Dissociable Roles of Pallidal Neuron Subtypes in Regulating Motor Patterns.

We have previously established that PV+ neurons and Npas1+ neurons are distinct neuron classes in the external globus pallidus (GPe): they have different topographical, electrophysiological, circuit, and functional properties. Aside from Foxp2+ neurons, which are a unique subclass within the Npas1+ class, we lack driver lines that effectively capture other GPe neuron subclasses. In this study, we examined the utility of Kcng4-Cre, Npr3-Cre, and Npy2r-Cre mouse lines (both males and females) for the delineation of GPe neuron subtypes. By using these novel driver lines, we have provided the most exhaustive investigation of electrophysiological studies of GPe neuron subtypes to date. Corroborating our prior studies, GPe neurons can be divided into two statistically distinct clusters that map onto PV+ and Npas1+ classes. By combining optogenetics and machine learning-based tracking, we showed that optogenetic perturbation of GPe neuron subtypes generated unique behavioral structures. Our findings further highlighted the dissociable roles of GPe neurons in regulating movement and anxiety-like behavior. We concluded that Npr3+ neurons and Kcng4+ neurons are distinct subclasses of Npas1+ neurons and PV+ neurons, respectively. Finally, by examining local collateral connectivity, we inferred the circuit mechanisms involved in the motor patterns observed with optogenetic perturbations. In summary, by identifying mouse lines that allow for manipulations of GPe neuron subtypes, we created new opportunities for interrogations of cellular and circuit substrates that can be important for motor function and dysfunction.SIGNIFICANCE STATEMENT Within the basal ganglia, the external globus pallidus (GPe) has long been recognized for its involvement in motor control. However, we lacked an understanding of precisely how movement is controlled at the GPe level as a result of its cellular complexity. In this study, by using transgenic and cell-specific approaches, we showed that genetically-defined GPe neuron subtypes have distinct roles in regulating motor patterns. In addition, the in vivo contributions of these neuron subtypes are in part shaped by the local, inhibitory connections within the GPe. In sum, we have established the foundation for future investigations of motor function and disease pathophysiology.

Npas1+-Nkx2.1+ Neurons Are an Integral Part of the Cortico-pallido-cortical Loop.

Within the basal ganglia circuit, the external globus pallidus (GPe) is critically involved in motor control. Aside from Foxp2+ neurons and ChAT+ neurons that have been established as unique neuron types, there is little consensus on the classification of GPe neurons. Properties of the remaining neuron types are poorly defined. In this study, we leverage new mouse lines, viral tools, and molecular markers to better define GPe neuron subtypes. We found that Sox6 represents a novel, defining marker for GPe neuron subtypes. Lhx6+ neurons that lack the expression of Sox6 were devoid of both parvalbumin and Npas1. This result confirms previous assertions of the existence of a unique Lhx6+ population. Neurons that arise from the Dbx1+ lineage were similarly abundant in the GPe and displayed a heterogeneous makeup. Importantly, tracing experiments revealed that Npas1+-Nkx2.1+ neurons represent the principal noncholinergic, cortically-projecting neurons. In other words, they form the pallido-cortical arm of the cortico-pallido-cortical loop. Our data further show that pyramidal-tract neurons in the cortex collateralized within the GPe, forming a closed-loop system between the two brain structures. Overall, our findings reconcile some of the discrepancies that arose from differences in techniques or the reliance on preexisting tools. Although spatial distribution and electrophysiological properties of GPe neurons reaffirm the diversification of GPe subtypes, statistical analyses strongly support the notion that these neuron subtypes can be categorized under the two principal neuron classes: PV+ neurons and Npas1+ neurons.SIGNIFICANCE STATEMENT The poor understanding of the neuronal composition in the external globus pallidus (GPe) undermines our ability to interrogate its precise behavioral and disease involvements. In this study, 12 different genetic crosses were used, hundreds of neurons were electrophysiologically characterized, and >100,000 neurons were histologically- and/or anatomically-profiled. Our current study further establishes the segregation of GPe neuron classes and illustrates the complexity of GPe neurons in adult mice. Our results support the idea that Npas1+-Nkx2.1+ neurons are a distinct GPe neuron subclass. By providing a detailed analysis of the organization of the cortico-pallidal-cortical projection, our findings establish the cellular and circuit substrates that can be important for motor function and dysfunction.

Applying fault tree analysis to the prevention of wrong-site surgery.

Wrong-site surgery (WSS) is a rare event that occurs to hundreds of patients each year. Despite national implementation of the Universal Protocol over the past decade, development of effective interventions remains a challenge. We performed a systematic review of the literature reporting root causes of WSS and used the results to perform a fault tree analysis to assess the reliability of the system in preventing WSS and identifying high-priority targets for interventions aimed at reducing WSS. Process components where a single error could result in WSS were labeled with OR gates; process aspects reinforced by verification were labeled with AND gates. The overall redundancy of the system was evaluated based on prevalence of AND gates and OR gates. In total, 37 studies described risk factors for WSS. The fault tree contains 35 faults, most of which fall into five main categories. Despite the Universal Protocol mandating patient verification, surgical site signing, and a brief time-out, a large proportion of the process relies on human transcription and verification. Fault tree analysis provides a standardized perspective of errors or faults within the system of surgical scheduling and site confirmation. It can be adapted by institutions or specialties to lead to more targeted interventions to increase redundancy and reliability within the preoperative process.

Endoscopic decompression of a C1 osteophyte causing bow hunter's syndrome in a 22-year-old male.

The patient is a 22-year-old male with a history of C1 avulsion fracture causing vertebral artery compression with pseudoaneurysm and symptomatic stroke. Cerebral angiography demonstrated dynamic compression of the V3 segment of the vertebral artery due to a chronic C1 avulsion fracture. The authors utilized a full endoscopic approach with intraoperative angiography for proximal control and Doppler ultrasound to confirm adequate decompression. The surgery duration was 3 hours with blood loss < 5 ml. The patient was discharged on postoperative day 1 with no complication and has been asymptomatic since surgery. This is the first documented use of endoscopic decompression to treat this condition. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23234.

A comparison of computed tomography angiography and digital subtraction angiography for the diagnosis of penetrating cerebrovascular injury: a prospective multicenter study.

OBJECTIVE: In this research, the authors sought to characterize the incidence and extent of cerebrovascular lesions after penetrating brain injury in a civilian population and to compare the diagnostic value of head computed tomography angiography (CTA) and digital subtraction angiography (DSA) in their diagnosis. METHODS: This was a prospective multicenter cohort study of patients with penetrating brain injury due to any mechanism presenting at two academic medical centers over a 3-year period (May 2020 to May 2023). All patients underwent both CTA and DSA. The sensitivity and specificity of CTA was calculated, with DSA considered the gold standard. The number of DSA studies needed to identify a lesion requiring treatment that had not been identified on CTA was also calculated. RESULTS: A total of 73 patients were included in the study, 33 of whom had at least 1 penetrating cerebrovascular injury, for an incidence of 45.2%. The injuries included 13 pseudoaneurysms, 11 major arterial occlusions, 9 dural venous sinus occlusions, 8 dural arteriovenous fistulas, and 6 carotid cavernous fistulas. The sensitivity of CTA was 36.4%, and the specificity was 85.0%. Overall, 5.6 DSA studies were needed to identify a lesion requiring treatment that had not been identified with CTA. CONCLUSIONS: Cerebrovascular injury is common after penetrating brain injury, and CTA alone is insufficient to diagnosis these injuries. Patients with penetrating brain injuries should routinely undergo DSA.

The Influence of Coagulopathy on Radiographic and Clinical Outcomes in Patients Undergoing Middle Meningeal Artery Embolization as Standalone Treatment for Non-acute Subdural Hematomas.

Middle meningeal artery embolization (MMAE) is emerging as a safe and effective standalone intervention for non-acute subdural hematomas (NASHs); however, the risk of hematoma recurrence after MMAE in coagulopathic patients is unclear. To characterize the impact of coagulopathy on treatment outcomes, we analyzed a multi-institutional database of patients who underwent standalone MMAE as treatment for NASH. We classified 537 patients who underwent MMAE as a standalone intervention between 2019 and 2023 by coagulopathy status. Coagulopathy was defined as use of anticoagulation/antiplatelet agents or pre-operative thrombocytopenia (platelets <100,000/µL). Demographics, pre-procedural characteristics, in-hospital course, and patient outcomes were collected. Thrombocytopenia, aspirin use, antiplatelet agent use, and anticoagulant use were assessed using univariate and multivariate analyses to identify any characteristics associated with the need for rescue surgical intervention, mortality, adverse events, and modified Rankin Scale score at 90-day follow-up. Propensity score-matched cohorts by coagulopathy status with matching covariates adjusting for risk factors implicated in surgical recurrence were evaluated by univariate and multivariate analyses. Minimal differences in pre-operative characteristics between patients with and those without coagulopathy were observed. On unmatched and matched analyses, patients with coagulopathy had higher rates of requiring subsequent surgery than those without (unmatched: 9.9% vs. 4.3%; matched: 12.6% vs. 4.6%; both p < 0.05). On matched multivariable analysis, patients with coagulopathy had an increased odds ratio (OR) of requiring surgical rescue (OR 3.95; 95% confidence interval [CI] 1.68-9.30; p < 0.01). Antiplatelet agent use (ticagrelor, prasugrel, or clopidogrel) was also predictive of surgical rescue (OR 4.38; 95% CI 1.51-12.72; p = 0.01), and patients with thrombocytopenia had significantly increased odds of in-hospital mortality (OR 5.16; 95% CI 2.38-11.20; p < 0.01). There were no differences in follow-up radiographic and other clinical outcomes in patients with and those without coagulopathy. Patients with coagulopathy undergoing standalone MMAE for treatment of NASH may have greater risk of requiring surgical rescue (particularly in patients using antiplatelet agents), and in-hospital mortality (in thrombocytopenic patients).

General Versus Nongeneral Anesthesia for Middle Meningeal Artery Embolization for Chronic Subdural Hematomas: Multicenter Propensity Score Matched Study.

BACKGROUND AND OBJECTIVES: The choice of anesthesia type (general anesthesia [GA] vs nongeneral anesthesia [non-GA]) in middle meningeal artery embolization (MMAE) procedures for chronic subdural hematomas (cSDH) differs between institutions and left to care team discretion given lack of standard guidelines. We compare the outcomes of GA vs non-GA in MMAE. METHODS: Consecutive patients receiving MMAE for cSDH at 14 North American centers (2018-2023) were included. Clinical, cSDH characteristics, and technical/clinical outcomes were compared between the GA/non-GA groups. Using propensity score matching (PSM), patients were matched controlling for age, baseline modified Rankin Scale, concurrent/prior surgery, hematoma thickness/midline shift, and baseline antiplatelet/anticoagulation. The primary end points included surgical rescue and radiographic success rates (≥50% reduction in maximum hematoma thickness with minimum 2 weeks of imaging). Secondary end points included technical feasibility, procedural complications, and functional outcomes. RESULTS: Seven hundred seventy-eight patients (median age 73 years, 73.2% male patients) underwent 956 MMAE procedures, 667 (70.4%) were non-GA and 280 were GA (29.6%). After running 1:3 PSM algorithm, this resulted in 153 and 296 in the GA and non-GA groups, respectively. There were no baseline/procedural differences between the groups except radial access more significantly used in the non-GA group (P = .001). There was no difference between the groups in procedural technical feasibility, complications rate, length of stay, surgical rescue rates, or favorable functional outcome at the last follow-up. Subsequent 1:1 sensitivity PSM retained the same results. Bilateral MMAE procedures were more performed under non-GA group (75.8% vs 67.2%; P = .01); no differences were noted in clinical/radiographic outcomes between bilateral vs unilateral MMAE, except for longer procedure duration in the bilateral group (median 73 minutes [IQR 48.3-100] vs 54 minutes [39-75]; P < .0001). Another PSM analysis comparing GA vs non-GA in patients undergoing stand-alone MMAE retained similar associations. CONCLUSION: We found no significant differences in radiological improvement/clinical outcomes between GA and non-GA for MMAE.

Embolization and Resection of Epidural Spinal Arteriovenous Malformations: Case Report.

BACKGROUND AND IMPORTANCE: Spinal vascular malformations (sVMs) are relatively uncommon, accounting for 5% to 10% of all spinal cord lesions. Spetzler and Kim developed a paradigm to classify sVMs based on a variety of characteristics into 1 of 6 types, including a subcategory for exclusively epidural sVMs. There is a paucity of literature focused on this category, specifically sources describing the clinical manifestation and management of these lesions. CLINICAL PRESENTATION: We report 2 cases of purely epidural spinal arteriovenous fistula, with an emphasis on the radiographic features and combined endovascular and microsurgical treatment. We report 2 patients known to have epidural spinal arteriovenous fistula who underwent both embolization and surgical resection between May 2019 and August 2020 at our institution. Data collected included demographic, clinical, and operative course, including age, sex, medical history, presenting symptoms, and preoperative and postoperative imaging. Both of these patients were managed with a combination of an endovascular approach for embolization of feeding arterial source and surgical exploration/resection. In both cases, no residual vascular malformation was identified, and the patients went on to be symptom free after 6 weeks. CONCLUSION: This report describes the use of a combination of endovascular and surgical approaches to achieve maximal benefit for 2 patients. These cases reinforce the value of a staged multimodal treatment approach in achieving good functional outcomes for patients with these rare and challenging entities.

Analysis of socioeconomic and demographic factors on post-treatment outcomes for metastatic spinal tumors.

OBJECTIVE: Sociodemographic factors may play a role in incidence and treatment of metastatic spinal tumors, as there is a delay in diagnosis and increased incidence of relevant primaries. There has yet to be a detailed analysis of the impact of sociodemographic factors on surgical outcomes for spinal metastases. We sought to examine the influence of socioeconomic factors on outcomes for patients with metastatic spinal tumors. METHODS: Two hundred and sixty-three patients who underwent surgery for metastatic spinal tumors were identified. Sociodemographic characteristics were then collected and assigned to patients based on their ZIP code. The Chi-square test and the Mann-Whitney-U test were used for binary and continuous variables, respectively. Multivariate regression models were also used to control for age, smoking status, body mass index, and Charlson Comorbidity Index. RESULTS: Males had significantly lower rates of post-treatment complication compared to females (22.7 % vs 39.3 %, p = 0.0052), and those in high educational attainment ZIP codes had significantly shorter length of stay (LOS) compared to low educational attainment ZIP codes (9.3 days vs 12.2 days, p = 0.0058). Multivariate regression revealed that living in a high percentage white ZIP code and being male significantly decreased risk of post-treatment complication by 19 % (p = 0.042) and 14 % (p = 0.032), respectively. Living in a high educational attainment ZIP code decreased LOS by 3 days (p = 0.019). CONCLUSIONS: Males had significantly lower rates of post-treatment complication. Patients in high percentage white areas also had decreased rate of post-treatment complications. Patients living in areas with high educational attainment had shorter length of stay.

Impact of Postoperative Stereotactic Body Radiation Therapy on Survival of Patients with Spinal Metastases in the Context of Additional Systemic Adjuvant Therapy.

BACKGROUND: Stereotactic body radiotherapy (SBRT) has been established as a safe and effective treatment modality for control of long-term pain and tumor growth. However, few studies have investigated the efficacy of postoperative SBRT versus conventional external beam radiation therapy (EBRT) in extending survival within the context of systemic therapy. METHODS: A retrospective chart review of patients who underwent surgery for spinal metastasis at our institution was conducted. Demographic, treatment, and outcome data were collected. SBRT was compared with EBRT and non-SBRT, and analyses were stratified by whether patients received systemic therapy. Survival analysis was conducted using propensity score matching. RESULTS: Bivariate analysis in the nonsystemic therapy group revealed longer survival with SBRT compared with EBRT and non-SBRT. Further analysis also showed that primary cancer type and preoperative mRS significantly affected survival. Within patients who received systemic therapy, overall median survival for patients receiving SBRT was 22.7 months (95% confidence interval [CI] 12.1-52.3) versus 16.1 months (95% CI 12.7-44.0; P = 0.28) for patients who received EBRT and 16.1 months (95% CI: 12.2-21.9; P = 0.07) for patients without SBRT. Within patients who did not receive systemic therapy, overall median survival for patients with SBRT was 62.1 months (95% CI 18.1-unknown) versus 5.3 months (95% CI 2.8-unknown; P = 0.08) for patients with EBRT and 6.9 months (95% CI 5.0-45.6; P = 0.02) for patients without SBRT. CONCLUSIONS: In patients who do not receive systemic therapy, treatment with postoperative SBRT may increase survival time compared with patients not receiving SBRT.

Angiographically Silent Ruptured Dural Arteriovenous Fistula Presenting As Subdural Hematoma.

Dural arteriovenous fistulas (dAVF) are aberrant vascular communications that can have devastating effects ranging from headaches to death. Typically, these malformations are identifiable on a CT angiogram (CTA) and confirmed via catheter angiography. We present a case of a female patient who presented with a headache and was found to have a large holohemispheric subdural hematoma. Given the lack of trauma, a CTA was performed. The CTA revealed abnormal vessels in the anterior temporal lobe spanning her hematoma. A diagnostic cerebral angiogram was performed; no early venous drainage was detected. When the patient was taken to the operating room for subdural hematoma evacuation, an aberrant connection from a superficial cortical vein to the middle meningeal artery was identified and ligated. Although rare, this case demonstrates that patients can present with ruptured vascular malformations that are radiographically silent on cerebral angiography.

Low-molecular-weight Heparin (enoxaparin) versus unfractionated heparin for venous thromboembolism prophylaxis in patients undergoing craniotomy.

OBJECTIVE: To explore the difference in post-operative DVT, PE, and ICH complications following administration of prophylactic UFH or enoxaparin in patients undergoing craniotomy. METHODS: A retrospective chart review was conducted for 542 patients at our institution receiving either 5000units/0.5 mL UFH (BID or TID; 180 patients) or single daily 40 mg/0.4 mL enoxaparin (362 patients) following craniotomy. Multivariate linear regression models were developed comparing rates of postoperative DVT, PE, and reoperation for bleeding in patients given enoxaparin versus UFH prophylaxis while controlling for age at surgery, history of VTE, surgery duration, number of post-operative hospital days, reoperation, post-operative infections, and reason for surgery (tumor type, genetics, etc.). Mann Whitney U tests were subsequently performed comparing rates of postoperative DVT, PE, and ICH for each group. RESULTS: Patients receiving prophylactic enoxaparin, when compared to UFH, exhibited similar rates of postoperative DVT (22 % vs 20.6 %, p = 0.86), PE (9.7 % vs 8.9 %, p = 0.86), and reoperation for bleeding (0.4 % vs 0.2 %, p = 0.58), while controlling for the factors described above. CONCLUSION: In patients undergoing craniotomy, rates for DVT, PE, and ICH were similar between patients treated with either prophylactic enoxaparin or UFH. Further studies are needed to understand whether a certain subset of patients demonstrate improved benefit from either prophylactic anticoagulant.

Impact of intraoperative direct cortical stimulation dynamics on perioperative seizures and afterdischarge frequency in patients undergoing awake craniotomy.

OBJECTIVE: Intraoperative stimulation is used as a crucial adjunct in neurosurgical oncology, allowing for greater extent of resection while minimizing morbidity. However, limited data exist regarding the impact of cortical stimulation on the frequency of perioperative seizures in these patients. METHODS: A retrospective chart review of patients undergoing awake craniotomy with electrocorticography data by a single surgeon at the authors' institution between 2013 and 2020 was conducted. Eighty-three patients were identified, and electrocorticography, stimulation, and afterdischarge (AD)/seizure data were collected and analyzed. Stimulation characteristics (number, amplitude, density [stimulations per minute], composite score [amplitude × density], total and average stimulation duration, and number of positive stimulation sites) were analyzed for association with intraoperative seizures (ISs), ADs, and postoperative clinical seizures. RESULTS: Total stimulation duration (p = 0.005), average stimulation duration (p = 0.010), and number of stimulations (p = 0.020) were found to significantly impact AD incidence. A total stimulation duration of more than 145 seconds (p = 0.04) and more than 60 total stimulations (p = 0.03) resulted in significantly higher rates of ADs. The total number of positive stimulation sites was associated with increased IS (p = 0.048). Lesions located within the insula (p = 0.027) were associated with increased incidence of ADs. Patients undergoing repeat awake craniotomy were more likely to experience IS (p = 0.013). Preoperative antiepileptic drug use, seizure history, and number of prior resections of any type showed no impact on the outcomes considered. The charge transferred to the cortex per second during mapping was significantly higher in the 10 seconds leading to AD than at any other time point examined in patients experiencing ADs, and was significantly higher than any time point in patients not experiencing ADs or ISs. Although the rate of transfer for patients experiencing ISs was highest in the 10 seconds prior to the seizure, it was not significantly different from those who did not experience an AD or IS. CONCLUSIONS: The data suggest that intraoperative cortical stimulation is a safe and effective technique in maximizing extent of resection while minimizing neurological morbidity in patients undergoing awake craniotomies, and that surgeons may avoid ADs and ISs by minimizing duration and total number of stimulations and by decreasing the overall charge transferred to the cortex during mapping procedures.

Unfractionated Heparin TID Dosing Regimen Is Associated With a Lower Rate of Pulmonary Embolism When Compared With BID Dosing in Patients Undergoing Craniotomy.

BACKGROUND: Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), and intracranial hemorrhage (ICH) may complicate the post-operative course of patients undergoing craniotomy. While prophylaxis with unfractionated heparin (UFH) has been shown to reduce VTE rates, twice-daily (BID) and three-times-daily (TID) UFH dosing regimens have not been compared in neurosurgical procedures. The objective of this study was to explore the association between UFH dosing regimen and rates of VTE and ICH in craniotomy patients. METHODS: A retrospective chart review was conducted for 159 patients at Northwestern University receiving 5000 units/0.5 mL UFH injections either BID (n = 132) or TID (n = 27). General linear regression models were run to predict rates of DVT, PE, and reoperation due to bleeding from UFH dosing regimen while controlling for age at surgery, sex, VTE history, craniotomy for tumor resection, surgery duration, length of stay, reoperation, infections, and IDH/MGMT mutations. RESULTS: Receiving UFH TID was significantly associated with a lower rate of PE when compared with receiving UFH BID (ß = -0.121, P = 0.044; TID rate = 0%, BID rate = 10.6%). UFH TID also showed a trend toward lower rates of DVT (ß = -0.0893, P = 0.295; TID rate = 18.5%, BID rate = 21.2%) when compared with UFH BID. UFH TID showed no significant difference in rate of reoperation for bleeding when compared to UFH BID (ß = -0.00623, P = 0.725; TID rate = 0%, BID rate = 0.8%). CONCLUSIONS: UFH TID dosing is associated with lower rates of PE when compared with BID dosing in patients undergoing craniotomy.

Preoperative Opioid Use and Clinical Outcomes in Spine Surgery: A Systematic Review.

BACKGROUND: Prescription opioid use and opioid-related deaths have become an epidemic in the United States, leading to devastating economic and health ramifications. Opioids are the most commonly prescribed drug class to treat low back pain, despite the limited body of evidence supporting their efficacy. Furthermore, preoperative opioid use prior to spine surgery has been reported to range from 20% to over 70%, with nearly 20% of this population being opioid dependent. OBJECTIVE: To review the medical literature on the effect of preoperative opioid use in outcomes in spine surgery. METHODS: We reviewed manuscripts published prior to February 1, 2019, exploring the effect of preoperative opioid use on outcomes in spine surgery. We identified 45 articles that analyzed independently the effect of preoperative opioid use on outcomes (n = 32 lumbar surgery, n = 19 cervical surgery, n = 7 spinal deformity, n = 5 "other"). RESULTS: Preoperative opioid use is overwhelmingly associated with negative surgical and functional outcomes, including postoperative opioid use, hospitalization duration, healthcare costs, risk of surgical revision, and several other negative outcomes. CONCLUSION: There is an urgent and unmet need to find and apply extensive perioperative solutions to combat opioid use, particularly in patients undergoing spine surgery. Further investigations are necessary to determine the optimal method to treat such patients and to develop opioid-combative strategies in patients undergoing spine surgery.

Analysis of risk factors and clinical sequelae of direct electrical cortical stimulation-induced seizures and afterdischarges in patients undergoing awake mapping.

OBJECTIVE: Intraoperative stimulation has emerged as a crucial adjunct in neurosurgical oncology, aiding maximal tumor resection while preserving sensorimotor and language function. Despite increasing use in clinical practice of this stimulation, there are limited data on both intraoperative seizure (IS) frequency and the presence of afterdischarges (ADs) in patients undergoing such procedures. The objective of this study was to determine risk factors for IS or ADs, and to determine the clinical consequences of these intraoperative events. METHODS: A retrospective chart review was performed for patients undergoing awake craniotomy (both first time and repeat) at a single institution from 2013 to 2018. Hypothesized risk factors for ADs/ISs in patients were evaluated for their effect on ADs and ISs, including tumor location, tumor grade (I-IV), genetic markers (isocitrate dehydrogenase 1/2, O 6-methylguanine-DNA methyltransferase [MGMT] promoter methylation, chromosome 1p/19q codeletion), tumor volume, preoperative seizure status (yes/no), and dosage of preoperative antiepileptic drugs for each patient. Clinical outcomes assessed in patients with IS or ADs were duration of surgery, length of stay, presence of perioperative deficits, and postoperative seizures. Chi-square analysis was performed for binary categorical variables, and a Student t-test was used to assess continuous variables. RESULTS: A total of 229 consecutive patients were included in the analysis. Thirty-five patients (15%) experienced ISs. Thirteen (37%) of these 35 patients had experienced seizures that were appreciated clinically and noted on electrocorticography simultaneously, while 8 patients (23%) experienced ISs that were electrographic alone (no obvious clinical change). MGMT promoter methylation was associated with an increased prevalence of ISs (OR 3.3, 95% CI 1.2-7.8, p = 0.02). Forty patients (18%) experienced ADs. Twenty-three percent of patients (9/40) with ISs had ADs prior to their seizure, although ISs and ADs were not statistically associated (p = 0.16). The presence of ADs appeared to be correlated with a shorter length of stay (5.1 ± 2.6 vs 6.1 ± 3.7 days, p = 0.037). Of the clinical features assessed, none were found to be predictive of ADs. Neither IS nor AD, or the presence of either IS or AD (65/229 patients), was a predictor for increased length of stay, presence of perioperative deficits, or postoperative seizures. CONCLUSIONS: ISs and ADs, while commonly observed during intraoperative stimulation for brain mapping, do not negatively affect patient outcomes.

Ghost Aneurysms in Acute Subdural Hematomas: A Report of Two Cases.

OBJECTIVE: Acute subdural hematoma (aSDH) is a common pathology encountered in neurosurgery. Although most cases are associated with trauma and injuries to draining veins, traumatic aSDH from injury to arteries or spontaneous aSDH because of a ruptured intracranial aneurysm can occur. For some patients without a clear clinical history, it can be difficult to distinguish between these etiologies purely based on radiography. The objective of this research was to describe a case series in which imaging was suggestive of the presence of distal cortical intracranial aneurysm associated with aSDH, but operative management demonstrated no evidence of aneurysm. METHODS: We retrospectively reviewed 2 patients known to have aSDH with suspicion for associated aneurysm between May 2019 and September 2019 at our institution. Data collected included demographic, clinical, and operative course, including age, gender, past medical history, presenting symptoms, and pre and postoperative imaging. RESULTS: In 2 patients presenting with aSDH with preoperative radiographic imaging suggesting distal middle cerebral artery aneurysms, surgical exploration revealed no aneurysm. In both cases, noniatrogenic active arterial bleeding from an injured cortical middle cerebral artery branch was identified. CONCLUSIONS: Although there are prior reports of arterial aSDH, to our knowledge, this is the first to describe the radiographic "ghost aneurysm" sign. It is important for clinicians to be aware of this potential misleading radiographic sign, which indicates active extravasation into a spherical cast of clot.

Surgical versus conservative treatment of unilateral subaxial non-subluxed facet fractures: A systematic review and meta-analysis.

BACKGROUND AND OBJECTIVE: Unilateral subaxial non-subluxed facet fractures (USNSFF) are a pathology seen in traumatic events such as motor vehicle accidents. Management involves either rigid collar bracing or surgical intervention. There currently is no consensus on the treatment of these injuries; this review aims to examine the extant data for recommendations as to which treatment is more effective. METHODS: MEDLINE, Scopus, and the Cochrane trial register were all searched on January 16, 2020, comparing outcomes for surgical and conservative therapy for USNSFF. The meta-analysis examined rates of treatment failure (need for subsequent operative management) in conservative versus surgical management. The meta-analysis was performed using a random effects model, with visualization in forest and L'Abbé plots. RESULTS: We identified six retrospective studies describing 270 patients, with three studies describing 137 patients used in the meta-analysis. Overall, a surgical success rate of 97.7 % and a non-operative success rate of 79.7 % was observed. A random effects model risk ratio of 1.66 (95 % CI: 0.61-4.52) was obtained, suggesting efficacy of surgical management over conservative management. CONCLUSION: The need for surgical intervention subsequent to initial management in the treatment of USNSFF was found to be lower in surgical treatment in contrast to conservative management. However, the studies that were included in the meta-analysis had patient cohorts with much higher rates of neurological deficit and ligamentous injury on presentation, indicating that these may be prognostic indicators of conservative management failure. Furthermore, those that did fail conservative management did not develop severely debilitating conditions. Accordingly, conservative treatment is generally sufficient as a first step in a majority of cases of USNSFF lacking neurological deficit or ligamentous involvement.

Continuous, noninvasive wireless monitoring of flow of cerebrospinal fluid through shunts in patients with hydrocephalus.

Hydrocephalus is a common disorder caused by the buildup of cerebrospinal fluid (CSF) in the brain. Treatment typically involves the surgical implantation of a pressure-regulated silicone tube assembly, known as a shunt. Unfortunately, shunts have extremely high failure rates and diagnosing shunt malfunction is challenging due to a combination of vague symptoms and a lack of a convenient means to monitor flow. Here, we introduce a wireless, wearable device that enables precise measurements of CSF flow, continuously or intermittently, in hospitals, laboratories or even in home settings. The technology exploits measurements of thermal transport through near-surface layers of skin to assess flow, with a soft, flexible, and skin-conformal device that can be constructed using commercially available components. Systematic benchtop studies and numerical simulations highlight all of the key considerations. Measurements on 7 patients establish high levels of functionality, with data that reveal time dependent changes in flow associated with positional and inertial effects on the body. Taken together, the results suggest a significant advance in monitoring capabilities for patients with shunted hydrocephalus, with potential for practical use across a range of settings and circumstances, and additional utility for research purposes in studies of CSF hydrodynamics.

Impact of medical student involvement on outcomes following spine surgery: A single center analysis of 6485 patients.

Medical student (MS) observation and assistance in the operating room (OR) is a critical component of medical education. Though participation in the operating room has many benefits to the medical student, the potential cost of these experiences to the patients must be taken into account. Other studies have shown differences in outcomes with resident involvement, but the effect of medical students in the OR has been poorly understood. The objective of this study was to understand how medical students and residents impacted surgical outcomes in posterior spinal fusions, anterior cervical discectomy and fusions (ACDFs), and lumbar discectomies. We conducted a retrospective study of patients undergoing posterior spinal fusions, ACDFs, and lumbar discectomies over 15 years. There were 6485 patients met the inclusion criteria of either undergoing a posterior fusion, ACDF or lumbar discectomy (1250 posterior fusion, 1381 ACDF, 3854 lumbar discectomies). Overall, little difference was observed when a medical student was present for surgical outcomes including length of stay, infection, and readmission. For ACDFs, having a medical student present had a significantly longer procedure durations (OR = 1.612, p = 0.001) than cases without. Besides slightly longer operative time (in posterior fusions), there were no major differences in outcomes when a medical student was present in the OR.