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Background: Stereotactic radiosurgery (SRS) is widely accepted as a minimally invasive alternative to surgery in the management of arteriovenous malformations (AVMs). Dilated AVM outflow veins or varices may be caused by high-flow or partial outflow obstruction, which may increase the risk of a hemorrhage before or after SRS., Objective: To compare the obliteration and hemorrhage risks in patients with and without AVM varices (AVMv)., Methods: From our prospective database of 1012 AVM patients who underwent Gamma Knife® (Elekta) SRS, we identified 103 patients with AVMv, and 847 patients without varices. The median follow-up was 52 mo. Balancing variable score matching was performed to compare obliteration and hemorrhage rates between the 2 groups., Results: Obliteration rates in the AVMv group were 38% at 3 yr, 65% at 4 yr, and 70% at 5 yr. Patients with an AVMv had no difference in the final obliteration rate compared to patients who did not have variceal drainage (P = .35). Actuarial hemorrhage after SRS in the matched patients with AVMv was 4.9%, 13%, and 13.7%, at 1, 3, and 5 yr, respectively. The rate of hemorrhage in the group with no varix was 2.9%, 5.4%, and 9.1% at 1, 3, and 5 yr, respectively (P = .14)., Conclusion: The presence of AVM variceal venous drainage did not affect the obliteration rate and did not confer a higher risk of a subsequent hemorrhage both before and after SRS., (© Congress of Neurological Surgeons 2021.)

Background: Pediatric brain arteriovenous malformations (AVMs) are a significant cause of morbidity but the role of multimodal therapy in the treatment of these lesions is not well understood., Objective: To compare the outcomes of stereotactic radiosurgery (SRS) with and without prior embolization for pediatric AVMs., Methods: We retrospectively evaluated the International Radiosurgery Research Foundation pediatric AVM database. AVMs were categorized, based on use of pre-embolization (E + SRS) or lack thereof (SRS-only). Outcomes were compared in unadjusted and inverse probability weight (IPW)-adjusted models. Favorable outcome was defined as obliteration without post-SRS hemorrhage or permanent radiation-induced changes (RIC)., Results: The E + SRS and SRS-only cohorts comprised 91 and 448 patients, respectively. In unadjusted models, the SRS-only cohort had higher rates of obliteration (68.5% vs 43.3%,  < .001) and favorable outcome (61.2% vs 36.3%, P < .001) but a lower rate of symptomatic RIC (9.0% vs 16.7%, P = .031). The IPW-adjusted rates of every outcome were similar between the 2 cohorts. However, cumulative obliteration rates at 3, 5, 8, and 10 yr remained higher in the absence of prior embolization (46.3%, 64.6%, 72.6%, and 77.4% for SRS-only vs 24.4%, 37.2%, 44.1%, and 48.7% for E + SRS cohorts, respectively; SHR = 0.449 [0.238-0.846], P = .013)., Conclusion: Embolization appears to decrease cumulative obliteration rates after SRS for pediatric AVMs without affecting the risk of post-treatment hemorrhage or adverse radiation effects arguing against the routine use of pre-SRS embolization. While endovascular therapy can be considered for occlusion of high-risk angioarchitectural features prior to SRS, future studies are necessary to clarify its role., (© Congress of Neurological Surgeons 2021.)

Background: Atypical and anaplastic meningiomas have reduced progression-free/overall survival (PFS/OS) compared to benign meningiomas. Stereotactic radiosurgery (SRS) for atypical meningiomas (AMs) and anaplastic meningiomas (malignant meningiomas, MMs) has not been adequately described., Objective: To define clinical/radiographic outcomes for patients undergoing SRS for AM/MMs., Methods: An international, multicenter, retrospective cohort study was performed to define clinical/imaging outcomes for patients receiving SRS for AM/MMs. Tumor progression was assessed with response assessment in neuro-oncology (RANO) criteria. Factors associated with PFS/OS were assessed using Kaplan-Meier analysis and a Cox proportional hazards model., Results: A total of 271 patients received SRS for AMs (n = 233, 85.9%) or MMs (n = 38, 14.0%). Single-fraction SRS was most commonly employed (n = 264, 97.4%) with a mean target dose of 14.8 Gy. SRS was used as adjuvant treatment (n = 85, 31.4%), salvage therapy (n = 182, 67.2%), or primary therapy (1.5%). The 5-yr PFS/OS rate was 33.6% and 77.0%, respectively. Increasing age (hazard ratio (HR) = 1.01, P < .05) and a Ki-67 index > 15% (HR = 1.66, P < .03) negatively correlated with PFS. MMs (HR = 3.21, P < .05), increased age (HR = 1.04, P = .04), and reduced KPS (HR = 0.95, P = .04) were associated with shortened OS. Adjuvant versus salvage SRS did not impact PFS/OS. A shortened interval between surgery and SRS improved PFS for AMs (HR = 0.99, P = .02) on subgroup analysis. Radiation necrosis occurred in 34 (12.5%) patients. Five-year rates of repeat surgery/radiation were 33.8% and 60.4%, respectively., Conclusion: AM/MMs remain challenging tumors to treat. Elevated proliferative indices are associated with tumor recurrence, while MMs have worse survival. SRS can control AM/MMs in the short term, but the 5-yr PFS rates are low, underscoring the need for improved treatment options for these patients., (© Congress of Neurological Surgeons 2021.)

Background: Choroid plexus tumors (CPT) are rare epithelial tumors of the choroid plexus. Gross total resection (GTR) may be curative, but it is not always possible., Objective: To evaluate the role of Gamma Knife stereotactic radiosurgery (GKSRS) as either a primary or adjuvant management option for WHO grade I-III CPT through a multicenter project., Methods: A total of 32 patients (20 females) with a total of 43 treated tumors were included in the analysis. A total of 25 patients (78%) had undergone initial surgical resection. The median total tumor volume was 2.2 cc, and the median margin and maximum doses were 13 and 25.5 Gy, respectively., Results: Local tumor control was achieved in 69% of cases. Local tumor progression-free survival (PFS) rate for low-grade tumors at 1, 3, and 5 yr was 90%, 77%, 58%, respectively. The actuarial local tumor PFS rate for high-grade tumors at 1, 3, and 5 yr was 77%, 62%, and 62%, respectively. There was no significant difference in local tumor control rates between low- and high-grade CPT (P = .3). Gender, age, and degree of resection were not associated with treated tumor PFS. Distant intracranial spread developed in 6 patients at a median of 22 mo after initial SRS. Actuarial distant brain tumor PFS rate at 1, 2, 5, and 10 yr was 93%, 88%, 78%, and 65%, respectively. Three patients (9%) developed persistent symptomatic adverse radiation effects at a median of 11 mo after the procedure., Conclusion: GKSRS represents a minimally invasive alternative management strategy for imaging defined or surgically recurrent low- and high-grade CPT., (© Congress of Neurological Surgeons 2020.)

Background: Facial nerve schwannomas are rare, challenging tumors to manage due to their nerve of origin. Functional outcomes after stereotactic radiosurgery (SRS) are incompletely defined., Objective: To analyze the effect of facial nerve segment involvement on functional outcome for these tumors., Methods: Patients who underwent single-session SRS for facial nerve schwannomas with at least 3 mo follow-up at 11 participating centers were included. Preoperative and treatment variables were recorded. Outcome measures included radiological tumor response and neurological function., Results: A total of 63 patients (34 females) were included in the present study. In total, 75% had preoperative facial weakness. Mean tumor volume and margin dose were 2.0 ± 2.4 cm3 and 12.2 ± 0.54 Gy, respectively. Mean radiological follow-up was 45.5 ± 38.9 mo. Progression-free survival at 2, 5, and 10 yr was 98.1%, 87.2%, and 87.2%, respectively. The cumulative proportion of patients with regressing tumors at 2, 5, and 10 yr was 43.1%, 63.6%, and 63.6%, respectively. The number of involved facial nerve segments significantly predicted tumor progression (P = .04). Facial nerve function was stable or improved in 57 patients (90%). Patients with involvement of the labyrinthine segment of the facial nerve were significantly more likely to have an improvement in facial nerve function after SRS (P = .03). Hearing worsened in at least 6% of patients. Otherwise, adverse radiation effects included facial twitching (3 patients), facial numbness (2 patients), and dizziness (2 patients)., Conclusion: SRS for facial nerve schwannomas is effective and spares facial nerve function in most patients. Some patients may have functional improvement after treatment, particularly if the labyrinthine segment is involved., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Despite a high incidence of brain metastases in patients with small-cell lung cancer (SCLC), limited data exist on the use of stereotactic radiosurgery (SRS), specifically Gamma Knife™ radiosurgery (Elekta AB), for SCLC brain metastases., Objective: To provide a detailed analysis of SCLC patients treated with SRS, focusing on local failure, distant brain failure, and overall survival (OS)., Methods: A multi-institutional retrospective review was performed on 293 patients undergoing SRS for SCLC brain metastases at 10 medical centers from 1991 to 2017. Data collection was performed according to individual institutional review boards, and analyses were performed using binary logistic regression, Cox-proportional hazard models, Kaplan-Meier survival analysis, and competing risks analysis., Results: Two hundred thirty-two (79%) patients received SRS as salvage following prior whole-brain irradiation (WBRT) or prophylactic cranial irradiation, with a median marginal dose of 18 Gy. At median follow-up after SRS of 6.4 and 18.0 mo for surviving patients, the 1-yr local failure, distant brain failure, and OS were 31%, 49%, and 28%. The interval between WBRT and SRS was predictive of improved OS for patients receiving SRS more than 1 yr after initial treatment (21%, <1 yr vs 36%, >1 yr, P = .01). On multivariate analysis, older age was the only significant predictor for OS (hazard ratio 1.63, 95% CI 1.16-2.29, P = .005)., Conclusion: SRS plays an important role in the management of brain metastases from SCLC, especially in salvage therapy following WBRT. Ongoing prospective trials will better assess the value of radiosurgery in the primary management of SCLC brain metastases and potentially challenge the standard application of WBRT in SCLC patients., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Long-term data regarding stereotactic radiosurgery (SRS) as a standalone therapy for unruptured pediatric brain arteriovenous malformations (AVMs) are incompletely defined., Objective: To evaluate, in a multicenter, retrospective cohort study, the outcomes after SRS for unruptured, intervention-naïve pediatric AVMs., Methods: To retrospectively analyze the International Radiosurgery Research Foundation pediatric AVM database from 1987 to 2018. Pediatric patients with unruptured, previously untreated AVMs who underwent SRS were included. The primary endpoint was a composite of hemorrhagic stroke, death, or permanently symptomatic radiation-induced changes., Results: The study cohort comprised 101 patients (mean follow-up 80.8 mo). The primary endpoint occurred in 14%, comprising hemorrhagic stroke, death, and permanent radiation-induced changes in 6%, 3%, and 8%, respectively. Estimated probabilities of the primary endpoint were 5.2%, 10.8%, and 23.0% at 2, 5, and 10 yr, respectively. Estimated probabilities of AVM obliteration at 5 and 10 yr were 64% and 82%, respectively. Single SRS treatment (P = .007) and higher margin dose (P = .005) were predictors of obliteration. Subgroup analysis of Spetzler-Martin grade I-III AVMs estimated primary endpoint probabilities of 3.7%, 8.4%, and 18.7% at 2, 5, and 10 yr, respectively., Conclusion: Treatment of unruptured, intervention-naïve AVMs in the pediatric population with SRS carries an approximately 2% annual risk of morbidity and mortality, which appears to plateau after 10 yr. The poorly described natural history of pediatric AVMs renders any comparison of SRS vs conservative management imperfect., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: There are presently no grading scales that specifically address the outcomes of cranial dural arteriovenous fistula (dAVF) after stereotactic radiosurgery (SRS)., Objective: To design a practical grading system that would predict outcomes after SRS for cranial dAVFs., Methods: From the International Radiosurgery Research Foundation (University of Pittsburgh [41 patients], University of Pennsylvania [6 patients], University of Sherbrooke [2 patients], University of Manitoba [1 patient], West Virginia University [2 patients], University of Puerto Rico [1 patient], Beaumont Health System 1 [patient], Na Homolce Hospital [13 patients], the University of Virginia [48 patients], and Yale University [6 patients]) centers, 120 patients with dAVF treated with SRS were included in the study. The factors predicting favorable outcome (obliteration without post-SRS hemorrhage) after SRS were assessed using logistic regression analysis. These factors were pooled with the factors that were found to be predictive of obliteration from 7 studies with 736 patients after a systematic review of literature. These were entered into stepwise multiple regression and the best-fit model was identified., Results: Based on the predictive model, 3 factors emerged to develop an SRS scoring system: cortical venous reflux (CVR), prior intracerebral hemorrhage (ICH), and noncavernous sinus location. Class I (score of 0-1 points) predicted the best favorable outcome of 80%. Class II patients (2 points score) had an intermediate favorable outcome of 57%, and class III (score 3 points) had the least favorable outcome at 37%. The ROC analysis showed better predictability to prevailing grading systems (AUC = 0.69; P = .04). Kaplan-Meier analysis showed statistically significant difference between the 3 subclasses of the proposed grading system for post-SRS dAVF obliteration (P = .001)., Conclusion: The proposed dAVF grading system incorporates angiographic, anatomic, and clinical parameters and improves the prediction of the outcomes following SRS for dAVF as compared to the existing scoring systems., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Targeted stereotactic radiosurgery (SRS) with sparing of the residual pituitary is the traditional radiosurgical method for pituitary adenomas. Whole-sella SRS is an alternative choice for radiologically indeterminate or large adenomas, the safety and efficacy of which has yet to be determined., Objective: To determine if whole-sella SRS in acromegaly would have comparable radiographic and biochemical control to targeted SRS. We performed a multicenter, retrospective matched cohort study to compare outcomes between groups., Methods: We conducted a retrospective review of acromegalic patients who underwent SRS from 1990 to 2016 at 10 centers participating in the International Radiosurgery Research Foundation. Whole-sella and targeted SRS patients were then matched in a 1:1 ratio., Results: A total of 128 patients were eligible for inclusion. Whole-sella patients had a higher pre-SRS random serum growth hormone, larger treatment volume, and higher maximum point dose to the optic apparatus. The rates of initial/durable endocrine remission, new loss of pituitary function, and new cranial neuropathy were similar between groups. Mortality and new visual deficit were higher in the whole-sella cohort, though not statistically significant., Conclusion: There was no difference in biochemical remission or recurrence between treatment groups. Although not statistically significant, the higher rates of tumor regression and lower rates of mortality and new visual deficit may suggest consideration of targeted SRS over whole-sella SRS in acromegaly treatment. Further research is needed to determine the association between visual deficits and mortality with whole-sella SRS., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Dural arteriovenous fistulas (DAVFs) can be categorized based on location., Objective: To compare stereotactic radiosurgery (SRS) outcomes between cavernous sinus (CS) and non-CS DAVFs and to identify respective outcome predictors., Methods: This is a retrospective study of DAVFs treated with SRS between 1988 and 2016 at 10 institutions. Patients' variables, DAVF characters, and SRS parameters were included for analyses. Favorable clinical outcome was defined as angiography-confirmed obliteration without radiological radiation-induced changes (RIC) or post-SRS hemorrhage. Other outcomes were DAVFs obliteration and adverse events (including RIC, symptomatic RIC, and post-SRS hemorrhage)., Results: The overall study cohort comprised 131 patients, including 20 patients with CS DAVFs (15%) and 111 patients with non-CS DAVFs (85%). Rates of favorable clinical outcome were comparable between the 2 groups (45% vs 37%, P = .824). Obliteration rate after SRS was higher in the CS DAVFs group, even adjusted for baseline difference (OR = 4.189, P = .044). Predictors of favorable clinical outcome included higher maximum dose (P = .014) for CS DAVFs. Symptomatic improvement was associated with obliteration in non-CS DAVFs (P = .005), but symptoms improved regardless of whether obliteration was confirmed in CS DAVFs. Non-CS DAVFs patients with adverse events after SRS were more likely to be male (P = .020), multiple arterial feeding fistulas (P = .018), and lower maximum dose (P = .041)., Conclusion: After SRS, CS DAVFs are more likely to obliterate than non-CS ones. Because these 2 groups have different total predictors for clinical and radiologic outcomes after SRS, they should be considered as different entities., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Stereotactic radiosurgery (SRS) is a highly effective management approach for patients with vestibular schwannomas (VS), with 10-yr control rates up 98%. When it fails, however, few data are available to guide management., Objective: To perform a retrospective analysis of patients who underwent 2 SRS procedures on the same VS to assess the safety and efficacy of this practice., Methods: This study was opened to centers of the International Gamma Knife Research Foundation (IGKRF). Data collected included patient characteristics, clinical symptoms at the time of SRS, radiosurgery dosimetric data, imaging response, clinical evolution, and survival. Actuarial analyses of tumor responses were performed., Results: Seventy-six patients from 8 IGKRF centers were identified. Median follow-up from the second SRS was 51.7 mo. Progression after the first SRS occurred at a median of 43 mo. Repeat SRS was performed using a median dose of 12 Gy. Actuarial tumor control rates at 2, 5, and 10 yr following the second SRS were 98.6%, 92.2%, and 92.2%, respectively. Useful hearing was present in 30%, 8%, and 5% of patients at first SRS, second SRS, and last follow-up, respectively. Seventy-five percent of patients reported stable or improved symptoms following the second SRS. Worsening of facial nerve function attributable to SRS occurred in 7% of cases. There were no reports of radionecrosis, radiation-associated edema requiring corticosteroids, radiation-related neoplasia, or death attributable to the repeat SRS procedure., Conclusion: Patients with progressing VS after radiosurgery can be safely and effectively managed using a second SRS procedure., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: Stereotactic radiosurgery (SRS) is a treatment option for persistent or recurrent acromegaly secondary to a growth hormone secreting pituitary adenoma, but its efficacy is inadequately defined., Objective: To assess, in a multicenter, retrospective cohort study, the outcomes of SRS for acromegaly and determine predictors., Methods: We pooled and analyzed data from 10 participating institutions of the International Gamma Knife Research Foundation for patients with acromegaly who underwent SRS with endocrine follow-up of ≥6 mo., Results: The study cohort comprised 371 patients with a mean endocrine follow-up of 79 mo. IGF-1 lowering medications were held in 56% of patients who were on pre-SRS medical therapy. The mean SRS treatment volume and margin dose were 3.0 cm3 and 24.2 Gy, respectively. The actuarial rates of initial and durable endocrine remission at 10 yr were 69% and 59%, respectively. The mean time to durable remission after SRS was 38 mo. Biochemical relapse after initial remission occurred in 9%, with a mean time to recurrence of 17 mo. Cessation of IGF-1 lowering medication prior to SRS was the only independent predictor of durable remission (P = .01). Adverse radiation effects included the development of ≥1 new endocrinopathy in 26% and ≥1 cranial neuropathy in 4%., Conclusion: SRS is a definitive treatment option for patients with persistent or recurrent acromegaly after surgical resection. There appears to be a statistical association between the cessation of IGF-1 lowering medications prior to SRS and durable remission., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: Facial pain response (PR) to various surgical interventions in patients with multiple sclerosis (MS)-related trigeminal neuralgia (TN) is much less optimal. No large patient series regarding stereotactic radiosurgery (SRS) has been published., Objective: To evaluate the clinical outcomes of MS-related TN treated with SRS., Methods: This is a retrospective cohort study. A total of 263 patients contributed by 9 member tertiary referral Gamma Knife centers (2 in Canada and 7 in USA) of the International Gamma Knife Research Consortium (IGKRF) constituted this study., Results: The median latency period of PR after SRS was 1 mo. Reasonable pain control (Barrow Neurological Institute [BNI] Pain Scores I-IIIb) was achieved in 232 patients (88.2%). The median maintenance period from SRS was 14.1 months (range, 10 days to 10 years). The actuarial reasonable pain control maintenance rates at 1 yr, 2 yr, and 4 yr were 54%, 35%, and 24%, respectively. There was a correlation between the status of achieving BNI-I and the maintenance of facial pain recurrence-free rate. The median recurrence-free rate was 36 mo and 12.2 mo in patients achieving BNI-I and BNI > I, respectively (P = .046). Among 210 patients with known status of post-SRS complications, the new-onset of facial numbness (BNI-I or II) after SRS occurred in 21 patients (10%)., Conclusion: In this largest series SRS offers a reasonable benefit to risk profile for patients who have exhausted medical management. More favorable initial response to SRS may predict a long-lasting pain control.

Background: Stereotactic radiosurgery (SRS) is a potentially important option for intracranial ependymoma patients., Objective: To analyze the outcomes of intracranial ependymoma patients who underwent SRS as a part of multimodality management., Methods: Seven centers participating in the International Gamma Knife Research Foundation identified 89 intracranial ependymoma patients who underwent SRS (113 tumors). The median patient age was 16.3 yr (2.9-80). All patients underwent previous surgical resection and radiation therapy (RT) of their ependymomas and 40 underwent previous chemotherapy. Grade 2 ependymomas were present in 42 patients (52 tumors) and grade 3 ependymomas in 48 patients (61 tumors). The median tumor volume was 2.2 cc (0.03-36.8) and the median margin dose was 15 Gy (9-24)., Results: Forty-seven (53%) patients were alive and 42 (47%) patients died at the last follow-up. The overall survival after SRS was 86% at 1 yr, 50% at 3 yr, and 44% at 5 yr. Smaller total tumor volume was associated with longer overall survival (P = .006). Twenty-two patients (grade 2: n = 9, grade 3: n = 13) developed additional recurrent ependymomas in the craniospinal axis. The progression-free survival after SRS was 71% at 1 yr, 56% at 3 yr, and 48% at 5 yr. Adult age, female sex, and smaller tumor volume indicated significantly better progression-free survival. Symptomatic adverse radiation effects were seen in 7 patients (8%)., Conclusion: SRS provides another management option for residual or recurrent progressive intracranial ependymoma patients who have failed initial surgery and RT.

Background: The management of brainstem arteriovenous malformations (bAVMs) is a formidable challenge. bAVMs harbor higher morbidity and mortality compared to other locations., Objective: To review the outcomes following stereotactic radiosurgery (SRS) of bAVMs in a multicenter study., Methods: Six medical centers contributed data from 205 patients through the International Gamma Knife Research Foundation. Median age was 32 yr (6-81). Median nidus volume was 1.4 mL (0.1-69 mL). Favorable outcome (FO) was defined as AVM obliteration and no post-treatment hemorrhage or permanent symptomatic radiation-induced complications., Results: Overall obliteration was reported in 65.4% (n = 134) at a mean follow-up of 69 mo. Obliteration was angiographically proven in 53.2% (n = 109) and on MRA in 12.2% (n = 25). Actuarial rate of obliteration at 2, 3, 5, 7, and 10 yr after SRS was 24.5%, 43.3%, 62.3%, 73%, and 81.8% respectively. Patients treated with a margin dose >20 Gy were more likely to achieve obliteration (P = .001). Obliteration occurred earlier in patients who received a higher prescribed margin dose (P = .05) and maximum dose (P = .041). Post-SRS hemorrhage occurred in 8.8% (n = 18). Annual postgamma knife latency period hemorrhage was 1.5%. Radiation-induced complications were radiologically evident in 35.6% (n = 73), symptomatic in 14.6% (n = 30), and permanent in 14.6% (n = 30, which included long-tract signs and new cranial nerve deficits). FO was achieved in 64.4% (n = 132). Predictors of an FO were a higher Virginia radiosurgery AVM scale score (P = .003), prior hemorrhage (P = .045), and a lower prescribed maximum dose (P = .006)., Conclusion: SRS for bAVMs results in obliteration and avoids permanent complications in the majority of patients., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: The role of intervention in the management of unruptured brain arteriovenous malformations (AVM) is controversial., Objective: To analyze in a multicenter, retrospective cohort study, the outcomes following radiosurgery for unruptured AVMs and determine predictive factors., Methods: We evaluated and pooled AVM radiosurgery data from 8 institutions participating in the International Gamma Knife Research Foundation. Patients with unruptured AVMs and ≥12 mo of follow-up were included in the study cohort. Favorable outcome was defined as AVM obliteration, no postradiosurgical hemorrhage, and no permanently symptomatic radiation-induced changes., Results: The unruptured AVM cohort comprised 938 patients with a median age of 35 yr. The median nidus volume was 2.4 cm 3 , 71% of AVMs were located in eloquent brain areas, and the Spetzler-Martin grade was III or higher in 57%. The median radiosurgical margin dose was 21 Gy and follow-up was 71 mo. AVM obliteration was achieved in 65%. The annual postradiosurgery hemorrhage rate was 1.4%. Symptomatic and permanent radiation-induced changes occurred in 9% and 3%, respectively. Favorable outcome was achieved in 61%. In the multivariate logistic regression analysis, smaller AVM maximum diameter ( P = .001), the absence of AVM-associated arterial aneurysms ( P = .001), and higher margin dose ( P = .002) were found to be independent predictors of a favorable outcome. A margin dose ≥ 20 Gy yielded a significantly higher rate of favorable outcome (70% vs 36%; P < .001)., Conclusion: Radiosurgery affords an acceptable risk to benefit profile for patients harboring unruptured AVMs. These findings justify further prospective studies comparing radiosurgical intervention to conservative management for unruptured AVMs., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: Vestibular schwannoma patients with Gardner-Robertson (GR) class I hearing seek to maintain high-level hearing whenever possible., Objective: To evaluate hearing outcomes at 2 to 3 years in GR class I patients who underwent Gamma Knife radiosurgery (GKRS)., Methods: Sixty-eight patients with GR class I hearing were identified between 2006 and 2009. Twenty-five patients had no subjective hearing loss (group A) and 43 patients reported subjective hearing loss (group B) before GKRS. The median tumor volume (1 cm) and tumor margin dose (12.5 Gy) were the same in both groups., Results: Serviceable hearing retention rates (GR grade I or II) were 100% for group A compared with 81% at 1 year, 60% at 2 years, and 57% at 3 years after GKRS for group B patients. Group A patients had significantly higher rates of hearing preservation in either GR class I (P < .001) or GR class II (P < .001). Patients with a pure tone average (PTA) <15 dB before GKRS had significantly higher rates of preservation of GR class I or II hearing., Conclusion: At 2 to 3 years after GKRS, patients without subjective hearing loss or a PTA <15 dB had higher rates of grade I or II hearing preservation. Modification of the GR hearing classification into 2 groups of grade I hearing (group A, those with no subjective hearing loss and a PTA <15 dB; and group B, those with subjective hearing loss and a PTA >15 dB) may be useful to help predict hearing preservation rates at 2 to 3 years after GKRS.

Background: Resection of cerebellopontine angle (CPA) meningiomas may result in significant neurological morbidity. Radiosurgery offers a minimally invasive alternative to surgery., Objective: To evaluate, in a multicenter cohort study, the outcomes of patients harboring CPA meningiomas who underwent Gamma Knife radiosurgery (GKRS)., Methods: From 7 institutions participating in the North American Gamma Knife Consortium, 177 patients with benign CPA meningiomas treated with GKRS and at least 6 months radiologic follow-up were included for analysis. The mean age was 59 years and 84% were female. Dizziness or imbalance (48%) and cranial nerve (CN) VIII dysfunction (45%) were the most common presenting symptoms. The median tumor volume and prescription dose were 3.6 cc and 13 Gy, respectively. The mean radiologic and clinical follow-up durations were 47 and 46 months, respectively. Multivariate regression analyses were performed to identify the predictors of tumor progression and neurological deterioration., Results: The actuarial rates of progression-free survival at 5 and 10 years were 93% and 77%, respectively. Male sex (P = .014), prior fractionated radiation therapy (P = .010), and ataxia at presentation (P = .002) were independent predictors of tumor progression. Symptomatic adverse radiation effects and permanent neurological deterioration were observed in 1.1% and 9% of patients, respectively. Facial spasms at presentation (P = .007) and lower maximal dose (P = .011) were independently associated with neurological deterioration., Conclusion: GKRS is an effective therapy for CPA meningiomas. Depending on the patient and tumor characteristics, radiosurgery can be an adjuvant treatment to initial surgical resection or a standalone procedure that obviates the need for resection in most patients.

Background: Stereotactic radiosurgery (SRS) to the resection bed of a brain metastasis is an important treatment option., Objective: To identify factors associated with tumor progression after SRS of the resection bed of a brain metastasis and to evaluate patterns of failure for patients who eventually had tumor progression., Methods: We performed a retrospective analysis of 120 patients who underwent tumor bed radiosurgery after an initial gross total resection. The mean imaging follow-up time was 55 weeks. The median margin dose was 16 Gy. Forty-seven patients (39.2%) underwent whole-brain radiation therapy before or shortly after SRS., Results: Local tumor control was achieved in 103 patients (85.8%). Progression-free survival was 96% at 6 months, 87% at 12 months, and 74% at 24 months. Recurrence most commonly occurred deep in the cavity (65%) outside the planned treatment volume (PTV) margin (53%). PTV, cavity diameter, and a margin dose < 16 Gy significantly correlated with local failure. For patients with PTVs ≥ 8.0 cm, local progression-free survival declined to 93% at 6 months, 83% at 12 months, and 65% at 24 months. Development or progression of distant metastases occurred in 40% of patients. Whole-brain radiation therapy was not associated with improved local control., Conclusion: Resection bed SRS for brain metastases provided excellent local control. The cavity PTV is predictive of tumor control. Because failure usually occurs outside the PTV, inclusion of a judicious 2- to 3-mm margin beyond the area of postoperative enhancement may be prudent.

Background: Stereotactic radiosurgery (SRS) is an important option for patients with cavernous sinus meningiomas., Objective: To evaluate cranial nerve outcomes in patients who underwent SRS for cavernous sinus meningiomas with or without prior microsurgery., Methods: During a 23-year interval, 272 patients underwent Gamma Knife SRS for cavernous sinus meningiomas (70 men, 202 women; median age, 54 years). In this series, 99 patients underwent prior microsurgical resection. The median tumor volume was 7.9 cm and median marginal dose was 13 Gy. The median follow-up period was 62 months (range, 6-209 months)., Results: The progression-free survival after SRS was 96% at 3 years, 94% at 5 years, and 86% at 10 years. After SRS, 13 of 91 patients (14%) who underwent prior microsurgery had improvement of preexisting cranial nerve symptoms or signs. In comparison, 54 of 145 patients (37%) without prior microsurgery had improvement of preexisting cranial nerve symptoms or signs. The improvement rate of cranial nerve deficits after SRS in patients without prior microsurgery was 20% at 1 year, 34% at 2 years, 36% at 3 years, and 39% at 5 years. Patients who had not undergone prior microsurgery had significantly higher improvement rates of preexisting cranial nerve symptoms and signs (P = .001). After SRS, 29 patients (11%) developed new or worsened cranial nerve function., Conclusion: SRS provided long-term effective tumor control and a low risk of new cranial nerve deficits. Improvement in preexisting cranial neuropathies was detected in significantly more patients who had not undergone prior microsurgical procedures.

Background: Trigeminal neuralgia (TN) may recur after treatment by gamma knife stereotactic radiosurgery (GKSR)., Objective: To evaluate management outcomes in patients who underwent repeat GKSR for TN., Methods: The authors reviewed their experience with repeat GKSR in 119 patients with recurrent TN. The median patient age was 74 years (range, 34-96 years). The median interval between procedures was 26 months. The median target dose for repeat GKSR was 70 Gy (range, 50-90 Gy) and the median cumulative dose was 145 Gy (range, 120-170 Gy). The median follow-up was 48 months (range, 6-187 months) after repeat GKSR., Results: After repeat GKSR, 87% of patients achieved initial pain relief (Barrow Neurological Institute pain score I-IIIb). Pain relief was maintained in 87.8% at 1 year, 69.8% at 3 years, and 44.2% at 5 years. Facial sensory dysfunction occurred in 21% of patients within 18 months after GKSR. Longer pain relief was observed in patients who had recurrent pain in a reduced pain distribution of the face compared with the pain distribution at the time of their initial GKSR, and in those who developed additional trigeminal sensory loss after a repeat procedure. A cumulative edge of brainstem dose ≥ 44 Gy was more likely to be associated with the development of sensory loss., Conclusion: Repeat GKSR provides a similar rate of pain relief as the first procedure. The best responses were observed in patients who had good pain control after the first procedure and those who developed new sensory dysfunction in the affected trigeminal distribution.

Background: Although whole-brain radiation therapy (WBRT) has been a standard palliative management for brain metastases from renal cell carcinoma, its benefit has been elusive because of radiobiological resistance., Objective: To evaluate the role of stereotactic radiosurgery (SRS) in the management of brain metastases from renal cell carcinoma., Methods: We reviewed records from 158 consecutive patients (men = 111, women = 47) who underwent SRS for 531 brain metastases from renal cell carcinoma. The median patient age was 61 years (range, 38-83 years), and the median number of tumors per patient was 1 (range, 1-10). Seventy-nine patients (50%) had solitary brain metastasis. Fifty-seven patients (36%) underwent prior WBRT. The median total tumor volume for each patient was 3.0 cm3 (range, 0.09-47 cm)., Results: The overall survival after SRS was 60%, 38%, and 19% at 6, 12, and 24 months, respectively, with a median survival of 8.2 months. Factors associated with longer survival included younger age, longer interval between primary diagnosis and brain metastases, lower recursive partitioning analysis class, higher Karnofsky performance status, smaller number of brain metastases, and no prior WBRT. Median survival for patients with < 2 brain metastases, higher Karnofsky performance status (> 90), and no prior WBRT was 12 months after SRS. Sustained local tumor control was achieved in 92% of patients. Symptomatic adverse radiation effects occurred in 7%. Overall, 70% of patients improved or remained neurologically stable., Conclusion: Stereotactic radiosurgery is an especially valuable option for patients with higher Karnofsky performance status and smaller number of brain metastases from renal cell carcinoma.

Background: Nonfunctional pituitary adenomas (NFPAs) represent approximately 50% of all pituitary tumors., Objective: To evaluate the long-term outcomes of stereotactic radiosurgery for NFPAs., Methods: We evaluated the management outcomes of Gamma Knife radiosurgery in 125 patients with NFPAs over an interval of 22 years. The median patient age was 54 years (range, 16-88 years). One hundred ten patients (88%) had residual or recurrent tumors after ≥ 1 surgical procedures, and 17 (14%) had undergone prior fractionated radiation therapy. The median target volume was 3.5 cm3 (range, 0.4-28.1 cm3), and the median tumor margin dose was 13.0 Gy (range, 10-25 Gy)., Results: Tumor volume decreased in 66 patients (53%), remained stable in 46 (37%), and increased in 13 (10.4%) during a median of 62 months (maximum, 19 years) of imaging follow-up. The actuarial tumor control rates at 1, 5, and 10 years were 99%, 94%, and 76%, respectively. Factors associated with a reduced progression-free survival included larger tumor volume (≥ 4.5 cm3) and ≥ 2 prior recurrences. Of 88 patients with residual pituitary function, 21 (24%) suffered new hormonal deficits at a median of 24 months (range, 3-114 months). Prior radiation therapy increased the risk of developing new pituitary hormonal deficits. One patient (0.8%) had a decline in visual function, and 2 (1.6%) developed new cranial neuropathies without tumor progression., Conclusion: Stereotactic radiosurgery can provide effective management for patients with newly diagnosed NFPAs and for those after prior resection and/or radiation therapy.

Background: Approximately 20 to 40% of patients with systemic malignancies develop brain metastases., Objective: To assess the potential role of stereotactic radiosurgery (SRS) for larger metastatic brain tumors, we reviewed our recent experience., Methods: Between 2004 and 2008, 70 patients with a metastatic brain tumor larger than 3 cm in maximum diameter underwent Gamma knife SRS. Thirty-three patients had received previous whole brain radiation therapy (WBRT) and 37 received only SRS., Results: The overall median follow-up was 8.1 months. At the first planned imaging follow-up at 2 months, 29 (41%) tumors had >50% volume reduction, 22 (31%) had 10 to 50% volume reduction, and 19 (28%) were stable or larger. We also evaluated brain edema using MRI T2 images. In 11 patients (16%) the peritumoral edema volume was reduced by more than 50%, in 25 (36%) it was reduced by 10 to 50%, in 21 (30%) it was stable, and in 13 (19%) it was increased. Twenty (36%) discontinued corticosteroids by the time of first imaging follow-up. Because of persistent symptoms, 7 patients (10%) required a craniotomy to remove the tumor. Tumor volume reduction (>50%) was associated with a single metastasis (P=.012), no previous WBRT (P=.002), and a tumor volume<16 cm3 (P=.002). The better peritumoral edema volume reduction (>50%) was associated with a single metastasis (P=.024), no previous WBRT (P=.05), and breast cancer histology (P=.044)., Conclusion: Surgical resection remains the primary approach for larger brain metastases if feasible. Tumor volume is a better indicator than maximum diameter. Tumor volume and edema responded better in patients who underwent SRS alone.

Background: Although considered slow-growing, low-grade malignancies, chordomas are locally aggressive and destructive tumors with high recurrence rates., Objective: To assess patient survival, tumor control, complications, and selected variables that predict outcome in patients who underwent Gamma Knife stereotactic radiosurgery (SRS) as primary, adjuvant, or salvage management for chordomas of the skull base., Methods: Six participating centers of the North American Gamma Knife Consortium identified 71 patients who underwent SRS for chordoma. The median patient age was 45 years (range, 7-80 years). The median SRS target volume was 7.1 cm³ (range, 0.9-109 cm³), and median margin dose was 15.0 Gy (range, 9-25 Gy)., Results: At a median follow-up of 5 years (range, 0.6-14 years) after SRS, 23 patients died of tumor progression. The 5-year actuarial overall survival after SRS was 80% for the entire group, 93% for the no prior fractionated radiation therapy (RT) group (n = 50), and 43% for the prior RT group (n = 21). Younger age, longer interval between initial diagnosis and SRS, no prior RT, < 2 cranial nerve deficits, and smaller total tumor volume were significantly associated with longer patient survival. The 5-year treated tumor control rate after SRS was 66% for the entire group, 69% for the no prior RT group, and 62% for the prior RT group. Older age, recurrent group, prior RT, and larger tumor volume were significantly associated with worse tumor control., Conclusion: Stereotactic radiosurgery is a potent treatment option for small sized chordomas, especially in younger patients and as part of a multipronged attack that includes surgical resection when possible.

Background: Trigeminal neuralgia (TN) that recurs after surgery can be difficult to manage., Objective: To define management outcomes in patients who underwent gamma knife stereotactic radiosurgery (GKSR) after failing 1 or more previous surgical procedures., Methods: We retrospectively reviewed outcomes after GKSR in 193 patients with TN after failed surgery. The median patient age was 70 years (range, 26-93 years). Seventy-five patients had a single operation (microvascular decompression, n=40; glycerol rhizotomy, n=24; radiofrequency rhizotomy, n=11). One hundred eighteen patients underwent multiple operations before GKSR. Patients were evaluated up to 14 years after GKSR., Results: After GKSR, 85% of patients achieved pain relief or improvement (Barrow Neurological Institute grade I-IIIb). Pain recurrence was observed in 73 of 168 patients 6 to 144 months after GKSR (median, 6 years). Factors associated with better long-term pain relief included no relief from the surgical procedure preceding GKSR, pain in a single branch, typical TN, and a single previous failed surgical procedure. Eighteen patients (9.3%) developed new or increased trigeminal sensory dysfunction, and 1 developed deafferentation pain. Patients who developed sensory loss after GKSR had better long-term pain control (Barrow Neurological Institute grade I-IIIb: 86% at 5 years)., Conclusion: GKSR proved to be safe and moderately effective in the management of TN that recurs after surgery. Development of sensory loss may predict better long-term pain control. The best candidates for GKSR were patients with recurrence after a single failed previous operation and those with typical TN in a single trigeminal nerve distribution.

Background: Treatment options for dural arteriovenous fistulas (DAVFs) have expanded with the application of stereotactic radiosurgery (SRS)., Objective: To assess the role of SRS with or without embolization, we reviewed our entire DAVF experience., Methods: Between 1991 and 2006, 40 patients with 44 DAVFs underwent Gamma knife SRS. Twenty-eight patients had upfront SRS before or after embolization and 12 patients underwent delayed SRS for recurrent or residual DAVFs after initial embolization. The median patient age was 60 years (range, 29-90). DAVFs were diagnosed in 7 patients after they sustained an intracranial hemorrhage. The median SRS target volume was 2.0 mL (range, 0.2-8.2 mL) and the median marginal dose was 21.0 Gy (range, 15-25 Gy)., Results: At a median follow-up of 45 months (range, 23-116 mo), a total of 28 patients (harboring 32 DAVFs) had obliteration confirmed by imaging. We found a 83% obliteration rate in patients who had upfront SRS with embolization and a 67% obliteration rate in patients who only had SRS. One patient died of an intracerebral hemorrhage 2 months after SRS. Cavernous carotid fistulas were associated with higher rates of occlusion (P = .012) and symptom improvement (P = .010) than were transverse-sigmoid sinus-related fistulas., Conclusion: When upfront SRS is possible in conjunction with embolization, successful DAVF obliteration is possible in most patients, especially those with carotid cavernous fistulas. SRS should target the entire fistula regardless of whether it precedes or follows embolization. In selected patients with a small-volume, low-risk DAVF, SRS alone is an effective treatment option in most patients.

Objective: We define magnetic resonance imaging (MRI) and clinical criteria that differentiate radiation effect (RE) from tumor progression after stereotactic radiosurgery (SRS)., Methods: We correlated postoperative imaging and histopathological data in 68 patients who underwent delayed resection of a brain metastasis after SRS. Surgical resection was required in these patients because of clinical and imaging evidence of lesion progression 0.3 to 27.7 months after SRS. At the time of SRS, the median target volume was 7.1 mL (range, 0.5-26 mL), which increased to 14 mL (range, 1.3-81 mL) at the time of surgery. After initial SRS, routine contrast-enhanced MRI was used to assess tumor response and to detect potential adverse radiation effects. We retrospectively correlated these serial MRIs with the postoperative histopathology to determine if any routine MRI features might differentiate tumor progression from RE., Results: The median time from SRS to surgical resection was 6.9 months (range, 0.3-27.7 months). A shorter interval from SRS to resection was associated with a higher rate of tumor recurrence (P = .014). A correspondence between the contrast-enhanced volume on T1-weighted images and the low signal-defined lesion margin on T2-weighted images ("T1/T2 match") was associated with tumor progression at histopathology (P < .0001). Lack of a clear and defined lesion margin on T2-weighted images compared to the margin of contrast uptake on T1-weighted images ("T1/T2 mismatch") was significantly associated with a higher rate of RE in pathological specimens (P < .0001). The sensitivity of the T1/T2 mismatch in identifying RE was 83.3%, and the specificity was 91.1%., Conclusions: We found that time to progression and T1/T2 mismatch were able to differentiate tumor progression from RE in most patients. When REs are suspected, surgery may not be necessary if patients respond to conservative measures. When tumor progression is suspected, resection or repeat radiosurgery can be effective, depending on the degree of mass effect.

Objective: Hemangiomas are rare but highly vascular tumors that may develop in the cavernous sinus or orbit. These tumors pose diagnostic as well as therapeutic challenges to neurosurgeons during attempted removal. We analyzed our increasing experience using stereotactic radiosurgery (SRS)., Methods: Eight symptomatic patients with hemangiomas underwent SRS between 1988 and 2007. The presenting symptoms included headache, orbital pain, diplopia, ptosis, proptosis and impaired visual acuity. The hemangiomas were located in either the cavernous sinus (7 patients) or the orbit (1 patient). Four patients underwent SRS as primary treatment modality based on clinical and imaging criteria. Four patients had previous microsurgical partial excision or biopsy. The median target volume was 6.8 mL (range, 2.5-18 mL). The median prescription dose delivered to the margin was 14.5 Gy (range, 12.5-19 Gy). The dose to the optic nerve in all patients was less than 9 Gy (range, 4.5-9 Gy)., Results: The median follow-up period after SRS was 80 months (range, 40-127 months). Six patients had symptomatic improvement; 2 patients reported persistent diplopia. Follow-up imaging revealed tumor regression in 7 patients and no change in tumor volume in 1 patient. All the patients improved after SRS., Conclusion: Our extended experience confirms that SRS is an effective management strategy for symptomatic intracavernous and intraorbital hemangiomas. Our study is the first long-term report on the safety and efficacy of SRS.

Objective: Management options for patients with vestibular schwannoma include observation, surgical resection, stereotactic radiosurgery (SRS), and stereotactic radiation therapy. In younger patients, resection is often advocated because of concern regarding the long-term effects of radiation. We studied tumor response and clinical outcomes after SRS in such patients., Methods: We reviewed long-term outcomes in 55 patients with vestibular schwannomas. Patients were 40 years of age or younger, underwent gamma knife (GK) SRS between 1987 and 2003, and were followed up for a minimum of 4 years. The median patient age was 35 years (range, 13-40 years). Forty-one patients had Gardner-Robertson class 1 to 4 hearing. Thirteen patients (24%) had undergone surgical removal. The median tumor volume was 1.7 mm. The median tumor margin dose was 13.0 Gy (range, 11-20 Gy)., Results: At a median of 5.3 years, (range, 4-20 years), 2 of 55 patients underwent GK SRS for a second time; 1 of these patients had had a recurrence after initial resection. The 5-year rate of freedom from additional management was 96%. Hearing preservation rates (i.e., remaining within the same Gardner-Robertson hearing class) were 93%, 87%, and 87% at 3, 5, and 10 years, respectively. In patients with serviceable hearing before SRS, it was maintained in 100%, 93%, and 93% of patients at 3, 5, and 10 years, respectively. Hearing preservation was related to a margin dose lower than 13 Gy (P = 0.017). At the last assessment, facial and trigeminal nerve function was preserved in 98.2% and 96.4% of patients, respectively; the only facial deficit (House-Brackmann grade III) occurred in a patient who received a tumor dose of 20 Gy early in our experience (1988). None of the patients treated with doses lower than 13 Gy experienced facial or trigeminal neuropathy. All patients continued their previous level of activity or employment after GK SRS. No patient developed a secondary radiation-related tumor., Conclusion: Our experience indicates that GK SRS is an effective management strategy for younger patients with vestibular schwannoma, most of whom have no additional cranial nerve dysfunction.

Objective: Radiation-induced meningiomas of the brain are typically managed with surgical resection. Stereotactic radiosurgery (SRS) has become an important primary or adjuvant management for patients with intracranial meningiomas, but the value of this approach for radiation-induced tumors is unclear., Methods: This series consisted of 19 patients (mean age, 40 years) with 24 tumors. The patients met criteria for a radiation-induced meningioma and underwent gamma knife radiosurgery. Seven patients had undergone a previous resection. The World Health Organization tumor grades for those with prior histology were Grade I (n = 5) and Grade II (n = 2). The median tumor volume was 4.4 cm3. Radiosurgery was performed using a median margin dose of 13 Gy., Results: Serial imaging was evaluated in all patients at a median follow-up of 44 months. The control rate was 75% after primary radiosurgery. Delayed resection after radiosurgery was performed in 5 patients (26%) at an average of 39 months. The median latency between radiation therapy for original disease and SRS for radiation-induced meningiomas was 29.7 years (range, 7.3-59.0 years). The overall survival after SRS was 94.1% and 80.7% at 3 and 5 years, respectively. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 5.3% (1 optic neuropathy). Asymptomatic peritumoral imaging changes compatible with an adverse radiation effect developed in 1 patient., Conclusion: SRS provides satisfactory control rates either after resection or as an alternative to resection. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection.

Objective: To develop outcome predictors after stereotactic radiosurgery (SRS) in patients with intracranial ependymomas who had received previous fractionated radiation therapy, we compared tumor control, survival, and complications with tumor grade, volume, age of patients, and imaging characteristics., Methods: We retrospectively reviewed records of 39 consecutive ependymoma patients who underwent SRS for 56 tumors. The median patient age was 22.8 years (range, 2.9-71.1 years). All patients had previous surgical resection of their ependymomas followed by radiotherapy, and 14 patients underwent previous chemotherapy. Twenty-five patients had low-grade ependymomas (34 tumors), and 14 patients had anaplastic ependymomas (22 tumors). The median radiosurgery target volume was 3.6 cm (range, 0.1-36.8 cm), and the median margin dose was 15.0 Gy (range, 10-22 Gy)., Results: At a median of 23.5 months after SRS (range, 6.1-155.2 months), 25 patients died as a result of metastases (12 patients) or disease progression (13 patients). The overall survival rates after SRS were 60.1, 36.1, and 32.1% at 1, 3, and 5 years, respectively. The progression-free survival rates after SRS at 1, 3, and 5 years were 81.6, 45.8, and 45.8%, respectively, for all grades of ependymomas. Lower histological tumor grade was not significantly associated with better progression-free survival (P = 0.725). Factors associated with an improved progression-free survival included smaller tumor volume and homogeneous tumor contrast enhancement in low-grade ependymomas., Conclusion: SRS provides another management option for patients with residual or recurrent ependymomas that have failed surgery and radiation therapy. Predictors of response include smaller volume and homogeneous contrast enhancement.

Objective: One of the key limitations of gamma knife surgery arises from the radiation safety tolerance limit of the brainstem. The authors conducted an analysis of patients with intra-axial brainstem lesions and documented the incidence of adverse radiation imaging effects (ARIE) and new neurological deficits after gamma knife surgery., Methods: Thirty-eight patients (39 lesions) with intra-axial brainstem astrocytomas or vascular malformations underwent gamma knife surgery during a 6-year interval. Brainstem exposure volume was calculated by subtracting the volume within the 12-Gy isodose line (12 Gray volume) from the prescription volume. ARIE was defined as a new parenchymal signal alteration on follow-up magnetic resonance imaging sequences., Results: The average prescription volume was 1.46 cm, 12 Gy volume was 2.03 cm, and brainstem exposure volume was 0.57 cm. Seven (18.4%) patients developed ARIE. ARIE correlated only with the presence of new neurological deficits and age younger than 40 years. Three (7.9%) patients developed minor residual deficits without any ARIE. There was no mortality., Conclusion: Exposure of the brainstem to more than 12 Gy at volumes as low as 0.1 cm can produce ARIE and new neurological deficits. The tolerance of the brainstem to radiosurgery is related to patient age, lesion volume, and pathology. Analysis of the exposed volume of brainstem tissue may be useful in radiosurgical planning for individual patients.

Objective: To evaluate the role of stereotactic radiosurgery (SRS) in the management of recurrent or residual intracranial hemangioblastomas, we assessed tumor control, survival, and complications in 32 consecutive patients., Methods: We retrospectively reviewed records of 32 consecutive hemangioblastoma patients (74 intracranial tumors) who underwent gamma knife SRS. The median patient age was 43.8 years (range, 21.3-79.4 yr). Thirty-one patients had undergone previous surgical resections. Nineteen patients had sporadic lesions (22 tumors), and 13 patients had von Hippel-Lindau disease-associated hemangioblastomas (52 tumors). The median SRS target volume was 0.72 mL (range, 0.08-16.6 mL), and the median marginal dose was 16.0 Gy (range, 11-20 Gy)., Results: At a median of 50.1 months (range, 6.0-165.4 mo), seven patients had died from disease progression, and one patient had died secondary to heart failure. The overall survival after radiosurgery was 100%, 94.4%, and 68.7% at 1, 3, and 7 years, respectively. Follow-up imaging studies demonstrated tumor control in 68 tumors (91.9%). The progression-free survival after SRS at 1, 3, and 5 years was 96.9%, 95.0%, and 89.9%, respectively. Factors associated with an improved progression-free survival included von Hippel-Lindau disease-associated hemangioblastoma, solid tumor, lower tumor volume, and greater marginal dose., Conclusion: SRS is an important tool in the management of hemangioblastomas and is associated with a high tumor control rate and a low risk of adverse radiation effects.