Long-Term Outcomes for Pediatric Patients with Brain Arteriovenous Malformations Treated with Gamma Knife Radiosurgery, Part 2: The Incidence of Cyst Formation, Encapsulated Hematoma, and Radiation-Induced Tumor

Long-term outcomes and safety of Gamma Knife radiosurgery in pediatric arteriovenous malformations

PURPOSE

Despite the unique challenges presented by pediatric intracranial AVMs, little data is available on the use of GKRS in the pediatric population. Therefore, we aimed to present our experience with GKRS in treating pediatric AVMs, determining the factors that influence nidus obliteration and poor outcomes, with a focus on delayed complications.

METHODS

This retrospective review examined patients ≤18 years who underwent GKRS between January 2013 and December 2021 for intracranial AVMs. Factors that predicted residual nidus and poor outcomes were analyzed. The utility of AVM size reduction at follow-up in predicting eventual nidus obliteration was tested.

RESULTS

We treated 101 pediatric patients for AVMs with a mean age of 14.2 ± 2.8 years. The mean dose delivered was 22.7 ± 2.4 Gy. After a mean follow-up of 41.4 months, 78 AVMs (77.8%) were obliterated. Residual nidus was associated with prior embolization (HR 4.953; 95% CI 1.343, 18.268; p = 0.016) and age ≥14 years (HR 5.920; 95% CI 1.559, 22.480; p = 0.009) while presentation with bleed (HR 0.178; 95% CI 0.05, 0.631; p = 0.008) was protective. Reduction in size of a nidus during early follow-up closely correlated with eventual obliteration, with increasing accuracy at 6-month, 12-month, and 24-month follow-up (67.6%, 80.2%, and 86.5% respectively). Twelve patients developed perilesional edema, while one patient each developed a chronic encapsulated hematoma (CEH), cyst formation, and rebleed. Dose > 22 Gy (HR 25.641; 95% CI 2.257, 250; p = 0.009) and volume ≥ 3 cc (HR 7.189; 95% CI 1.176, 43.945; p = 0.033) predicted poor outcomes on multivariate analysis.

CONCLUSIONS

GKRS delivers a high rate of AVM nidus obliteration in the pediatric population, with prior embolization, older age, and unruptured presentation associated with residual nidus. The incidence of delayed complications, although low, warrants regular surveillance in the pediatric population due to their greater life expectancy.

Chronic encapsulated intracerebral haematoma following stereotactic radiosurgery for cerebral arteriovenous malformation

Chronic encapsulated intracerebral haematoma (CEIH) is a rare, delayed complication of stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations. There are no evidence-based guidelines for CEIH management. Current practice patterns range from conservative management with steroids to surgical excision. Here, we report a very delayed case of CEIH that ultimately required surgical resection 24 years following SRS. To our knowledge, this is one of the longest documented cases of recurrent haemorrhages secondary to CEIH, which failed extensive attempts at conservative treatments including steroids, hyperbaric oxygen, vitamin E and pentoxifylline. This case suggests early surgical intervention may be warranted to prevent persistent and recurrent haemorrhages.

Recurrence of chronic encapsulated hematoma following cyst formation after stereotactic radiosurgery for brain arteriovenous malformations: a case report

BACKGROUND

Delayed radiation-induced complications after stereotactic radiosurgery (SRS) for arteriovenous malformations (AVM) have scarcely been described in the literature, and their incidence, pathophysiology, and treatment remain unclear. Additionally, the literature regarding these complications is confusing. The authors present a well-documented case report describing these late complications, adding evidence to the possible common pathophysiological mechanism underlying them, and illustrating an effective treatment modality when they occur.

CASE PRESENTATION

A case of a 28-year-old male with an increasing cyst formation (CF) appearing 10 years after SRS for AVM is presented. Despite surgical treatment, due to the incomplete resection of the angiomatous nodule, recurrence as a chronic encapsulated expanding hematoma (CEEH) occurred. This relapse required a second treatment, which could have been avoided if aggressive surgical treatment had been performed initially.

CONCLUSIONS

This case highlights the continuum between CF and CEEH, challenging existing confusion in the literature. Complete resection of the angiomatous nodule associated with CF is imperative for achieving resolution and preventing recurrence.

Radiation-induced malignancies after stereotactic radiosurgery for brain arteriovenous malformations: a large single-center retrospective study and systematic review

Stereotactic radiosurgery (SRS) is widely utilized to treat small- and medium-sized brain arteriovenous malformations (BAVMs); however, radiation-induced malignancies (RIMs) have been reported as extremely rare yet potentially life-threatening complications of SRS. This study aimed to investigate the risk of RIMs after SRS for BAVMs. The outcomes of patients who underwent single-session SRS for BAVMs at our institution and were followed for ≥ 5 years were analyzed to calculate the incidence of RIMs. In addition, a systematic review was conducted using the existing literature reporting RIMs after SRS for BAVMs in compliance with the PRISMA guideline. Regarding the in-hospital analysis, only one (0.18%) RIM (gliosarcoma) was observed among 569 patients, with a median follow-up period of 151 months (interquartile range, 103-255 months). The 15, 20, and 25-year cumulative incidences of RIMs were 0%, 0%, and 1.01%, respectively, whereas the overall incidence rate was 0.12 per 1,000 patient-years. In the systematic review, 14 studies were included, with the incidence of RIMs ranging from 0.00 to 0.24%. Eight patients with RIMs were identified, and the most common pathology was glioblastoma. The median time until the diagnosis of RIM was 7.1 years (range, 4-19 years) after SRS, and their clinical courses were largely dismal, with the post-diagnosis survival periods being 1-10 months. RIM constitutes an extremely rare but potentially fatal complication following SRS for BAVMs, with its incidence rate being at most 0.24%.

Beyond surgical resection: evaluating stereotactic brachytherapy iodine-125 for low-grade gliomas: a systematic review and meta-analysis

Stereotactic Brachytherapy Iodine-125 (SBT I-125) has been investigated by some studies for the treatment of lowgrade gliomas. We performed a meta-analysis to assess the efficacy and safety of SBT I-125 Brachytherapy for treatment of patients with Low-Grade Gliomas. PubMed, Cochrane, Web of Science, and EMBASE databases were searched for randomized and observational studies. This systematic review and meta-analysis was conducted according to the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines. We used relative risk (RR) with 95% confidence intervals and random effects model to compare the effects of I-125 SBT treatment on the interest outcomes. We evaluated heterogeneity using I2 statistics; we considered heterogeneity to be significant if the p-value was less than 0.05 and I2 was higher than 35%. We performed statistical analysis using the software R (version 4.2.3). A total of 20 studies with a cohort of 988 patients with low grade gliomas who received SBT I-125 as a treatment option. The pooled analysis evidenced: (1) Complication rate of 10% (95% CI: 7-12%; I² = 60%); (2) 5-year PFS of 66% (99% CI: 45-86%; I²= 98%); (3) 10-year PFS was 66% (99% CI: 45-86%; I²= 98%); (4) Malignant transformation rate of 26% (95% CI: 8-45%; I²=0); (5) Mortality of 33% (95% CI: 15-51%; I² = 0%). Our systematic review and meta-analysis of SBT I-125 for low-grade gliomas have revealed significant concerns regarding its safety and efficacy. Despite a proportion of patients remaining progression-free, elevated rates of complications and mortality cast doubt on the intervention's reliability. Future research should prioritize long-term follow-up studies, standardized protocols, and comparative effectiveness research.

Long-Term Outcomes After Stereotactic Radiosurgery for Pediatric Brain Arteriovenous Malformations: A Systematic Review

BACKGROUND

The long-term outcomes after stereotactic radiosurgery (SRS) for pediatric brain arteriovenous malformations (AVMs) remain poorly understood given the paucity of longitudinal studies. A systematic review was conducted to pool cumulative incidences for all outcomes.

METHODS

PubMed, Embase, and Web of Science were queried to systematically extract potential references. The articles relating to AVMs treated via SRS were required to be written in English, involve pediatric patients (<18 years of age), and include a mean follow-up period of >5 years. Individual patient data were obtained to construct a pooled Kaplan-Meier plot on obliteration rates over time.

RESULTS

Among the 6 studies involving 1315 pediatric patients averaging a follow-up period of 86.6 months (range, 6-276), AVM obliteration was observed in 66.1% with cumulative probabilities of 48.28% (95% confidence interval [CI], 41.89-54.68), 76.11% (95% CI, 67.50-84.72), 77.48% (95% CI, 66.37-88.59) over 3, 5, and 10 years, respectively. The cumulative incidence of post-SRS hemorrhage, tumors, cysts, and de novo seizures was 7.2%, 0.3%, 1.6%, and 1.5%, respectively. The cumulative incidence of radiation-induced necrosis, edema, radiologic radiation-induced changes (RICs), symptomatic RICs, and permanent RICs were 8.0%, 1.4%, 28.0%, 8.7%, and 4.9%, respectively.

CONCLUSIONS

Studies assessing long-term outcomes after SRS are moderate in quality and retrospective. Thus, interpretation with caution is advised given the variable degree of loss to follow-up, which suggests that complication rates may be higher than the values stated in the literature. Future prospective studies are needed to validate these findings.

Biologically Effective Dose and Prediction of Obliteration of Arteriovenous Malformations in Pediatric Patients Treated by Gamma Knife Radiosurgery

BACKGROUND AND OBJECTIVES

Stereotactic radiosurgery (SRS) represents an effective treatment for pediatric arteriovenous malformations (AVMs). Biological effective dose (BED) has shown promising results in 2 previous studies as a predictive variable for outcomes in adults, but its role has never been studied in pediatric outcomes.

METHODS

Retrospective data for patients 18 years or younger treated with a single-session SRS for AVMs were collected from 1989 to 2019. BED calculations were performed using an α/β ratio of 2.47. Kaplan-Meier analysis was used to evaluate obliteration, new hemorrhage, and radiation-induced changes (RIC). Cox-regression analysis was used for obliteration prediction using 2 models (margin dose vs BED).

RESULTS

One hundred ninety-seven patients (median age = 13.1 years, IQR = 5.2) were included; 72.6% (143/197) of them presented initially with spontaneous hemorrhage. A median margin dose of 22 Gy (IQR = 4.0) with a median BED of 183.2 Gy (IQR = 70.54) was used to treat AVM with a median volume of 2.8 cm 3 (IQR = 2.9). After SRS, obliteration was confirmed in 115/197 patients (58.4%) using magnetic resonance imaging and angiography at a median follow-up of 2.85 years (IQR = 2.26). The cumulative obliteration probability was 43.6% (95% CI = 36.1-50.3), 60.5% (95% CI+ = 2.2-67.4), and 66.0% (95% CI = 56.0-73.7) at 3, 5, and 10 years, respectively. In Cox multivariate analysis, a BED >180 Gy (hazard ratio [HR] = 2.11, 95% CI = 1.30-3.40, P = .002) in model 1 and a margin dose >20 Gy (HR = 1.90, 95% CI = 1.15-3.13, P = .019) in model 2 were associated with obliteration. An AVM nidus volume >4 cm 3 was associated with lower obliteration rates in both models. The probability of symptomatic RIC at 10 years was 8.6% (95% CI = 3.5-13.4). Neither BED nor margin dose was associated with RIC occurrence, with the only predictive factor being deep AVM location (HR = 3, 95% CI = 1-9.1, P = .048).

CONCLUSION

This study confirms BED as a predictor for pediatric AVM obliteration. Optimization of BED in pediatric AVM SRS planning may improve cumulative obliteration rates.

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.

Long-term follow-up of an overexposure radiation incident in a cohort treated with linear accelerator-based stereotactic radiosurgery for intracranial arteriovenous malformations

OBJECTIVE

Dosimetric radiosurgery incidents are rare and probably insufficiently reported in scientific publications. After a long follow-up (FU), the authors studied the outcomes of patients treated with overexposure radiation for arteriovenous malformation (AVM) administered via stereotactic radiosurgery (SRS) at their department.

METHODS

Between May 2006 and June 2007, 22 patients were treated for AVM with SRS. The mean (range) patient age was 43.5 (11.8-78) years. Previous treatments were embolization (n = 10), SRS (1), and surgery (1). The average (range) volume was 2.1 (0.2-6.4) cm3. The median prescribed minimal dose was 18.0 Gy. An initial error in the estimation of scatter factors led to overexposure to radiation. Due to this incident, the median delivered minimum dose was 25.0 Gy. All patients were prospectively followed with clinical examination and imaging.

RESULTS

The mean (range) clinical FU was 14.5 (12.0-15.2) years. AVM obliteration after SRS was completed in 90.9% of patients at a mean (range) of 39.4 (24.4-70.4) months. No patient had post-SRS AVM bleeding. Three patients (13.6%) had new permanent deficits due to radiation-induced changes (RICs). Obliteration without new deficits was achieved in 18 patients (81.8%). Two patients had new epilepsy that was probably due to RIC but well controlled. The median (range) MRI FU was 13.8 (2.5-14.9) years. During MRI FU, two RIC periods were observed: one classic period during the first 3 years showed T1-weighted annular irregular enhancement (13%), and the other period between 5 and 15 years after SRS showed the occurrence of cystic and hemorrhagic lesions (22.7%). There were no cases of radiation-induced tumor.

CONCLUSIONS

The present long-term report showed that this overexposure incident probably increased the AVM obliteration rate. This overexposure seems to have induced RIC and in particular a higher rate of cystic and hemorrhagic late lesions with nevertheless moderate clinical consequences. Long-term FU for AVM is mandatory due to the risk of late RIC.

Chronic Encapsulated Expanding Hematomas After Stereotactic Radiosurgery for Intracranial Arteriovenous Malformations: An International Multicenter Case Series

BACKGROUND

Stereotactic radiosurgery (SRS) offers a minimally invasive treatment modality for appropriately selected intracranial arteriovenous malformations (AVMs). Recent reports have described the development of rare, delayed chronic encapsulated expanding hematomas (CEEHs) at the site of an angiographically confirmed obliterated AVM.

OBJECTIVE

To elucidate the incidence, characteristics, and management of CEEH in patients with AVM after SRS.

METHODS

The records of all patients who underwent SRS for an intracranial AVM at 4 institutions participating in the International Radiosurgery Research Foundation between 1987 and 2021 were retrospectively reviewed. Data regarding characteristics of the AVM, SRS treatment parameters, CEEH presentation, management, and outcomes were collected and analyzed.

RESULTS

Among 5430 patients, 15 developed a CEEH at a crude incidence of 0.28%. Nine patients were female, and the mean age was 43 ± 14.6 years. Nine patients underwent surgical evacuation, while 6 were managed conservatively. The median CEEH development latency was 106 months after SRS. The patients were followed for a median of 32 months, and 9 patients improved clinically, while 6 patients remained stable. No intraoperative complications were reported after CEEH resection, although 1 patient recovered from postoperative meningitis requiring intravenous antibiotics.

CONCLUSION

CEEH is a rare, late complication of AVM SRS with an incidence of 0.28% and a median latency of 106 months. In the presence of a delayed and symptomatic expanding hematoma in the bed of an angiographically obliterated AVM, surgical resection resulted in clinical improvement in most patients. Conservative management is possible in asymptomatic patients with stable, small-sized hematomas in deeply seated locations.

Effect of embolization before stereotactic radiosurgery for brain arteriovenous malformations: a case-control study with propensity score matching

OBJECTIVE

The aim of this study was to evaluate whether endovascular embolization prior to stereotactic radiosurgery (SRS) has a negative impact on nidus obliteration for patients with arteriovenous malformations (AVMs).

METHODS

A total of 704 eligible patients with AVM who did not undergo prior surgery or radiotherapy were evaluated. Of these patients, 593 were treated with SRS only, and 111 were treated with embolization followed by SRS (E+SRS). Most patients in the E+SRS group (88%) underwent embolization with n-butyl-2-cyanoacrylate. In the comparison of radiosurgical outcomes between patients treated with SRS only and E+SRS, these groups were matched in a 1:1 ratio using propensity score matching to eliminate differences in basic characteristics. The primary outcome was to compare the nidus obliteration rates between the SRS-only and E+SRS groups. The secondary outcomes were the comparison of cumulative hemorrhage rates and the incidence of cyst formation or chronic encapsulated hematoma after SRS between these groups.

RESULTS

In the unmatched cohorts, the actuarial 3-, 5-, and 8-year nidus obliteration rates after a single SRS session were 49.6%, 69.4%, and 74.1% in the SRS-only group, respectively, and 30.7%, 50.9%, and 68.6% in the E+SRS group, respectively (p = 0.001). In the matched cohort of 98 patients in each group, the rates were 47.1%, 62.0%, and 69.6% in the SRS-only group and 32.5%, 55.3%, and 75.0% in the E+SRS group, respectively (p = 0.24). There was no significant difference in either cumulative hemorrhage or the incidence of cyst formation or chronic encapsulated hematoma between the groups.

CONCLUSIONS

Pre-SRS embolization did not affect nidus obliteration rates, cumulative hemorrhage rates, or the incidence of cyst formation or chronic encapsulated hematoma as late adverse radiation effects in patients with AVM treated with SRS.

Long-Term Risks of Hemorrhage and Adverse Radiation Effects of Stereotactic Radiosurgery for Brain Arteriovenous Malformations

BACKGROUND

The information about long-term risks of hemorrhage and late adverse radiation effects (AREs) after stereotactic radiosurgery for brain arteriovenous malformations (AVMs) is lacking.

OBJECTIVE

To evaluate the long-term risks of hemorrhage and late ARE rates in patients with AVM treated with Gamma Knife surgery (GKS).

METHODS

We examined 1249 patients with AVM treated with GKS. The Spetzler-Martin grade was I in 313 patients (25%), II in 394 (32%), III in 458 (37%), and IV/V in 84 (7%). The median treatment volume was 2.5 cm3, and the median marginal dose was 20 Gy.

RESULTS

The median follow-up period was 61 months. The 5- and 10-year nidus obliteration rates were 63% and 82%, respectively. The 5- and 10-year cumulative hemorrhage rates were 7% and 10%, respectively. The annual hemorrhage rate was 1.5% for the first 5 years post-GKS, which decreased to 0.5% thereafter. During the follow-up period, 42 symptomatic cyst formations/chronic encapsulated hematomas ([CFs/CEHs], 3%) and 3 radiation-induced tumors (0.2%) were observed. The 10- and 15-year cumulative CF/CEH rates were 3.7% and 9.4%, respectively.

CONCLUSION

GKS is associated with reduced hemorrhage risk and high nidus obliteration rates in patients with AVM. The incidence of late AREs tended to increase over time. The most common ARE was CF/CEH, which can be safely removed; however, careful attention should be paid to the long-term development of fatal radiation-induced tumors.

Current concepts and perspectives on brain arteriovenous malformations: A review of pathogenesis and multidisciplinary treatment

Brain arteriovenous malformations (bAVMs) are unusual vascular pathologies characterized by the abnormal aggregation of dilated arteries and veins in the brain parenchyma and for which the absence of a normal vascular structure and capillary bed leads to direct connections between arteries and veins. Although bAVMs have long been believed to be congenital anomalies that develop during the prenatal period, current studies show that inflammation is associated with AVM genesis, growth, and rupture. Interventional treatment options include microsurgery, stereotactic radiosurgery, and endovascular embolization, and management often comprises a multidisciplinary combination of these modalities. The appropriate selection of patients with brain arteriovenous malformations for interventional treatment requires balancing the risk of treatment complications against the risk of hemorrhaging during the natural course of the pathology; however, no definitive guidelines have been established for the management of brain arteriovenous malformations. In this paper, we comprehensively review the current basic and clinical studies on bAVMs and discuss the contemporary status of multidisciplinary management of bAVMs.

Chronic encapsulated expanding hematomas after stereotactic radiosurgery for intracranial arteriovenous malformations

OBJECTIVE

Cerebral arteriovenous malformations (AVMs) are rare cerebral vascular lesions that are associated with high morbidity and mortality from hemorrhage; however, stereotactic radiosurgery (SRS) is a well-validated treatment modality. Few reports have delineated a subgroup of patients who develop delayed chronic encapsulated expanding hematomas (CEEHs) despite angiographic evidence of AVM obliteration following radiosurgery. In this report, the authors performed a retrospective review of more than 1000 radiosurgically treated intracranial AVM cases to delineate the incidence and management of this rare entity.

METHODS

Between 1988 and 2019, 1010 patients with intracranial AVM underwent Gamma Knife SRS at the University of Pittsburgh Medical Center. In addition to a review of a prospective institutional database, the authors performed a retrospective chart review of the departmental AVM database to specifically identify patients with CEEH. Pertinent clinical and radiological characteristics as well as patient outcomes were recorded and analyzed.

RESULTS

Nine hundred fifty patients with intracranial AVM (94%) had sufficient clinical follow-up for analysis. Of these, 6 patients with CEEH underwent delayed resection (incidence rate of 0.0045 event per person-year). These patients included 4 males and 2 females with a mean age of 45.3 ± 13.8 years at the time of initial SRS. Four patients had smaller AVM volumes (4.9-10 cm3), and 3 of them were treated with a single SRS procedure. Two patients had larger-volume AVMs (55 and 56 cm3), and both underwent multimodal management that included staged SRS and embolization. Time to initial recognition of the CEEH after initial SRS ranged between 66 and 243 months. The time between CEEH recognition and resection ranged from 2 to 9 months. Resection was required because of progressive neurological symptoms that correlated with imaging evidence of gradual hematoma expansion. All 6 patients had angiographically confirmed obliteration of their AVM. Pathology revealed a mixed chronicity hematoma with areas of fibrosed blood vessels and rare areas of neovascularization with immature blood vessels but no evidence of a persistent AVM. All 6 patients reported persistent clinical improvement after hematoma resection.

CONCLUSIONS

CEEH after SRS for AVM is a rare complication with an incidence rate of 0.0045 event per person-year over the authors' 30-year experience. When clinical symptoms progress and imaging reveals progressive enlargement over time, complete resection of a CEEH results in significant clinical recovery. Knowledge of this rare entity facilitates timely detection and eventual surgical intervention to achieve optimal outcomes.

Recognizing Radiation-induced Changes in the Central Nervous System: Where to Look and What to Look For

Radiation therapy (RT) continues to play a central role as an effective therapeutic modality for a variety of tumors and vascular malformations in the central nervous system. Although the planning and delivery techniques of RT have evolved substantially during the past few decades, the structures surrounding the target lesion are inevitably exposed to radiation. A wide variety of radiation-induced changes may be observed at posttreatment imaging, which may be confusing when interpreting images. Histopathologically, radiation can have deleterious effects on the vascular endothelial cells as well as on neuroglial cells and their precursors. In addition, radiation induces oxidative stress and inflammation, leading to a cycle of further cellular toxic effects and tissue damage. On the basis of the time of expression, radiation-induced injury can be divided into three phases: acute, early delayed, and late delayed. Acute and early delayed injuries are usually transient and reversible, whereas late delayed injuries are generally irreversible. The authors provide a comprehensive review of the timeline and expected imaging appearances after RT, including the characteristic imaging features after RT with concomitant chemotherapy. Specific topics discussed are imaging features that help distinguish expected posttreatment changes from recurrent disease, followed by a discussion on the role of advanced imaging techniques. Knowledge of the RT plan, the amount of normal structures included, the location of the target lesion, and the amount of time elapsed since RT is highly important at follow-up imaging, and the reporting radiologist should be able to recognize the characteristic imaging features after RT and differentiate these findings from tumor recurrence. ^©RSNA, 2020.

Pediatric Intracranial Arteriovenous Malformation: Long-Term Outcomes with Linear Accelerator (LINAC)-Based Radiosurgery

Purpose

To analyze and report the long-term outcomes of intracranial arteriovenous malformations (AVM) treated with linear accelerator (LINAC)-based radiosurgery (LBRS) in the pediatric population.

Methods and Materials

A series of 34 pediatric patients (≤18 years old) who were treated between 2002 and 2016 were analyzed. All patients were treated with LBRS in a single fraction, with a median dose of 16.8 Gy to the 80% isodose line. Median age at treatment was 14.4 years (range 5.5-18.9). Median AVM volume was 2.91 mL (range 0.228-27.313). Median modified radiosurgery-based AVM score was 0.83 (range 0.18-2.96). The most common presenting symptom was intracranial hemorrhage (ICH) (n = 22, 64.7%). Nine patients underwent intervention before LBRS, which included prior embolization or resection. Seven lesions were in eloquent locations, defined as basal ganglia, thalamus, or brainstem. Cerebral angiography was done to confirm obliteration.

Results

Median follow-up time was 98 months (range 36-200 months). Twenty-two of the 34 lesions were obliterated (64.7%) with median time to obliteration of 37 months (range 14-79). No deaths occurred during the follow up period; however, two patients experienced ICH after treatment. Three other patients were treated for symptomatic radiation necrosis.

Conclusions

Treatment of intracranial AVM with LBRS in the pediatric population is demonstrated to be safe and effective with long-term follow up.

Late complications of radiosurgery for cerebral arteriovenous malformations: report of 5 cases of chronic encapsulated intracerebral hematomas and review of the literature

Background

Chronic encapsulated intracerebral hematomas (CEIHs) are a rare, late complication of radiosurgery for intracranial AVM. We present 5 cases treated mostly by surgical excision and review the literature.

Methods

Patients (age 39, 42, 36, 31, 62) presented with headache, paresthesia, hemiparesis or were asymptomatic. CEIHs presented 10 to 13 years (median 12 years) post radiosurgery. Three patients had demonstrated early radiation induced changes post radiosurgery. Angiographic cure, assessed with DSA, was present in all cases except 1 case with a small nidus remnant. MRI demonstrated mixed lesions with a solid enhancing part, organized hematoma and extensive surrounding edema while three cases had also a cystic component.

Results

Excision of the CEIHs with complete or partial removal of the capsule was performed in 4 patients and resulted in marked clinical improvement. One patient was managed conservatively with administration of steroids as surgery was judged excessively hazardous with eventual stabilization of his symptoms.

Conclusions

CEIHs are rare, late complications of radiosurgery for cranial AVM. They may be asymptomatic or provoke symptoms and may be preceded by early radiation induced changes. Complete removal of CEIHS is an effective treatment. Because of the long latency period of CEIHs, patients who had radiosurgery for brain AVMs should be followed by MRI at least 10 years even after complete obliteration.

Pathological Changes in Surgically Resected Cystic Cerebral Cavernous Malformation 13 Years After Radiosurgery: Case Report and Review of the Literature

BACKGROUND

Stereotactic radiosurgery (SRS) as a treatment for cerebral cavernous malformation (CCM) has been controversial, but there are few pathological reports showing its long-term therapeutic effect, and literature reporting the CCM cyst formation after SRS is also rare.

CASE DESCRIPTION

We present a 30-year-old woman with a ruptured right parietal CCM treated with SRS 13 years ago. The post-SRS imaging follow-up revealed CCM rehemorrhage and cyst formation. Surgical resection was performed, and a subsequent pathological examination revealed that the CCM still had some incomplete occluded vessels and a large number of newly formed capillaries, and hemorrhagic band and hemosiderin were seen around the nodule.

CONCLUSIONS

Recurrent hemorrhage after SRS for CCM could be related to incomplete occluded vessels and newly formed capillaries. Repeated hemorrhage from CCM newly formed capillaries into the small cavity increased the osmotic pressure, resulting in fluid entering the cavity and cyst enlargement.

Gamma Knife Radiosurgery Followed by Flow-Reductive Embolization for Ruptured Arteriovenous Malformation

Background: Aggressive treatment to achieve complete obliteration of brain arteriovenous malformation (AVM) is necessary in patients with a recent history of hemorrhage. The major drawback of Gamma knife radiosurgery (GKRS) alone for AVM is risk of bleeding during the latent period until the AVM occludes. At our center, patients who present with ruptured AVMs are frequently offered GKRS followed by embolization. The goal of this study was to compare outcomes of embolization for patients who have previously undergone GKRS for ruptured AVMs. Methods: A database including 150 GKRS for ruptured AVMs between November 2008 and October 2017 was reviewed. The embolized group was selected by including AVMs with post-GKRS embolization. The non-embolized group was defined as AVMs treated by GKRS alone. Outcomes including obliteration rate, incidence of repeat hemorrhage, and delayed cyst formation were compared between two groups. The predictive factors related to AVM obliteration and complications were analyzed. Results: The study consisted of 81 patients in the non-embolized group and 17 patients in the embolized group. Statistically significant differences were detected between the two groups with respect to age, Pollock-Flickinger score, Spetzler-Martin (SM) grade, eloquence of adjacent brain, and presence of aneurysms. The embolized group included more AVMs with larger median nidus volume. The predictive factors for the obliteration of ruptured AVMs were nidus volume, SM grade, Virginia Radiosurgery AVM Scale (VRAS), and Pollock-Flickinger score and for the subsequent hemorrhage were marginal dose, nidus volume, SM grade, VRAS, and Pollock-Flickinger score. The obliteration rates and complication rates after GKRS between groups were not significantly different. However, this study demonstrated statistically significant difference in the cumulative incidence of obliteration in AVMs with SM grade III and IV (p = 0.037). Conclusion: Although the current study demonstrated similar results in patients who underwent GKRS with and without embolization, the embolized group included more AVMs with larger nidus volume, higher SM grade, Pollock-Flickinger score, and aneurysm, which have a lower chance of obliteration and a higher probability of repeat hemorrhage. GKRS followed by embolization appears to be a beneficial approach for the treatment of ruptured AVMs that are at risk for obliteration failure and repeat hemorrhage during the latency period after single-session GKRS alone. Further studies involving a larger number of cases and continuous follow-up are necessary to confirm our conclusions.

Gamma Knife Radiosurgery in Patients with Crooke Cell Adenoma

BACKGROUND

Crooke cell adenoma is a very rare subtype of pituitary neoplasm that is known to be clinically aggressive. These tumors can secrete adrenocorticotropic hormone or may be endocrinologically silent. We evaluated the effect of Gamma Knife radiosurgery (GKRS) on endocrine remission and tumor control.

MATERIALS AND METHODS

This study comprised 5 patients (2 men, 3 women; median age at GKRS, 55 years [range, 21-65 years]) with pathology-confirmed Crooke cell adenoma treated with GKRS at the Gamma Knife Center of the University of Virginia. The median time interval between transsphenoidal resection and GKRS was 5.8 months. The median margin dose was 25 Gy (range, 18-25 Gy). Median treated adenoma volume was 3.12 mL. Median follow-up was 107 months (range, 44-122 months).

RESULTS

Tumor control was achieved in all patients. Three patients achieved endocrine remission at the last follow-up. The median time interval to cortisol normalization when off of anti-hormone secreting medication was 12 months (range, 6-24 months). Newly developed or worsening endocrinopathy occurred in 3 patients at 6, 15, and 18 months, respectively. Cranial nerve III neuropathy developed in 1 patient. Two patients required bilateral adrenalectomy at 44 months and 50 months, respectively, following GKRS.

CONCLUSIONS

GKRS appears to be a safe and reasonably effective treatment option for Crooke cell adenoma. Multicenter studies with larger numbers of patients are needed to verify these findings.

Gamma Knife Radiosurgery For Brain Vascular Malformations: Current Evidence And Future Tasks

Gamma Knife radiosurgery (GKRS) has long been used for treating brain vascular malformations, including arteriovenous malformations (AVMs), dural arteriovenous fistulas (DAVFs), and cavernous malformations (CMs). Herein, current evidence and controversies regarding the role of stereotactic radiosurgery for vascular malformations are described. 1) It has already been established that GKRS achieves 70–85% obliteration rates after a 3–5-year latency period for small to medium-sized AVMs. However, late radiation-induced adverse events (RAEs) including cyst formation, encapsulated hematoma, and tumorigenesis have recently been recognized, and the associated risks, clinical courses, and outcomes are under investigation. SRS-based therapeutic strategies for relatively large AVMs, including staged GKRS and a combination of GKRS and embolization, continue to be developed, though their advantages and disadvantages warrant further investigation. The role of GKRS in managing unruptured AVMs remains controversial since a prospective trial showed no benefit of treatment, necessitating further consideration of this issue. 2) Regarding DAVFs, GKRS achieves 41–90% obliteration rates at the second post-GKRS year with a hemorrhage rate below 5%. Debate continues as to whether GKRS might serve as a first-line solo therapeutic modality given its latency period. Although the post-GKRS outcomes are thought to differ among lesion locations, further outcome analyses regarding DAVF locations are required. 3) GKRS is generally accepted as an alternative for small or medium-sized CMs in which surgery is considered to be too risky. The reported hemorrhage rates ranged from 0.5–5% after GKRS. Higher dose treatments (>15 Gy) were performed during the learning curve, while, with the current standard treatment, a dose range of 12–15 Gy is generally selected, and has resulted in acceptable complication rates (< 5%). Nevertheless, further elucidation of long-term outcomes is essential.