Presence of a fundal fluid cap on preoperative magnetic resonance imaging may predict long-term facial nerve function after resection of vestibular schwannoma via the retrosigmoid approach

J Neurosurg 138:972–980, 2023

Preservation of neurological function is a priority when performing a resection of a vestibular schwannoma (VS). Few studies have examined the radiographic value of a fundal fluid cap—i.e., cerebrospinal fluid in the lateral end of a VS within the internal auditory canal—for prediction of postoperative neurological function. The aim of this study was to clarify whether the presence of a fundal fluid cap on preoperative magnetic resonance images has a clinical impact on facial nerve function after resection of VSs.

METHODS The presence of a fundal fluid cap and its prognostic impact on long-term postoperative facial nerve function were analyzed.

RESULTS A fundal fluid cap was present in 102 of 143 patients who underwent resection of sporadic VSs via the retrosigmoid approach. Facial nerve function was acceptable (House-Brackmann grade I–II) immediately after surgery in 82 (80.4%) patients with a fundal fluid cap and in 26 (63.4%) of those without this sign. The preservation rate of facial nerve function increased in a time-dependent manner after surgery in patients with a fundal fluid cap but plateaued by 3 months postoperatively in those without a fundal fluid cap; the difference was statistically significant at 12 months (96.1% vs 82.9%, p = 0.013) and 24 months (97.1% vs 82.9%, p = 0.006) after surgery. The presence of a fundal fluid cap had a significantly positive effect on long-term facial nerve function at 24 months after surgery when tumor size and intraoperative neuromonitoring response were taken into account (OR 5.55, 95% CI 1.12–27.5, p = 0.034).

CONCLUSIONS Neuromonitoring-guided microsurgery for total resection of VSs is more likely to be successful in terms of preservation of facial nerve function if a fundal fluid cap is present. This preoperative radiographic sign could be helpful when counseling patients and deciding the treatment strategy.

Volumetric Growth and Growth Curve Analysis of Residual Intracranial Meningioma

Neurosurgery 92:734–744, 2023

After meningioma surgery, approximately 1 in 3 patients will have residual tumor that requires ongoing imaging surveillance. The precise volumetric growth rates of these tumors are unknown.

OBJECTIVE: To identify the volumetric growth rates of residual meningioma, growth trajectory, and factors associated with progression.

METHODS: Patients with residual meningioma identified at a tertiary neurosurgery center between 2004 and 2020 were retrospectively reviewed. Tumor volumewas measured using manual segmentation, after surgery and at every follow-up MRI scan. Growth rates were ascertained using a linear mixed-effects model and nonlinear regression analysis of growth trajectories. Progression was defined according to the Response Assessment in Neuro- Oncology (RANO) criteria (40% volume increase).

RESULTS: There were 236 patients with residual meningioma. One hundred and thirtytwo patients (56.0%) progressed according to the RANO criteria, with 86 patients being conservatively managed (65.2%) after progression. Thirteen patients (5.5%) developed clinical progression. Over a median follow-up of 5.3 years (interquartile range, 3.5–8.6 years), the absolute growth rate was 0.11 cm3 per year and the relative growth rate 4.3% per year. Factors associated with residual meningioma progression in multivariable Cox regression analysis were skull base location (hazard ratio [HR] 1.60, 95% CI 1.02–2.50) and increasing Ki-67 index (HR 3.43, 95% CI 1.19–9.90). Most meningioma exhibited exponential and logistic growth patterns (median R2 value 0.84, 95% CI 0.60–0.90).

CONCLUSION: Absolute and relative growth rates of residual meningioma are low, but most meet the RANO criteria for progression. Location and Ki-67 index can be used to stratify adjuvant treatment and surveillance paradigms.

Nomogram for predicting an individual prospective hemorrhage risk in untreated brainstem cavernous malformations

J Neurosurg 138:910–921, 2023

In this study, the authors aimed to create a nomogram for precisely predicting the 5-year prospective hemorrhage risk in brainstem cavernous malformations (BSCMs).

METHODS Patients with confirmed BSCMs in a single-center prospective observational series from January 2012 to December 2016 were included in the present study for nomogram building and validation. The concordance index (C-index), calibration curves, and decision curve analysis were used to evaluate the predictive accuracy, discriminative ability, and clinical usefulness of the nomogram. Then, a nomogram-based risk stratification model for untreated BSCMs was developed.

RESULTS In total, 600 patients were included in the study; 417 patients who had been enrolled before July 2015 were divided into the training and validation cohorts, and 183 subsequently enrolled patients were used as the external validation cohort. By applying a backward stepwise procedure in the multivariable Cox model, variables, including prior hemorrhage (HR 1.69), hemorrhage on admission (HR 3.33), lesion size > 1.5 cm (HR 1.84), lesion depth (HR 2.35), crossing the axial midpoint (HR 1.94), and developmental venous anomaly (HR 2.62), were incorporated to develop a nomogram. The Harrell C-index values for a 5-year prospective hemorrhage were 0.752 (95% CI 0.687–0.816), 0.801 (95% CI 0.665–0.936), and 0.758 (95% CI 0.674–0.842) in the training, internal validation, and external validation cohorts, respectively. The nomogram performed well in terms of consistency between prediction and actual observation according to the calibration curve. The patients could be classified into three distinct (low, medium, and high) risk groups using the final score of this nomogram.

CONCLUSIONS Independent predictors of the 5-year hemorrhage risk in untreated BSCMs were selected to create the first nomogram for predicting individual prospective hemorrhage. The nomogram was able to stratify patients into different risk groups and assist in clinical decision-making.

Microsurgical clipping and endovascular management of unruptured anterior circulation aneurysms: how age, frailty, and comorbidity indexes influence outcomes

J Neurosurg 138:922–932, 2023

Frailty is one of the important factors in predicting the outcomes of surgery. Many surgical specialties have adopted a frailty assessment in the preoperative period for prognostication; however, there are limited data on the effects of frailty on the outcomes of cerebral aneurysms. The object of this study was to find the effect of frailty on the surgical outcomes of anterior circulation unruptured intracranial aneurysms (UIAs) and compare the frailty index with other comorbidity indexes.

METHODS A retrospective study was performed utilizing the National Inpatient Sample (NIS) database (2016–2018). The Hospital Frailty Risk Score (HFRS) was used to assess frailty. On the basis of the HFRS, the whole cohort was divided into low-risk (0–5), intermediate-risk (> 5 to 15), and high-risk (> 15) frailty groups. The analyzed outcomes were nonhome discharge, complication rate, extended length of stay, and in-hospital mortality.

RESULTS In total, 37,685 patients were included in the analysis, 5820 of whom had undergone open surgical clipping and 31,865 of whom had undergone endovascular management. Mean age was higher in the high-risk frailty group than in the low-risk group for both clipping (63 vs 55.4 years) and coiling (64.6 vs 57.9 years). The complication rate for open surgical clipping in the high-risk frailty group was 56.1% compared to 0.8% in the low-risk group. Similarly, for endovascular management, the complication rate was 60.6% in the high-risk group compared to 0.3% in the low-risk group. Nonhome discharges were more common in the high-risk group than in the low-risk group for both open clipping (87.8% vs 19.7%) and endovascular management (73.1% vs 4.4%). Mean hospital charges for clipping were $341,379 in the high-risk group compared to $116,892 in the low-risk group. Mean hospital charges for coiling were $392,861 in the high-risk frailty group and $125,336 in the low-risk group. Extended length of stay occurred more frequently in the highrisk frailty group than in the low-risk group for both clipping (82.9% vs 10.7%) and coiling (94.2% vs 12.7%). Frailty had higher area under the receiver operating characteristic curve values than those for other comorbidity indexes and age in predicting outcomes.

CONCLUSIONS Frailty affects surgical outcomes significantly and outperforms age and other comorbidity indexes in predicting outcome. It is imperative to include frailty assessment in preoperative planning.

Surgical treatment of brain arteriovenous malformations: clinical outcomes of patients included in the registry of a pragmatic randomized trial

The Treatment of Brain Arteriovenous Malformations Study (TOBAS) is a pragmatic study that includes 2 randomized trials and registries of treated or conservatively managed patients. The authors report the results of the surgical registry.

METHODS TOBAS patients are managed according to an algorithm that combines clinical judgment and randomized allocation. For patients considered for curative treatment, clinicians selected from surgery, endovascular therapy, or radiation therapy as the primary curative method, and whether observation was a reasonable alternative. When surgery was selected and observation was deemed unreasonable, the patient was not included in the randomized controlled trial but placed in the surgical registry. The primary outcome of the trial was mRS score > 2 at 10 years (at last follow-up for the current report). Secondary outcomes include angiographic results, perioperative serious adverse events, and permanent treatment-related complications leading to mRS score > 2.

RESULTS From June 2014 to May 2021, 1010 patients were recruited at 30 TOBAS centers. Surgery was selected for 229/512 patients (44%) considered for curative treatment; 77 (34%) were included in the surgery versus observation randomized trial and 152 (66%) were placed in the surgical registry. Surgical registry patients had 124/152 (82%) ruptured and 28/152 (18%) unruptured arteriovenous malformations (AVMs), with the majority categorized as low-grade SpetzlerMartin grade I–II AVM (118/152 [78%]). Thirteen patients were excluded, leaving 139 patients for analysis. Embolization was performed prior to surgery in 78/139 (56%) patients. Surgical angiographic cure was obtained in 123/139 all-grade (89%, 95% CI 82%–93%) and 105/110 low-grade (95%, 95% CI 90%–98%) AVM patients. At the mean follow-up of 18.1 months, 16 patients (12%, 95% CI 7%–18%) had reached the primary safety outcome of mRS score > 2, including 11/16 who had a baseline mRS score ≥ 3 due to previous AVM rupture. Serious adverse events occurred in 29 patients (21%, 95% CI 15%–28%). Permanent treatment-related complications leading to mRS score > 2 occurred in 6/139 patients (4%, 95% CI 2%–9%), 5 (83%) of whom had complications due to preoperative embolization.

CONCLUSIONS The surgical treatment of brain AVMs in the TOBAS registry was curative in 88% of patients. The participation of more patients, surgeons, and centers in randomized trials is needed to definitively establish the role of surgery in the treatment of unruptured brain AVMs.

Innovative design of bone quality-targeted intervertebral spacer: accelerated functional fusion guiding oriented collagen and apatite microstructure without autologous bone graft

The Spine Journal 23 (2023) 609−620

Although autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting.

PURPOSE: We developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure.

STUDY DESIGN: This was an in vivo animal study.

METHODS: Intervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2−L3 or L4−L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests.

RESULTS: The spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The pushout load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix.

CONCLUSIONS: The developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft.

CLINICAL SIGNIFICANCE: Our results provide a foundation for designing future spacers for interbody fusion in human.

The Angiographic and Clinical Follow-up Outcomes of the Wide-Necked and Complex Intracranial Aneurysms Treated With LVIS EVO–Assisted Coiling

Neurosurgery 92:827–836, 2023

The Low Profile Visible Intraluminal Support EVO (LVIS EVO) is a selfexpandable braided stent, which was recently introduced for the treatment of intracranial aneurysms. Full visibility of the stent and a relatively high metal coverage ratio are the unique features of the LVIS EVO.

OBJECTIVE: To assess the safety, efficacy, and midterm durability of LVIS EVO stentassisted coiling for the treatment of wide-necked intracranial aneurysms.

METHODS: The endovascular databases were reviewed to identify patients treated with LVIS EVO–assisted coiling. The technical success and immediate clinical/angiographic outcomes were assessed. Periprocedural and delayed complications were evaluated. The follow-up angiographic/clinical outcomes were investigated. The preprocedural/followup neurological statuses were assessed with the modified Rankin Scale.

RESULTS: One hundred three aneurysms in 103 patients (63 females) with a mean age of 54.9 ± 11.3 years were included. The mean maximum sac diameter was 6.2 ± 2.9 mm. The procedural technical success rate was 100%. Immediate postprocedural angiography showed complete occlusion in 77.7%. The mean duration of the angiographic follow-up was 8.8 ± 3.6 months. Follow-up angiography showed complete aneurysm occlusion in 89% of the 82 patients with angiographic follow-up. Recanalization was observed in 7.3% of 82 patients. Two patients (2.4%) required retreatment. In addition, 8.7% of the patients had at least 1 complication, and 2.9% of the patients developed a permanent morbidity. All patients had mRS scores ≤2.

CONCLUSION: The results of this study demonstrate that SAC with LVIS EVO is a relatively safe, efficient, and durable treatment for wide-necked and complex intracranial aneurysms.

Technique for Validation of Intraoperative Navigation in Minimally Invasive Spine Surgery

Operative Neurosurgery 24:451–454, 2023

Intraoperative 3-dimensional navigation is an enabling technology that has quickly become a commonplace in minimally invasive spine surgery (MISS). It provides a useful adjunct for percutaneous pedicle screw fixation. Although navigation is associated with many benefits, including improvement in overall screw accuracy, navigation errors can lead to misplaced instrumentation and potential complications or revision surgery. It is difficult to confirm navigation accuracy without a distant reference point.

OBJECTIVE: To describe a simple technique for validating navigation accuracy in the operating room during MISS.

METHODS: The operating room is set up in a standard fashion for MISS with intraoperative cross-sectional imaging available. A 16-gauge needle is placed within the bone of the spinous process before intraoperative cross-sectional imaging. The entry level is chosen such that the space between the reference array and the needle encompasses the surgical construct. Before placing each pedicle screw, accuracy is verified by placing the navigation probe over the needle.

RESULTS: This technique has identified navigation inaccuracy and led to repeat crosssectional imaging. No screws have been misplaced in the senior author’s cases since adopting this technique, and there have been no complications attributable to the technique.

CONCLUSION: Navigation inaccuracy is an inherent risk in MISS, but the described technique may mitigate this risk by providing a stable reference point.

Oblique lumbar interbody fusion combined with stress end plate augmentation and anterolateral screw fixation for degenerative lumbar spinal stenosis with osteoporosis

The Spine Journal 23 (2023) 523−532

Oblique lumbar interbody fusion (OLIF) has been proven to be effective in treating degenerative lumbar spinal stenosis (DLSS). Whether OLIF is suitable for treating patients with DLSS with osteoporosis (OP) is still controversial. Bone cement augmentation is widely used to enhance the internal fixation strength of osteoporotic spines. However, the effectiveness of OLIF combined with bone cement stress end plate augmentation (SEA) and anterolateral screw fixation (AF) for DLSS with OP have not confirmed yet.

PURPOSE: To evaluate the clinical, radiological, and functional outcomes of OLIF-AF versus OLIF-AF-SEA in the treatment of DLSS with OP.

STUDY DESIGN: Retrospective case-control study.

PATIENT SAMPLE: A total of 60 patients with OP managed for DLSS at L4−L5.

OUTCOME MEASURES: Visual analog scale (VAS) score of the lower back and leg, Oswestry Disability Index (ODI), disk height (DH), lumbar lordosis (LL), segmental lordosis (SL), cage subsidence and fusion rate.

METHODS: The study was performed as a retrospective matched-pair case‒controlled study. Patients with OP managed for DLSS at L4−L5 between October 2017 and June 2020 and completed at least 2 years of follow-up were included, which were 30 patients treated by OLIF-AF and 30 patients undergoing OLIF-AF-SEA. The demographics and radiographic data, fusion status and functional outcomes were therefore compared to evaluate the efficacy of the two approaches.

RESULTS: Pain and disability improved similarly in both groups at the 24-month follow-up. However, the SEA group had lower pain and functional disability at 3 months postoperatively (p<.05). The mean postoperative disc height decrease (4DH) was significantly lower in the SEA group than in the control group (1.17§0.81 mm vs 2.89§2.03 mm; p<.001). There was no significant difference in lumbar lordosis (LL) or segmental lordosis (SL) between the groups preoperatively and 1 day postoperatively. However, a statistically significant difference was observed in SL and LL between the groups at 24 months postoperatively (p<.05). CS was observed in 4 cases (13.33%) in the SEA group and 17 cases (56.67%) in the control group (p<.001). A nonsignificant difference was observed in the fusion rate between the SEA and control groups (p=.347) at 24 months postoperatively.

CONCLUSIONS: This study revealed that OLIF-AF-SEA was safe and effective in the treatment of DLSS with OP. Compared with OLIF-AF, OLIF-AF-SEA results in a minor postoperative disc height decrease, a lower rate of CS, better sagittal balance, and no adverse effect on interbody fusion.

Refining the Anatomy of Percutaneous Trigeminal Rhizotomy: A Cadaveric, Radiological, and Surgical Study

Operative Neurosurgery 24:341–349, 2023

Percutaneous trigeminal rhizotomy (PTR) is a widely used procedure for trigeminal neuralgia. However, comprehensive analyses that combine anatomic, radiological, and surgical considerations are rare.

OBJECTIVE: To present high-quality anatomic dissections and radiological studies that highlight the technical nuances of this procedure.

METHODS: Six silicon-injected postmortem heads underwent PTR. The surgical corridors were dissected, and the neurovascular relationships were studied. In addition, 20 dried human skulls and 50 computed tomography angiography and MRI scans were collected to study the anatomic relationships for a customized puncture corridor.

RESULTS: The PTR corridor was divided into 3 segments: the buccal segment (length, 34.76 ± 7.20 mm), the inferior temporal fossa segment (length, 42.06 ± 6.92 mm), and the Meckel cave segment (length, 24.75 ± 3.34 mm). The puncture sagittal (α) and axial (β) angles measured in this study were 38.32° ± 4.62° and 19.13° ± 2.82°, respectively. The precondylar reference line coincided with the foramen ovale in 75% of the computed tomography angiography scans, and the postcondylar line coincided with the carotid canal in 70% of the computed tomography angiography scans; these lines serve as the intraoperative landmarks for PTR. The ovale-carotid-pterygoid triangle, delineated by drawing a line from the foramen ovale to the carotid canal and the lateral pterygoid plate, is a distinguished landmark to use for avoiding neurovascular injury during fluoroscopy.

CONCLUSION: Knowledge of the anatomic and radiological features of PTR is essential for a successful surgery, and a customized technical flow is a safe and effective way to access the foramen ovale.

Application of Intraoperative Rapid Molecular Diagnosis in Precision Surgery for Glioma: Mimic the World Health Organization CNS5 Integrated Diagnosis

Neurosurgery 92:762–771, 2023

With the advent of the molecular era, the diagnosis and treatment systems of glioma have also changed. A single histological type cannot be used for prognosis grade. Only by combining molecular diagnosis can precision medicine be realized.

OBJECTIVE: To develop an automatic integrated gene detection system (AIGS) for intraoperative detection in glioma and to explore its positive role in intraoperative diagnosis and treatment.

METHODS: We analyzed the isocitrate dehydrogenase 1 (IDH1) mutation status of 105 glioma samples and evaluated the product’s potential value for diagnosis; 37 glioma samples were detected intraoperatively to evaluate the feasibility of using the product in an actual situation. A blinding method was used to evaluate the effect of the detection technology on the accuracy of intraoperative histopathological diagnosis by pathologists. We also reviewed the current research status in the field of intraoperative molecular diagnosis.

RESULTS: Compared with next-generation sequencing, the accuracy of AIGS in detecting IDH1 was 100% for 105 samples and 37 intraoperative samples. The blind diagnostic results were compared between the 2 groups, and the molecular information provided by AIGS increased the intraoperative diagnostic accuracy of glioma by 16.2%. Using the technical advantages of multipoint synchronous detection, we determined the tumor molecular margins for 5 IDH-positive patients and achieved accurate resection at the molecular level. CONCLUSION: AIGS can quickly and accurately provide molecular information during surgery. This methodology not only improves the accuracy of intraoperative pathological diagnosis but also provides an important molecular basis for determining tumor margins to facilitate precision surgery.

Correlation between the spinopelvic type and morphological characteristics of lumbar facet joints in degenerative lumbar spondylolisthesis

J Neurosurg Spine 38:425–435, 2023

The correlation between the spinopelvic type and morphological characteristics of lumbar facet joints in patients with degenerative lumbar spondylolisthesis (DLS) was investigated.

METHODS One hundred forty-two patients with L4 DLS were enrolled (DLS group), and 100 patients with lumbar disc herniation without DLS were selected as the control group (i.e., non–lumbar spondylolisthesis [NL] group). Morphological parameters of L4–5 facet joints and L4–5 disc height and angle were measured on 3D reconstructed CT images; namely, the facet joint angle (FJA), pedicle–facet joint angle (PFA), facet joint tropism, and facet joint osteoarthritis (OA). The L4 slip percentage, sacral slope, and lumbar lordosis were measured on radiographs. Patients in the DLS and NL groups were divided into 4 subgroups according to Roussouly classification (types I, II, III, and IV).

RESULTS In the DLS and NL groups, as the spinopelvic type changed from type II to type IV, the facet joint morphology showed a gradual sagittal orientation in the FJA, a gradual horizontal orientation in the PFA, a gradual severity in OA, and a gradual increase in the slip percentage, but changes were completely opposite from type I to type II. Additionally, compared with the NL group, the facet joint morphology in the DLS group had more horizontal orientation in PFA, more sagittal orientation in the FJA, and the facet joint tropism and OA were more severe.

CONCLUSIONS Facet joint morphology was correlated with spinopelvic type in the slip segment of DLS. Facet joint morphology was part of the joint configuration in different spinopelvic types, not just the result of joint remodeling after DLS. Moreover, morphological changes of the facet joints and DLS interacted with each other. Additionally, morphological remodeling of the facet joints in DLS played an important role in spinal balance and should be taken into consideration when designing a surgical approach.

A Case Series of Trigeminal Neuralgia With Pure Venous Compression: Postoperative Outcomes Associated With Intraoperative Venous Transposition Versus Coagulation

Operative Neurosurgery 24:377–382, 2023

Microvascular decompressions (MVDs) are effective open-surgical procedures for trigeminal neuralgia (TN). Intraoperative management of compressive veins may include either venous transposition or coagulation. Although both are generally considered safe,which technique results in optimal postoperative outcomes remains unclear.

OBJECTIVE: To compare postoperative pain and numbness outcomes after an MVD in patients with TN of exclusive venous compression.

METHODS: We retrospectively reviewed all patients with TN who underwent MVDs at our institution from 2007 to 2020. Patients with TN of pure venous compression were identified using MRI imaging, which was subsequently confirmed intraoperatively. Patient demographics, procedural characteristics, and postoperative pain and numbness scores were recorded and compared. Factors associated with pain recurrence were assessed using survival analyses and multivariate regressions.

RESULTS: We identified 181 patients who presented with TN of pure venous compression. Using a multivariate linear regression, adjusted for age, sex, and presence of multiple sclerosis, use of venous transposition vs coagulation was not significantly associated with the Barrow Neurological Institute pain score at final follow-up, although venous transposition was significantly predictive of a worse postoperative Barrow Neurological Institute numbness score (P = .003). Using a Kaplan–Meier survival analysis and a multivariate Cox proportional hazards regression, respectively, venous transposition was significantly associated with faster (P = .01) as well as higher risk for pain recurrence (P = .01).

CONCLUSION: The use of venous coagulation during an MVD is associated with better postoperative pain and numbness outcomes. The results of our study may help inform preoperative patient counseling and surgical management for TN cases that involve pure venous compression.

Newly Diagnosed Adult Basal Ganglia Gliomas Treated With Laser Interstitial Thermal Therapy

Operative Neurosurgery 24:383–390, 2023

Few cytoreductive surgical tools are available for newly diagnosed basal ganglia gliomas. Current reports showed high associated morbidity and mortality. Given their deep localization, laser interstitial thermal therapy (LITT) is still a rare indication. Moreover, few reports account for which of the available options have better outcomes.

OBJECTIVE: To retrospectively analyze our experience with LITT and compare its safety, feasibility, and efficacy with needle biopsy for the management of adult basal ganglia gliomas.

METHODS: Twenty-two patients with gliomas from the midline (e.g. thalamus and lenticular nucleus) managed with either LITT/biopsy or needle biopsy from 2015 to 2021 were included. Records regarding location, diagnosis, Karnofsky Performance Score, length of hospital stay, preoperative lesion and ablation volume, perioperative complications, and data of adjuvant treatment were collected. Overall survival was evaluated with Kaplan-Meier analysis.

RESULTS: Seven patients had LITT, and 15 underwent biopsy. The overall mean age was 60.9 years (25-82 years). The average tumor volume in the former was 16.99 cm3 and 17.65 cm3 in the latter. No postsurgical complications were found in the LITT group, and 1 patient had a postsurgical hemorrhage after biopsy. The mean overall survival was 20.28 ± 9.63 months in the LITT group, which was greater but not statistically significant than in the biopsy group (13.85 ± 4.48 months; P = .78).

CONCLUSION: Our results show that laser ablation may be both feasible and safe in adult basal ganglia gliomas. Given the lack of safe cytoreductive treatment options, LITT should be considered as a valid choice for these patients.

Exploring the Pathogenesis of Atlanto-Occipital Instability in ChiariMalformationWith Type II Basilar Invagination: A Systematic Morphological Study

Neurosurgery 92:837–853, 2023

Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI).

OBJECTIVE: To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction.

METHODS: Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ).

RESULTS: Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI.

CONCLUSION: Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.

Feasibility and Accuracy of Robot-Assisted, Stereotactic Biopsy Using 3-Dimensional Intraoperative Imaging and Frameless Registration Tool

Neurosurgery 92:803–811, 2023

Robot-assisted stereotactic biopsy is evolving: 3-dimensional intraoperative imaging tools and new frameless registration systems are spreading.

OBJECTIVE: To investigate the accuracy and effectiveness of a new stereotactic biopsy procedure.

METHODS: Observational, retrospective analysis of consecutive robot-assisted stereotactic biopsies using the Neurolocate (Renishaw) frameless registration system and intraoperative O-Arm (Medtronic) performed at a single institution in adults (2019-2021) and comparisonwith a historical series from the same institution (2006-2016) not using the Neurolocate nor the O-Arm.

RESULTS: In 100 patients (55%men), 6.2 ± 2.5 (1-14) biopsy sampleswere obtained at 1.7 ± 0.7 (1-3) biopsy sites. An histomolecular diagnosis was obtained in 96% of cases. The mean duration of the procedure was 59.0 ± 22.3 min. Themean distance between the planned and the actual target was 0.7 ± 0.7 mm. On systematic postoperative computed tomography scans, a hemorrhage ≥10 mm was observed in 8 cases (8%) while pneumocephalus was distant from the biopsy site in 76%. A Karnofsky Performance Status score decrease ≥20 points postoperatively was observed in 4%. The average dose length product was 159.7 ± 63.4mGy cm. Compared with the historical neurosurgical procedure, this newprocedure had similar diagnostic yield (96 vs 98.7%; P = .111) and rate of postoperative disability (4.0 vs 4.2%, P = .914) but was shorter (57.8 ± 22.9 vs 77.8 ± 20.9 min; P < .001) despite older patients.

CONCLUSION: Robot-assisted stereotactic biopsy using the Neurolocate frameless registration system and intraoperative O-Arm is a safe and effective neurosurgical procedure. The accuracy of this robot-assisted surgery supports its effectiveness for daily use in stereotactic neurosurgery.

Clival Chordomas in the Endoscopic Endonasal Era: Comparison With Management With Open Skull Base Approaches

Neurosurgery 92:756–761, 2023

The most significant paradigm shift in surgical management of skull base chordomas has been the adoption of the endoscopic endonasal approach, but the impact on patient outcomes compared with open skull base approaches remains unclear.

OBJECTIVE: To compare a large series of patients treated by a single surgeon using primarily endoscopic endonasal approaches with previously published outcomes by the same surgeon using open skull base approaches.

METHODS: Between 2006 and 2020, 68 patients with skull base chordoma underwent resection using primarily endoscopic endonasal approaches. Outcomes and complications were compared with previously published results of resection of chordomas from 1991 to 2005 using open skull base approaches.

RESULTS: Compared with the prior cohort, the current principally endoscopic cohort demonstrated similar rates of OS (P = .86) and progression-free survival (P = .56), but patients undergoing first-time resection had significantly higher rates of radical resection (82.9% compared with 64.3%, P = .05) and required fewer staged surgeries (9.8% compared with 33.3%, P = .01).

CONCLUSION: There was no difference in survival rates for patients treated in the current era, primarily using endoscopic endonasal techniques, compared with previously published results using open skull-base approaches by the same surgeon. Although use of endoscopic endonasal approach resulted in higher rates of radical resection, patients undergoing first-time resection and fewer staged surgeries were required.

Long-term outcomes after surgery for brainstem cavernous malformations: analysis of 46 consecutive cases

J Neurosurg 138:900–909, 2023

The objective of this study was to evaluate the long-term outcomes after resection of brainstem cavernous malformations (BSCMs) and to assess the usefulness of the Lawton grading system in these cases.

METHODS This retrospective study analyzed 46 consecutive patients with BSCMs operated on between July 1990 and December 2020. Outcomes at the last follow-up were defined as favorable (modified Rankin Scale [mRS] score 0–2) or unfavorable (mRS score > 2).

RESULTS The study cohort comprised 24 men (52%) and 22 women (48%), ranging in age from 8 to 78 years old (median 37 years). In 19 patients (41%), the preoperative mRS score was > 2. All patients had hemorrhagic BSCM. There were 12 (26%) mesencephalic, 19 (41%) pontine, 7 (15%) medullary, and 8 (17%) cerebellar peduncle lesions, with a maximal diameter ranging from 5 to 40 mm (median 15 mm). In total, 24 BSCMs (52%) had bilateral extension crossing the brainstem midline. Lawton grades of 0, I, II, III, IV, V, and VI were defined in 3 (7%), 2 (4%), 10 (22%), 11 (24%), 8 (17%), 7 (15%), and 5 (11%) cases, respectively. Total resection of BSCMs was attained in 43 patients (93%). There were no perioperative deaths. Excluding the 3 most recent cases, the length of follow-up ranged from 56 to 365 months. The majority of patients demonstrated good functional recovery, but regress of the preexisting oculomotor nerve deficit was usually incomplete. No new hemorrhagic events were noted after total resection of BSCMs. In 42 patients (91%), the mRS score at the time of last follow-up was ≤ 2 (favorable outcome), and in 18 (39%), it was 0 (absence of neurological symptoms). Forty-four patients (96%) demonstrated clinical improvement and 2 (4%) had no changes compared with the preoperative period. Multivariate analysis revealed that only lower Lawton grade had a statistically significant independent association (p = 0.0280) with favorable long-term outcome. The area under the receiver operating characteristic curve for prediction of favorable outcome with 7 available Lawton grades of BSCM was 0.93.

CONCLUSIONS Resection of hemorrhagic BSCMs by an experienced neurosurgeon may be performed safely and effectively, even in severely disabled patients. In the authors’ experience, preexisting oculomotor nerve palsy represents the main cause of permanent postoperative neurological morbidity. The Lawton grading system effectively predicts longterm outcome after surgery.

Clival Chordomas in the Endoscopic Endonasal Era: Clinical Management, Outcomes, and Complications

Neurosurgery 92:876–883, 2023

Surgical management of skull base chordomas has changed significantly in the past 2 decades, most notably with use of the endoscopic endonasal approach (EEA), although high quality outcome data using these modern approaches remain scarce.

OBJECTIVE: To evaluate outcomes in a large series of patients treated by a single surgeon, using primarily the EEA.

METHODS: Between 2006 and 2020, 68 patients with skull base chordoma underwent resection using mostly the EEA. Complications, outcomes, and potential contributing factors were evaluated using Kaplan-Meier survival analysis and univariable and multivariable Cox proportional hazards models.

RESULTS: Overall 5-year survival was 76.3% (95%CI 61.5%-86.0%), and 5-year progressionfree survival was 55.9%(95% CI 40.0%-69.0%). Inmultivariable analysis, radical resection was associated with significant reduction in risk of death (hazard ratio [HR] 0.04, 95% CI 0.005- 0.33, P = .003) and disease progression (HR 0.05, 95% CI 0.01-0.18, P < .001). Better preoperative function status reduced risk of death (HR 0.42 per 10-point increase in Karnofsky Performance Scale, 95% CI 0.28-0.63, P < .001) and progression (HR 0.60 per 10-point increase in Karnofsky Performance Scale, 95% CI 0.45-0.78, P < .001). Localization at the clivus reduced risk of death (HR 0.02, 95% CI 0.002-0.15, P < .001) and progression (HR 0.24, 95% CI 0.09-0.68, P = .007) compared with tumors at the craniovertebral junction.

CONCLUSION: In multivariable analysis, overall survival and progression-free survival of chordoma resection was most positively affected by radical resection, better preoperative functional status, and tumor location at the clivus rather than craniovertebral junction.