One-Point Technique in Brainstem Cavernous Malformation Surgery: Evaluation of Approaches and Outcomes From a Different Perspective.

BACKGROUND AND OBJECTIVES: Brainstem cavernous malformations (BCMs) are a distinct clinical entity that carry a high risk of patient morbidity because of location and risk of hemorrhage. Surgical management of these lesions requires intimate knowledge of surgical anatomy and skull base approaches. This article is intended to highlight a modern approach for the treatment of BCMs, with an emphasis on the use of the one-point technique to guide resection. METHODS: We describe a case series of BCMs treated through a variety of skull base approaches, describing our decision-making strategy. We review the concept of the one-point technique focusing on the safest access to the malformation through 2 representative cases and also perform a retrospective review of 32 consecutive patients who underwent BCM resection to present outcomes and the comparison of two-point vs one-point techniques. RESULTS: Consecutive series of 32 patients in whom the one-point technique was used is presented. In 8 patients (25%), the traditional two-point technique would suggest a different trajectory than the one-point technique. Postoperative MRI confirmed complete resection in 30 patients (95%), and 29 patients (91%) had modified Rankin Scale (0-2) at follow-up. All patients in whom the one-point technique guided a different trajectory had gross total removal of the cavernous malformation, with one patient having long-term new neurological impairment from the surgery. There were no mortalities. CONCLUSION: Despite surgical advances in recent decades and more widespread understanding of surgical anatomy and safe entry zones, surgical resection of BCMs remains a formidable challenge. While not necessarily the shortest access, the one-point technique offers a safe approach considering all the different modalities in our armamentarium and can be used as part of a strategy to determine the optimal approach to resect BCMs.

Evolution of Surgical Outcomes in Endoscopic Endonasal Resection of Craniopharyngiomas.

Introduction Wide variations exist in the management of craniopharyngiomas, including pituitary stalk preservation/sacrifice. This study examines the practice patterns over 16 years using the endoscopic endonasal approach for the resection of craniopharyngiomas and it examines the effects of stalk preservation. Methods Retrospective analysis was conducted for 66 patients who underwent endoscopic transsphenoidal surgery for resection of craniopharyngiomas. Patients were stratified into three epochs: 2005 to 2009 ( N = 20), 2010 to 2015 ( N = 23), and 2016 to 2020 ( N = 20), to examine the evolution of surgical outcomes. Subgroup analysis between stalk preservation/stalk sacrifice was conducted for rate of gross total resection, anterior pituitary function preservation, and development of new permanent diabetes insipidus. Results Gross total resection rates across the first, second, and third epochs were 20, 65, and 52%, respectively ( p = 0.042). Stalk preservation across epochs were 100, 5.9, and 52.6% ( p = 0.0001). New permanent diabetes insipidus did not significantly change across epochs (37.5, 68.4, 71.4%; p = 0.078). Preservation of normal endocrine function across epochs was 25, 0, and 23.8%; ( p = 0.001). Postoperative cerebrospinal fluid (CSF) leaks significantly decreased over time (40, 4.5, and 0%; [ p = 0.0001]). Stalk preservation group retained higher normal endocrine function (40.9 vs. 0%; p = 0.001) and less normal-preoperative to postoperative panhypopituitarism (18.4 vs. 56%; p = 0.001). Stalk sacrifice group achieved higher GTR (70.8 vs. 28%, p = 0.005). At last follow-up, there was no difference in recurrence/progression rates between the two groups. Conclusion There is a continuous evolution in the management of craniopharyngiomas. Gross total resection, higher rates of pituitary stalk and hormonal preservation, and low rates of postoperative CSF leak can be achieved with increased surgical experience.

Radiation of meningioma dural tail may not improve tumor control rates.

Introduction: Dural tails are thickened contrast-enhancing portions of dura associated with some meningiomas. Prior studies have demonstrated the presence of tumor cells within the dural tail, however their inclusion in radiation treatment fields remains controversial. We evaluated the role of including the dural tail when treating a meningioma with stereotactic radiation and the impact on tumor recurrence. Methods: This is a retrospective, single-institution, cohort study of patients with intracranial World Health Organization (WHO) grade 1 meningioma and identified dural tail who were treated with stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) from January 2012 to December 2018. SRS and FSRT subgroups were categorized based on coverage or non-coverage of the dural tail by the radiation fields, as determined independently by a radiation oncologist and a neurosurgeon. Demographics, tumor characteristics, radiation plans, and outcomes were evaluated. High grade tumors were analyzed separately. Results: A total of 187 WHO grade 1 tumors from 177 patients were included in the study (median age: 62 years, median follow-up: 40 months, 78.1% female) with 104 receiving SRS and 83 receiving FSRT. The dural tail was covered in 141 (75.4%) of treatment plans. There was no difference in recurrence rates (RR) or time to recurrence (TTR) between non-coverage or coverage of dural tails (RR: 2.2% vs 3.5%, P = 1.0; TTR: 34 vs 36 months, P = 1.00). There was no difference in the rate of radiation side effects between dural tail coverage or non-coverage groups. These associations remained stable when SRS and FSRT subgroups were considered separately, as well as in a high grade cohort of 16 tumors. Conclusion: Inclusion of the dural tail in the SRS or FSRT volumes for meningioma treatment does not seem to reduce recurrence rate. Improved understanding of dural tail pathophysiology, tumor grade, tumor spread, and radiation response is needed to better predict the response of meningiomas to radiotherapy.

Targeted Therapy in the Management of Modern Craniopharyngiomas.

BACKGROUND: The proximity of craniopharyngiomas (CPs) to critical neurovascular structures can lead to a host of neurologic and endocrine complications that lead to difficulty with surgical management. In this review, we examine the molecular and genetic markers implicated in CP, their involvement in tumorigenic pathways, and their impact on CP prognosis and treatment. METHODS: We undertook a focused review of relevant articles, clinical trials, and molecular summaries regarding CP. RESULTS: Genetic and immunological markers show variable expression in different types of CP. BRAF is implicated in tumorigenesis in papillary CP (pCP), whereas CTNNB1 and EGFR are often overexpressed in adamantinomatous CP (aCP) and VEGF is overexpressed in aCP and recurrent CP. Targeted treatment modalities inhibiting these pathways can shrink or halt progression of CP. In addition, EGFR inhibitors may sensitize tumors to radiation therapy. These drugs show promise in medical management and neoadjuvant therapy for CP. Immunotherapy, including anti-interleukin-6 (IL-6) drugs and interferon treatment, are also effective in managing tumor growth. Ongoing clinical trials in CP are limited but are testing BRAF/MET inhibitors and IL-6 monoclonal antibodies. CONCLUSIONS: Genetic and immunological markers show variable expression in different subtypes of CP. Several current molecular treatments have shown some success in the management of this disease. Additional clinical trials and targeted therapies will be important to improve CP patient outcomes.

Delayed symptomatic hyponatremia in transsphenoidal surgery: Systematic review and meta-analysis of its incidence and prevention with water restriction.

BACKGROUND: Delayed symptomatic hyponatremia (DSH) is an unpredictable postoperative complication after transsphenoidal pituitary surgery. Universal postoperative sodium screening and water restriction are two strategies to detect or prevent the development of DSH. We performed a meta-analysis of studies characterizing the rate of DSH using sodium screening and water restriction protocols. METHODS: Literature search was done using MEDLINE/PUBMED, EMBASE, and Cochrane databases. Inclusion criteria are (1) development of DSH after endoscopic or microscopic transsphenoidal, sellar surgery, and (2) reporting of a standardized postoperative sodium screening protocol for monitoring or prevention of DSH. RESULTS: A total of 23 publications fulfilled the inclusion criteria resulted in a total of 5870 patients. Two meta-analyses were conducted. Of the 19 studies (N = 4488 patients) examining rate of DSH after sodium screening, DSH rates ranged from 0% to 19.7%. In the first meta-analysis, using a random-effect estimate of the combined proportions, the overall rate of DSH was 5.60% (4.0%-7.1%, I2 = 96.54%, T2 = 0.0007). In the second meta-analysis, a fixed-effect model of four studies consisted of 1382 patients. Eight hundred fifty-two patients were included prior to and 530 were included after water restriction protocol. Meta-analysis showed an odds ratio (OR) of 5.02 (95% CI: 2.16-11.65) favoring water restriction. CONCLUSION: This meta-analysis summarized rates of DSH with sodium screening protocol to be 5.60% (4.0%-7.1%) and showed a decreased risk of DSH after implementation of a water restriction protocol. The results are limited due to few studies examining fluid restriction (N = 4) and heterogeneity in water restriction protocols. No adverse events were seen with fluid restriction protocol. Prospective and multicenter studies should be conducted to further investigate the utility of water restriction following transsphenoidal pituitary surgery.

Retrosigmoid transhorizontal fissure approach to lateral pontine cavernous malformation: comparison to transpetrosal presigmoid retrolabyrinthine approach.

OBJECTIVE: The retrosigmoid (RS) approach is a classic route used to access deep-seated brainstem cavernous malformation (CM). The angle of access is limited, so alternatives such as the transpetrosal presigmoid retrolabyrinthine (TPPR) approach have been used to overcome this limitation. Here, the authors evaluated a modification to the RS approach, horizontal fissure dissection by using the RS transhorizontal (RSTH) approach. METHODS: Relevant clinical parameters were evaluated in 9 patients who underwent resection of lateral pontine CM. Cadaveric dissection was performed to compare the TPPR approach and the RSTH approach. RESULTS: Five patients underwent the TPPR approach, and 4 underwent the RSTH approach. Dissection of the horizontal fissure allowed for access to the infratrigeminal safe entry zone, with a direct trajectory to the middle cerebellar peduncle similar to that used in TPPR exposure. Operative time was longer in the TPPR group. All patients had a modified Rankin Scale score ≤ 2 at the last follow-up. Cadaveric dissection confirmed increased anteroposterior working angle and middle cerebellar peduncle exposure with the addition of horizontal fissure dissection. CONCLUSIONS: The RSTH approach leads to a direct lateral path to lateral pontine CM, with similar efficacy and shorter operative time compared with more extensive skull base exposure. The RSTH approach could be considered a valid alternative for resection of selected pontine CM.

Interdisciplinary treatment of posterior fossa dural arteriovenous fistulas.

BACKGROUND: Posterior fossa dural arteriovenous fistulas (dAVFs) are rare vascular lesions with variable risk of hemorrhage, mostly depending on the pattern of the venous drainage. While endovascular embolization is the mainstay treatment for most dAVFs, some posterior fossa lesions require a multidisciplinary approach including surgery. The goal of our study was to examine the outcome of an interdisciplinary treatment for posterior fossa dAVFs. METHODS: A retrospective review of patients treated for posterior fossa dAVFs was conducted. RESULTS: A total of 28 patients with a mean age of 57.8 years were included. Patients presented with a Cognard grade I in 2 (7%), II a in 5 (18 %), II b in 7 (25%), II a + b in 5 (18%), III in 3 (11%), and IV in 6 (21%) cases. Hemorrhage was the initial presentation in 2 (22%) patients with Cognard grade IV, in 3 with Cognard grade III (33%), in 1 (11%) with Cognard II a + b, and 3 (33%) with Cognard II b. A complete angiographic cure was achieved in 24 (86%) patients-after a single-session embolization in 16 (57%) patients, multiple embolization sessions in 2 (7%), a multimodal treatment with embolization and surgical disconnection in 3 (11%), and with an upfront surgery in 3 (11%). Complete long-term obliteration was demonstrated in 18/22 (82%) at the mean follow-up of 17 months. Fistulas were converted into asymptomatic Cognard I lesion in 4 (14%) patients. CONCLUSION: Posterior fossa dAVFs represent a challenging vascular pathology; however, despite their complexity, an interdisciplinary treatment can achieve high rates of angiographic and symptomatic cure with low morbidity and mortality rates. Long-term surveillance is warranted as late recurrences may occur.

Patient Safety Analysis in Radiation Burden of Head Computed Tomography Imaging in 1185 Neurosurgical Inpatients.

OBJECTIVE: We performed a retrospective analysis in a cohort of 1185 patients at our institution who were identified as undergoing ≥1 head computed tomography (CT) examinations during their inpatient stay on the neurosurgery service, to quantify the number, type, and associated radiation burden of head CT procedures performed by the neurosurgery service. METHODS: CT procedure records and radiology reports were obtained via database search and directly validated against records retrieved from manual chart review. Next, dosimetry data from the head CT procedures were extracted via automated text mining of electronic radiology reports. RESULTS: Among 4510 identified adult head CT procedures, 88% were standard head CT examinations. A total of 3.65 ± 3.60 head CT scans were performed during an average adult admission. The most common primary diagnoses were neoplasms, trauma, and other hemorrhage. The median cumulative effective dose per admission was 5.66 mSv (range, 1.06-84.5 mSv; mean, 8.56 ± 8.95 mSv). The median cumulative effective dose per patient was 6.4 mSv (range, 1.1-127 mSv; mean, 9.26 ± 10.0 mSv). CONCLUSIONS: The median cumulative radiation burden from head CT imaging in our cohort equates approximately to a single chest CT scan, well within accepted limits for safe CT imaging in adults. Refined methods are needed to characterize the safety profile of the few pediatric patients identified in our study.

Systemic Antimicrobial Prophylaxis and Antimicrobial-Coated External Ventricular Drain Catheters for Preventing Ventriculostomy-Related Infections: A Meta-Analysis of 5242 Cases.

BACKGROUND: External ventricular drain (EVD) placement is essential for the management of many neurocritical care patients. However, ventriculostomy-related infection (VRI) is a serious complication, and there remains no well-established protocol guiding use of perioperative or extended antibiotic prophylaxis to minimize risk of VRI. OBJECTIVE: To analyze published evidence on the efficacy of extended prophylactic antimicrobial therapy and antibiotic-coated external ventricular drains (ac-EVDs) in reducing VRI incidence. METHODS: We searched PubMed for studies related to VRIs and antimicrobial prophylaxis. Eligible articles reported VRI incidence in control and treatment cohorts evaluating prophylaxis with either extended systemic antibiotics (> 24 hr) or ac-EVD. Risk ratios and VRI incidence were aggregated by prophylactic strategy, and pooled estimates were determined via random or mixed effects models. Study heterogeneity was quantified using I2 and Cochran's Q statistics. Rigorous assessment of study bias was performed, and PRISMA guidelines were followed throughout. RESULTS: Across 604 articles, 19 studies (3%) met eligibility criteria, reporting 5242 ventriculostomy outcomes. Extended IV and ac-EVD prophylaxis were associated with risk ratios of 0.36 [0.14, 0.93] and 0.39 [0.21, 0.73], respectively. Mixed effects analysis yielded expected VRI incidence of 13% to 38% with no prophylaxis, 7% to 18% with perioperative IV prophylaxis, 3% to 9% with either extended IV or ac-EVD prophylaxis as monotherapies, and as low as 0.8% to 2% with extended IV and ac-EVD dual prophylaxis. CONCLUSION: Management with both extended systemic antibiotics and ac-EVDs could lower VRI risk in ventriculostomy patients, but the impact on associated morbidity and mortality, healthcare costs, and length of stay remain unclear.

Timing of adjuvant radiation therapy and survival outcomes after surgical resection of intracranial non-small cell lung cancer metastases.

OBJECTIVE: To investigate if delay of adjuvant radiotherapy (ART) beyond 6 post-operative weeks affects survival outcomes in patients undergoing craniotomy or craniectomy for resection of non-small cell lung cancer (NSCLC) intracranial metastases. PATIENTS AND METHODS: We performed a retrospective analysis of 28 patients undergoing resection of intracranial metastases and ART at our institution from 2001 to 2016. We assessed survival outcomes for patients who received delayed versus non-delayed ART, as well as associated risk factors. RESULTS: Among 28 patients, 8 (29%) had delayed ART beyond 6 post-operative weeks. Fifteen received stereotactic radiotherapy (SRT), 8 (29%) received whole brain radiotherapy (WBRT), and 5 (18%) received combination WBRT + SRT. There were no significant differences in ART modality or dosing, age, sex, number of intracranial metastases, primary metastasis volume, rates of chemotherapy, extracranial metastases, or post-operative functional scores between groups. Expected post-operative survival was shorter with delayed ART (7 months versus 28 months, P = 0.01). The most common reason for delayed ART was complicated post-operative course (n = 3.38%). Significant risk factors for delayed ART included non-routine discharge (P = 0.01) and additional invasive procedures between surgery and ART start date (P = 0.02). CONCLUSIONS: Our results suggest delayed ART in patients undergoing surgical resection of intracranial NSCLC metastases is associated with shorter overall survival. However, risk factors for delayed ART, including non-routine discharge and the need for additional invasive procedures, may have in themselves reflected poorer clinical courses that may have also contributed to the observed survival differences.

Age-related differences in social media use in the neurosurgical community: A multi-institutional study.

OBJECTIVES: Social media is evolving and growing at an exponential rate today. From a healthcare perspective, these platforms can be used to enhance professional networking, education, organizational promotion, patient care, patient education, and public health programs without the limitations of geographic and time-related access barriers. Given the possible importance of social media in medicine, and the conflicting reports in literature about its use in healthcare, it is important to identify its utility within the neurosurgical community. We set out to measure the use of social media platforms among neurosurgery faculty, fellows, and residents. PATIENTS AND METHODS: An online survey using the SurveyMonkey platform was sent to the program directors of 102 accredited neurosurgery programs across the United States. Program directors then distributed these surveys to the residents, fellows, and attendings at their respective institutions once each month between October 2017 and December 2017. Neurosurgeons participated anonymously, voluntarily, and received no compensation for their participation. Statistical analysis was performed using the IBM SPSS Statistics for Windows, Version 25 (IBM SPSS Statistics for Windows, IBM Corporation, Armonk, NY). RESULTS: 137 attendings, 96 residents, and 8 fellows responded to the survey (81% male). Most (70%) stated that they used social media for professional purposes. Sixty percent of all respondents believed that social media can be beneficial in terms of professional development. Younger neurosurgeons in training were more likely to read journal articles found via social media and were more likely to believe social media could be beneficial than older neurosurgeons at later stages in their career. CONCLUSIONS: Results point toward differences in social media use based on age or level of training. Further studies should include a larger sample cohort over a longer time period to determine whether these trends will change over time.

Survival Outcomes After Intracranial Hemorrhage in Liver Disease.

BACKGROUND: Survival outcomes for patients with liver disease who suffer an intracranial hemorrhage (ICH) have not been thoroughly investigated. OBJECTIVE: To understand survival outcomes for 3 groups: (1) patients with an admission diagnosis of liver disease (end-stage liver disease [ESLD] or non-ESLD) who developed an ICH in the hospital, (2) patients with ESLD who undergo either operative vs nonoperative management, and (3) patients with ESLD on the liver transplant waitlist who developed an ICH in the hospital. METHODS: We retrospectively reviewed hospital charts from March 2006 through February 2017 of patients with liver disease and an ICH evaluated by the neurosurgery service at a single academic medical center. The primary outcome was survival. RESULTS: We included a total of 53 patients in this study. The overall survival for patients with an admission diagnosis of liver disease who developed an ICH (n = 29, 55%) in the hospital was 22%. Of those patients with an admission diagnosis of liver disease, 27 patients also had ESLD. Kaplan-Meier analysis found no significant difference in survival for ESLD patients (n = 33, 62%) according to operative status. There were 11 ESLD patients on the liver transplant waitlist. The overall survival for patients with ESLD on the liver transplant waitlist who suffered an in-hospital ICH (n = 7, 13%) was 14%. CONCLUSION: ICH in the setting of liver disease carries a grave prognosis. Also, a survival advantage for surgical hematoma evacuation in ESLD patients is not clear.

Stereotactic Radiosurgery for Neurosurgical Patients: A Historical Review and Current Perspectives.

Today, stereotactic radiosurgery is an effective therapy for a variety of intracranial pathology that were treated solely with open neurosurgery in the past. The technique was developed from the combination of therapeutic radiation and stereotactic devices for the precise localization of intracranial targets. Although stereotactic radiosurgery was originally performed as a partnership between neurosurgeons and radiation oncologists, this partnership has weakened in recent years, with some procedures being performed without neurosurgeons. At the same time, neurosurgeons across the United States and Canada have found their stereotactic radiosurgery training during residency inadequate. Although neurosurgeons, residency directors, and department chairs agree that stereotactic radiosurgery education and exposure during neurosurgery training could be improved, a limited number of resources exist for this kind of education. This review describes the history of stereotactic radiosurgery, assesses the state of its use and education today, and provides recommendations for the improvement of neurosurgical education in stereotactic radiosurgery for the future.

Red Blood Cell Transfusions Following Resection of Skull Base Meningiomas: Risk Factors and Clinical Outcomes.

Objective This article identifies risk factors for and investigates clinical outcomes of postoperative red blood cell transfusion in patients with skull base meningiomas. Design Retrospective cohort study. Setting Single academic medical center. Participants The transfusion group included patients who had skull base meningiomas and who received packed red blood cell (RBC) transfusion within 7 days of surgery. The no transfusion group included patients who had skull base meningiomas but who did not have RBCs transfused within 7 days of surgery. Main Outcome Measures In-hospital complication rate, length of stay (LOS), and discharge disposition. Results One hundred and ninety-six patients had a craniotomy for resection of a meningioma at our institution from March 2013 to January 2017. Seven patients had skull base meningiomas and received RBC transfusion within 7 days of surgery (the transfusion group). The skull base was an independent risk factor for transfusion after we controlled for the effect of meningioma size (OR 3.89, 95% CI 1.34, 11.25). Operative time greater than 10 hours was an independent risk factor for prolonged hospital stay (OR 8.84, 95% CI 1.08, 72.10) once we controlled for the effect of transfusion. In contrast, transfusion did not independently impact LOS or discharge disposition once we controlled for the effect of operative time. Conclusions The skull base is an independent predictor of RBC transfusion. However, RBC transfusion alone cannot predict LOS or discharge disposition in patients who undergo surgical resection of a skull base meningioma.

The Meningioma Vascularity Index: a volumetric analysis of flow voids to predict intraoperative blood loss in nonembolized meningiomas.

OBJECTIVEMeningiomas that appear hypervascular on neuroimaging could be amenable to preoperative embolization. However, methods for measuring hypervascularity have not been described, nor has the benefit of preoperative embolization been adjudicated. The objective of this study was to show a relationship between flow void volume (measured on MRI) and intraoperative estimated blood loss (EBL) in nonembolized meningiomas.METHODSThe authors performed volumetric analyses of 51 intracranial meningiomas (21 preoperatively embolized) resected at their institution. Through the use of image segmentation software and a voxel-based segmentation method, flow void volumes were measured on T2-weighted MR images. This metric was named the Meningioma Vascularity Index (MVI). The primary outcomes were intraoperative EBL and perioperative blood transfusion.RESULTSIn the nonembolized group, the MVI correlated with intraoperative EBL when controlling for tumor volume (r = 0.55, p = 0.002). The MVI also correlated with perioperative blood transfusion (point-biserial correlation [rpb] = 0.57, p = 0.001). A greater MVI was associated with an increased risk of blood transfusion (odds ratio [OR] 5.79, 95% confidence interval [CI] 1.15-29.15) and subtotal resection (OR 7.64, 95% CI 1.74-33.58). In the embolized group, those relationships were not found. There were no significant differences in MVI, intraoperative EBL, or blood transfusion across groups.CONCLUSIONSThis study clearly shows a relationship between MVI and intraoperative EBL in nonembolized meningiomas when controlling for tumor volume. The MVI is a potential biomarker for tumors that would benefit from embolization.

Planned Subtotal Resection of Vestibular Schwannoma Differs from the Ideal Radiosurgical Target Defined by Adaptive Hybrid Surgery.

OBJECTIVE: To retrospectively compare ideal radiosurgical target volumes defined by a manual method (surgeon) to those determined by Adaptive Hybrid Surgery (AHS) operative planning software in 7 patients with vestibular schwannoma (VS). METHODS: Four attending surgeons (3 neurosurgeons and 1 ear, nose, and throat surgeon) manually contoured planned residual tumors volumes for 7 consecutive patients with VS. Next, the AHS software determined the ideal radiosurgical target volumes based on a specified radiotherapy plan. Our primary measure was the difference between the average planned residual tumor volumes and the ideal radiosurgical target volumes defined by AHS (dRVAHS-planned). RESULTS: We included 7 consecutive patients with VS in this study. The planned residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (1.6 vs. 4.5 cm3, P = 0.004). On average, the actual post-operative residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (2.2 cm3 vs. 4.5 cm3; P = 0.02). The average difference between the ideal radiosurgical target volume defined by AHS and the planned residual tumor volume (dRVAHS-planned) was 2.9 ± 1.7 cm3, and we observed a trend toward larger dRVAHS-planned in patients who lost serviceable facial nerve function compared with patients who maintained serviceable facial nerve function (4.7 cm3 vs. 1.9 cm3; P = 0.06). CONCLUSIONS: Planned subtotal resection of VS diverges from the ideal radiosurgical target defined by AHS, but whether that influences clinical outcomes is unclear.