Month: August 2021

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The effect of minimally invasive lumbar decompression surgery on sagittal spinopelvic alignment in patients with lumbar spinal stenosis

J Neurosurg Spine 35:177–184, 2021

Several studies have examined the relationship between sagittal spinopelvic alignment and clinical outcomes after spinal surgery. However, the long-term reciprocal changes in sagittal spinopelvic alignment in patients with lumbar spinal stenosis after decompression surgery remain unclear. The aim of this study was to investigate radiographic changes in sagittal spinopelvic alignment and clinical outcomes at the 2-year and 5-year follow-ups after minimally invasive lumbar decompression surgery.

METHODS The authors retrospectively studied the medical records of 110 patients who underwent bilateral decompression via a unilateral approach for lumbar spinal stenosis. Japanese Orthopaedic Association (JOA) and visual analog scale (VAS) scores for low-back pain (LBP), leg pain, leg numbness, and spinopelvic parameters were evaluated before surgery and at the 2-year and 5-year follow-ups. Sagittal malalignment was defined as a sagittal vertical axis (SVA) ≥ 50 mm.

RESULTS Compared with baseline, lumbar lordosis significantly increased after decompression surgery at the 2-year (30.2° vs 38.5°, respectively; p < 0.001) and 5-year (30.2° vs 35.7°, respectively; p < 0.001) follow-ups. SVA significantly decreased at the 2-year follow-up compared with baseline (36.1 mm vs 51.5 mm, respectively; p < 0.001). However, there was no difference in SVA at the 5-year follow-up compared with baseline (50.6 mm vs 51.5 mm, respectively; p = 0.812). At the 5-year follow-up, 82.5% of patients with preoperative normal alignment maintained normal alignment, whereas 42.6% of patients with preoperative malalignment developed normal alignment. Preoperative sagittal malalignment was associated with the VAS score for LBP at baseline and 2-year and 5-year follow-ups and the JOA score at the 5-year follow-up. Postoperative sagittal malalignment was associated with the VAS score for LBP at the 2-year and 5-year follow-ups and the VAS score for leg pain at the 5-year follow-up. There was a trend toward deterioration in clinical outcomes in patients with persistent postural malalignment compared with other patients.

CONCLUSIONS After minimally invasive surgery, spinal sagittal malalignment can convert to normal alignment at both short-term and long-term follow-ups. Sagittal malalignment has a negative impact on the VAS score for LBP and a weakly negative impact on the JOA score after decompression surgery.

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What have we learned from 8 years of deep brain stimulation of the anterior thalamic nucleus? Experiences and insights of a single center

J Neurosurg 135:619–628, 2021

In the absence of a standard or guideline for the treatment of epilepsy patients with deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT), systematic single-center investigations are essential to establish effective approaches. Here, the authors report on the long-term results of one of the largest single-center ANT DBS cohorts.

METHODS The outcome data of 23 consecutive patients with transventricularly implanted electrodes were retrospectively analyzed with regard to adverse events, lead placement, stimulation-related side effects, and changes in seizure frequency. Depression and quality-of-life scores were collected in a subgroup of 9 patients.

RESULTS All but 2 patients initially underwent bilateral implantation, and 84.4% of all DBS leads were successfully located within the ANT. The mean follow-up time was 46.57 ± 23.20 months. A seizure reduction > 50% was documented in 73.9% of patients, and 34.6% achieved an Engel class I outcome. In 3 patients, clinical response was achieved by switching the electrode contact or changing from the monopolar to bipolar stimulation mode. Unilateral implantation seemed ineffective, whereas bilateral stimulation with successful ANT implantation only on one side led to a clinical response. Double stimulation with additional vagus nerve stimulation was safe. Changes in cycling mode or stimulation amplitude influenced therapy tolerability and, only to a lesser extent, seizure frequency. Side effects were rare and typically vanished by lowering the stimulation amplitude or changing the active electrode contact. Furthermore, depression and aspects of quality of life significantly improved with ANT DBS treatment.

CONCLUSIONS The transventricular approach as well as double stimulation proved safe. The anteroventral ANT appeared to be the most efficacious stimulation site. This systematic investigation with reluctant medication changes allowed for the development of a better idea of the association between parameter changes and outcome in ANT DBS patients, but larger samples are still needed to assess the potential of bipolar stimulation and distinct cycling frequencies. Furthermore, more multifaceted and objective assessments of treatment outcome are needed to fully assess the effects of ANT DBS treatment.

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A Novel Framework for Network-Targeted Neuropsychiatric Deep Brain Stimulation

Neurosurgery 89:E116–E121, 2021

Deep brain stimulation (DBS) has emerged as a promising therapy for neuropsychiatric illnesses, including depression and obsessive-compulsive disorder, but has shown inconsistent results in prior clinical trials. We propose a shift away from the empirical paradigm for developing new DBS applications, traditionally based on testing brain targets with conventional stimulation paradigms. Instead, we propose a multimodal approach centered on an individualized intracranial investigation adapted from the epilepsy monitoring experience, which integrates comprehensive behavioral assessment, such as the Research Domain Criteria proposed by the National Institutes of Mental Health. In this paradigm-shifting approach, we combine readouts obtained from neurophysiology, behavioral assessments, and self-report during broad exploration of stimulation parameters and behavioral tasks to inform the selection of ideal DBS parameters. Such an approach not only provides a foundational understanding of dysfunctional circuits underlying symptom domains in neuropsychiatric conditions but also aims to identify generalizable principles that can ultimately enable individualization and optimization of therapy without intracranial monitoring.

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Surgery versus radiosurgery for facial nerve schwannoma

J Neurosurg 135:542–553, 2021

Intracranial facial nerve schwannomas (FNS) requiring treatment are frequently recommended for surgery or stereotactic radiosurgery (SRS). The objective of this study was to compare facial nerve function outcomes between these two interventions for FNS via a systematic review and meta-analysis.

METHODS A search of the Ovid EMBASE, PubMed, SCOPUS, and Cochrane databases from inception to July 2019 was conducted following PRISMA guidelines. Articles were screened against prespecified criteria. Facial nerve out- comes were classified as improved, stabilized, or worsened by last follow-up. Incidence was pooled by random-effects meta-analysis of proportions.

RESULTS Thirty-three articles with a pooled cohort of 519 patients with FNS satisfied all criteria. Twenty-five articles described operative outcomes in 407 (78%) patients; 10 articles reported SRS outcomes in 112 (22%). In the surgical cohort, facial nerve function improved in 23% (95% CI 15%–32%), stabilized in 41% (95% CI 32%–50%), and worsened in 30% (95% CI 21%–40%). In the SRS cohort, facial nerve function was improved in 20% (95% CI 9%–34%), stable in 66% (95% CI 54%–78%), and worsened in 9% (95% CI 3%–16%). Compared with SRS, microsurgery was associated with a significantly lower incidence of stable facial nerve function (p < 0.01) and a significantly higher incidence of wors- ened facial nerve function (p < 0.01). Tumor progression and complication rates were comparable. Outcome certainty assessments were very low to moderate for all parameters.

CONCLUSIONS Unfavorable facial nerve function outcomes are associated with surgical treatment of intracranial FNS, whereas stable facial nerve function outcomes are associated with SRS. Therefore, SRS should be recommended to patients with FNS who require treatment, and surgery should be reserved for patients with another indication, such as decompression of the brainstem. Further study is required to definitively optimize and validate management strategies for these rare skull base tumors.

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Tumor Growth Rate as a New Predictor of Progression-Free Survival After Chordoma Surgery

Neurosurgery 89:291–299, 2021

Currently, different postoperative predictors of chordoma recurrence have been identified. Tumor growth rate (TGR) is an image-based calculation that provides quantitative information of tumor’s volume changing over time and has been shown to predict progression-free survival (PFS) in other tumor types.

OBJECTIVE: To explore the usefulness of TGR as a new preoperative radiological marker for chordoma recurrence.

METHODS: A retrospective single-institution study was carried out including patients reflecting these criteria: confirmed diagnosis of chordoma on pathological analysis, no history of previous radiation, and at least 2 preoperative thin-slice magnetic resonance images available to measure TGR. TGR was calculated for all patients, showing the percentage change in tumor size over 1 mo.

RESULTS: A total of 32 patients were retained for analysis. Patients with a TGR ≥ 10.12%/m had a statistically significantly lower mean PFS (P<.0001). TGR≥10.12%/m (odds ratio=26, P=.001) was observed more frequently in recurrent chordoma. In a subgroup analysis, we found that the association of Ki-67 labeling index≥6% and TGR≥10.12%/m was correlated with recurrence (P = .0008).

CONCLUSION: TGR may be considered as a preoperative radiological indicator of tumor proliferation and seems to preoperatively identify more aggressive tumors with a higher tendency to recur. Our findings suggest that the therapeutic strategy and clinical radiological follow-up of patients with chordoma can be adapted also according to this new parameter.

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Use of zero-profile device for contiguous three-level anterior cervical discectomy and fusion: comparison with cage and plate construct

J Neurosurg Spine 35:219–226, 2021

The aim of this study was to compare a traditional cervical cage with a zero-profile (ZP) fixation device in patients who underwent three-level anterior cervical decompression and fusion (ACDF) in terms of patient-reported outcomes (visual analog scale [VAS], Japanese Orthopaedic Association [JOA], and Neck Disability Index [NDI] scores), radiographic findings (sagittal alignment 2 years after surgery and likelihood of fusion), and complications.

METHODS This study was a retrospective case series. Between January 2012 and December 2016, 58 patients with cervical spondylotic myelopathy (CSM) who required three-level ACDF procedures, as identified by spinal surgeons, were treated with three-level ACDF and an anterior cage-plate construct (ACPC) (n = 38) or a three-level stand-alone ZP device (n = 20). On the basis of patient choice, patients were divided into two groups (ACPC group and ZP group). All patients completed a minimum of 2 years of follow-up. Patient-reported outcome scores included VAS, JOA, and NDI scores. The radiographic findings included sagittal alignment and likelihood of fusion 2 years after surgery. Data related to patient-reported outcomes and sagittal alignment were collected preoperatively, postoperatively, and at the final follow-up. Intraoperative and postoperative complications were also documented and analyzed.

RESULTS The clinical outcomes, including VAS, JOA, and NDI scores, showed improvement in both groups, and no significant difference was observed between the two groups. Sagittal alignment and height of the fused segments were restored in all patients. However, the authors found no differences between the ZP and ACPC groups, and the groups exhibited similar fusion rates. The authors found no differences in complications, including dysphagia, adjacent-segment degeneration, and postoperative hematoma, between the groups.

CONCLUSIONS Use of ZP implants yielded satisfactory long-term clinical and radiological outcomes that were similar to those of the standard ACPC. Additionally, the rates of complications between the groups were not significantly different. Although the best surgical option for multilevel CSM remains controversial, the results of this work suggest that ACDF with the ZP device is feasible, safe, and effective, even for multilevel CSM.

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An endoscopic endonasal approach to craniopharyngioma via the infrachiasmatic corridor

Acta Neurochirurgica (2021) 163:2253–2268

The infrachiasmatic corridor is the most important surgical access route for craniopharyngiomas and was identified and used in clinical series. The aims of this study were to describe the characteristics that assist dissection and resection rates in endoscopic surgery of solid, cystic, and recurrent cases and their importance in the infrachiasmatic corridor in endoscopic surgery.

Methods One hundred operations on 84 patients with pathologically identified craniopharyngioma were included in the study. The MRI findings were evaluated, and the location of the lesions was classified as (1) infrasellar; (2) sellar; or (3) suprasellar. In the sagittal plane, we measured the longest diameter of cystic and solid components and the height of chiasm-sella. Images were assessed for the extent of resection and were classified as gross total resection. This was deemed as the absence of residual tumor and subtotal resection, which had residual tumor.

Results The infrasellar location was reported in 7/84 (8.3%) patients, the sellar location in 8/84 (9.5%), and the suprasellar location in 69/84 (82.1%) patients. The narrow and high chiasm-sella were observed in 28/69 (40.5%) and 41/69 patients (59.4%), respectively. The mean distance of the chiasm-sella was 9.46± 3.76. Gross total tumor resection was achieved in 60/ 84 (71.4%) and subtotal tumor resection was performed in 24/84 (28.6%) patients. The results revealed that suprasellar location (OR: 0.068; p = 0.017) and recurrent cases (OR: 0.011; p<0.001) were negative predictive factors on GTR. Increasing the experience (OR: 42,504; p = 0.001) was a positive predictor factor for GTR.

Conclusion An EETS approach that uses the infrachiasmatic corridor is required for skull base lesions extending into the suprasellar area. The infrachiasmatic corridor can determine the limitations of endoscopic craniopharyngioma surgery. This corridor is a surgical safety zone for inferior approaches.

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The effect of augmented reality on the accuracy and learning curve of external ventricular drain placement

Neurosurg Focus 51 (2):E8, 2021

The traditional freehand technique for external ventricular drain (EVD) placement is most frequently used, but remains the primary risk factor for inaccurate drain placement. As this procedure could benefit from image guidance, the authors set forth to demonstrate the impact of augmented-reality (AR) assistance on the accuracy and learning curve of EVD placement compared with the freehand technique.

METHODS Sixteen medical students performed a total of 128 EVD placements on a custom-made phantom head, both before and after receiving a standardized training session. They were guided by either the freehand technique or by AR, which provided an anatomical overlay and tailored guidance for EVD placement through inside-out infrared tracking. The outcome was quantified by the metric accuracy of EVD placement as well as by its clinical quality.

RESULTS The mean target error was significantly impacted by either AR (p = 0.003) or training (p = 0.02) in a direct comparison with the untrained freehand performance. Both untrained (11.9 ± 4.5 mm) and trained (12.2 ± 4.7 mm) AR performances were significantly better than the untrained freehand performance (19.9 ± 4.2 mm), which improved after training (13.5 ± 4.7 mm). The quality of EVD placement as assessed by the modified Kakarla scale (mKS) was significantly impacted by AR guidance (p = 0.005) but not by training (p = 0.07). Both untrained and trained AR performances (59.4% mKS grade 1 for both) were significantly better than the untrained freehand performance (25.0% mKS grade 1). Spatial aptitude testing revealed a correlation between perceptual ability and untrained AR-guided performance (r = 0.63).

CONCLUSIONS Compared with the freehand technique, AR guidance for EVD placement yielded a higher outcome accuracy and quality for procedure novices. With AR, untrained individuals performed as well as trained individuals, which indicates that AR guidance not only improved performance but also positively impacted the learning curve. Future efforts will focus on the translation and evaluation of AR for EVD placement in the clinical setting.

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Microsurgical clipping of middle cerebral artery aneurysms: preoperative planning using virtual reality to reduce procedure time

Neurosurg Focus 51 (2):E12, 2021

The authors sought to evaluate the impact of virtual reality (VR) applications for preoperative planning and rehearsal on the total procedure time of microsurgical clipping of middle cerebral artery (MCA) ruptured and unruptured aneurysms compared with standard surgical planning.

METHODS A retrospective review of 21 patients from 2016 to 2019 was conducted to determine the impact on the procedure time of MCA aneurysm clipping after implementing VR for preoperative planning and rehearsal. The control group consisted of patients whose procedures were planned with standard CTA and DSA scans (n = 11). The VR group consisted of patients whose procedures were planned with a patient-specific 360° VR (360VR) model (n = 10). The 360VR model was rendered using CTA and DSA data when available. Each patient was analyzed and scored with a case complexity (CC) 5-point grading scale accounting for aneurysm size, incorporation of M2 branches, and aspect ratio, with 1 being the least complex and 5 being the most complex. The mean procedure times were compared between the VR group and the control group, as were the mean CC score between the groups. Comorbidities and aneurysm conduction (ruptured vs unruptured) were also taken into consideration for the comparison.

RESULTS The mean CC scores for the control group and VR group were 2.45 ± 1.13 and 2.30 ± 0.48, respectively. CC was not significantly different between the two groups (p = 0.69). The mean procedure time was significantly lower for the VR group compared with the control group (247.80 minutes vs 328.27 minutes; p = 0.0115), particularly for the patients with a CC score of 2 (95% CI, p = 0.0064). A Charlson Comorbidity Index score was also calculated for each group, but no statistical significance was found (VR group, 2.8 vs control group, 1.8, p = 0.14).

CONCLUSIONS In this study, usage of 360VR models for planning the craniotomy and rehearsing with various clip sizes and configurations resulted in an 80-minute decrease in procedure time. These findings have suggested the potential of VR technology in improving surgical efficiency for aneurysm clipping procedures regardless of complexity, while making the procedure faster and safer.

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Recurrence and risk factors of posterior communicating artery aneurysms after endovascular treatment

Acta Neurochirurgica (2021) 163:2319–2326

Endovascular treatment (EVT) of posterior communicating artery aneurysms (PcomA) is challenging because of posterior communicating artery (Pcom) architecture. Additionally, these aneurysms have a high risk of recanalization compared with those located elsewhere.

Methods The radiographic findings of 171 patients treated with EVT at two institutions were retrospectively reviewed. Univariate and multivariate analyses were performed, and subgroup analyses were performed based on Pcom characteristics.

Results Recanalization of PcomAs occurred in 53 patients (30.9%). Seven patients (4.0%) were retreated (six endovascularly and one with microsurgical clipping). The mean follow-up duration was 27.7 months (range: 3.5–78.6). The maximum diameter (odds ratio [OR] 1.23, P = .006, 95% CI 1.07–1.44), a Raymond–Roy classification of grade II or III (OR 2.26, P = .03, 95% CI 1.08–4.82), and the presence of reinforcement (balloon or/and stent, OR 0.44, P = .03, 95% CI 0.20–0.91) were associated with recanalization using multivariate logistic regression. Significant differences were found in maximum aneurysm diameter (P = .03) between normal- and fetal-type Pcoms on analysis of variance.

Conclusions The recanalization rate of PcomAs after EVT was 30.9%; the retreatment rate was 4.0%. Maximum diameter, Raymond–Roy classification, and presence of reinforcement were significantly associated with recanalization but not associated with fetal-type Pcom. Aneurysm size was larger in patients with a fetal-type Pcom than in those with a normal Pcom. Pcom size was not related to recanalization rate.

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How I do it: endoscopic endonasal resection of tuberculum sellae meningioma

Acta Neurochirurgica (2021) 163:2193–2197

Tuberculum sellae meningiomas (TSMs) adherent to neurovascular structures are particularly challenging lesions requiring delicate and precise microneurosurgery. There is an ongoing debate about the optimal surgical approach.

Method We describe technical nuances and challenges in TSM resection using the endoscopic endonasal approach (EEA) in two cases of fibrous tumors with adherence to neurovascular structures. The cases are illustrated with a video (case 1) and figures (cases 1 and 2).

Conclusion A dedicated team approach and precise microsurgical technique facilitate safe resection of complex TSMs through the EEA.

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The comparative accuracy and safety of fluoroscopic and navigation-based techniques in cervical pedicle screw fixation: systematic review and meta-analysis

J Neurosurg Spine 35:194–201, 2021

The goal of this study was to evaluate the comparative accuracy and safety of navigation-based approaches for cervical pedicle screw (CPS) placement over fluoroscopic techniques.

METHODS A systematic search of the literature published between January 2006 and December 2019 relating to CPS instrumentation and the comparative accuracy and safety of fluoroscopic and intraoperative computer-based navigation techniques was conducted. Several databases, including the Cochrane Library, PubMed, and EMBASE, were systematically searched to identify potentially eligible studies. Data relating to CPS insertion accuracy and associated complications, in particular neurovascular complications, were extrapolated from the included studies and summarized for analysis.

RESULTS A total of 17 studies were identified from the search methodology. Eleven studies evaluated CPS placement under traditional fluoroscopic guidance and 6 studies addressed outcomes following navigation-assisted placement (3D C-arm or CT-guided placement). Overall, a total of 4278 screws were placed in 1065 patients. Misplacement rates of CPS were significantly lower (p < 0.0001) in navigation-assisted techniques (12.51% [range 2.5%–20.5%]) compared to fluoroscopy-guided techniques (18.8% [range 0%–43.5%]). Fluoroscopy-guided CPS insertion was associated with a significantly higher incidence of postoperative complications relating to neurovascular injuries (p < 0.038), with a mean incidence of 1.9% compared with 0.3% in navigation-assisted techniques.

CONCLUSIONS This systematic review supports a logical conclusion that navigation-based techniques confer a statistically significantly more accurate screw placement and resultant lower complication rates.

 

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Impact of vestibular nerve preservation on facial and hearing outcomes in small vestibular schwannoma surgery

Acta Neurochirurgica (2021) 163:2219–2224

Management of small vestibular schwannomas (VSs) remains controversial. When surgery is chosen, the preservation of facial and cochlear nerve function is a priority. In this report, we introduce and evaluate a technique to anatomically preserve the vestibular nerves to minimize manipulation and preserve the function of the facial and cochlear nerves.

Methods The vestibular nerve preservation technique was prospectively applied to resect small VS tumors in patients with serviceable preoperative hearing (American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) class A or B). Clinical and radiological data were recorded and analyzed.

Results Ten patients met the inclusion criteria. The mean (SD) age was 40.4 (12.5) years. Follow-up ranged from 6 weeks to 2 years. The maximum tumor diameter parallel to the internal auditory canal ranged from 10 to 20 mm (mean, 14.9 (3.1) mm). There were three Koos grade 3 and seven Koos grade 2 tumors. Gross total resection was achieved in all cases. Both the facial and cochlear nerves were anatomically preserved in all cases. Postoperatively, 7 patients (70%) remained in the AAO-HNS class A or B hearing category. None of the patients had new vestibular symptoms, and all had House–Brackmann grade 1 facial function. Nervus intermedius dysfunction was observed in 1 patient preoperatively, which worsened postoperatively. Two patients had new nervus intermedius symptoms postoperatively.

Conclusion Improvement of facial nerve and hearing outcomes is feasible through the intentional preservation of the vestibular nerves in the resection of small VSs. Longer follow-up is required to rule out tumor recurrence.

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Microneurosurgical removal of thalamic lesions: surgical results and considerations from a large, single-surgeon consecutive series

J Neurosurg 135:458–468, 2021

The object of this study was to present the surgical results of a large, single-surgeon consecutive series of patients who had undergone transcisternal (TCi) or transcallosal-transventricular (TCTV) endoscope-assisted microsurgery for thalamic lesions.

METHODS This is a retrospective study of a consecutive series of patients harboring thalamic lesions and undergoing surgery at one institution between February 2007 and August 2019. All surgical and patient-related data were prospectively collected. Depending on the relationship between the lesion and the surgically accessible thalamic surfaces (lateral ventricle, velar, cisternal, and third ventricle), one of the following surgical TCi or TCTV approaches was chosen: anterior interhemispheric transcallosal (AIT), posterior interhemispheric transtentorial subsplenial (PITS), perimedian supracerebellar transtentorial (PeST), or perimedian contralateral supracerebellar suprapineal (PeCSS). Since January 2018, intraoperative MRI has also been part of the protocol. The main study outcome was extent of resection. Complete neurological examination took place preoperatively, at discharge, and 3 months postoperatively. Descriptive statistics were calculated for the whole cohort.

RESULTS In the study period, 92 patients underwent surgery for a thalamic lesion: 81 gliomas, 6 cavernous malformations, 2 germinomas, 1 metastasis, 1 arteriovenous malformation, and 1 ependymal cyst. In none of the cases was a transcortical approach adopted. Thirty-five patients underwent an AIT approach, 35 a PITS, 19 a PeST, and 3 a PeCSS. The mean follow-up was 38 months (median 20 months, range 1–137 months). No patient was lost to follow-up. The mean extent of resection was 95% (median 100%, range 21%–100%), and there was no surgical mortality. Most patients (59.8%) experienced improvement in their Karnofsky Performance Status. New permanent neurological deficits occurred in 8 patients (8.7%). Early postoperative (< 3 months after surgery) problems in CSF circulation requiring diversion occurred in 7 patients (7.6%; 6/7 cases in patients with high-grade glioma).

CONCLUSIONS Endoscope-assisted microsurgery allows for the removal of thalamic lesions with acceptable morbidity. Surgeons must strive to access any given thalamic lesion through one of the four accessible thalamic surfaces, as they can be reached through either a TCTV or TCi approach with no or minimal damage to normal brain parenchyma. Patients harboring a high-grade glioma are likely to develop a postoperative disturbance of CSF circulation. For this reason, the AIT approach should be favored, as it facilitates a microsurgical third ventriculocisternostomy and allows intraoperative MRI to be done.

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Large and small vestibular schwannomas: same, yet different tumors

Acta Neurochirurgica (2021) 163:2199–2207

Vestibular schwannomas (VS) present at variable size with heterogeneous symptomatology. Modern treatment paradigms for large VS include gross total resection, subtotal resection (STR) in combination with observation, and/or radiation to achieve optimal function preservation, whereas treatment is felt to be both easier and safer for small VS. The objective is to better characterize the presentation and surgical outcomes of large and small VS.

Methods We collected data of patients who had surgically treated VS with a posterior fossa diameter of 4.0 cm or larger (large tumor group, LTG) and smaller than 1.0 cm in cisternal diameter (small tumor group, STG). Statistical significance was defined as p < 0.05.

Results LTG included 48 patients (average tumor size: 44.9 mm) and STG 38 (7.9 mm). Patients in STG presented more frequently with tinnitus and sudden hearing loss. Patients in LTG underwent more STR than STG (50.0% vs. 2.6%, p < 0.0001). LTG had more complications (31.3% vs. 13.2%, p = 0.049). Postoperative facial nerve function in STG was significantly better than LTG. STG had better hearing preoperatively (p < 0.0001) and postoperatively than LTG (p = 0.0002). Postoperative headache was more common in STG (13.2% vs. 2.1%, p = 0.045). The rate of recurrence/progression needing treatment was not statistically different between the groups (12.5% in LTG vs. 7.9% in STG, p = 0.49). Those patients who required periprocedural cerebrospinal fluid diversion had higher risk of infection (20.8% vs 4.8%, p = 0.022).

Conclusion Large and small VS present differently. LTG showed more unsatisfactory outcomes in facial nerve function and postoperative hearing despite maximal efforts undertaken toward function-preservation strategy; however, similar tumor control was achieved.

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Transforaminal lumbar interbody fusion using a novel minimally invasive expandable interbody cage

J Neurosurg Spine 35:170–176, 2021

The goal of this study was to evaluate the clinical and radiographic outcomes of a novel multidirectional in situ expandable minimally invasive surgery (MIS) transforaminal lumbar interbody fusion (TLIF) cage.

METHODS A retrospective analysis of 69 consecutive patients undergoing a 1- or 2-level MIS TLIF using an expandable cage was performed over a 2-year period. Standard MIS techniques with pedicle screw fixation were used in all cases. Upright lateral dynamic flexion/extension radiographs were reviewed prior to and at 1 year after surgery. Clinical metrics included numeric rating scale for back and leg pain, Oswestry Disability Index, and the SF-12 and VR-12 physical and mental health surveys. Radiographic parameters included anterior and posterior disc height, neuroforaminal height, spondylolisthesis, segmental lordosis, lumbar lordosis, and fusion rate.

RESULTS A total of 69 patients representing 75 operative levels met study inclusion criteria. The mean patient age at surgery was 63.4 ± 1.2 years, with a female predominance of 51%. The average radiographic and clinical follow-ups were 372 and 368 days, respectively. A total of 63 patients (91%) underwent 1-level surgery and 6 patients (9%) underwent 2-level surgery. Significant reductions of numeric rating scale scores for back and leg pain were observed—from 6.1 ± 0.7 to 2.5 ± 0.3 (p < 0.0001) and 4.9 ± 0.6 to 1.9 ± 0.2 (p < 0.0001), respectively. A similar reduction in Oswestry Disability Index from 38.0 ± 4.6 to 20.0 ± 2.3 (p < 0.0001) was noted. Likewise, SF-12 and VR-12 scores all showed statistically significant improvement from baseline (p < 0.001). The mean anterior and posterior disc heights improved from 8.7 ± 1.0 mm to 13.4 ± 1.5 mm (p = 0.0001) and 6.5 ± 0.8 mm to 9.6 ± 1.1 mm (p = 0.0001), respectively. Neuroforaminal height improved from 17.6 ± 2.0 mm to 21.9 ± 2.5 mm (p = 0.0001). When present, spondylolisthesis was, on average, reduced from 4.3 ± 0.5 mm to 1.9 ± 0.2 mm (p = 0.0001). Lumbar lordosis improved from 47.8° ± 5.5° to 58.5° ± 6.8° (p = 0.2687), and no significant change in segmental lordosis was observed. The overall rate of radiographic fusion was 93.3% at 1 year. No perioperative complications requiring operative revision were encountered.

CONCLUSIONS In this series of MIS TLIFs, use of this novel interbody cage was shown to be safe and effective. Significant improvements in pain and disability were observed. Effective and durable restoration of disc height and neuroforaminal height and reduction of spondylolisthesis were obtained, with concurrent gains in lumbar lordosis. Taken together, this device offers excellent clinical and radiographic outcomes via an MIS approach.

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Clinical Pearls and Methods for Intraoperative Awake Language Mapping

Neurosurgery 89:143–153, 2021

Intraoperative language mapping of tumor and peritumor tissue is a well-established technique for avoiding permanent neurological deficits and maximizing extent of resection.

Although there are several components of language that may be tested intraoperatively (eg, naming, writing, reading, and repetition), there is a lack of consistency in how patients are tested intraoperatively as well as the techniques involved to ensure safety during an awake procedure.

Here, we review appropriate patient selection, neuroanesthetic techniques, cortical and subcortical language mapping stimu- lation paradigms, and selection of intraoperative language tasks used during awake craniotomies.

We also expand on existing language mapping reviews by considering how intensity and timing of electrical stimulation may impact interpretation of mapping results.

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Intracranial Meningiomas Decrease in Volume on Magnetic Resonance Imaging After Discontinuing Progestin

Neurosurgery 89:308–314, 2021

The behavior of meningiomas under influence of progestin therapy remains unclear.

OBJECTIVE: To investigate the relationship between growth kinetics of intracranial meningiomas and usage of the progestin cyproterone acetate (PCA).

METHODS: This study prospectively followed 108 women with 262 intracranial meningiomas and documented PCA use. A per-meningioma analysis was conducted. Changes in meningioma volumes over time, and meningioma growth velocities, were measured on magnetic resonance imaging (MRI) after stopping PCA treatment.

RESULTS: Mean follow-up time was 30 (standard deviation [SD] 29) mo. Ten (4%) meningiomas were treated surgically at presentation. The other 252 meningiomas were followed after stopping PCA treatment. Overall, followedmeningiomas decreased their volumes by 33% on average (SD 28%). A total of 188 (72%) meningiomas decreased, 51 (19%) meningiomas remained stable, and 13 (5%) increased in volume of which 3 (1%) were surgically treated because of radiological progression during follow-up after PCA withdrawal. In total, 239 of 262 (91%) meningiomas regressed or stabilized during follow-up. Subgroup analysis in 7 women with 19 meningiomas with follow-up before and after PCA withdrawal demonstrated that meningioma growth velocity changed statistically significantly (P = .02). Meningiomas grew (average velocity of 0.25mm3/day) while patients were using PCA and shrank (average velocity of −0.54 mm3/day) after discontinuation of PCA.

CONCLUSION: Ninety-one percent of intracranial meningiomas in female patients with long-term PCA use decrease or stabilize on MRI after stopping PCA treatment. Meningioma growth kinetics change significantly from growth during PCA usage to shrinkage after PCA withdrawal.

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Impact of C‑shaped skin incision on surgical operability in the retrosigmoid approach: when a good start is half of the job

Acta Neurochirurgica (2021) 163:2155–2163

The retrosigmoid approach (RSA) is one of the routes of choice to approach tumors and vascular lesions of the cerebellopontine angle. Among different types of skin incisions and soft tissue dissection techniques, the most widely used variants comprise the straight/lazy S-shaped and the C-shaped incisions. Several reports discuss advantages in terms of functional and clinical outcomes of the C-shaped incision, but scientific considerations about the critical impact of this kind of incision on surgical operability are still extremely limited.

Object Authors comparatively analyze the advantage provided by C-shaped incision in RSA in terms of anatomic exposure and surgical operability, compared with straight/lazy S-shaped one.

Methods A comparative microanatomical laboratory investigation was conducted. The operability score (OS) was applied for quantitative analysis of surgical operability.

Results C-shaped incision, providing a significant reduction of the overall working distance (–13%) together with an overall increase of the maneuverability area (+ 204.9%), did improve the conizing effect on the surgical corridor. It optimized overall maneuverability of surgical instruments, in terms of angle of attack (+ 27.7%), as well as maneuverability arc (+ 122%), on the entire surgical field. C-shaped incision ensured good operability on all surgical targets (OS ranging from 2 to 3), most significantly improving surgical maneuverability at the porus trigeminus and internal acoustic meatus.

Conclusion C-shaped incision in the RSA significantly improves anatomic exposure and surgical operability as compared with straight/lazy S-shaped incision.

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Cerebral venous drainage in patients with dural arteriovenous fistulas: correlation with clinical presentation

J Neurosurg 135:440–448, 2021

Dural arteriovenous fistulas (DAVFs) are abnormal, acquired arteriovenous connections within the dural leaflets. Their associated symptoms may be mild or severe and are related to the patient’s venous anatomy. With the hypothesis that the patient’s venous anatomy determines the development of symptoms, the authors aimed to identify which venous anatomy elements are important in the development of major symptoms in patients with a DAVF.

METHODS A multicenter study was performed based on the retrospective analysis of cerebral angiographies with systematic assessment of brain drainage pathways (including fistula drainage) in patients over 18 years of age with a single DAVF. The patients were divided into two groups: those with minor (group 1, n = 112) and those with major (group 2, n = 89) symptoms. Group 2 was subdivided into two groups: patients with hemorrhage (group 2a, n = 47) and patients with severe nonhemorrhagic symptoms (group 2b, n = 42).

RESULTS The prevalence of stenosis in DAVF venous drainage and the identification of tiny anastomoses between venous territories were significantly higher in group 2 (32.6% and 19.1%, respectively) compared with group 1 (2.68% and 5.36%, respectively). Stenosis of DAVF venous drainage was significantly more frequent in group 2a than in group 2b (51.1% vs 11.9%, p < 0.001). Group 2b patients had increased prevalence of shared use of the cerebral main drainage pathway (85.0% vs 53.2%, p = 0.002), the absence of an alternative route (45.0% vs 17.0%, p = 0.004), and the presence of contrast stagnation (62.5% vs 29.8%, p = 0.002) compared with group 2a patients. In patients with high-grade fistulas, the group with major symptoms had increased prevalence of a single draining direction (31.3% vs 8.33%, p = 0.003), stenosis in the draining vein (35.0% vs 6.25%, p = 0.000), the absence of an alternative pathway for brain drainage (31.3% vs 12.5%, p = 0.017), and the presence of contrast stagnation (48.8% vs 22.9%, p = 0.004).

CONCLUSIONS Major symptoms were observed when normal brain tissue venous drainage was impaired by competition with DAVF (predominance in group 2b) or when DAVF venous drainage had anatomical characteristics that hindered drainage, with consequent venous hypertension on the venous side of the DAVF (predominance in group 2a). The same findings were observed when comparing two groups of patients with high-grade lesions: those with major versus those with minor symptoms.

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