Vascular compactness of unruptured brain arteriovenous malformation predicts risk of hemorrhage after stereotactic radiosurgery

The aim of the study was to investigate whether morphology (i.e. compact/diffuse) of brain arteriovenous malformations (bAVMs) correlates with the incidence of hemorrhagic events in patients receiving Stereotactic Radiosurgery (SRS) for unruptured bAVMs. This retrospective study included 262 adult patients with unruptured bAVMs who underwent upfront SRS. Hemorrhagic events were defined as evidence of blood on CT or MRI. The morphology of bAVMs was evaluated using automated segmentation which calculated the proportion of vessel, brain tissue, and cerebrospinal fluid in bAVMs on T2-weighted MRI. Compactness index, defined as the ratio of vessel to brain tissue, categorized bAVMs into compact and diffuse types based on the optimal cutoff. Cox proportional hazard model was used to identify the independent factors for post-SRS hemorrhage. The median clinical follow-ups was 62.1 months. Post-SRS hemorrhage occurred in 13 (5.0%) patients and one of them had two bleeds, resulting in an annual bleeding rate of 0.8%. Multivariable analysis revealed bAVM morphology (compact versus diffuse), bAVM volume, and prescribed margin dose were significant predictors. The post-SRS hemorrhage rate increased with larger bAVM volume only among the diffuse nidi (1.7 versus 14.9 versus 30.6 hemorrhage per 1000 person-years in bAVM volume < 20 cm3 versus 20-40 cm3 versus > 40 cm3; p = 0.022). The significantly higher post-SRS hemorrhage rate of Spetzler-Martin grade IV-V compared with grade I-III bAVMs (20.0 versus 3.3 hemorrhages per 1000 person-years; p = 0.001) mainly originated from the diffuse bAVMs rather than the compact subgroup (30.9 versus 4.8 hemorrhages per 1000 person-years; p = 0.035). Compact and smaller bAVMs, with higher prescribed margin dose harbor lower risks of post-SRS hemorrhage. The post-SRS hemorrhage rate exceeded 2.2% annually within the diffuse and large (> 40 cm3) bAVMs and the diffuse Spetzler-Martin IV-V bAVMs. These findings may help guide patient selection of SRS for the unruptured bAVMs.

Natural History and Histopathology of Expanding Cysts and Hematomas After Stereotactic Radiosurgery for Arteriovenous Malformations of the Brain: A Case Series

BACKGROUND

We reviewed the clinical course and histopathologic findings for cases involving the formation of expanding cysts and/or hematomas after gamma knife surgery (GKS) for arteriovenous malformations (AVMs).

METHODS

We report a single-center retrospective review of 18 patients who presented with cyst and/or hematoma expansion after GKS for AVMs between 1993 and 2023. Expanding cysts and hematomas were defined as well-demarcated cavities filled with fluid or well-marginated heterogenous hematomas presenting with expansion proximal to or in the location of the original AVM, respectively. Patient demographics, AVM characteristics, history of interventions and surgeries, and imaging and histopathologic features of expanding cysts and hematomas were collected for analysis.

RESULTS

Among 1072 AVM patients treated using GKS, 18 presented with expanding cysts or hematomas during a total follow-up period of 16,757 patient-years (0.11 case/100 persons/patient-year). The time to cyst or hematoma identification was 4-13 years after initial GKS, with a mean duration of 8.6 years. Among the patients examined, 7 (38.9%) presented mainly with hematoma, 10 (55.6%) presented mainly with cysts, and 1 presented with approximately equal components of both. Among the 18 patients, 13 (72.2%) underwent craniotomy to treat cyst or hematoma expansion. All the specimens had similar histopathologic characteristics, including organizing hematoma with fresh and old hemorrhage, fibrinoid necrosis of the vessels, gliosis of normal brain tissue, infiltration of hemosiderin-laden histiocytes, and extravascular protein leakage.

CONCLUSIONS

Our findings suggest that the formation of these 2 complications can be attributed to a common mechanism involving radiation-induced vascular damage in brain tissue adjacent to the AVM and subsequent chronic inflammation and capillary dilatation.

Association Between Pseudoprogression of Vestibular Schwannoma After Radiosurgery and Radiological Features of Solid and Cystic Components

BACKGROUND AND OBJECTIVES

The pathophysiology of vestibular schwannoma (VS) pseudoprogression after Gamma Knife radiosurgery (GKRS) remains unclear. Radiological features in pretreatment magnetic resonance images may help predict VS pseudoprogression. This study used VS radiological features quantified using an automated segmentation algorithm to predict pseudoprogression after GKRS treatment.

METHODS

This is a retrospective study comprising 330 patients with VS who received GKRS. After image preprocessing and T2W/contrast-enhanced T1-weighted image (CET1W) image generation, with fuzzy C-means clustering, VSs were segmented into solid and cystic components and classified as solid and cystic. Relevant radiological features were then extracted. The response to GKRS was classified into "nonpseudoprogression" and "pseudoprogression/fluctuation". The Z test for two proportions was used to compare solid and cystic VS for the likelihood of pseudoprogression/fluctuation. Logistic regression was used to assess the correlation between clinical variables and radiological features and response to GKRS.

RESULTS

The likelihood of pseudoprogression/fluctuation after GKRS was significantly higher for solid VS compared with cystic VS (55% vs 31%, P < .001). For the entire VS cohort, multivariable logistic regression revealed that a lower mean tumor signal intensity (SI) in T2W/CET1W images was associated with pseudoprogression/fluctuation after GKRS ( P = .001). For the solid VS subgroup, a lower mean tumor SI in T2W/CET1W images ( P = .035) was associated with pseudoprogression/fluctuation after GKRS. For the cystic VS subgroup, a lower mean SI of the cystic component in T2W/CET1W images ( P = .040) was associated with pseudoprogression/fluctuation after GKRS.

CONCLUSION

Pseudoprogression is more likely to occur in solid VS compared with cystic VS. Quantitative radiological features in pretreatment magnetic resonance images were associated with pseudoprogression after GKRS. In T2W/CET1W images, solid VS with a lower mean tumor SI and cystic VS with a lower mean SI of cystic component were more likely to have pseudoprogression after GKRS. These radiological features can help predict the likelihood of pseudoprogression after GKRS.

Improved survival and intracranial tumor control of EGFR-mutated NSCLC patients with newly developed brain metastases following stereotactic radiosurgery and EGFR-TKI: a large retrospective cohort study and meta-analyses

PURPOSE

To examine the differential effects of SRS and TKI on EGFR-mutated NSCLC patients with brain metastases (BMs) and outcomes following continuation of the same TKI agent in case of new BMs.

METHODS

This study included 608 NSCLC patients (2,274 BMs) while meta-analyses included 1,651 NSCLC patients (> 3,944 BMs). Overall survival (OS) and intracranial progression free survival (iPFS) were estimated using Kaplan-Meier methods. Hazard ratios (95% CI) of prognostic factors were estimated using Cox regression models.

RESULTS

The median OS/iPFS (95% CI) (months) for patients with wildtype EGFR/ALK, EGFR mutations, and ALK rearrangements were 17.7 (12.9-23.6)/12.1 (9.8-15.6), 28.9 (23.8-33.3)/17.7 (14.8-21.2), and 118.0 (not reached)/71.7 (15.1-not reached), respectively. In EGFR-mutated patients, meta-analyses combining our data showed significantly improved OS and iPFS of patients who received SRS and TKI (OS:35.1 months, iPFS:20.0 months) when compared to those who have SRS alone (OS:20.8 months, iPFS:11.8 months) or TKI alone (OS:24.3 months, iPFS:13.8 months). Having SRS for newly diagnosed BMs while keeping the existing TKI agent yielded OS (30.0 vs. 32.1 months, p = 0.200) non-inferior to patients who started combined SRS and TKI therapy for their newly diagnosed NSCLC with BMs. Multivariable analyses showed that good performance score and TKI therapy were associated with improved outcomes.

CONCLUSIONS

Combined SRS and TKI resulted in favorable outcomes in EGFR-mutated NSCLC patients with newly diagnosed BMs. Continuation of the same TKI agent plus SRS in case of new brain metastases yielded good clinical outcomes and may be considered a standard-of-care treatment.

Stereotactic radiosurgery for orbital cavernous hemangiomas

OBJECTIVE

The goal of this study was to assess the safety and efficacy of single-session Gamma Knife radiosurgery (GKRS) for orbital cavernous hemangiomas (OCHs).

METHODS

Patients who presented with an OCH between September 1999 and May 2022 and were treated with single-session GKRS were included in this single-center cohort study.

RESULTS

There were 23 patients (7 males and 16 females) in this study. The median margin dose was 12 Gy (range 11-13 Gy). The median clinical and radiological follow-ups were 45 months (range 5-190 months) and 45 months (range 6-190 months), respectively. Nine (69.2%) of 13 patients with visual acuity impairment had improvement in best corrected visual acuity. Of the 8 patients with visual field defects, 5 patients (62.5%) had complete resolution. Tumor regression was observed in 22 patients (95.7%). The mean relative reduction in tumor volume was 82.6% ± 23.7%. The relative reductions in tumor volume were 33%, 49%, 72%, 84%, and 89% at 6, 12, 24, 36, and 48 months, respectively. Adverse effects of radiation were not observed.

CONCLUSIONS

GKRS appears to be safe and efficacious for treating OCHs over long-term follow-up. The treatment is associated with a high rate of regression in OCHs and remarkable improvement in both visual acuity and visual field deficits.

Compactness index: a radiosurgery outcome predictor for patients with unruptured brain arteriovenous malformations

OBJECTIVE

The goal of the study was to define and quantify brain arteriovenous malformation (bAVM) compactness and to assess its effect on outcomes after Gamma Knife radiosurgery (GKRS) for unruptured bAVMs.

METHODS

Unsupervised machine learning with fuzzy c-means clustering was used to differentiate the tissue constituents of bAVMs on T2-weighted MR images. The percentages of vessel, brain, and CSF were quantified. The proposed compactness index, defined as the ratio of vasculature tissue to brain tissue, categorized bAVM morphology into compact, intermediate, and diffuse types according to the tertiles of this index. The outcomes of interest were complete obliteration and radiation-induced changes (RICs).

RESULTS

A total of 209 unruptured bAVMs treated with GKRS were retrospectively included. The median imaging and clinical follow-up periods were 49.2 and 72.3 months, respectively. One hundred seventy-three bAVMs (82.8%) achieved complete obliteration after a median latency period of 43.3 months. The rates of RIC and permanent RIC were 76.1% and 3.8%, respectively. Post-GKRS hemorrhage occurred in 14 patients (6.7%), resulting in an annual bleeding risk of 1.0%. Compact bAVM, smaller bAVM volume, and exclusively superficial venous drainage were independent predictors of complete obliteration. Diffuse bAVM morphology, larger bAVM volume, and higher margin dose were independently associated with RICs.

CONCLUSIONS

The compactness index quantitatively describes the compactness of unruptured bAVMs. Moreover, compact bAVMs may have a higher obliteration rate and a smaller risk of RICs than diffuse bAVMs. This finding could help guide decision-making regarding GKRS treatment for patients with unruptured bAVMs.

Leukoencephalopathy in patients with brain metastases who received radiosurgery with or without whole brain radiotherapy

BACKGROUND

Whole brain radiation therapy (WBRT) for brain metastases (BMs) is a common cause of radiation-induced leukoencephalopathy; however the safety of alternative stereotactic radiosurgery (SRS) remains unclear. This study examined the incidence of leukoencephalopathy in patients treated with SRS alone versus WBRT plus SRS for BMs with a focus on the relationship between prognostic factors and leukoencephalopathy.

METHODS

Analysis was performed between 2002 and 2021. The total enrollment was 993 patients with the distribution: WBRT plus SRS (n = 291) and SRS only (n = 702). Leukoencephalopathy was graded from 0 to 3 for changes in white matter indicated by the MRI after WBRT or SRS. Patient characteristics and SRS dosimetric parameters were reviewed to identify factors that contributed to the incidence of leukoencephalopathy or overall survival.

RESULTS

The incidence of leukoencephalopathy was consistently higher in WBRT plus SRS group than in SRS alone group (p < 0.001). Leukoencephalopathy was also associated with a larger total tumor volume (≧28cm³; p = 0.028) and age (> 77 years; p = 0.025). Nonetheless, the SRS integral dose to skull in the subgroup of WBRT plus SRS treatment was not demonstrated significance in development of leukoencephalopathy (p = 0.986 for integral dose 1-2 J, p = 0.776 for integral dose > 2 J).

CONCLUSIONS

This study revealed that SRS is safe for oligo-BMs in terms of leukoencephalopathy development. Patient age and total tumor volume were identified as important factors in assessing the development of leukoencephalopathy. The additional of SRS (even at an integral dose > 2 J) did not increase the incidence of leukoencephalopathy.

Leptomeningeal metastasis in patients with non-small cell lung cancer after stereotactic radiosurgery for brain metastasis

OBJECTIVE

Stereotactic radiosurgery (SRS) is an effective treatment for brain metastases (BMs) in patients with non-small cell lung cancer (NSCLC). However, factors associated with the development of post-SRS leptomeningeal metastasis (LM) remain unclear. The authors analyzed the incidence and risk factors of LM development in patients with NSCLC and BMs after SRS and examined the survival outcomes and prognostic factors after LM development.

METHODS

This retrospective study included patients with NSCLC treated with SRS for MRI-diagnosed BM from 2002 to 2021. The authors recorded various clinical and demographic data, including age, sex, tumor histology, molecular profile of tumors, extracranial disease status, previous craniotomy, Karnofsky Performance Status, systemic treatments, tumor volume, and number of BMs. The management and survival outcomes after LM diagnosis were also recorded.

RESULTS

LM developed in 13.7% of patients with NSCLC and BMs after SRS treatment. Large initial tumor volume and more than 5 BM lesions, but not EGFR mutation status and post-SRS treatment, were associated with LM development after SRS. Multivariate analysis revealed that chemotherapy and targeted therapy after LM were associated with better survival in patients with LM after SRS.

CONCLUSIONS

This study is the first to evaluate the risk factors for LM in a relatively large cohort of patients with NSCLC after SRS. In patients with BMs harboring risk factors for subsequent LM, such as initial tumor volume and number of metastatic lesions, aggressive therapies with high CNS penetrating ability should be considered.

Combined stereotactic radiosurgery and tyrosine kinase inhibitor therapy versus tyrosine kinase inhibitor therapy alone for the treatment of non-small cell lung cancer patients with brain metastases

OBJECTIVE

Whether combined radiation and tyrosine kinase inhibitor (TKI) therapy in non-small cell lung cancer (NSCLC) patients with brain metastases (BMs) and epidermal growth factor receptor (EGFR) mutations confers additional benefits over TKI therapy alone remains a matter of debate. The goal of this study was to compare outcomes between combined TKI therapy with stereotactic radiosurgery (SRS) versus TKI therapy alone in NSCLC patients with BMs and EGFR mutations.

METHODS

Consecutive cases of NSCLC patients with EGFR mutations and BMs treated with TKIs were selected for inclusion in this study. Patients were categorized into two groups based on SRS: TKI therapy alone (group I) and combined SRS and TKI therapy (group II). Patients who had SRS or TKI as salvage therapy and those with prior radiation treatment for BMs were excluded. Tumor control (< 10% increase in tumor volume) and overall survival (OS) rates were compared using Kaplan-Meier analyses. Independent predictors of tumor control and OS were identified using multivariable Cox regression analyses.

RESULTS

The study cohort comprised 280 patients (n = 90 in group I and n = 190 in group II). Cumulative tumor control rates were higher in group II than in group I (79.8% vs 31.2% at 36 months, p < 0.0001). Cumulative OS rates were comparable between groups I and II (43.8% vs 59.4% at 36 months, p = 0.3203). Independent predictors of tumor control were older age (p < 0.01, HR 1.03), fewer BMs (p < 0.01, HR 1.09), lack of extracranial metastasis (p < 0.02, HR 0.70), and combined SRS and TKI therapy (p < 0.01, HR 0.25). Independent predictors of OS were fewer BMs (p < 0.01, HR 1.04) and a higher Karnofsky Performance Status score (p < 0.01, HR 0.97).

CONCLUSIONS

Although the OS rate did not differ between TKI therapy with and without SRS, the addition of SRS to TKI therapy resulted in improvement of intracranial tumor control. The lack of effect on survival rate with the addition of SRS may be attributable to extracranial disease progression. The addition of SRS to TKI therapy is recommended for intracranial disease control in NSCLC patients with BMs and EGFR mutations. Potential benefits may include prevention of neurological deficits and seizures. Future prospective studies may help clarify the clinical outcome benefits of SRS in these patients.

Quantification of tumor response of cystic vestibular schwannoma to Gamma Knife radiosurgery by using artificial intelligence

OBJECTIVE

Gamma Knife radiosurgery (GKRS) is a common treatment modality for vestibular schwannoma (VS). The ability to predict treatment response is important in patient counseling and decision-making. The authors developed an algorithm that can automatically segment and differentiate cystic and solid tumor components of VS. They also investigated associations between the quantified radiological features of each component and tumor response after GKRS.

METHODS

This is a retrospective study comprising 323 patients with VS treated with GKRS. After preprocessing and generation of pretreatment T2-weighted (T2W)/T1-weighted with contrast (T1WC) images, the authors segmented VSs into cystic and solid components by using fuzzy C-means clustering. Quantitative radiological features of the entire tumor and its cystic and solid components were extracted. Linear regression models were implemented to correlate clinical variables and radiological features with the specific growth rate (SGR) of VS after GKRS.

RESULTS

A multivariable linear regression model of radiological features of the entire tumor demonstrated that a higher tumor mean signal intensity (SI) on T2W/T1WC images (p < 0.001) was associated with a lower SGR after GKRS. Similarly, a multivariable linear regression model using radiological features of cystic and solid tumor components demonstrated that a higher solid component mean SI (p = 0.039) and a higher cystic component mean SI (p = 0.004) on T2W/T1WC images were associated with a lower SGR after GKRS. A larger cystic component proportion (p = 0.085) was associated with a trend toward a lower SGR after GKRS.

CONCLUSIONS

Radiological features of VSs on pretreatment MRI that were quantified using fuzzy C-means were associated with tumor response after GKRS. Tumors with a higher tumor mean SI, a higher solid component mean SI, and a higher cystic component mean SI on T2W/T1WC images were more likely to regress in volume after GKRS. Those with a larger cystic component proportion also trended toward regression after GKRS. Further refinement of the algorithm may allow direct prediction of tumor response.

Effects of stereotactic radiosurgery versus conventional radiotherapy on body mass index in patients with craniopharyngioma

OBJECTIVE

Hypothalamic obesity is common among patients with craniopharyngioma. This study examined whether precise stereotactic radiosurgery reduces the risk of hypothalamic obesity in cases of craniopharyngioma with expected long-term survival.

METHODS

This cohort study included 40 patients who had undergone Gamma Knife radiosurgery (GKRS; n = 22) or fractionated radiotherapy (FRT; n = 18) for residual or recurrent craniopharyngioma. Neurological presentations, tumor volume changes, and BMI values were meticulously reviewed. The median clinical follow-up durations were 9.7 years in the GKRS group and 10.8 years in the FRT group.

RESULTS

The median ages at the time of GKRS and FRT were 9.0 years and 10.0 years, respectively. The median margin dose of GKRS was 12.0 Gy (range 10.0-16.0 Gy), whereas the median dose of FRT was 50.40 Gy (range 44.1-56.3 Gy). Prior to GKRS or FRT, the median BMI values were 20.5 kg/m2 in the GKRS cohort and 20.0 kg/m2 in the FRT cohort. The median BMIs after radiation therapy at final follow-up were 21.0 kg/m2 and 24.0 kg/m2 for the GKRS and FRT cohorts, respectively. In the FRT cohort, BMI curves rapidly increased beyond the 85th percentile of the upper limit of the general population. BMI curves in the GKRS cohort increased more gradually, and many of the patients merged into the normal growth curve after adolescence. However, the observed difference was not statistically significant (p = 0.409).

CONCLUSIONS

The study compared the two adjuvant radiation modalities most commonly used for recurrent and residual craniopharyngioma. The authors' results revealed that precise radiosurgery dose planning can mediate the subsequent increase in BMI. There is every indication that meticulous GKRS treatment is an effective approach to treating craniopharyngioma while also reducing the risk of hypothalamic obesity.

Stereotactic gamma knife radiosurgery for orbital cavernous hemangioma: clinical outcome and visual function protection

PURPOSE

Although rare, orbital cavernous hemangioma (OCH) is the most common benign orbital neoplasm in adults and may cause vision disturbance or loss due to optic nerve compression. The conventional treatment is surgical excision, which carries a risk of intraoperative nerve damage, whereas gamma knife radiosurgery (GKRS) can be a safe and effective alternative. Herein, we report the results of four patients with OCH treated with GKRS, and describe the method of treatment including the optic nerve protection.

METHODS

This retrospective study included four consecutive patients (three women, one man; mean age: 50 ± 14.7 years) with OCH treated with single-session GKRS between 2014 and 2020. Three patients had decreased visual acuity. During GKRS, the prescription dose delivered to the tumor margin was 12 Gy at the 55-58% isodose line. The dose to the optic nerve margin was < 12 Gy. Follow-up included sequential magnetic resonance imaging (MRI) and ophthalmological examinations at 6-month intervals.

RESULTS

The median follow-up period was 29.5 ± 23 months (range, 12-63 months). After GKRS, three patients with visual dysfunction had substantial vision improvement; the fourth patient continued to have normal vision without deterioration. Radiological outcomes after GKRS indicated an average tumor shrinkage of 70% ± 10.6% at the 6-month follow-up and 83% ± 2.64% at the 1-year follow-up. No adverse radiation effects were observed.

CONCLUSIONS

GKRS for OCH achieved favorable clinical outcomes, with substantial tumor volume reduction. OCH can be diagnosed based on characteristic MRI findings. GKRS may be considered a treatment option for OCH in selected cases.

Does the Diffuseness of the Nidus Affect the Outcome of Stereotactic Radiosurgery in Patients with Unruptured Cerebral Arteriovenous Malformations?

BACKGROUND

We proposed an algorithm to automate the components within the identification of components within the nidus of cerebral arteriovenous malformations (AVMs) which may be used to analyze the relationship between its diffuseness and treatment outcomes following stereotactic radiosurgery (SRS).

OBJECTIVES

to determine the impact of the diffuseness of the AVM nidus on SRS outcomes.

METHODS

This study conducted regular follow-ups of 209 patients with unruptured AVMs who underwent SRS. The diffuseness of the AVM nidus was estimated by quantifying the proportions of vascular nidal component, brain parenchyma, and cerebrospinal fluid in T2-weighted MRIs. We used Cox regression analysis to characterize the association between nidal diffuseness and treatment outcomes in terms of obliteration rate and radiation-induced change (RICs) rate following SRS.

RESULTS

The median AVM volume was 20.7 cm3. The median duration of imaging follow-up was 51 months after SRS. The overall AVM obliteration rate was 68.4%. RICs were identified in 156 of the 209 patients (74.6%). The median proportions of the nidus of AVM and brain parenchyma components within the prescription isodose range were 30.2 and 52.2%, respectively. Cox regression multivariate analysis revealed that the only factor associated with AVM obliteration rate after SRS was AVM volume. However, a larger AVM volume (>20 mL) and a larger proportion of brain parenchyma (>50%) within the prescription isodose range were both correlated with a higher RIC rate following SRS.

CONCLUSIONS

The diffuseness of the nidus indeed appears to affect the RIC rate following SRS in patients with unruptured AVMs.

Repeated gamma knife radiosurgery enables longer tumor control in cases of highly-recurrent intracranial ependymoma

PURPOSE

Stereotactic radiosurgery (SRS) is a potential re-irradiation treatment for recurrent intracranial ependymoma after prior radiation therapy. The purpose of this study was to examine the efficacy and safety of repeated SRS in the treatment of recurrent intracranial ependymomas.

METHODS

This is a retrospective study of consecutive patients with residual or recurrent intracranial ependymomas who were treated with SRS between 1993 and 2018. Tumor progression was defined as a ≥ 10% increase in tumor volume. Tumor regression was defined as a ≥ 10% reduction in tumor volume. A tumor that remained within 10% of its original volume was defined as stable. Tumor control comprised tumor regression and stability. Time-dependent analyses were performed using two treatment failure endpoint definitions: (1) evidence of local tumor progression or distant metastasis (single SRS analysis), and (2) lack of tumor response to SRS (repeated SRS analysis). These analyses were adjusted for the competing risk of death.

RESULTS

The study comprised 37 patients (65 intracranial ependymomas) who underwent multiple SRS sessions (range: 1-7). Median age was 10.2 years (range: 0.8-53.8 years), and median tumor volume was 1.5 mL (range: 0.01-22.5 mL). The median radiation dose was 13.3 Gy (range: 7.9-22.0 Gy) at a median isodose line of 57% (range: 50-90%). Overall tumor control rates in the single SRS analysis adjusting for the competing risk of death were 53.6%, 30.5%, and 23.6% at 1, 3, and 5 years, respectively. Overall tumor control rates in the repeated SRS analysis adjusting for the competing risk of death were 70.6%, 50.4%, and 43.1% at 1, 3, and 5 years, respectively. Prior gross total resection was the only independent predictor of overall tumor control after SRS (aHR = 25.62 (1.55-422.1), p = 0.02).

CONCLUSIONS

Repeated GKRS appeared to be an effective treatment strategy for recurrent or residual intracranial ependymomas, with acceptable complication rates.

Radiomics as prognostic factor in brain metastases treated with Gamma Knife radiosurgery

PURPOSE

Gamma Knife radiosurgery (GKRS) is a non-invasive procedure for the treatment of brain metastases. This study sought to determine whether radiomic features of brain metastases derived from pre-GKRS magnetic resonance imaging (MRI) could be used in conjunction with clinical variables to predict the effectiveness of GKRS in achieving local tumor control.

METHODS

We retrospectively analyzed 161 patients with non-small cell lung cancer (576 brain metastases) who underwent GKRS for brain metastases. The database included clinical data and pre-GKRS MRI. Brain metastases were demarcated by experienced neurosurgeons, and radiomic features of each brain metastasis were extracted. Consensus clustering was used for feature selection. Cox proportional hazards models and cause-specific proportional hazards models were used to correlate clinical variables and radiomic features with local control of brain metastases after GKRS.

RESULTS

Multivariate Cox proportional hazards model revealed that higher zone percentage (hazard ratio, HR 0.712; P = .022) was independently associated with superior local tumor control. Similarly, multivariate cause-specific proportional hazards model revealed that higher zone percentage (HR 0.699; P = .014) was independently associated with superior local tumor control.

CONCLUSIONS

The zone percentage of brain metastases, a radiomic feature derived from pre-GKRS contrast-enhanced T1-weighted MRIs, was found to be an independent prognostic factor of local tumor control following GKRS in patients with non-small cell lung cancer and brain metastases. Radiomic features indicate the biological basis and characteristics of tumors and could potentially be used as surrogate biomarkers for predicting tumor prognosis following GKRS.

Gamma Knife radiosurgery for cerebral cavernous malformation

This is a retrospective study examining the efficacy and safety of Gamma Knife radiosurgery (GKS) in treating patients with cerebral cavernous malformations (CCMs). Between 1993 and 2018, 261 patients with 331 symptomatic CCMs were treated by GKS. The median age was 39.9 years and females were predominant (54%). The median volume of CCMs was 3.1 mL. The median margin dose was 11.9 Gy treat to a median isodose level of 59%. Median clinical and imaging follow-up times were 69 and 61 months, respectively. After the initial hemorrhage that led to CCM diagnosis, 136 hemorrhages occurred in the period prior to GKS (annual incidence = 23.6%). After GKS, 15 symptomatic hemorrhages occurred within the first 2 years of follow-up (annual incidence = 3.22%), and 37 symptomatic hemorrhages occurred after the first 2 years of follow-up (annual incidence = 3.16%). Symptomatic radiation-induced complication was encountered in 8 patients (3.1%). Mortality related to GKS occurred in 1 patient (0.4%). In conclusion, GKS decreased the risk of hemorrhage in CCM patients presenting with symptomatic hemorrhage. GKS is a viable alternative treatment option for patients with surgically-inaccessible CCMs or significant medical comorbidities.

Epidermal growth factor receptor mutations: association with favorable local tumor control following Gamma Knife radiosurgery in patients with non-small cell lung cancer and brain metastases

OBJECTIVE

The presence of epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) has been associated with elevated radiosensitivity in vitro. However, results from clinical studies on radiosensitivity in cases of NSCLC with EGFR mutations are inconclusive. This paper presents a retrospective analysis of patients with NSCLC who underwent regular follow-up imaging after radiotherapy for brain metastases (BMs). The authors also investigated the influence of EGFR mutations on the efficacy of Gamma Knife radiosurgery (GKRS).

METHODS

This study included 264 patients (1069 BMs) who underwent GKRS treatment and for whom EGFR mutation status, demographics, performance status, and tumor characteristics were available. Radiological images were obtained at 3 months after GKRS and at 3-month intervals thereafter. Kaplan-Meier plots and Cox regression analysis were used to correlate EGFR mutation status and other clinical features with tumor control and overall survival.

RESULTS

The tumor control rates and overall 12-month survival rates were 87.8% and 65.5%, respectively. Tumor control rates in the EGFR mutant group versus the EGFR wild-type group were 90.5% versus 79.4% at 12 months and 75.0% versus 24.5% at 24 months. During the 2-year follow-up period after SRS, the intracranial response rate in the EGFR mutant group was approximately 3-fold higher than that in the wild-type group (p < 0.001). Cox regression multivariate analysis identified EGFR mutation status, extracranial metastasis, primary tumor control, and prescribed margin dose as predictors of tumor control (p = 0.004, p < 0.001, p = 0.004, and p = 0.026, respectively). Treatment with a combination of GKRS and tyrosine kinase inhibitors (TKIs) was the most important predictor of overall survival (p < 0.001).

CONCLUSIONS

The current study demonstrated that, among patients with NSCLC-BMs, EGFR mutations were independent prognostic factors of tumor control. It was also determined that a combination of GKRS and TKI had the most pronounced effect on prolonging survival after SRS. In select patient groups, treatment with SRS in conjunction with EGFR-TKIs provided effective tumor control for NSCLC-BMs.

Gamma knife radiosurgery for the treatment of cavernous sinus meningiomas: post-treatment long-term clinical outcomes, complications, and volume changes

PURPOSE

To evaluate the outcomes of patients who underwent Gamma Knife radiosurgery (GKRS) for the treatment of cavernous sinus (CS) meningiomas.

METHODS

We retrospectively reviewed the clinical and radiological outcomes of 95 patients with CS meningiomas at Taipei Veterans General Hospital between 1993 and 2011. The study cohort comprised 27 men and 68 women with a median age of 50 years (range 29-79 years). The median pre-GKRS tumor volume was 6.6 ml (range 0.9-35.7 ml). The median margin dose was 12 Gy (range 11-21 Gy). The clinical factors related to favorable outcomes were assessed.

RESULTS

The median follow-up period was 59 (range 12-209) months. At the final follow-up, the tumor volume regressed in 70 patients (74%) and progressed in eight (8%). Kaplan-Meier analysis revealed that the progression-free survival rates at 5 and 10 years were 92.7% and 81.2%, respectively. Three patients (3.2%) experienced exacerbated cranial nerve dysfunction following radiosurgery. Confined tumors were found to be an independent prognostic factor for tumor control and shorter times to regression in the multivariable analyses. No risk factor for tumor progression was identified in either the univariate or multivariate analyses.

CONCLUSIONS

GKRS provides good long-term tumor control and is associated with low cranial nerve-related morbidity development rates in patients with small- to medium-sized CS meningiomas. Confined tumor could be an independent prognostic factor for tumor control and shorter times to regression in multivariate analysis. Life-long follow-up is mandatory in such settings, even for outpatients with shrunken or stabilized tumors.

Empirical versus progression-guided stereotactic radiosurgery for non-functional pituitary macroadenomas after subtotal resection

OBJECTIVE

There is a lack of consensus regarding whether if residual non-functional macroadenomas (NFM) should undergo empirical stereotactic radiosurgery (SRS) or be monitored until tumor progression before SRS treatment. The aim of this study is to compare the risks and benefits of empirical versus progression-guided SRS for NFM after subtotal resection.

METHODS

This is a retrospective study of consecutive NFM patients who subtotal surgical resection followed by SRS between 1999 and 2014. Patients were dichotomized into two groups: empirical SRS (SRS without evidence of tumor progression) and progression-guided SRS (SRS after demonstration of tumor progression) groups. Tumor response was categorized into: (1) regression, ≥ 10% decrease in tumor volume; (2) stable, < 10% increase or decrease in tumor volume; and (3) progression, ≥ 10% increase in tumor volume. Tumor control comprised stable tumor response and tumor regression.

RESULTS

Of the 112 patients who underwent SRS for NFM, 106 patients were treated for residual NFM after surgical resection, and included in the final analysis. The empirical SRS and progression-guided SRS groups comprised 46 and 60 patients, respectively. Overall tumor control rate was 88.7%. Higher rate of tumor control was achieved in the empirical SRS group compared to the progression-guided SRS group (95.65% vs. 83.33%, p = 0.047). Rates of new visual field deficit, cranial neuropathy and endocrinopathy were comparable between the two groups. Empirical SRS group had higher rates of progression-free survival compared to progression-guided SRS group (p = 0.015). Actuarial progression-free survival rates for the empirical SRS group were 93.2%, 93.2%, and 81.5% at 3, 5, and 10 years after SRS. Actuarial progression-free survival rates for the progression-guided SRS were 86.4%, 82.1%, and 68.4% at 3, 5, and 10 years after SRS.

CONCLUSION

Empirical SRS offers higher rates of tumor control and progression-free survival compared to progression-guided SRS in patients with residual NFM after surgical resection. Rates of new hypopituitarism and cranial neuropathies were comparable between the two groups.

Fully automated tissue segmentation of the prescription isodose region delineated through the Gamma knife plan for cerebral arteriovenous malformation (AVM) using fuzzy C-means (FCM) clustering

Background

Gamma knife radiosurgery (GKRS) is a common treatment for cerebral arterio-venous malformations (AVMs), particularly in cases where the malformation is deep-seated, large, or in eloquent areas of the brain. Unfortunately, these procedures can result in radiation injury to brain parenchyma. The fact that every AVM is unique in its vascular morphology makes it nearly impossible to exclude brain parenchyma from isodose radiation exposure during the formulation of a GKRS plan. Calculating the percentages of the various forms of tissue exposed to specific doses of radiation is crucial to understanding the clinical responses and causes of brain parenchyma injury following GKRS for AVM.

Methods

In this study, we developed a fully automated algorithm using unsupervised classification via fuzzy c-means clustering for the analysis of T2 weighted images used in a Gamma knife plan. This algorithm is able to calculate the percentages of nidus, brain tissue, and cerebrospinal fluid (CSF) within the prescription isodose radiation exposure region.

Results

The proposed algorithm was used to assess the treatment plan of 25 patients with AVM who had undergone GKRS. The Dice similarity index (SI) was used to determine the degree of agreement between the results obtained using the algorithm and a visually guided manual method (the gold standard) performed by an experienced neurosurgeon. In the nidus, the SI was (74.86 ± 1.30%) (mean ± standard deviation), the sensitivity was (83.05 ± 11.91)%, and the specificity was (86.73 ± 10.31)%. In brain tissue, the SI was (79.50 ± 6.01)%, the sensitivity was (73.05 ± 9.77)%, and the specificity was (85.53 ± 7.13)%. In the CSF, the SI was (69.57 ± 15.26)%, the sensitivity was (89.86 ± 5.87)%, and the specificity was (92.36 ± 4.35)%.

Conclusions

The proposed clustering algorithm provides precise percentages of the various types of tissue within the prescription isodose region in the T2 weighted images used in the GKRS plan for AVM. Our results shed light on the causes of brain radiation injury after GKRS for AVM. In the future, this system could be used to improve outcomes and avoid complications associated with GKRS treatment.

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A novel image analytical method for the analysis of images of an AVM in a GKRS plan

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Fuzzy c-means clustering was used for analyses of T2w images in the GKRS plan.

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Automatic calculation of percentages of tissue inside the isodose line

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Brain tissue percentages of the nidus of the AVM predict risk of complication.

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Proposed method could be used to avoid complications associated after GKRS.

Stereotactic radiosurgery for hypervascular intracranial tumors

OBJECTIVE

To evaluate the safety and efficacy of SRS treatment of central neurocytomas (CNCs), cavernous sinus hemangiomas (CSHs), and glomus tumors (GTs); and to compare upfront stereotactic radiosurgery (SRS) and adjuvant SRS in the treatment of these hypervascular tumors.

METHODS

This was a retrospective review of consecutive CNCs, CSHs, and GTs treated with SRS between 1993 and 2017. Tumor response was categorized based on volumetric analysis on magnetic resonance imaging: (1) tumor regression [> 10% decrease in tumor volume (TV)]; (2) stable tumor (≤ 10% change in TV); or (3) tumor progression (> 10% increase in TV).

RESULTS

Sixty hypervascular tumors (CNC: 28; CSH: 16; GT: 16) underwent SRS between 1993 and 2017. Margin doses were 13 Gy, 12 Gy, and 14 Gy for CNCs, CSHs, and GTs, respectively. Tumor regression was observed in 54 tumors (90%) with initial SRS after a median follow-up of 82 months. Relative reductions in TVs for CNCs were 38%, 52%, and 73% at 12, 24, and 48 months, respectively. Relative reductions in TVs for CSHs were 51%, 68%, and 88% at 12, 24, and 48 months, respectively. Relative reductions in TVs for GTs were 22%, 31%, and 47% at 12, 24, and 48 months, respectively. Upfront SRS was performed in 26 patients (43%). No difference in relative TV reductions were found between upfront and adjuvant SRS. Adverse radiation effects were observed in five patients. No mortality was encountered.

CONCLUSION

SRS for hypervascular tumors is associated with high rates of tumor regression with low risk of complications. No significant difference in rates of relative TV reduction were found between upfront and adjuvant SRS. Hence, upfront SRS may be considered in select patients.

The timing of stereotactic radiosurgery for medically refractory trigeminal neuralgia: the evidence from diffusion tractography images

BACKGROUND

Diffusion tensor imaging (DTI) is a novel MRI technique that enables noninvasive evaluation of microstructural alterations in white matter of brain. Initially, DTI was used in intra- or inter-hemispheric association bundles. Recent technical advances are overcoming the challenges of imaging small white matter bundles, such as the cranial nerves. In this study, we use DTI to shed more light on the microstructure changes in long-standing trigeminal neuralgia. We also utilize DTI to study the effect of early stereotactic radiosurgery (SRS) on the microstructures of the trigeminal nerve and to predict the effectiveness of early SRS in the treatment of medically refractory trigeminal neuralgia (TN).

METHODS

To analyze the presentation of trigeminal nerve, the DTI was reconstructed in 21 cases pre- and post-SRS. DTI parameters recorded include fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), linear anisotropy coefficient (Cl), planar anisotropy coefficient (Cp), and spherical anisotropy coefficient (Cs). Comparisons between ipsilateral (symptomatic) and contralateral (asymptomatic) trigeminal nerves and symptom durations of < 5 and ≧ 5 years were performed.

RESULTS

The study cohort comprised 21 patients with TN with a median age of 66 years. Initial adequate facial pain relief (Barrow Neurological Institute facial pain scores I-IIIb) was achieved in 16 (76%) patients. For the pre-SRS DTI findings, ipsilateral trigeminal nerve was associated with higher baseline root entry zone (REZ) Cs compared to contralateral nerve (0.774 vs. 0.743, p = 0.04). Ipsilateral trigeminal nerve with symptoms of < 5 years was associated with higher baseline FA compared to trigeminal nerve with symptoms of ≧ 5 years (0.314 vs. 0.244, p = 0.02). For the post-SRS DTI findings, ipsilateral trigeminal nerves with symptoms of <5 years demonstrated decrease in Cl, while those with symptoms ≧ 5 years demonstrated increase in Cl after SRS at the ipsilateral REZ (- 0.025 vs. 0.018, p = 0.04). At the cisternal segment of ipsilateral trigeminal nerve, symptoms of < 5 years were associated with decreased FA and increased λ₂, while symptoms of ≧ 5 years were associated with increased FA and decreased λ₂ after SRS (FA - 0.068 vs. 0.031, p = 0.04, λ₂ 0.0003 vs. - 0.0002, p = 0.02).

CONCLUSIONS

SRS provides high rates of initial pain relief with moderate rates of facial hypoesthesia. Ipsilateral trigeminal nerve was associated with higher baseline REZ Cs, and baseline FA was associated with duration of symptoms. There were significant associations between duration of symptoms and changes in ipsilateral REZ Cl, cisternal segment FA, and cisternal segment λ₂ after SRS. These preliminary findings serve as comparisons for future studies investigating the use of DTI in radiosurgical planning for patients with TN.

Early Stereotactic Radiosurgery for Medically Refractory Trigeminal Neuralgia

OBJECTIVE

To evaluate effectiveness of early Gamma Knife radiosurgery (GKRS) in treatment of medically refractory trigeminal neuralgia (TN).

METHODS

This retrospective review comprised 108 consecutive patients with medically refractory idiopathic TN between 2006 and 2014. All patients underwent GKRS targeting the root entry zone with a median maximum dose of 90 Gy and isodose line of 20%. Outcomes pertaining to pain and facial numbness were scored using Barrow Neurological Institute scales.

RESULTS

Following a median latency period of 4 weeks, we observed complete or adequate pain relief (Barrow Neurological Institute scores of I-IIIB) in 86 of 108 patients (90%). At a median time of 17 months, 22 patients (26%) experienced pain recurrence. New-onset facial numbness was reported by 59 patients (55%). Treatment failure rates were highest among patients with a longer history of pain. Compared with patients with pain history of ≤5 years, patients with pain history of >5 years experienced longer latency before pain relief (P = 0.027). Univariate and multivariate analyses demonstrated that pain history of ≤5 years was a significant predictor of pain relief (P = 0.049 and P = 0.045, respectively).

CONCLUSIONS

GKRS achieves a high rate of pain relief among patients with medically refractory idiopathic TN. Pain history of ≤5 years is a reliable predictor of pain relief and appears to be associated with shorter latency to pain relief after GKRS. Therefore, early GKRS for patients with medically refractory idiopathic TN is recommended.

Forward treatment planning techniques to reduce the normalization effect in Gamma Knife radiosurgery

In Gamma Knife forward treatment planning, normalization effect may be observed when multiple shots are used for treating large lesions. This effect can reduce the proportion of coverage of high‐value isodose lines within targets. The aim of this study was to evaluate the performance of forward treatment planning techniques using the Leksell Gamma Knife for the normalization effect reduction. We adjusted the shot positions and weightings to optimize the dose distribution and reduce the overlap of high‐value isodose lines from each shot, thereby mitigating the normalization effect during treatment planning. The new collimation system, Leksell Gamma Knife Perfexion, which contains eight movable sectors, provides an additional means to reduce the normalization effect by using composite shots. We propose different techniques in forward treatment planning that can reduce the normalization effect. Reducing the normalization effect increases the coverage proportion of higher isodose lines within targets, making the high‐dose region within targets more uniform and increasing the mean dose to targets. Because of the increase in the mean dose to the target after reducing the normalization effect, we can set the prescribed marginal dose at a higher isodose level and reduce the maximum dose, thereby lowering the risk of complications.

Gamma Knife surgery for clival epidural-osseous dural arteriovenous fistulas

OBJECTIVE Clival epidural-osseous dural arteriovenous fistula (DAVF) is often associated with a large nidus, multiple arterial feeders, and complex venous drainage. In this study the authors report the outcomes of clival epidural-osseous DAVFs treated using Gamma Knife surgery (GKS). METHODS Thirteen patients with 13 clival epidural-osseous DAVFs were treated with GKS at the authors' institution between 1993 and 2015. Patient age at the time of GKS ranged from 38 to 76 years (median 55 years). Eight DAVFs were classified as Cognard Type I, 4 as Type IIa, and 1 as Type IIa+b. The median treatment volume was 17.6 cm³ (range 6.2-40.3 cm³). The median prescribed margin dose was 16.5 Gy (range 15-18 Gy). Clinical and radiological follow-ups were performed at 6-month intervals. Patient outcomes after GKS were categorized as 1) complete improvement, 2) partial improvement, 3) stationary, and 4) progression. RESULTS All 13 patients demonstrated symptomatic improvement, and on catheter angiography 12 of the 13 patients had complete obliteration and 1 patient had partial obliteration. The median follow-up period was 26 months (range 14-186 months). The median latency period from GKS to obliteration was 21 months (range 8-186 months). There was no intracranial hemorrhage during the follow-up period, and no deaths occurred. Two adverse events were observed following treatment, and 2 patients required repeat GKS treatment with eventual complete obliteration. CONCLUSIONS Gamma Knife surgery offers a safe and effective primary or adjuvant treatment modality for complex clival epidural-osseous DAVFs. All patients in this case series demonstrated symptomatic improvement, and almost all patients attained complete obliteration.

The management of incidental central neurocytoma

This article elucidates the role of stereotactic radiosurgery for the management of central neurocytoma. This rare intraventricular tumor is usually benign and is best treated with surgical excision if the tumor is large and symptomatic. However, some distinctive neuroimaging features are found in this tumor that help to identify the tumor based on detailed MRI and computed tomography examinations. The cumulative experience shows that single-session radiosurgery using Gamma Knife radiosurgery is an effective and safe alternative treatment of incidental central neurocytoma. After radiosurgery, a serial MRI examination performed every 6 months for long-term follow-up is necessary to monitor radiosurgical response of the tumor.

Cervical vestibular-evoked myogenic potential in vestibular schwannoma after gamma-knife surgery

OBJECTIVE

Gamma-knife radiosurgery (GKS) for vestibular schwannomas (VSs) has become popular during the last two decades, and a promising tumor control rate has been reported. Therefore, the evaluation and preservation of auditory-vestibular nerve function after GKS have become more and more important in these patients with long-term survival. We have traditionally used pure-tone audiometry (PTA) for evaluation of auditory nerve function, and the caloric test for superior vestibular nerve function. Vestibular-evoked myogenic potential (VEMP) has recently emerged from various neurophysiological examinations for assessment of the integrity of the inferior vestibular nerve function. This novel tool has been established to represent a sacculo-collic reflex. By using these three tools, the auditory-vestibular nerve function of VS patients can be evaluated and monitored before and after GKS.

METHODS

Fourteen patients with unilateral VS that underwent GKS were prospectively recruited. All of them received a battery of auditory-vestibular function tests including PTA, caloric, and cVEMP tests before and after GKS at each time point (1, 6, and 12 months). Our data also included the tumor volumes and their relationship with the PTA, caloric, and cVEMP test results.

RESULTS

The PTA, caloric, and cVEMP tests showed abnormal results before GKS in 85.7%, 78.6% and 78.6% of our VS patients, respectively. The PTA, caloric, and cVEMP results did not show strong correlations between each other. However, there was a tendency that when the tumor grew larger, the auditory-vestibular function deficits became more severe. The PTA and cVEMP test results remained stable during the 1-year follow-up after GKS. However, the caloric test showed transient deterioration at the 6th month follow-up, which then recovered by the 1-year follow-up.

CONCLUSION

The combination of these three tests can help us diagnose VS and assess the change in auditory-vestibular nerve function during the post-GKS follow-up period. The results of these three tests were independent for smaller tumors, but all tests may show abnormal findings with larger tumors. Although the study is still ongoing, the preliminary data showed that GKS treatment would not affect the auditory-vestibular nerve function within a 1-year follow-up period.

Stereotactic radiosurgery for intracranial dural arteriovenous fistulas: a systematic review

OBJECT

The goal of this study was to evaluate the obliteration rate of intracranial dural arteriovenous fistulas (DAVFs) in patients treated with stereotactic radiosurgery (SRS), and to compare obliteration rates between cavernous sinus (CS) and noncavernous sinus (NCS) DAVFs, and between DAVFs with and without cortical venous drainage (CVD).

METHODS

A systematic literature review was performed using PubMed. The CS DAVFs and the NCS DAVFs were categorized using the Barrow and Borden classification systems, respectively. The DAVFs were also categorized by location and by the presence of CVD. Statistical analyses of pooled data were conducted to assess complete obliteration rates in CS and NCS DAVFs, and in DAVFs with and without CVD.

RESULTS

Nineteen studies were included, comprising 729 patients harboring 743 DAVFs treated with SRS. The mean obliteration rate was 63% (95% CI 52.4%–73.6%). Complete obliteration for CS and NCS DAVFs was achieved in 73% and 58% of patients, respectively. No significant difference in obliteration rates between CS and NCS DAVFs was found (OR 1.72, 95% CI 0.66–4.46; p = 0.27). Complete obliteration in DAVFs with and without CVD was observed in 56% and 75% of patients, respectively. A significantly higher obliteration rate was observed in DAVFs without CVD compared with DAVFs with CVD (OR 2.37, 95% CI 1.07–5.28; p = 0.03).

CONCLUSIONS

Treatment with SRS offers favorable rates of DAVF obliteration with low complication rates. Patients harboring DAVFs that are refractory or not amenable to endovascular or surgical therapy may be safely and effectively treated using SRS.

Radiosurgery target location and individual anatomical variation in trigeminal nerves

OBJECT

The authors evaluated individual anatomical variations in the trigeminal nerves of patients with medically intractable trigeminal neuralgia and clarified the relationships among the variations, radiosurgical target locations, and the clinical outcomes after high-dose Gamma Knife surgery (GKS).

METHODS

From 2006 through 2011, the authors conducted a retrospective review of 106 cases of primary or secondary trigeminal neuralgia consecutively treated with GKS targeting the dorsal root entry zone (DREZ) for which a maximal dose of 90 Gy and a 20% isodose line to the brainstem were used. A questionnaire was used to evaluate patients' pre- and post-GKS clinical conditions. To evaluate individual anatomical variations among trigeminal nerves, the authors used 3 parameters: the length of the trigeminal nerve in the cistern (nerve length), the length of the target between the radiation shot and the brainstem (targeting length), and the ratio between nerve length and targeting length (targeting ratio).

RESULTS

The median length of the trigeminal nerves in the 106 patients was 9.6 mm (range 6.04-20.74 mm), the median targeting length was 3.8 mm (range 1.81-10.84 mm), and the median targeting ratio was 38% (range 13%- 80%). No statistically significant differences in pain relief and pain recurrence were detected among patients with these various nerve characteristics. However, radiation-induced facial hypesthesia correlated with nerve length and targeting ratio (p < 0.05) but not with absolute distance from the brainstem (targeting length).

CONCLUSIONS

In trigeminal neuralgia patients who received DREZ-targeted GKS, the rate of pain relief did not differ according to anatomical nerve variations. However, the frequency of facial hypesthesia was higher among patients in whom the nerve was longer (> 11 mm) or the targeting ratio was lower (< 36%). Adjusting the target according to the targeting ratio, especially for patients with longer nerves, can reduce facial hypesthesia and enable maintenance of effective pain control.

Microsurgery for vestibular schwannoma after Gamma Knife surgery: challenges and treatment strategies

OBJECT

Resection of vestibular schwannoma (VS) after Gamma Knife surgery (GKS) is infrequently performed. The goals of this study were to analyze and discuss the neurological outcomes and technical challenges of VS resection and to explore strategies for treating tumors that progress after GKS.

METHODS

In total, 708 patients with VS underwent GKS between 1993 and 2012 at Taipei Veterans General Hospital. The post-GKS clinical courses, neurological presentations, and radiological changes in these patients were analyzed. Six hundred patients with imaging follow-up of at least 1 year after GKS treatment were included in this study.

RESULTS

Thirteen patients (2.2%) underwent microsurgery on average 36.8 months (range 3-107 months) after GKS. The indications for the surgery included symptomatic adverse radiation effects (in 4 patients), tumor progression (in 6), and cyst development (in 3). No morbidity or death as a result of the surgery was observed. At the last follow-up evaluation, all patients, except 1 patient with a malignant tumor, had stable or near-normal facial function.

CONCLUSIONS

For the few VS cases that require resection after radiosurgery, maximal tumor resection can be achieved with modern skull-based techniques and refined neuromonitoring without affecting facial nerve function.

Gamma Knife surgery for craniopharyngioma: report on a 20-year experience

Object

Although craniopharyngiomas are benign intracranial tumors, their high recurrence rates and intimate associations with surrounding neurovascular structures make gross tumor resection challenging. Stereotactic radiosurgery has been introduced as a valuable adjuvant therapy for recurrent or residual craniopharyngiomas. However, studies with large patient populations documenting long-term survival and progression-free survival rates are rare in the literature. The current study aims to report the long-term radiosurgical results and to define the prognostic factors in a large cohort of patients with a craniopharyngioma.

Methods

A total of 137 consecutive patients who underwent 162 sessions of Gamma Knife surgery (GKS) treatments at the Taipei Veterans General Hospital between 1993 and 2012 were analyzed. The patients' median age was 30.1 years (range 1.5–84.9 years), and the median tumor volume was 5.5 ml (range 0.2–28.4 ml). There were 23 solid (16.8%), 23 cystic (16.8%), and 91 mixed solid and cystic (66.4%) craniopharyngiomas. GKS was indicated for residual or recurrent craniopharyngiomas. The median radiation dose was 12 Gy (range 9.5–16.0 Gy) at a median isodose line of 55% (range 50%–78%).

Results

At a median imaging follow-up of 45.7 months after GKS, the rates of tumor control were 72.7%, 73.9%, and 66.3% for the solid, cystic, and mixed tumors, respectively. The actuarial progression-free survival rates plotted by the Kaplan-Meier method were 70.0% and 43.8% at 5 and 10 years after radiosurgery, respectively. After repeated GKS, the actuarial progression-free survival rates were increased to 77.3% and 61.2% at 5 and 10 years, respectively. The overall survival rates were 91.5% and 83.9% at the 5- and 10-year follow-ups, respectively. Successful GKS treatment can be predicted by tumor volume (p = 0.011). Among the 137 patients who had clinical follow-up, new-onset or worsened pituitary deficiencies were detected in 11 patients (8.0%). Two patients without tumor growth had a worsened visual field, and 1 patient had a new onset of third cranial nerve palsy.

Conclusions

The current study suggests that GKS is a relatively safe modality for the treatment of recurrent or residual craniopharyngiomas, and it is associated with improved tumor control and reduced in-field recurrence rates. Acceptable rates of complications occurred.

Initial Gamma Knife radiosurgery for nonfunctioning pituitary adenomas

Object

Nonfunctioning pituitary adenomas (NFAs) are the most common type of pituitary adenoma and, when symptomatic, typically require surgical removal as an initial means of management. Gamma Knife radiosurgery (GKRS) is an alternative therapeutic strategy for patients whose comorbidities substantially increase the risks of resection. In this report, the authors evaluated the efficacy and safety of initial GKRS for NFAs.

Methods

An international group of three academic Gamma Knife centers retrospectively reviewed outcome data in 569 patients with NFAs.

Results

Forty-one patients (7.2%) underwent GKRS as primary management for their NFAs because of an advanced age, multiple comorbidities, or patient preference. The median age at the time of radiosurgery was 69 years. Thirty-seven percent of the patients had hypopituitarism before GKRS. Patients received a median tumor margin dose of 12 Gy (range 6.2–25.0 Gy) at a median isodose of 50%. The overall tumor control rate was 92.7%, and the actuarial tumor control rate was 94% and 85% at 5 and 10 years postradiosurgery, respectively. Three patients with tumor growth or symptom progression underwent resection at 3, 3, and 96 months after GKRS, respectively. New or worsened hypopituitarism developed in 10 patients (24%) at a median interval of 37 months after GKRS. One patient suffered new-onset cranial nerve palsy. No other radiosurgical complications were noted. Delayed hypopituitarism was observed more often in patients who had received a tumor margin dose > 18 Gy (p = 0.038) and a maximum dose > 36 Gy (p = 0.025).

Conclusions

In this study, GKRS resulted in long-term control of NFAs in 85% of patients at 10 years. This experience suggests that GKRS provides long-term tumor control with an acceptable risk profile. This approach may be especially valuable in older patients, those with multiple comorbidities, and those who have endocrine-inactive tumors without visual compromise due to mass effect of the adenoma.

Gamma Knife radiosurgery for the management of intracranial dural arteriovenous fistulas

BACKGROUND

This report presents our 15-year experience with Gamma Knife radiosurgery (GKS) for the treatment of 321 patients with dural arteriovenous fistulas (DAVFs) in different locations.

METHODS

The most common locations of DAVFs were the cavernous sinus (206 cases) and transverse-sigmoid sinus (72 cases), which together accounted for 86.6 % of cases. In all, 54 patients had undergone embolization or surgery prior to radiosurgery, and the other patients underwent GKS as the primary treatment. During GKS, radiation was confined to the involved sinus wall, which was considered the true nidus of the DAVF. Target volume ranged from 0.8 to 52 cm(3). Marginal and maximum doses to the nidus ranged from 14 to 25 Gy and from 25 to 36 Gy, respectively.

RESULTS

The mean follow-up time was 28 months (range 2-149 months). In 264 of 321 patients (82 %) available for follow-up study, 173 (66 %) showed complete obliteration of DAVFs with symptomatic resolution, 87 (33 %) had partial obliteration, 2 (0.8 %) had stationary status, 1 (0.4 %) had progression, and 1 (0.4 %) died from a new hemorrhagic episode. Complications were found in only two (0.8 %) patients, one with venous hemorrhage and one with focal brain edema after GKS.

CONCLUSIONS

GKS is a safe, effective treatment for DAVFs. It provides a minimally invasive therapeutic option for patients who harbor less-aggressive DAVFs but who suffer from intolerable clinical symptoms. For some aggressive DAVFs with extensive venous hypertension or hemorrhage, multimodal treatment with combined embolization or surgery is necessary.

Gamma Knife surgery for central neurocytomas

OBJECT

The optimal management of central neurocytoma (CN) remnants and recurrences is still not clear. To date no large series of patients treated with Gamma Knife surgery (GKS) for CNs has been published. For that reason the authors decided to combine data from 5 different centers so that they could analyze the largest population of patients treated with GKS for CN currently available.

METHODS

Data obtained in 42 patients who were treated for CN with GKS before July 1, 2010, were retrospectively collected and analyzed. The median prescribed dose was 13 Gy (range 11-25 Gy). The follow-up time in these patients ranged from 0.5 to 14.7 years (mean 6.1 years, median 4.9 years). Eleven patients were followed up for 5-10 years and 9 patients for more than 10 years. All patients were alive and well at the closing of the study except 1 patient, who died of injuries sustained in a traffic accident.

RESULTS

Two cases of local tumor progression and 2 cases of distant tumor recurrence occurred among the patient population, yielding 5- and 10-year tumor control rates of 91% and 81%, respectively. No permanent complications occurred. The findings were in line with results reported in earlier publications. Despite the high tumor control rate, enlargement of part of or the whole ventricular system was seen in 45% of patients.

CONCLUSIONS

The high tumor control rate and the low complication rate following GKS indicate that GKS is the preferred treatment for CN tumor remnants or recurrences following microsurgery. However, data from longer follow-up times in more patients are needed before this conclusion can be validated. The patients need to be closely monitored and potential hydrocephalus managed despite tumor control.

Brainstem cavernous malformations: the role of Gamma Knife surgery

OBJECT

The authors retrospectively reviewed the efficacy and safety of Gamma Knife surgery (GKS) in patients with brainstem cavernous malformations (CMs). The CMs had bled repeatedly and placed the patients at high risk with respect to surgical intervention.

METHODS

Between 1993 and 2010, 49 patients with symptomatic CMs were treated by GKS. The mean age in these patients was 37.8 years, and the predominant sex was female (59.2%). All 49 patients experienced at least 2 instances of repeated bleeding before GKS; these hemorrhages caused neurological deficits including cranial nerve deficits, hemiparesis, hemisensory deficits, spasticity, chorea or athetosis, and consciousness disturbance.

RESULTS

The mean size of the CMs at the time of GKS was 3.2 cm(3) (range 0.1-14.6 cm(3)). The mean radiation dose directed to the lesion was 11 Gy with an isodose level at 60.0%. The mean clinical and imaging follow-up time was 40.6 months (range 1.0-150.7 months). Forty-five patients participated in regularly scheduled follow-up. Twenty-nine patients (59.2%) were followed up for > 2 years, and 16 (32.7%) were followed up for < 2 years. The pre-GKS annual hemorrhage rate was 31.3% (69 symptomatic hemorrhages during a total of 220.3 patient-years). After GKS, 3 episodes of symptomatic hemorrhage were observed within the first 2 years of follow-up (4.29% [corrected] annual hemorrhage rate), and 3 episodes of symptomatic hemorrhage were observed after the first 2 years of follow-up (3.64% [corrected] annual hemorrhage rate). In this study of 49 patients, symptomatic radiation-induced complications developed in only 2 patients (4.1%; cyst formation in 1 patient and perifocal edema with neurological deficits in the other patient). There were no deaths in this group.

CONCLUSIONS

Gamma Knife surgery is effective in reducing the rate of recurrent hemorrhage. In the authors' experience, it was possible to control bleeding using a low-dose treatment. In addition, there were few symptomatic radiation-induced complications. As a result, the authors believe that GKS is a good alternative treatment for brainstem CMs.

Intracranial dural arteriovenous fistulas: natural history and rationale for treatment with stereotactic radiosurgery

Dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous communications within the dura. The symptoms depend on their location and the pattern of the venous drainage. Patients with cavernous sinus DAVFs often present with ocular manifestations such as exophthalmos, chemosis and diplopia. Patients with transverse or sigmoid sinus DAVFs frequently experience headache and tinnitus on the affected side. DAVFs with anterograde sinus or cortical venous drainage (CVD) have been clinically regarded as benign, whereas DAVFs with retrograde CVD are considered aggressive in behavior. Similar to other cerebral arteriovenous malformations, DAVFs can hemorrhage, with an estimated annual risk of approximately 1.8%. The recommended therapeutic intervention for a DAVF is dependent on the anticipated natural history of the lesion. Management options include surgical resection, embolization and radiosurgery. Radiosurgical treatment has been used for DAVFs in various locations including the anterior cranial fossa, cavernous sinus, transverse/sigmoid sinus, superior sagittal sinus and tentorium. We present an update on 321 DAVF patients treated at the Taipei Veterans General Hospital using Gamma Knife radiosurgery. The prescribed mean margin dose was 17.2 Gy. In our series, 98% of patients had a stable or improved clinical condition after radiosurgery. Stereotactic radiosurgery using the Gamma Knife is a safe and effective alternative for the treatment of DAVFs.

Gamma knife surgery for cavernous hemangiomas in the cavernous sinus

BACKGROUND

Cavernous hemangioma in the cavernous sinus (CS) is a rare vascular tumor. Direct microsurgical approach usually results in massive hemorrhage. Radiosurgery has emerged as a treatment alternative to microsurgery.

OBJECTIVE

To further investigate the role of Gamma Knife surgery (GKS) in treating CS hemangiomas.

METHODS

This was a retrospective analysis of 7 patients with CS hemangiomas treated by GKS between 1993 and 2008. Data from 84 CS meningiomas treated during the same period were also analyzed for comparison. The patients underwent follow-up magnetic resonance imaging at 6-month intervals. Data on clinical and imaging changes after radiosurgery were analyzed.

RESULTS

Six months after GKS, magnetic resonance imaging revealed an average of 72% tumor volume reduction (range, 56%-83%). After 1 year, tumor volume decreased 80% (range, 69%-90%) compared with the pre-GKS volume. Three patients had > 5 years of follow-up, which showed the tumor volume further decreased by 90% of the original size. The average tumor volume reduction was 82%. In contrast, tumor volume reduction of the 84 cavernous sinus meningiomas after GKS was only 29% (P < .001 by Mann-Whitney U test). Before treatment, 6 patients had various degrees of ophthalmoplegia. After GKS, 5 improved markedly within 6 months. Two patients who suffered from poor vision improved after radiosurgery.

CONCLUSION

GKS is an effective and safe treatment modality for CS hemangiomas with long-term treatment effect. Considering the high risks involved in microsurgery, GKS may serve as the primary treatment choice for CS hemangiomas.

Gamma knife radiosurgery for central neurocytoma: retrospective analysis of fourteen cases with a median follow-up period of sixty-five months

OBJECT

Central neurocytoma (CN) is considered to be a benign neuronal tumor with possible atypical behavior. Microsurgery, radiation therapy (RT) and radiosurgery all have been used in treating this rare disease during the past decade. In this study, the authors present the experience with gamma knife radiosurgery (GKRS) on 14 patients with CN during a median follow-up period of 65 months and document the safety and efficacy of GKRS in the treatment of CN.

METHODS

Between November 1997 and December 2009, 14 patients pathologically diagnosed with CN were treated with GKRS. Follow-up magnetic resonance imaging (MRI) was performed at 6-month intervals. Tumor volume and adverse radiation effects (ARE) were documented to evaluate tumor response to GKRS. The Karnofsky Performance Scale (KPS) and neurological status were used to assess clinical outcome. The mean radiation dose prescribed to the tumor margin was 12.1 Gy (ranging from 11 to 13 Gy). The mean tumor volume was 19.6 ml (ranging from 3.5 to 48.9 ml). The mean follow-up period was 70 months (ranging from 30 to 140 months), and the median follow-up period was 65 months.

RESULTS

Tumor shrinkage was found in all patients at the final MRI follow-up. The mean volume reduction was 69% (ranging from 47 to 87%). No tumor progression, ARE or radiation-related toxicity developed in any of the cases. The KPS scores of all patients were the same or had increased, and the neurological functions were all stable without deterioration at the final follow-up.

CONCLUSION

In our observations, GKRS was found to be an effective and safe alternative as adjuvant therapy for pathology-confirmed CN. The tumor volume and functional outcome can be controlled with a favorable result in long-term observation. Compared with RT and microsurgery, GKRS plays an important role in the treatment of CN as a minimally invasive technique with low morbidity. Regular long-term MRI follow-up should be mandatory to document the tumor response and possible recurrence. Multicenter consortia should be considered for further investigation and evaluation of GKRS for such a rare tumor.

Large vestibular schwannomas treated by Gamma Knife surgery: long-term outcomes

OBJECT

Although radiosurgery has been well accepted as a treatment for small- to medium-sized vestibular schwannomas (VSs), its application in the treatment of large VSs remains controversial because of unfavorable effects such as tumor swelling and potential compression of the brainstem. The authors present a retrospective study spanning 17 years, during which 21 patients underwent Gamma Knife surgery (GKS) for large VSs. Long-term outcomes are reported, and possible factors affecting tumor responses to GKS are analyzed.

METHODS

Five hundred thirteen patients harboring VSs underwent GKS between March 1993 and October 2009. A large VS was defined as a tumor whose diameter was > 3 cm. This paper focuses on 21 patients who harbored large VSs ranging in volume from 12.7 to 25.2 cm(3) (mean 17.3 cm(3)) and were treated by GKS. Fourteen of these patients had undergone 1 or more craniotomies previously to remove the tumor. Seven patients underwent GKS alone because of patient preference or a poor clinical condition that precluded microsurgery with general anesthesia. The mean radiation dose directed to the tumor ranged from 15 to 17.5 Gy. The mean radiation dose prescribed to the tumor margin was 11.9 Gy (range 11-14 Gy). The mean follow-up period was 66 months (range 12-155 months), and the median follow-up period was 53 months.

RESULTS

The tumor control rate was 90.5% (19 of 21 lesions). No deterioration in facial nerve or trigeminal nerve function was noted. Disturbances in balance (some temporary) occurred in 5 patients. Three of the 21 patients developed initial tumor swelling, which required minor surgical interventions, including aspiration using an Ommaya reservoir or placement of a ventriculoperitoneal shunt. All 3 patients recovered satisfactorily after aspiration of an enlarging cyst or ventriculoperitoneal shunt placement. There was no significant correlation between tumor control and the following factors: patient age or sex, tumor volume, radiation dose, previous operation, presence of brainstem compression, petrous bone invasion, T2 signal ratio between tumor and brainstem, and presence of a cyst. However, there was a significant correlation between the T2 signal ratio between tumor and brainstem and the duration of tumor swelling (p = 0.003).

CONCLUSIONS

Treatment of large VSs remains a challenge to neurosurgeons regardless of whether they perform microsurgery or radiosurgery. Control of tumor growth and preservation of neurological function are the main goals of treatment. Although delayed microsurgery was required in 2 patients (9.5%), the satisfactory tumor control rate and excellent preservation of facial and trigeminal nerve function are the great advantages of radiosurgery. Radiosurgery is not only a practical treatment for patients with small- to medium-sized VSs, but it is also an excellent tool for treating larger tumors up to 25 cm(3). In selected cases, radiosurgery plays an important role in treating large VSs with satisfactory results.

Gamma Knife surgery for low-grade astrocytomas: evaluation of long-term outcome based on a 10-year experience

OBJECT

The authors report the long-term treatment results of Gamma Knife surgery (GKS) for patients with low-grade astrocytomas who underwent surgery at a single institution.

METHODS

A series of 21 patients (median age 20 years) with 25 intracranial low-grade astrocytomas (World Health Organization Grades I and II) were treated with GKS between 1993 and 2003. Among them, four underwent GKS as a primary treatment. Two underwent GKS as a treatment boost after radiotherapy. In the other 15 patients, GKS was performed as an adjuvant or salvage treatment for residual/recurrent tumors after the patients had undergone craniotomy. Tumor volumes ranged from 0.2 to 13.3 ml (median 2.4 ml). Prescription margin doses ranged from 8 to 18 Gy (median 14.5 Gy). Radiation volumes were 1.3 to 21.6 ml (median 3.6 ml). Patients underwent regular follow up, with neurological evaluation and magnetic resonance imaging studies obtained at 6-month intervals. One patient was lost to follow-up. The clinical follow-up time was 5 to 144 months (median 67 months). Complete tumor remission was seen in three patients. The 10-year progression-free patient survival rate after GKS was 65%. Tumor progression was found in six patients of whom five received further salvage treatment. All the tumor progression occurred within the GKS-treated volumes. Mild-to-moderate adverse radiation effects (AREs) were found in eight patients. Both of the patients who had undergone GKS as a treatment boost after radiotherapy developed AREs, but with good shrinkage of tumors.

CONCLUSIONS

Gamma Knife surgery provides durable long-term local tumor control with acceptable toxicity for some patients with highly selected low-grade astrocytomas.

Staged radiosurgery for extra-large cerebral arteriovenous malformations: method, implementation, and results

OBJECT

The effectiveness and safety of radiosurgery for small- to medium-sized cerebral arteriovenous malformations (AVMs) have been well established. However, the management for large cerebral AVMs remains a great challenge to neurosurgeons. In the past 5 years the authors performed preplanned staged radiosurgery to treat extra-large cerebral AVMs.

METHODS

An extra-large cerebral AVM is defined as one with nidus volume > 40 ml. The nidus volume of cerebral AVM is measured from the dose plan-that is, as being the volume contained within the best-fit prescription isodose. From January 2003 to December 2007, the authors treated 6 patients with extra-large AVMs by preplanned staged GKS. Staged radiosurgery is implemented by rigid transformation with translation and rotation of coordinates between 2 stages. The average radiation-targeted volume was 60 ml (range 47-72 ml). The presenting symptoms were seizure in 4 patients and a bleeding episode in 2. One patient had undergone a previous craniotomy and evacuation of hematoma. The mean interval between the 2 radiosurgical sessions was 6.9 months (range 4.5-9.1 months). The prescribed marginal dose given to the nidus volume in each stage ranged from 16 to 18.6 Gy. The expected marginal dose of total nidus was 17-19 Gy. Regular follow-up MR imaging was performed every 6 months. The mean follow-up period was 28 months (range 12-54 months).

RESULTS

Most of the patients exhibited clinical improvement: relief of headache and reduced frequency of seizure attack. All patients had significant regression of nidus observed on MR imaging follow-up. Two patients had angiogram-confirmed complete obliteration of the nidus 45 and 60 months after the second-stage radiosurgical session. One patient experienced minor bleeding 8 months after the second-stage radiosurgery with mild headache. She had satisfactory recovery without clinical neurological deficit after conservative treatment.

CONCLUSIONS

These preliminary results indicate that staged radiosurgery is a practical strategy to treat patients with extra-large cerebral AVMs. It takes longer to obliterate the AVMs. The observed high signal T2 changes after the radiosurgery appeared clinically insignificant in 6 patients followed up for an average of 28 months. Longer follow-up is necessary to confirm its long-term safety.

Gamma Knife surgery for cerebral arteriovenous malformations in children: a 13-year experience

OBJECT

Studies on the efficacy of arteriovenous malformation (AVM) radiosurgery have largely been conducted in the adult population. Clinically, the results may not always be applicable to pediatric patients. Moreover, studies involving the pediatric population have largely comprised small- (< 3 cm3) and medium-sized (3-10 cm3) AVMs. For large (> 10 cm3) AVMs in children, sparse radiosurgical results are available. The current study was conducted to further clarify the role of radiosurgery in the treatment of pediatric AVMs.

METHODS

A retrospective analysis was performed of data obtained in 105 pediatric patients (< 18 years of age) with cerebral AVMs treated by Gamma Knife surgery (GKS) between 1993 and 2006. For statistical comparison the authors studied data acquired in 458 adult patients with AVMs treated during the same period. The patients underwent follow-up magnetic resonance imaging at 6-month intervals. Cerebral angiography was used to confirm the obliteration of the AVM.

RESULTS

In pediatric patients, the AVM obliteration rate at 48 months after a primary GKS was 65%. Repeated GKS in those in whom primary treatments failed further ablated some AVMs, for an overall obliteration rate of 81%. The efficacy of GKS correlated with the size of the AVM: 91% for small, 86% for medium, and 64% for large AVMs. The treatments were associated with an 8% morbidity rate and < 1% mortality rate. Posttreatment hemorrhage occurred in 4 (4%) of 105 patients. Obliteration rates at 48 months of small and extremely large (> 20 cm3) AVMs were similar in the pediatric and adult groups, whereas AVMs between 3 and 10 cm3 responded less efficaciously in children (p = 0.042). The AVMs with volumes ranging from 10 to 20 cm3 were also associated with a lower obliteration rate in children at 48 months, but statistical significance was not reached (p = 0.279).

CONCLUSIONS

Gamma Knife surgery is an effective and safe treatment alternative for pediatric AVMs. The medium (3-10-cm3) and large (10-20-cm3) AVMs tend to respond less efficaciously than those of comparable size in adults.

Gamma Knife surgery for the management of intracranial dural arteriovenous fistulas

Object

The purpose of this study was to assess the efficacy and safety of Gamma Knife surgery (GKS) for the treatment of cavernous sinus dural arteriovenous fistulas (CSDAVFs) and other intracranial dural arteriovenous fistulas (ODAVFs).

Methods

Among the 238 GKS procedures performed for intracranial DAVFs in the authors' institute, 227 cases (146 CSDAVFs and 81 OIDAVFs) with clinical follow up formed the database from which the authors determined clinical outcome and the incidence of untoward events. One hundred ninety-five cases (118 CSDAVFs and 77 ODAVFs) with imaging follow up formed the database from which the authors determined the imaging results.

Older age, female sex, higher incidence of diabetes, and shorter duration of symptoms were noted more in cases of CSDAVF than in ODAVFs. Most patients had symptomatic improvement after GKS. A symptomatic cure was observed in one patient with CSDAVFs as early as 6 weeks. The cumulative cure rate based on follow-up angiography of CSDAVFs approached 75% at 24 months, which was much better than that of ODAVFs (approximately 50% at 24 months). A neuroimaging-based cure lagged behind that of the clinical symptoms. Overall, there were only two nonfatal intracerebral hemorrhages during the follow-up period, both occurring less than 1 week after GKS and both being Cognard Type IIa+b with initial aggressive symptoms. Transient deterioration of neurological status without hemorrhage was noted in six patients with ODAVFs. Thrombosis of the superior ophthalmic vein occurred in 11 patients with CSDAVFs, in two of whom there were unilateral visual impairments. There were three cranial nerve neuropathies: transient in one CSDAVF and one ODAVF involving the jugular foramen, and another one was a CSDAVF previously treated by conventional radiotherapy.

Conclusions

Gamma Knife surgery provides a safe and effective option for treatment of intracranial DAVFs with a low risk of complications. In cases of DAVFs with benign clinical presentation, GKS can serve as a primary treatment. In some cases of aggressive DAVFs in which there is extensive retrograde cortical vein drainage, combined treatment with embolization or surgery is suggested.