Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Endoscopic Endonasal Middle-Inferior Clivectomy, Odontoidectomy, and Far-Medial Approach

Introduction  The clival, paraclival, and craniocervical junction regions are challenging surgical targets. To approach these areas, endoscopic endonasal transclival approaches (EETCAs) and their extensions (far-medial approach and odontoidectomy) have gained popularity as they obviate manipulating and working between neurovascular structures. Although several cadaveric studies have further refined these contemporary approaches, few provide a detailed step-by-step description. Thus, we aim to didactically describe the steps of the EETCAs and their extensions for trainees. Methods  Six formalin-fixed cadaveric head specimens were dissected. All specimens were latex-injected using a six-vessel technique. Endoscopic endonasal middle and inferior clivectomies, far-medial approaches, and odontoidectomy were performed. Results  Using angled endoscopes and surgical instruments, an endoscopic endonasal midclivectomy and partial inferior clivectomy were performed without nasopharyngeal tissue disruption. To complete the inferior clivectomy, far-medial approach, and partially remove the anterior arch of C1 and odontoid process, anteroinferior transposition of the Eustachian-nasopharynx complex was required by transecting pterygosphenoidal fissure tissue, but incision in the nasopharynx was not necessary. Full exposure of the craniocervical junction necessitated bilateral sharp incision and additional inferior mobilization of the posterior nasopharynx. Unobstructed access to neurovascular anatomy of the ventral posterior fossa and craniocervical junction was provided. Conclusion  EETCAs are a powerful tool for the skull-base surgeon as they offer a direct corridor to the ventral posterior fossa and craniocervical junction unobstructed by eloquent neurovasculature. To facilitate easier understanding of the EETCAs and their extensions for trainees, we described the anatomy and surgical nuances in a didactic and step-by-step fashion.

MALIGNANT TRANSFORMATION OF PREVIOULSY RADIATED VESTIBULAR SCHWANNOMA: 2D operative video

Malignant transformation of vestibular schwannomas, though rare, demands a comprehensive, multidisciplinary treatment approach to optimize patient outcomes. In this publication, we discuss the rare case of malignant transformation in a vestibular schwannoma post-radiation treatment, exemplified by a 58-year-old female patient. Initially diagnosed with a right cerebellopontine angle vestibular schwannoma, the patient underwent CyberKnife treatment 16 years ago, receiving 18 Gy across three fractions. Despite initial stability, the patient experienced progressive hearing loss, ultimately requiring a BAHA implant. Years later, she presented with rapid-onset facial weakness, dizziness, nausea, and vomiting, leading to a wheelchair-bound state and nutritional support upon admission. Advanced imaging revealed a significantly enlarged tumor, characterized by brain edema and suspicious hemorrhage, prompting urgent surgical intervention. Our multidisciplinary approach, including ENT collaboration, led to the decision for a right retrosigmoid craniotomy and meatotomy. This strategy aimed at maximal tumor resection while preparing for potential facial nerve sacrifice due to the suspected malignancy. Intraoperative findings confirmed the tumor's malignant nature, necessitating facial nerve resection. Postoperatively, the patient demonstrated clinical improvement and was discharged with plans for physical therapy and adjuvant radiation therapy, considering the tumor's malignant peripheral nerve sheath transformation. This case underscores the importance of vigilant monitoring for vestibular schwannoma patients, particularly those with rapid symptom progression and tumor growth, highlighting the crucial role of adjuvant radiotherapy in treatment regimens. This study received Institutional Review Board (IRB) approval. The patient featured in the video presentation provided informed consent for the use of their image and information.

Centromedian thalamic deep brain stimulation for idiopathic generalized epilepsy: Connectivity and target optimization

There are limited treatment options for individuals with drug-resistant idiopathic generalized epilepsy (IGE). Small, limited case series suggest that centromedian thalamus deep brain stimulation (CM-DBS) may be an effective treatment option. The optimal CM-DBS target for IGE is underexamined. Here, we present a retrospective analysis of CM-DBS targeting and efficacy for five patients with drug-resistant IGE. Volume of tissue activated (VTA) overlap with CM nucleus was performed using an open-source toolbox. Median follow-up time was 13 months. Median convulsive seizure frequency reduction was 66%. One patient had only absence seizures, with >99% reduction in absence seizure frequency. Four patients had electrode contacts positioned within the CM nucleus target, all of whom had >50% reduction in primary semiology seizure, with 85% median seizure reduction (p = .004, paired-sample t test). Volumetric "sweet-spot" mapping revealed that best outcomes were correlated with stimulation of the middle ventral CM nucleus. Connectivity strength between the sweet-spot region and central peri-Rolandic cortex was increased significantly relative to other cortical regions (p = 8.6 × 10-4, Mann-Whitney U test). Our findings indicate that CM-DBS can be an effective treatment for patients with IGE, highlight the importance of accurate targeting and targeting analysis, and within the context of prior work, suggest that ideal CM-DBS targets may be syndrome specific.

Defining the Spatial Resolution of Analyte Recovery during Microperfusion-Based Sampling of Brain Parenchyma

The unique architecture of the brain and the blood-brain barrier imposes challenges for the measurement of parenchyma-derived biomarkers that prevent sufficient understanding of transient neuropathogenic processes. One solution to this challenge is direct sampling of brain interstitial fluid via implanted microperfusion probes. Seeking to understand spatial limitations to microperfusion in the brain, we employed computational fluid dynamics modeling and empirical recovery of fluorescently labeled dextrans in an animal model. We found that dextrans were successfully recovered via microperfusion over a 6 h sampling period, especially at probes implanted 2 mm from the dextran infusion point relative to probes implanted 5 mm from the injection site. Experimental recovery was consistently around 1% of simulated, suggesting that this parameter can be used to set practical limits on the maximal tissue concentration of proteins measured in microperfusates and on the spatial domain sampled by our multimodal microperfusion probe.

Unplanned returns to the operating room: a quality improvement methodology for the comparison of institutional outcomes to national benchmarks

OBJECTIVE

Unplanned returns to the operating room (RORs) constitute an important quality metric in surgical practice. In this study, the authors present a methodology to compare a department's unplanned ROR rates with national benchmarks in the context of large-scale quality of care surveillance.

METHODS

The authors identified unplanned RORs within 30 days from the initial surgery at their institution during the period 2014-2018 using an institutional documentation platform that facilitates the collection of reoperation information by providers in the clinical setting. They divided the procedures into 28 groups by Current Procedural Terminology and International Classification of Diseases, 9th and 10th Revision codes. They estimated national benchmarks of unplanned RORs for these procedure groups via querying the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) registry during the period 2014-2018. Finally, they numerically assessed the unplanned ROR rates at their institution compared with those calculated from the ACS NSQIP registry.

RESULTS

Using the above methodology, the authors were able to classify 12,575 of the cases performed in their department during the period of interest, including 6037 (48%) cranial cases and 6538 (52%) spinal or peripheral nerve cases. Among those, 161 (1.3%) presented with complications that required an unplanned ROR within 30 days from the initial surgery. The respective cumulative unplanned ROR rate in the ACS NSQIP registry during the same timeframe was 3.6%. Among 15 categories of cranial procedures, the cumulative unplanned ROR rate was 1.3% in the authors' department and 5.6% in the ACS NSQIP registry. Among 13 categories of spinal and peripheral nerve procedures, the cumulative unplanned ROR rate was 1.3% in the authors' department and 2.8% in the ACS NSQIP registry. Unplanned ROR rates at the authors' institution were lower than the national average for each of the 28 procedure groups of interest. Yearly analysis of institutional ROR rates for the five most commonly performed procedures showed lower reoperation rates compared with the national benchmarks.

CONCLUSIONS

Using an institutional documentation tool and a widely available national database, the authors developed a reproducible and standardized method of comparing their department's outcomes with national benchmarks per procedure subgroup. This methodology accommodates longitudinal quality surveillance across the different subspecialties in a neurosurgical department and may illuminate potential shortcomings of care delivery in the future.

EEG Source Localization in Temporal Encephaloceles: Concordance With Surgical Resection and Clinical Outcomes

PURPOSE

Temporal encephaloceles are a cause of drug-resistant temporal lobe epilepsy; however, their relationship with epileptogenesis is unclear, and optimal surgical resection is uncertain. EEG source localization (ESL) may guide surgical decision-making.

METHODS

We reviewed patients at Mayo Clinic Rochester with drug-resistant temporal lobe epilepsy and temporal encephaloceles, who underwent limited resection and had 1-year outcomes. EEG source localization was performed using standard density scalp EEG of ictal and interictal activity. Distance from dipole and standardized low-resolution brain electromagnetic tomography (sLORETA) solutions to the encephalocele were measured. Concordance of ESL with encephalocele and surgical resection was compared with 1-year surgical outcomes.

RESULTS

Seventeen patients met criteria. The mean distances from ESL results to encephalocele center for dipole and sLORETA analyses were 23 mm (SD 9) and 22 mm (SD 11), respectively. Ten patients (55.6%) had Engel I outcomes at 1 year. Dipole-encephalocele distance and sLORETA-encephalocele distance were significantly longer in patients with Engel I outcome and patients whose encephalocele was contained by sLORETA had worse outcome as well; however, multiple logistic regression analysis found that only containment of encephalocele by the sLORETA current density was significant ( P < 0.05), odds ratio 0.12 (95% confidence interval [0.021, 0.71]).

CONCLUSIONS

EEG source localization of scalp EEG localizes near encephaloceles, however, typically not in the encephalocele itself; this may be due to scalp EEG sampling propagated activity or alternatively that the seizure onset zone extends beyond the herniated cortex. Surprisingly, we observed increased ESL to encephalocele distances in patients with excellent surgical outcomes. Larger cohort studies including intracranial EEG data are needed to further explore this finding.

Recurrence morbidity of olfactory neuroblastoma

BACKGROUND

With modern treatment paradigms, olfactory neuroblastoma (ONB) has favorable overall survival (OS); however, the incidence of recurrence remains high. The primary aims of this study were to delineate the prognosis of recurrence of ONB and explore how recurrence subsites are associated with OS, disease-specific survival (DSS), and further recurrence.

METHODS

A retrospective chart review of ONB cases from nine academic centers between 2005 and 2021 was completed. Tumor characteristics, recurrence subsites, timelines to recurrence, additional recurrences, and survival estimates were determined using descriptive and time-to-event analyses.

RESULTS

A final cohort of 233 patients was identified, with 70 (30.0%) patients recurring within 50.4 (standard deviation ±40.9) months of diagnosis on average, consisting of local (50%), neck (36%), intracranial (9%), and distant (6%) recurrence. Compared with subjects without recurrence, patients with recurrence had significantly different primary American Joint Committee on Cancer T stage (p < 0.001), overall stage (p < 0.001), and modified Kadish scores (p < 0.001). Histopathology identified that dural involvement and positive margins were significantly greater in recurrent cases. First recurrence was significantly associated with worse 5-year DSS (hazard ratio = 5.62; p = 0.003), and subjects with neck or local recurrence had a significantly better DSS compared to intracranial or distant recurrence.

CONCLUSIONS

Recurrent cases of ONB have significantly different stages and preoperative imaging factors. Patients with local or neck recurrence, however, have better DSS than those with intracranial or distant recurrence, independent of initial tumor stage or Hyams grade. Identifying specific factors that confer an increased risk of recurrence and DSS is important for patient counseling in addition to surveillance planning.

Extraocular muscle electromyographic recordings for intraoperative monitoring of cranial nerves III, IV, and VI: a single-center experience with intraorbital electrodes

OBJECTIVE

The objective of this study was to describe the quantitative features of intraoperative electromyographic recordings obtained from cranial nerve III, IV, and VI neuromonitoring using 25-mm intraorbital electrodes, in the larger context of demonstrating the practicality of this technique during neurosurgical cases.

METHODS

A 25-mm-long shaft-insulated intraorbital needle electrode is routinely used at the authors' institution for extraocular muscle (EOM) electromyographic monitoring of the inferior rectus, superior oblique, and/or lateral rectus muscles when their function is at risk. Cases monitored between January 1, 2021, and December 31, 2022, were reviewed for patient demographics, tumor location and pathology, EOMs monitored, pre- and postoperative examination, and complications from electrode placement. Compound muscle action potentials on triggered electromyography, as well as neurotonic discharges on free-run electromyography, were described quantitatively.

RESULTS

There were 141 cases in 139 patients reviewed during the 24-month time span, with 278 EOMs monitored (inferior rectus/superior oblique/lateral rectus muscles 68/68/142). Triggered electromyography yielded biphasic or triphasic compound muscle action potentials from EOMs with a mean onset latency of 1.51 msec (range 0.94-3.22 msec), mean maximal peak-to-trough amplitude of 1073.93 μV (range 76.75-7796.29 μV), and high specificity for the channel in nearly all cases. Neurotonic discharges were recorded in 30 of the 278 EOMs (with all 3 muscles represented) and associated with a greater incidence of new or worsened ophthalmoparesis (OR 4.62, 95% CI 1.3-16.4). There were 2 cases of small periorbital ecchymosis attributed to needle placement; additionally, 1 case of needle-related intraorbital hematoma occurred after the review period.

CONCLUSIONS

The 25-mm shaft-insulated intraorbital electrode facilitates robust and consistent electromyographic recordings of EOMs that are advantageous over existing techniques. Combined with the relative ease of needle placement and low rate of complications, the technique is practical for neuromonitoring during craniotomies.

Patterns of recurrence and disease progression in patients with positive-margin olfactory neuroblastoma following primary resection

OBJECTIVE

Olfactory neuroblastoma (ONB) is a rare, malignant tumor of the sinonasal tract that arises from olfactory epithelium. Although surgery is the preferred first-line treatment, tumor involvement of adjacent structures may preclude the ability to achieve negative margins during initial resection. Herein, the authors examine the oncological outcomes of patients with positive margins after primary resection of ONB, with the aim of determining predictors of disease progression and patterns of recurrence.

METHODS

The authors performed an institutional review of 25 patients with positive-margin ONB after resection. Cox survival analyses were used to determine any statistically significant predictors of worse progression-free survival (PFS) and overall survival (OS).

RESULTS

A total of 93 patients who were diagnosed with ONB were identified, of whom 25 patients had positive margins following their primary resection. Eleven (44%) had a delayed finding of positive margins that were initially negative in the operating room but returned as positive on final pathology. Four patients had subtotal resection (STR), whereas the remaining patients underwent gross-total resection. Twenty-four patients received adjuvant radiotherapy (96%), and 15 additionally received adjuvant chemotherapy (60%). Fourteen patients (56%) experienced recurrence/progression at a median time of 35 months following resection (IQR 19-70 months). Local recurrence occurred in 10 patients (40%), regional in 9 (36%), and distant metastasis in 2 (8%). In Cox survival analyses, the 5-year PFS and OS were 55.1% and 79.2%, respectively. Kadish stage D was predictive of worse PFS in univariate (hazard ratio [HR] 15.67, 95% CI 3.38-72.61, p < 0.001) and multivariate (HR 15.46, 95% CI 1.45-164.91, p = 0.023) analyses. Hyams grade, adjuvant chemotherapy, and primary radiotherapy were not associated with PFS. Furthermore, Kadish stage D and STR were predictive of worse OS in univariate analysis (HR 12.64, 95% CI 2.03-78.86, p = 0.007; HR 7.31, 95% CI 1.45-36.84, p = 0.016; respectively). However, local and regional recurrence was not associated with worse OS.

CONCLUSIONS

Approximately half of patients with positive-margin ONB may experience disease recurrence. Patients with an advanced disease stage (Kadish D) may have a higher likelihood of developing recurrence/progression. Furthermore, patients with tumor burden following resection (STR and Kadish D) may have worse OS. However, in positive-margin ONB with no gross disease following initial resection, the presence of disease recurrence does not significantly alter survival when receiving salvage therapy.

Correlation of older age with better progression-free survival despite less aggressive resection in nonfunctioning pituitary adenomas

OBJECTIVE

Nonfunctioning pituitary adenomas (NFPAs) present at a wide range of ages; it is possible that variable outcomes are based on patient age at presentation. This study aimed to explore long-term outcomes of patients with NFPAs following endonasal transsphenoidal surgery (ETS), considering age stratification.

METHODS

This retrospective study included 228 patients with NFPAs who underwent ETS, with a median follow-up period of 63 months. The outcomes included progression-free survival (PFS) rates and neurological and endocrinological outcomes. Age-stratified Kaplan-Meier and Cox proportional hazards analyses were performed. Patients were classified into four age groups: ≤ 49, 50-59, 60-69, and ≥ 70 years.

RESULTS

Age-stratified analysis showed a significant correlation between age and PFS in NFPAs (5-year PFS rates: 63.0% in those ≤ 49 years, 76.7% in those 50-59 years, 85.0% in those 60-69 years, and 88.1% in those ≥ 70 years; p = 0.001, log-rank test). Bivariate (HR 1.03, 95% CI 1.01-1.05; p = 0.001) and multivariable (HR 1.03, 95% CI 1.02-1.05; p = 0.001) analyses demonstrated that older age was significantly associated with longer PFS. Multivariable analysis also demonstrated that smaller maximum tumor diameter (HR 0.77, 95% CI 0.60-0.99; p = 0.036) and gross-total resection (HR 8.55, 95% CI 3.90-18.75; p = 0.001) were significantly associated with longer PFS. Multivariable logistic regression analysis demonstrated that only younger age was associated with postoperative improvement of male hypogonadism (HR 0.91, 95% CI 0.84-0.99; p = 0.019). Other postoperative neurological and endocrinological outcomes were not significantly associated with age.

CONCLUSIONS

Older patients with NFPAs treated with ETS demonstrated a longer PFS. Of endocrinological outcomes studied, only male hypogonadism improvement was associated with younger patient age.

Surgical treatment of cystic pituitary adenomas: literature-based definitions and postoperative outcomes

BACKGROUND AND OBJECTIVES

To survey the applied definitions of 'cystic' among pituitary adenomas and evaluate whether postoperative outcomes differ relative to non-cystic counterparts.

METHODS

A literature search and meta-analysis was performed using PRISMA guidelines. Studies were eligible if novel data were reported regarding the applied definition of 'cystic' and postoperative outcomes among cases of surgically treated pituitary adenomas. Data were pooled with random effects meta-analysis models into cohorts based on the applied definition of 'cystic'. Categorical meta-regressions were used to investigate differences between cohorts. Among studies comparing cystic and non-cystic pituitary adenomas, meta-analysis models were applied to determine the Odds Ratio [95% Confidence Interval]. Statistical analyses were performed using Comprehensive Meta-Analysis (CMA, 4.0), with a priori significance defined as P < 0.05.

RESULTS

Ten studies were eligible yielding 283 patients with cystic pituitary adenomas. The definitions of 'cystic' mainly varied between the visual appearance of cystic components on preoperative magnetic resonance imaging and a volumetric definition requiring 50% or greater of tumor volume exhibiting cystic components. Tumor diameter was seldom reported with an associated standard deviation/error, limiting meta-analyses. When the data were pooled in accordance with the definition applied, there were no significant differences in the rates of gross total resection (P = 0.830), endocrinologic remission (P = 0.563), and tumor recurrence (P = 0.320). Meta-analyses on studies comparing cystic versus non-cystic pituitary adenomas indicated no significant difference in the rates of gross total resection (P = 0.729), endocrinologic remission (P = 0.857), and tumor recurrence (P = 0.465).

CONCLUSION

Despite some individual studies describing a significant influence of pituitary adenoma texture on postoperative outcomes, meta-analyses revealed no such differences between cystic and non-cystic pituitary adenomas. This discrepancy may be explained in part by the inconsistent definition of 'cystic' and between-group differences in tumor size. A notion of a field-standard definition of 'cystic' among pituitary adenomas should be established to facilitate inter-study comparisons.

SupraPetrous InfraTemporal Approach: A Supplemental Approach to Supracerebellar Infratentorial for Inferior Amygdala and Hippocampal Head Access-A Cadaveric Study With Case Illustrations

BACKGROUND AND OBJECTIVES

Access to the amygdala and hippocampus (A/H) is complex. To address the limitations and invasiveness of traditional approaches, including the Transsylvian, Subtemporal, and Supracerebellar infratentorial approaches, we developed the suprapetrous infratemporal (SPIT) approach. This study describes the nuances of this approach in both cadaveric studies and clinical cases.

METHODS

Three unilateral exposures were performed using microscopic and endoscopic methodologies in the SPIT approach. After cadaveric investigation, this approach was successfully implemented in representative clinical cases.

RESULTS

The SPIT approach enabled direct access to the inferior A/H, circumventing the requirement for temporal lobe retraction and detachment of the temporal lobe from the dura through a subtemporal route by drilling the upper part of the mastoid, consequently mitigating tension on the vein of Labbé. This enabled a bottom-up view because one would gain with a zygomatic osteotomy and forward projection like a mini-posterior petrosal view by using a transmastoid view, without cutting down the zygomatic arch and opening the dura subtemporally, limiting patient pain and preventing case comorbidity. The SPIT approach was performed in 2 cases of mesial temporal cavernoma presenting with seizures. The lesion was visualized intraoperatively and was successfully removed in these cases. The postoperative course was excellent with no complications, and gross total resection was radiographically confirmed with Engel Class 1a seizure freedom.

CONCLUSION

The SPIT approach is a complementary approach for inferior A/H disease, combining the combined middle fossa approach modified for intradural pathology. Limited drilling of the upper aspect of the mastoid with a medial dural opening at the level of the arcuate eminence provides a direct trajectory with minimal brain retraction. Additional research encompassing a larger patient cohort and extended follow-up periods is required to substantiate the advantages of SPIT in the management of inferior A/H lesions.

A Cadaveric Feasibility Study of the Biportal Endoscopic Transfrontal Sinus Approach: A Minimally Invasive Approach to the Anterior Cranial Fossa

BACKGROUND AND OBJECTIVES

The trans-sinus transglabellar and bifrontal approaches offer direct access to the anterior cranial fossa. However, these approaches present potential drawbacks. We propose the biportal endoscopic transfrontal sinus (BETS) approach, adapting endoscopic endonasal approach (EEA) techniques for minimally invasive access to the anterior fossa, reducing tissue manipulation, venous sacrifice, and brain retraction.

METHODS

Six formalin specimens were used. BETS approach involves 2 incisions over the medial aspect of both eyebrows from the supraorbital notch to the medial end of the eyebrow. A unilateral pedicled pericranial flap is harvested. A craniotomy through the anterior table of the frontal sinus (FS) and a separate craniotomy through the posterior table are performed. Two variants of the approach (preservative vs cranialization) are described for opening and reconstruction of the FS based on the desired pathology to access. Bone flap replacement can be performed with titanium plates and filling of the external table defect with bone cement.

RESULTS

Like in EEA, this approach provides access for endoscope and multiple working instruments to be used simultaneously. The approach allows wide access to the anterior cranial fossa, subfrontal, and interhemispheric corridors, all the way up to the suprachiasmatic corridor and through the lamina terminalis to the third ventricle. BETS provides direct access to the anterior fossa, minimizing the level of frontal lobe retraction and providing potentially less tissue disruption and improved cosmesis. Cerebrospinal fluid fistula risk remains one of the major concerns as the narrow corridor limits achieving a watertight closure which can be mitigated with a pedicled flap. Mucocele risk is minimized with full cranialization or reconstruction of the FS.

CONCLUSION

The BETS approach is a minimally invasive approach that translates the concepts of EEA to the FS. It allows excellent access to the anterior cranial fossa structures with minimal frontal lobe retraction.

Predicting the Need for Occipitocervical Fusion for Patients with Lower Clival Chordoma: A Single-Center Retrospective Study

OBJECTIVE

To assess the impact of tumor extension into the occipital condyle (OC) in lower clival chordoma management and the need for occipito-cervical fusion (OCF).

METHODS

A retrospective analysis was conducted on 35 patients with lower clival chordoma. The preoperative area of the intact OCs, Hounsfield units, and the integrity of the apical ligament and the tectorial membrane were assessed using preoperative imaging.

RESULTS

Seven (20%) patients were in the OCF group. The OCF group exhibited a higher prevalence of preoperative pain in the neck or head (P = 0.006), ligament absence (P = 0.022), and increased propensity for postoperative wound issues (P = 0.022) than the non-OCF group. The OCF group had less intact OCs (P < 0.001) and higher spinal instability neoplastic score (P = 0.002) than the non-OCF group. All patients with intact OCs < 60% underwent OCF, and those with OCs ≥ 70% were treated without OCF. Those with OCs between 60% and 69% underwent OCF if the ligaments were eroded, and did not undergo OCF if the ligaments were intact. Treatment strategies varied, with endoscopic endonasal approach alone being common. Radiation therapy was administered to 89% of patients. All 3 patients treated with OCF after tumor resection had wound issues; none treated with OCF before resection had wound issues. None developed atlanto-occipital instability. Survival rates did not significantly differ between groups.

CONCLUSIONS

In the absence of mobility-related neck pain, patients with lower clival chordoma and intact OC ≥ 60%, intact apical ligament, and intact tectorial membrane, may not require OCF.

Stereotactic depth electrode placement for chronic subthreshold cortical stimulation: surgical technique video

Neurostimulation is an increasingly common treatment option for medically intractable epilepsy. SANTE (Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy) and Responsive Neurostimulation (RNS) System are landmark neurostimulation trials that utilized either duty cycle or a responsive stimulation paradigm. A seizure-free outcome is rarely observed with responsive and duty cycle neurostimulation devices. Chronic subthreshold cortical stimulation (CSCS) is a promising treatment for adult drug-resistant epilepsy involving eloquent cortex and has demonstrated safety and efficacy. Herein, the authors describe the surgical technique as well as details of stimulation programming involved in CSCS placement to facilitate the adoption of this promising treatment. The video can be found here: https://stream.cadmore.media/r10.3171/2024.4.FOCVID2422.

Improved quantification of tumor adhesion in meningiomas using MR elastography-based slip interface imaging

Meningiomas, the most prevalent primary benign intracranial tumors, often exhibit complicated levels of adhesion to adjacent normal tissues, significantly influencing resection and causing postoperative complications. Surgery remains the primary therapeutic approach, and when combined with adjuvant radiotherapy, it effectively controls residual tumors and reduces tumor recurrence when complete removal may cause a neurologic deficit. Previous studies have indicated that slip interface imaging (SII) techniques based on MR elastography (MRE) have promise as a method for sensitively determining the presence of tumor-brain adhesion. In this study, we developed and tested an improved algorithm for assessing tumor-brain adhesion, based on recognition of patterns in MRE-derived normalized octahedral shear strain (NOSS) images. The primary goal was to quantify the tumor interfaces at higher risk for adhesion, offering a precise and objective method to assess meningioma adhesions in 52 meningioma patients. We also investigated the predictive value of MRE-assessed tumor adhesion in meningioma recurrence. Our findings highlight the effectiveness of the improved SII technique in distinguishing the adhesion degrees, particularly complete adhesion. Statistical analysis revealed significant differences in adhesion percentages between complete and partial adherent tumors (p = 0.005), and complete and non-adherent tumors (p<0.001). The improved technique demonstrated superior discriminatory ability in identifying tumor adhesion patterns compared to the previously described algorithm, with an AUC of 0.86 vs. 0.72 for distinguishing complete adhesion from others (p = 0.037), and an AUC of 0.72 vs. 0.67 for non-adherent and others. Aggressive tumors exhibiting atypical features showed significantly higher adhesion percentages in recurrence group compared to non-recurrence group (p = 0.042). This study validates the efficacy of the improved SII technique in quantifying meningioma adhesions and demonstrates its potential to affect clinical decision-making. The reliability of the technique, coupled with potential to help predict meningioma recurrence, particularly in aggressive tumor subsets, highlights its promise in guiding treatment strategies.

The dynamic impact of location and resection on the glioma CSF proteome

While serial sampling of glioma tissue is rarely performed prior to recurrence, cerebrospinal fluid (CSF) is an underutilized longitudinal source of candidate glioma biomarkers for understanding therapeutic impacts. However, the impact of key variables to consider in longitudinal CSF samples, including anatomical location and post-surgical changes, remains unknown. To that end, pre- versus post-resection intracranial CSF samples were obtained at early (1-16 days; n=20) or delayed (86-153 days; n=11) timepoints for patients with glioma. Paired lumbar-versus-intracranial glioma CSF samples were also obtained (n=14). Using aptamer-based proteomics, we identify significant differences in the CSF proteome between lumbar, subarachnoid, and ventricular CSF. Our analysis of serial intracranial CSF samples suggests the early potential for disease monitoring and evaluation of pharmacodynamic impact of targeted therapies. Importantly, we found that resection had a significant, evolving longitudinal impact on the CSF proteome. Proteomic data are provided with individual clinical annotations as a resource for the field.

One Sentence Summary

Glioma cerebrospinal fluid (CSF) accessed intra-operatively and longitudinally via devices can reveal impacts of treatment and anatomical location.

Long-term outcome of primary clival chordomas: a single-center retrospective study with an emphasis on the timing of recurrences based on the primary treatment

OBJECTIVE

This study aimed to provide data on extended outcomes in primary clival chordomas, focusing on progression-free survival (PFS) and overall survival (OS).

METHODS

A retrospective single-center analysis was conducted on patients with clival chordoma treated between 1987 and 2022 using surgery, stereotactic radiosurgery, or proton radiation therapy (PRT).

RESULTS

The study included 100 patients (median age 44 years, 51% male). Surgery was performed using the endoscopic endonasal approach in 71 patients (71%). Gross-total resection (GTR) or near-total resection (NTR) was attained in 39 patients (39%). Postoperatively, new cranial nerve deficits occurred in 7%, CSF leak in 4%, and meningitis in none of the patients. Radiation therapy was performed in 79 patients (79%), with PRT in 50 patients (50%) as the primary treatment. During the median follow-up period of 73 (interquartile range [IQR] 38-132) months, 41 recurrences (41%) and 31 deaths (31%) were confirmed. Patients with GTR/NTR had a median PFS of 41 (IQR 24-70) months. Patients with subtotal resection or biopsy had a median PFS of 38 (IQR 16-97) months. The median PFS of patients who received radiation therapy was 43 (IQR 26-86) months, while that of patients who did not receive radiation therapy was 18 (IQR 5-62) months. The Kaplan-Meier method showed that patients with GTR/NTR (p = 0.007) and those who received radiation therapy (p < 0.001) had longer PFS than their counterparts. The PFS rates following primary treatment at 5, 10, 15, and 20 years were 51%, 25%, 17%, and 7%, respectively. The OS rates at the same intervals were 84%, 60%, 42%, and 34%, respectively. Multivariate Cox regression analysis showed that age < 44 years (p = 0.02), greater extent of resection (EOR; p = 0.03), and radiation therapy (p < 0.001) were associated with lower recurrence rates. Another multivariate analysis showed that age < 44 years (p = 0.01), greater EOR (p = 0.04), and freedom from recurrence (p = 0.02) were associated with lower mortality rates. Regarding pathology data, brachyury was positive in 98%, pan-cytokeratin in 93%, epithelial membrane antigen in 85%, and S100 in 74%. No immunohistochemical markers were associated with recurrence.

CONCLUSIONS

In this study, younger age, maximal safe resection, and radiation therapy were important factors for longer PFS in patients with primary clival chordomas. Preventing recurrences played a crucial role in achieving longer OS.

Delayed vagal nerve compressive neuropathy following placement of vagal nerve stimulator: case report

Vagal neuropathy causing vocal fold palsy is an uncommon complication of vagal nerve stimulator (VNS) placement. It may be associated with intraoperative nerve injury or with device stimulation. Here we present the first case of delayed, compressive vagal neuropathy associated with VNS coil placement which presented with progressive hoarseness and vocal cord paralysis. Coil removal and vagal neurolysis was performed to relieve the compression. Larger 3 mm VNS coils were placed for continuation of therapy. Coils with a larger inner diameter should be employed where possible to prevent this complication. The frequency of VNS-associated vagal nerve compression may warrant further investigation.

Treatment modalities and outcomes of granular cell tumors and spindle cell oncocytomas of the pituitary gland: an analysis of two national cancer databases

BACKGROUND

Spindle cell oncocytomas (SCO) and granular cell tumors (GCT) are rare primary pituitary neoplasms; the optimal treatment paradigms for these lesions are unknown and largely unexplored. Thus, using national registries, we analyze the epidemiology, management patterns, and surgical outcomes of SCOs and GCTs.

METHODS

The National Cancer Database (NCDB; years 2003-2017) and the Surveillance, Epidemiology, and End Results Program (SEER; years 2004-2018) were queried for patients with pituitary SCOs or GCTs. Incidence, extent of surgical resection, and rate of postoperative radiation use for subtotally resected lesions comprised the primary outcomes of interest. All-cause mortality was also analyzed via time-to-event Kaplan-Meier curves.

RESULTS

SCOs and GCTs have an annual incidence of 0.017 and 0.023 per 1,000,000, respectively. They comprise 0.1% of the benign pituitary tumors registered in NCDB. A total of 112,241 benign pituitary tumors were identified in NCDB during the study period, of which 83 (0.07%) were SCOs and 59 (0.05%) were GCTs. Median age at diagnosis was 55 years, 44% were females, and median maximal tumor diameter at presentation was 2.1 cm. Gross total resection was achieved in 54% patients. Ten patients (7%) had postoperative radiation. Comparing patients with GCTs versus SCOs, the former were more likely to be younger at diagnosis (48.0 vs. 59.0, respectively; p < 0.01) and female (59% vs. 34%, p = 0.01). GCTs and SCOs did not differ in terms of size at diagnoses (median maximal diameter: 1.9 cm vs. 2.2 cm, respectively; p = 0.59) or gross total resection rates (62% vs. 49%, p = 0.32). After matching SCOs and GCTs with pituitary adenomas on age, sex, and tumor size, the former were less likely to undergo gross total resection (53% vs. 72%; p = 0.03). Patients with SCOs and GCTs had a shorter overall survival when compared to patients with pituitary adenomas (p < 0.01) and a higher rate of thirty-day mortality (3.1% vs 0.0%; p = 0.013).

CONCLUSION

SCOs and GCTs are rare pituitary tumors, and their management entails particular challenges. Gross total resection is often not possible, and adjuvant radiation might be employed following subtotal resection.

Acute to long-term characteristics of impedance recordings during neurostimulation in humans

Objective.This study aims to characterize the time course of impedance, a crucial electrophysiological property of brain tissue, in the human thalamus (THL), amygdala-hippocampus, and posterior hippocampus over an extended period.Approach.Impedance was periodically sampled every 5-15 min over several months in five subjects with drug-resistant epilepsy using an investigational neuromodulation device. Initially, we employed descriptive piecewise and continuous mathematical models to characterize the impedance response for approximately three weeks post-electrode implantation. We then explored the temporal dynamics of impedance during periods when electrical stimulation was temporarily halted, observing a monotonic increase (rebound) in impedance before it stabilized at a higher value. Lastly, we assessed the stability of amplitude and phase over the 24 h impedance cycle throughout the multi-month recording.Main results.Immediately post-implantation, the impedance decreased, reaching a minimum value in all brain regions within approximately two days, and then increased monotonically over about 14 d to a stable value. The models accounted for the variance in short-term impedance changes. Notably, the minimum impedance of the THL in the most epileptogenic hemisphere was significantly lower than in other regions. During the gaps in electrical stimulation, the impedance rebound decreased over time and stabilized around 200 days post-implant, likely indicative of the foreign body response and fibrous tissue encapsulation around the electrodes. The amplitude and phase of the 24 h impedance oscillation remained stable throughout the multi-month recording, with circadian variation in impedance dominating the long-term measures.Significance.Our findings illustrate the complex temporal dynamics of impedance in implanted electrodes and the impact of electrical stimulation. We discuss these dynamics in the context of the known biological foreign body response of the brain to implanted electrodes. The data suggest that the temporal dynamics of impedance are dependent on the anatomical location and tissue epileptogenicity. These insights may offer additional guidance for the delivery of therapeutic stimulation at various time points post-implantation for neuromodulation therapy.

Lower Cranial Nerve Schwannomas: Cohort Study and Systematic Review

BACKGROUND AND OBJECTIVES

Schwannomas originating from the lower cranial nerves (LCNS) are rare and pose a significant surgical challenge. Resection is the mainstay treatment; however, risk of treatment morbidity is considerable, and the available literature regarding differential treatment outcomes in this vulnerable population is sparse.

METHODS

A single-institution cohort study and systematic literature review of LCNS were performed.

RESULTS

Fifty-eight patients were included: 34 underwent surgical resection and 24 underwent stereotactic radiosurgery (SRS). The median age at diagnosis was 48 years (range 17-74). Presenting symptoms were dysphagia (63%), dysarthria/hypophonia (47%), imbalance (33%), and hearing loss/tinnitus (30%). Tumor size was associated with surgical resection, as compared with initial SRS (4.1 cm vs 1.5 cm, P = .0001). Gross total resection was obtained in 52%, with tumor remnants predominantly localized to the jugular foramen (62%). Post-treatment worsening of symptoms occurred in 68% of surgical and 29% of SRS patients ( P = .003). Postoperative symptoms were mostly commonly hypophonia/hoarseness (63%) and dysphagia (59%). Seven patients (29%) had new neurological issues after SRS treatment, but symptoms were overall milder. The median follow-up was 60 months (range 12-252); 98% demonstrated meaningful clinical improvement. Eighteen surgical patients (53%) underwent adjuvant radiation at a median of 5 months after resection (range 2-32). At follow-up, tumor control was 97% in the surgical cohort and 96% among SRS patients.

CONCLUSION

Although LCNS resection is potentially morbid, most postoperative deficits are transient, and patients achieve excellent tumor control-particularly when paired with adjuvant SRS. For minimally symptomatic patients undergoing surgical intervention, we advise maximally safe resection with intracapsular dissection to preserve nerve integrity where possible. For residual or as a primary treatment modality, SRS is associated with low morbidity and high rates of long-term tumor control.

Longitudinal treatment outcomes of recurrent clival chordomas: a single-center retrospective study

OBJECTIVE

The objective of this study was to clarify the detailed clinical course of recurrent clival chordoma and the outcomes of each treatment modality.

METHODS

A single-center retrospective analysis was conducted on patients seen for recurrent clival chordoma. The cohort was identified from those who underwent surgery, stereotactic radiosurgery, or proton therapy at the authors' institution between 1990 and 2022.

RESULTS

A total of 95 recurrences in 40 patients with a median (interquartile range [IQR]) follow-up of 43 (18-79) months were identified. The median (IQR) age at the time of diagnosis was 48 (36-62) years, and 55% of patients were male. Twenty-three patients were treated with surgery followed by adjuvant radiation before the first recurrence. The median (range) number of recurrences per patient was 2 (1-8), and the median (IQR) time to the first recurrence was 29 (9-51) months. The recurrences were treated with one or more of the following therapies: surgery, radiation, systemic therapy, and laser interstitial thermal therapy (LITT). Surgery was performed for 44 recurrences in 25 patients. Radiation was used to treat 42 recurrences in 28 patients. Patients with recurrences treated with surgery plus radiation had the longest progression-free survival (PFS) (median [95% CI] overall survival [OS] 120 [0-245] months, p < 0.01, log-rank test). Patients with recurrences but without prior radiation had longer PFS than those patients with prior radiation. The median (95% CI) OS after the first recurrence was 68 (54-82) months, 5-year OS after the first recurrence was 48%, and 10-year OS was 27%. Multivariate Cox regression analysis showed that mortality after the first recurrence was significantly associated with no adjuvant radiation (HR 0.149, 95% CI 0.038-0.59, p = 0.0067), older age at the time of the first recurrence (HR 1.04, 95% CI 1.01-1.08, p = 0.021), and total number of recurrences (p = 0.032). Seven patients received systemic therapy, and the median (95% CI) OS of these patients since initiation of systemic therapy was 31 (11-51) months. Imatinib and/or nivolumab were used in 6 patients (15%). One patient (3%) was treated with LITT for his fourth recurrence.

CONCLUSIONS

Despite the aggressive nature of recurrent chordoma, 14 of 29 patients (48%) survived for more than 5 years after the initial recurrence using combined therapies. Multiple treatment options may contribute to the long-term survival of patients with this intractable tumor.

The association of thromboembolic complications and the use of tranexamic acid during resection of intracranial meningiomas: systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

Antifibrinolytics, such as tranexamic acid (TXA), have been shown to decrease intraoperative blood loss across multiple surgical disciplines. However, they carry the theoretical risk of thromboembolic events secondary to induced hypercoagulability. Therefore, the aim of this study was to systematically review the available literature and perform a meta-analysis on the use of TXA in meningioma resection to assess thromboembolic risks.

METHODS

The PubMed, Web of Science, and Google Scholar databases were reviewed for all randomized controlled trials presenting primary data on TXA use during resection of intracranial meningiomas. Data were gathered on operative duration, venous thromboembolic complications, deep venous thrombosis, use of allogeneic blood transfusion, estimated blood loss (EBL), and postoperative hemoglobin. Patients who received TXA were compared with controls who did not receive TXA intraoperatively using random-effects models.

RESULTS

A total of 508 unique articles were identified, of which 493 underwent full-text review. Ultimately, 6 studies with 381 total patients (190 receiving TXA) were included in the final analysis. All 6 trials were randomized, blinded, and placebo controlled with a TXA administration rate of a 20-mg/kg load followed by a 1-mg/kg/hr infusion. All studies were performed in lower-middle-income countries. There were no reported instances of venous thromboembolism (VTE) in the TXA and non-TXA cohorts. Patients receiving TXA exhibited fewer allogeneic transfusions (21.5% vs 41.6% [OR 0.26, 95% CI 0.09-0.77], p = 0.02) and lower EBL (MD -282.48 mL [95% CI -367.77 to -197.20 mL], p < 0.001) compared with patients who did not receive TXA, and they also had lower rates of perioperative complications (10.7% vs 19.9% [OR 0.47, 95% CI 0.2-0.95], p = 0.04).

CONCLUSIONS

Current literature suggests that TXA is not associated with increased risk for VTE when administered during resection of intracranial meningioma. TXA appears to decrease intraoperative blood loss and allogeneic transfusion requirements during meningioma resection and thus may improve the safety of surgical management of this pathology.