is not clinically seizing, it is because the epileptogenic zone is inhibited by other regions. We developed an algorithm that identifies two groups of nodes from the interictal iEEG network: those that are continuously inhibiting a set of neighbouring nodes ('sources') and the inhibited nodes themselves ('sinks'). Specifically, patient-specific dynamical network models were estimated from minutes of iEEG and their connectivity properties revealed top sources and sinks in the network, with each node being quantified by source-sink metrics. We validated the algorithm in a retrospective analysis of 65 patients. The source-sink metrics identified epileptogenic regions with 73% accuracy and clinicians agreed with the algorithm in 93% of seizure-free patients. The algorithm was further validated by using the metrics of the annotated epileptogenic zone to predict surgical outcomes. The source-sink metrics predicted outcomes with an accuracy of 79% compared to an accuracy of 43% for clinicians' predictions (surgical success rate of this dataset). In failed outcomes, we identified brain regions with high metrics that were untreated. When compared with high frequency oscillations, the most commonly proposed interictal iEEG feature for epileptogenic zone localization, source-sink metrics outperformed in predictive power (by a factor of 1.2), suggesting they may be an interictal iEEG fingerprint of the epileptogenic zone.

Spinal cord stimulator for the treatment of central neuropathic pain secondary to cervical syringomyelia: illustrative case.

BACKGROUND: Central neuropathic pain (CNP) of the cervical and/or thoracic spinal cord has many etiologies, both natural and iatrogenic. Frequently, CNP is medically refractory and requires surgical treatment to modulate the perception of pain. Spinal cord stimulation is a modality commonly used in adults to treat this type of refractory pain; however, it is rarely used in the pediatric population. OBSERVATIONS: The authors reported a case involving a common pediatric condition, Chiari malformation type I with syrinx, that led to a debilitating complex regional pain syndrome. The associated life-altering pain was successfully alleviated following placement of a spinal cord stimulator. LESSONS: CNP, or the syndromic manifestations of the pain (complex regional pain syndrome), can alter an individual's life in dramatic ways. Spinal cord stimulator placement in carefully selected pediatric patients should be considered in these difficult pain treatment paradigms.

sEEG for expansion of a surgical epilepsy program: Safety and efficacy in 152 consecutive cases.

OBJECTIVE: Stereoelectroencephalography (sEEG) is an intracranial encephalography method of expanding use. The need for increased epilepsy surgery access has led to the consideration of sEEG adoption by new or expanding surgical epilepsy programs. Data regarding safety and efficacy are uncommon outside of high-volume, well-established centers, which may be less applicable to newer or low-volume centers. The objective of this study was to add to the sEEG outcomes in the literature from the perspective of a rapidly expanding center. METHODS: A retrospective chart review of consecutive sEEG cases from January 2016 to December 2019 was performed. Data extraction included demographic data, surgical data, and outcome data, which pertinently examined surgical method, progression to therapeutic procedure, clinically significant adverse events, and Engel outcomes. RESULTS: One hundred and fifty-two sEEG procedures were performed on 131 patients. Procedures averaged 10.5 electrodes for a total of 1603 electrodes. The majority (84%) of patients progressed to a therapeutic procedure. Six clinically significant complications occurred: three retained electrodes, two hemorrhages, and one failure to complete investigation. Only one complication resulted in a permanent deficit. Engel 1 outcome was achieved in 63.3% of patients reaching one-year follow-up after a curative procedure. SIGNIFICANCE: New or expanding epilepsy surgery centers can appropriately consider the use of sEEG. The complication rate is low and the majority of patients progress to therapeutic surgery. Procedural safety, progression to therapeutic intervention, and Engel outcomes are comparable to cohorts from long-established epilepsy surgery programs.

Rapid high-fidelity contour shaping of titanium mesh implants for cranioplasty defects using patient-specific molds created with low-cost 3D printing: A case series.

BACKGROUND: Cranioplasty is a neurosurgical procedure to repair skull defects. Sometimes, the patients' bone flap cannot be used for various reasons. Alternatives include a custom polyether ether ketone (PEEK) implant or titanium mesh; both incur an additional cost. We present a technique that uses a 3D printer to create a patient- specific 3D model used to mold a titanium mesh preoperatively. CASE DESCRIPTION: We included three patients whose bone flap could not be used. We collected the patients' demographics, cost, and time data for implants and the 3D printer. The patients' computed tomography DICOM images were used for 3D reconstruction of the cranial defect. A 3D printer (Flashforge, CA) was used to print a custom mold of the defect, which was used to shape the titanium mesh. All patients had excellent cosmetic results with no complications. The time required to print a 3D model was ~ 6 h and 45 min for preoperative shaping of the titanium implant. The intraoperative molding (IOM) of a titanium mesh needed an average of 60 min additional operative room time which incurred $4000. The average cost for PEEK and flat titanium mesh is $12,600 and $6750. Our method resulted in $4000 and $5500 cost reduction in comparison to flat mesh with IOM and PEEK implant. CONCLUSION: 3D printing technology can create a custom model to shape a titanium mesh preoperatively for cranioplasty. It can result in excellent cosmetic results and significant cost reduction in comparison to other cranioplasty options.

Verification of the Deep Brain Stimulation Electrode Position Using Intraoperative Electromagnetic Localization.

BACKGROUND: Electromagnetic (EM) localization has typically been used to direct shunt catheters into the ventricle. The objective of this study was to determine if this method of EM tracking could be used in a deep brain stimulation (DBS) electrode cannula to accurately predict the eventual location of the electrode contacts. METHODS: The Medtronic AxiEMTM system was used to generate the cannula tip location directed to the planned target site. Prior to clinical testing, a series of phantom modelling observations were made. RESULTS: Phantom trials (n = 23) demonstrated that the cannula tip could be accurately located at the target site with an error of between 0.331 ± 0.144 and 0.6 ± 0.245 mm, depending on the orientation of the delivery system to the axis of the phantom head. Intraoperative EM localization of the DBS cannula was performed in 84 trajectories in 48 patients. The average difference between the planned target and the EM stylet location at the cannula tip was 1.036 ± 0.543 mm. The average error between the planned target coordinates and the actual target electrode location (by CT) was 1.431 ± 0.607 and 1.145 ± 0.636 mm for the EM stylet location in the cannula (p = 0.00312), indicating that EM localization reflected the position of the target electrode more accurately than the planned target. CONCLUSIONS: EM localization can be used to verify the position of DBS electrodes intraoperatively with a high accuracy.

Atlanto-occipital dislocation.

Atlanto-occipital dislocation (AOD) is being increasingly recognized as a potentially survivable injury as a result of improved prehospital management of polytrauma patients and increased awareness of this entity, leading to earlier diagnosis and more aggressive treatment. However, despite overall improved outcomes, AOD is still associated with significant morbidity and mortality. The purpose of this paper is to review the biomechanical aspects, clinical features, radiologic criteria, and treatment strategies of AOD. Given that the diagnosis of AOD can be very challenging, a high degree of clinical suspicion is essential to ensure timely recognition and treatment, thus preventing neurological decline or death.

Harvey Cushing's early experience with the surgical treatment of head trauma.

The evolution of techniques to manage patients with head injuries has served as the basis for the treatment of other neurosurgical disorders, including brain tumors, intracranial infections, and cerebrovascular disease. In the nineteenth century, advances in anesthesia, asepsis, and cerebral localization slowly took hold and created the groundwork for modern neurosurgery. To better understand the advances in the treatment of brain injuries in the late 1800s and early 1900s, we examine relevant historical literature and, through the courtesy of the Alan Mason Chesney Medical Archives, we review Dr. Harvey Cushing's patient records (1898-1909) in the Johns Hopkins Hospital surgical archives. The original case histories of 10 patients (6 in detail) who suffered head injuries and underwent treatment by Cushing illustrate some of Cushing's early attempts at intracranial surgery. We also examine the influences on Cushing as he developed into a leader in the new era of modern neurosurgery.

Racial disparities in Medicaid patients after brain tumor surgery.

The presence of healthcare-related disparities is an ongoing, widespread, and well-documented societal and health policy issue. We investigated the presence of racial disparities among post-operative patients either with meningioma or malignant, benign, or metastatic brain tumors. We used the Medicaid component of the Thomson Reuter's MarketScan database from 2000 to 2009. Univariate and multivariate analysis assessed death, 30-day post-operative risk of complications, length of stay, and total charges. We identified 2321 patients, 73.7% were Caucasian, 57.8% were women; with Charlson comorbidity scores of <3 (56.2%) and treated at low-volume centers (73.4%). Among all, 26.3% of patients were of African-American ethnicity and 22.1% had meningiomas. Mortality was 2.0%, mean length of stay (LOS) was 9 days, mean total charges were US$42,422, an adverse discharge occurred in 22.5% of patients, and overall 30-day complication rate was 23.4%. In a multivariate analysis, African-American patients with meningiomas had higher odds of developing a 30-day complication (p=0.05) and were significantly more likely to have longer LOS (p<0.001) and greater total charges (p<0.001) relative to Caucasian counterparts. The presence of one post-operative complication doubled LOS and nearly doubled total charges, while the presence of two post-operative complications tripled these outcomes. Patients of African-American ethnicity had significantly higher post-operative complications than those of Caucasian ethnicity. This higher rate of complications seems to have driven greater healthcare utilization, including greater LOS and total charges, among African-American patients. Interventions aimed at reducing complications among African-American patients with brain tumor may help reduce post-operative disparities.

Extramedullary spinal ependymoma: a diagnostic challenge and review of the literature.

Of the 15 cases of intradural extramedullary ependymomas in the literature, only 3 patients were male. The authors report the fourth case to be diagnosed in a male patient and discuss the pathogenesis, presentation, and treatment of this rare form of ependymoma. These cases most commonly show a similar clinical preoperative course to that of a benign meningioma. Although most instances have been reported in females, hormonal influence may not completely explain this neoplasm's pathogenesis. Close follow-up is warranted because of potential recurrence, metastasis, and anaplastic transformation. An ependymoma should be included in the differential diagnosis of intradural extramedullary tumors.