Stereotactic Radiosurgery For Arteriovenous Malformations Research Articles

LINAC radiosurgery for cerebral arteriovenous malformations: A single centre prospective analysis and review of the literature

Stereotactic radiosurgery (SRS) is a well established, minimally invasive treatment option for patients diagnosed with cerebral arteriovenous malformations (AVM). We present the experience in linear accelerator-based SRS for cerebral AVM treated over 14years. We prospectively followed 67 patients with 69 AVM treated with SRS from 1994 to 2008, inclusive. The mean patient age was 37years (range 7–69) with 36 women and 31 men. The median AVM size, as defined by maximal diameter, was 2.5cm (range 0.5–4.6cm) and the median marginal dose was 18Gy in one fraction. The crude angiographic obliteration rate was 55% with a 3 and 5year actuarial rate of 39% and 65%, respectively. Median time to obliteration was 4.2years. Higher treatment dose (p<0.0001) and smaller maximal AVM diameter (p=0.002) were associated with an increased obliteration rate. There were no deaths from treatment. Post-treatment neurological complications occurred in 10 patients (15%) including hemorrhage in two. Twelve patients (18%) required a second SRS procedure. Larger AVM diameter was associated with increased odds of requiring re-treatment (p=0.02). Radiosurgery for intracerebral AVM is a non-invasive therapeutic option with low morbidity and a reasonable likelihood of nidus obliteration. Treatment dose and AVM diameter are the main determinants of obliteration.

Treatment of Brain Arteriovenous Malformations With Stereotactic Radiosurgery Following Embolization

Treatment of intracranial arteriovenous malformations (AVMs) is complex and multimodal. Some series have suggested embolization (embo) followed by stereotactic radiosurgery (SRS) is associated with poor outcomes. We examine the effect of post-embo SRS for AVMs.

Angiographic features help predict outcome after stereotactic radiosurgery for the treatment of pediatric arteriovenous malformations

Arteriovenous malformations (AVMs) are a frequent cause of hemorrhagic stroke in children. Stereotactic radiosurgery (SRS) is an established treatment for these lesions, particularly those that are surgically inaccessible. Because only complete AVM obliteration is believed to protect against the future risk of hemorrhage, identifying lesion characteristics that predict response to therapy is an important objective. The goal of this study is to evaluate the influence of angiographic features of AVMs on the rate of obliteration following treatment with SRS. This is a retrospective cohort study of pediatric patients (age ≤18 years) treated with Gamma Knife SRS for cerebral AVMs between 2000 and 2012. Detailed angiographic data at the time of initial angiographic evaluation were prospectively recorded by experienced neurointerventional radiologists. The primary outcome was the rate of obliteration on a 3-year follow-up angiogram. We identified 42 pediatric patients treated with SRS for cerebral AVMs. Twenty-seven patients completed 3-year angiographic follow-ups. Complete obliteration was seen in 30%, partial response in 67%, and no response in 4%. Higher SRS dose was associated with complete obliteration. Larger AVM diameter, presence of multiple draining veins, and presence of multiple draining veins reaching a sinus were associated with partial response. In this small cohort, diffuse AVM borders, presence of aneurysm, and pre-SRS embolization were not associated with obliteration. Our study identifies AVMs in the pediatric population with a nidus diameter of <2.5 cm and a solitary draining vein as the most likely to undergo complete obliteration after SRS treatment.

Long-term outcome of Gamma Knife stereotactic radiosurgery for arteriovenous malformations graded by the Spetzler-Martin classification

The object of this study was to assess outcomes in patients with arteriovenous malformations (AVMs) treated by Gamma Knife stereotactic radiosurgery (SRS); lesions were stratified by size, symptomatology, and Spetzler-Martin (S-M) grade. The authors performed a retrospective analysis of 102 patients treated for an AVM with single-dose or staged-dose SRS between 1993 and 2004. Lesions were grouped by S-M grade, as hemorrhagic or nonhemorrhagic, and as small (< 3 cm) or large (≥ 3 cm). Outcomes included death, morbidity (new neurological deficit, new-onset seizure, or hemorrhage/rehemorrhage), nidus obliteration, and Karnofsky Performance Scale score. The mean follow-up was 8.5 years (range 5-16 years). Overall nidus obliteration (achieved in 75% of patients) and morbidity (19%) correlated with lesion size and S-M grade. For S-M Grade I-III AVMs, nonhemorrhagic and hemorrhagic combined, treatment yielded obliteration rates of 100%, 89%, and 86%, respectively; high functional status (Karnofsky Performance Scale Score ≥ 80); and 1% mortality. For S-M Grade IV and V AVMs, outcomes were less favorable, with obliteration rates of 54% and 0%, respectively. The AVMs that were not obliterated had a mean reduction in nidus volume of 69% (range 35%-96%). On long-term follow-up, 10% of patients experienced hemorrhage/rehemorrhage (6% mortality rate), which correlated with lesion size and S-M grade; the mean interval to hemorrhage was 81 months. For patients with S-M Grade I-III AVMs, SRS offers outcomes that are favorable and that, except for the timing of obliteration, appear to be comparable to surgical outcomes reported for the same S-M grades. Staged-dose SRS results in lesion obliteration in half of patients with S-M Grade IV lesions.

Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of arteriovenous malformations and acoustic neuromas

PurposeWe investigated the influence of beam modulation on treatment planning by comparing four available stereotactic radiosurgery (SRS) modalities: Gamma-Knife-Perfexion, Novalis-Tx Dynamic-Conformal-Arc (DCA) and Dynamic-Multileaf-Collimation-Intensity-Modulated-radiotherapy (DMLC-IMRT), and Cyberknife. Material and methodsPatients with arteriovenous malformation (n=10) or acoustic neuromas (n=5) were planned with different treatment modalities. Paddick conformity index (CI), dose heterogeneity (DH), gradient index (GI) and beam-on time were used as dosimetric indices. ResultsGamma-Knife-Perfexion can achieve high degree of conformity (CI=0.77±0.04) with limited low-doses (GI=2.59±0.10) surrounding the inhomogeneous dose distribution (DH=0.84±0.05) at the cost of treatment time (68.1min±27.5). Novalis-Tx-DCA improved this inhomogeneity (DH=0.30±0.03) and treatment time (16.8min±2.2) at the cost of conformity (CI=0.66±0.04) and Novalis-TX-DMLC-IMRT improved the DCA CI (CI=0.68±0.04) and inhomogeneity (DH=0.18±0.05) at the cost of low-doses (GI=3.94±0.92) and treatment time (21.7min±3.4) (p<0.01). Cyberknife achieved comparable conformity (CI=0.77±0.06) at the cost of low-doses (GI=3.48±0.47) surrounding the homogeneous (DH=0.22±0.02) dose distribution and treatment time (28.4min±8.1) (p<0.01). ConclusionsGamma-Knife-Perfexion will comply with all SRS constraints (high conformity while minimizing low-dose spread). Multiple focal entries (Gamma-Knife-Perfexion and Cyberknife) will achieve better conformity than High-Definition-MLC of Novalis-Tx at the cost of treatment time. Non-isocentric beams (Cyberknife) or IMRT-beams (Novalis-Tx-DMLC-IMRT) will spread more low-dose than multiple isocenters (Gamma-Knife-Perfexion) or dynamic arcs (Novalis-Tx-DCA). Inverse planning and modulated fluences (Novalis-Tx-DMLC-IMRT and CyberKnife) will deliver the most homogeneous treatment. Furthermore, Linac-based systems (Novalis and Cyberknife) can perform image verification at the time of treatment delivery.

Frameless Angiogram-Based Stereotactic Radiosurgery for Treatment of Arteriovenous Malformations

Stereotactic radiosurgery (SRS) is an effective alternative to microsurgical resection or embolization for definitive treatment of arteriovenous malformations (AVMs). Digital subtraction angiography (DSA) is the gold standard for pretreatment diagnosis and characterization of vascular anatomy, but requires rigid frame (skull) immobilization when used in combination with SRS. With the advent of advanced proton and image-guided photon delivery systems, SRS treatment is increasingly migrating to frameless platforms, which are incompatible with frame-based DSA. Without DSA as the primary image, target definition may be less than optimal, in some cases precluding the ability to treat with a frameless system. This article reports a novel solution. Fiducial markers are implanted into the patient's skull before angiography. Angiography is performed according to the standard clinical protocol, but, in contrast to the previous practice, without the rigid frame. Separate images of a specially designed localizer box are subsequently obtained. A target volume projected on DSA can be transferred to the localizer system in three dimensions, and in turn be transferred to multiple CT slices using the implanted fiducials. Combined with other imaging modalities, this "virtual frame" approach yields a highly precise treatment plan that can be delivered by frameless SRS technologies. Phantom measurements for point and volume targets have been performed. The overall uncertainty of placing a point target to CT is 0.4 mm. For volume targets, deviation of the transformed contour from the target CT image is within 0.6 mm. The algorithm and software are robust. The method has been applied clinically, with reliable results. A novel and reproducible method for frameless SRS of AVMs has been developed that enables the use of DSA without the requirement for rigid immobilization. Multiple pairs of DSA can be used for better conformality. Further improvement, including using nonimplanted fiducials, is potentially feasible.

Stereotactic Radiosurgery for Arteriovenous Malformations Located in Deep Critical Regions

Radiosurgery is widely used to treat deep eloquent arteriovenous malformations (AVMs). To evaluate how anatomic location, AVM size, and treatment parameters define outcome. Retrospective analysis of 356 thalamic/basal ganglia and 160 brainstem AVMs treated with gamma knife radiosurgery. Median volume was 2 cm (range, 0.02-50) for supratentorial and 0.5 cm (range, 0.01-40) for brainstem AVMs; the marginal treatment doses were 17.5 to 25 Gy. After single treatment, obliteration was achieved in 65% of the brainstem, in 69% of the supratentorial, and 40% of the peritectal AVMs. Obliteration of lesions <4 cm was better in the brainstem (70%) and in the supratentorium (80%), but not in the peritectal region (40%). Complications were rare (6%-15%) and mild (≤ modified Rankin scale [MRS] 2). Rebleed rate increased with size, but was not higher than before treatment. AVMs >4 cm in the brainstem were treated with unacceptable morbidity and low cure rate. Obliteration of large supratentorial AVMs was 65% to 47% with more complications ≥ MRS3. Repeat radiosurgical treatment led to obliteration in 66% of the cases with minor morbidity. Deep eloquent AVMs <4 cm can be treated safely and effectively with radiosurgery. Obliteration of peritectal AVMs is significantly lower after a single treatment. However, morbidity is low, and repeat treatment leads to good obliteration. Radiosurgical treatment >4 cm in the brainstem is not recommended. Supratentorial deep AVMs >8 cm can be treated with radiosurgery with higher risk and lower obliteration rate. However, these lesions are difficult to treat with other treatment modalities, and a 50% success rate makes radiosurgery a good alternative even in this challenging group.

Factors Predictive of Obliteration After Arteriovenous Malformation Radiosurgery

To investigate predictive factors of complete obliteration following treatment with linac-based stereotactic radiosurgery for intracerebral arteriovenous malformations. Archived plans for 48 patients treated at the British Columbia Cancer Agency and who underwent post-treatment digital subtraction angiography to assess obliteration were studied. Actuarial estimates of obliteration were calculated using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazards models were used for analysis of incidence of obliteration. Log-rank test was used to search for parameters associated with obliteration. Complete nidus obliteration was achieved in 38/48 patients (79.2%). Actuarial rate of obliteration was 75.9% at 4 years (95% confidence interval 63.1%-88.6%). On univariate analysis, prescribed dose to the margin (p=0.002) and dose to isocentre (p=0.022) showed statistical significance. No parameters were significant in a multivariate model. According to the log-rank test, prescribed dose to the margin of >20 Gy (p=0.004) and dose to the isocentre of >25 Gy (p=0.004) were associated with obliteration. Reported series in the literature suggest a number of different factors are predictive of complete obliteration of arteriovenous malformations following radiosurgery. However, differing definitions of volume and complete obliteration makes direct comparison between series difficult. This study demonstrates that complete obliteration of the nidus following linear accelerator-based stereotactic radiosurgery for arteriovenous malformations appears to be most closely related to the prescribed marginal dose. In particular, a marginal dose of >20 Gy is strongly associated with obtaining complete obliteration of the nidus.

Outcomes of Radiosurgery for Brainstem Arteriovenous Malformations

Arteriovenous malformations (AVMs) in the brainstem yield a high risk of hemorrhage. Although stereotactic radiosurgery (SRS) is accepted, because of high surgical morbidity and mortality, outcomes are still unclear. We previously reported the early results of SRS for brainstem AVMs. Here, we obtained data from a longer follow-up for a larger number of patients and present precise outcomes based on the latest follow-up data. Forty-four patients with brainstem AVMs were treated by SRS. Outcomes such as the rates of obliteration, hemorrhage after treatment, and adverse effects were retrospectively analyzed. The annual hemorrhage rate before SRS was 17.5%. The mean follow-up period after SRS was 71 months (range, 2-168 months). The actuarial obliteration rate confirmed by angiography was 52% at 5 years. Factors associated with higher obliteration rate were previous hemorrhage (P = .048) and higher margin dose (P = .048). For patients treated with a margin dose of ≥ 18 Gy, the obliteration rate was 71% at 5 years. Persistent worsening of neurological symptoms was observed in 5%. The annual hemorrhage rate after SRS was 2.4%. Four patients died of rebleeding, and disease-specific survival rate was 86% at 10 years after treatment. Nidus obliteration must be achieved for brainstem AVMs because they possibly cause lethal hemorrhage even after SRS. Treatment with a high margin dose is desirable to obtain favorable outcomes for these lesions. Additional treatment should be considered for an incompletely obliterated nidus.

Integration of Three-Dimensional Rotational Angiography in Radiosurgical Treatment Planning of Cerebral Arteriovenous Malformations

Accuracy in delineating the target volume is a major issue for successful stereotactic radiosurgery for arteriovenous malformations. The aim of the present study was to describe a method to integrate three-dimensional (3D) rotational angiography (3DRA) into CyberKnife treatment planning and to investigate its potential advantages compared with computed tomography angiography (CTA) and magnetic resonance angiography. A total of 20 patients with a diagnosis of cerebral arteriovenous malformation were included in the present study. All patients underwent multislice computed tomography and 3D-volumetric CTA, 3DRA, and 3D magnetic resonance angiography. The contouring of the target and critical volumes was done separately using CTA and thereafter directly using 3DRA. The composite, conjoint, and disjoint volumes were measured. The use of CTA or 3DRA resulted in significant differences in the target and critical volumes. The target volume averaged 3.49 ± 3.01 mL measured using CTA and 3.26 ± 2.93 mL measured using 3DRA, for a difference of 8% (p < .05). The conjoint and disjoint volume analysis showed an 88% volume overlap. The qualitative evaluation showed that the excess volume obtained using CTA was mostly tissue surrounding the nidus and venous structures. The mean contoured venous volume was 0.67 mL measured using CTA and 0.88 mL (range, 0.1-2.7) measured using 3DRA (p < .05). 3DRA is a volumetric angiographic study that can be integrated into computer-based treatment planning. Although whether 3DRA provides superior accuracy has not yet been proved, its high spatial resolution is attractive and offers a superior 3D view. This allows a better 3D understanding of the target volume and distribution of the radiation doses within the volume. Additional technical efforts to improve the temporal resolution and the development of software tools aimed at improving the performance of 3D contouring are warranted.

Contribution of technological progress, inter-operator difference and experience of operators in Gamma Knife radiosurgery for arteriovenous malformation

Outcomes of microsurgical resection for cerebral arteriovenous malformation (AVM) largely depend on the skill and experience of the operator, but it is still unknown whether such individual differences similarly exists in stereotactic radiosurgery (SRS) for AVM. The purpose of this study was to assess the influence of the inter-operator difference and technological progress in SRS for AVM. During the past 20 years, 514 patients with AVM were treated by SRS by four neurosurgeons. Until 1992, angiography was solely used for dose planning, and computed tomography (CT) or magnetic resonance imaging (MRI) was jointly used thereafter. In the early years, dose planning was calculated with the first-generation computer system, KULA, and manually superimposed on the radiographical images. After 1998, treatment planning was made on the computer monitor with sophisticated dose-planning software, GammaPlan. The influence of inter-operator difference, the operator's experience, and radiographical or radiosurgical technologies on the rates of obliteration and morbidity was assessed by multivariate analyses. The factors associated with higher obliteration rates were higher margin dose (p = 0.003) and the presence of hemorrhagic event before SRS (p = 0.002). There was no significant difference in either obliteration rate or morbidity among the five operators. However, after introduction of CT and MRI on dose planning, the risk of adverse events was significantly decreased. Especially for AVM larger than 3 cm in maximum diameter, each operator's experience (p = 0.040) and use of GammaPlan (p = 0.015) reduced morbidity. Inter-operator difference was not a significant factor associated with the rates of obliteration and the risk of adverse events after SRS for AVM in the multivariate analyses. Progress of the sophisticated planning software and the experience of the operator were associated with lower morbidity for larger lesions.

Chronic encapsulated intracerebral hematoma formation after radiosurgery for cerebral arteriovenous malformation

We report a rare case of chronic encapsulated intracerebral hematoma (CEIH) after radiosurgery for a cerebral arteriovenous malformation (AVM). A 49-year-old male underwent transarterial embolization and surgical excision of a cerebral AVM presenting with cerebral hemorrhage in the left temporal lobe. Stereotactic radiosurgery (SRS) was done after 12 months. Magnetic resonance imaging (MRI) 14 months after SRS showed a small-enhancing lesion close to the left lateral ventricle and marked white matter edema. At that time a diagnosis of radiation-induced necrosis was made and steroids administered. At 43 months after SRS, MRI showed a small-enhancing mass close to the lateral ventricle with a hematoma cavity. Surgical excision was performed and histological examination revealed that the capsule consisted of an outer collagenous layer and an inner granulated layer with deposits of hemosiderin, which was compatible with CEIH. CEIH should be considered after SRS for AVM.

Chronic encapsulated intracerebral hematoma: a rare complication after stereotactic radiosurgery for cerebral arteriovenous malformation

We read with great interest the article entitled “Operative intervention for delayed symptomatic radionecrotic masses developing following stereotactic radiosurgery for cerebral arteriovenous malformations-case analysis and literature review” by Foroughi et al. [1] in the May 2010 issue of this journal. The authors presented two cases of delayed masses that had developed following stereotactic radiosurgery (SRS) for the treatment of cerebral arteriovenous malformations (AVMs) and discussed the relevant literature. They pointed out that some cases had presented with hemorrhage in the cystic cavity. We would like to add a comment regarding this point. Chronic encapsulated intracerebral hematoma (CEIH) is a rare cerebrovascular disease that behaves as a slowly expanding lesion with a gradual onset [2]. We previously reported a case of delayed CEIH that developed after SRS for a cerebral AVM, which was treated by a single aspiration following the placement of a reservoir [3]. Furthermore, we experienced a similar case of a delayed mass that developed after SRS for an AVM. This patient underwent surgical excision and was diagnosed as CEIH by a pathological method. We suppose that SRS for an AVM can cause the formation of CEIH. Based on our experiences, it is suggested that some delayed masses with hemorrhage after SRS for an AVM may be CEIH.

Long-term Outcomes of Stereotactic Radiosurgery for Arteriovenous Malformations in the Thalamus

Arteriovenous malformations (AVMs) in the thalamus carry a high risk of hemorrhage. Although stereotactic radiosurgery (SRS) is widely accepted because of the high surgical morbidity and mortality of these lesions, precise long-term outcomes are largely unknown. To review our experience with SRS for thalamic AVMs based on the latest follow-up data. Forty-eight patients with thalamic AVMs were treated by SRS using the Leksell Gamma Knife and were followed. Long-term outcomes including the obliteration rate, hemorrhage after treatment, and adverse effects were retrospectively analyzed. The annual hemorrhage rate before SRS was 14%. The mean follow-up period after SRS was 66 months (range 6-198 months). The actuarial obliteration rate confirmed by angiography was 82% at 5 years after treatment, and the annual hemorrhage rate after SRS was 0.36%. Factors associated with higher obliteration rates were previous hemorrhage (P = .004) and treatment using new planning software (P = .001). Persistent worsening of neurological symptoms was observed in 17% and more frequently seen in patients who were treated using older planning software (P = .04) and a higher margin dose (P = .02). The morbidity rate for patients who received treatment planned using new software with a margin dose not more than 20 Gy was 12%. SRS for thalamic AVMs achieved a high obliteration rate and effectively decreased the risk of hemorrhage, with less morbidity compared with other modalities. Longer follow-up to evaluate the risk of delayed complications and the effort to minimize the morbidity is necessary.

Hyperbaric oxygen therapy for treatment of adverse radiation effects after stereotactic radiosurgery of arteriovenous malformations: case report and review of literature

Background Adverse radiation effects are a known complication after the use of SRS for AVMs, although it is difficult to predict which patients will manifest with these side effects. Treatment of swelling due to ARE is usually medical, but refractory cases may require surgical decompression. Case Description This report presents a case of a patient who experienced AREs after SRS (edema, headaches, and nausea) that failed to respond to steroid treatment but was successfully treated with HBO. The treatment characteristics of this and of 5 other cases of radiation injury after SRS for AVM managed with HBO therapy are reviewed, and the pathophysiology is discussed. Conclusion Hyperbaric oxygen therapy provides a therapeutic option to treat AREs following SRS of cerebral AVMs.

Prognostic Factors for Complete Obliteration of Arteriovenous Malformations Treated with LINAC-Based Stereotactic Radiosurgery

Few series analyzing prognostic fac tors predicting for obliteration of arteriovenous malformations (AVMs) following linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) have been reported. We analyzed prognostic variables, outcomes, and toxicities in 88 patients undergoing LINAC-based SRS for AVMs. Following IRB approval, patient records were retrospectively analyzed to identify independent predictors of complete response (obliteration) (CR) and time-to-CR. The majority of AVMs were treated using multiple isocenters and non-coplanar arcs. The median AVM volume was 2.67 cm3 (0.05 - 33.51). Median marginal and maximal doses were 17 (12-24) and 26.1 Gy (15-40), with a median prescription isodose surface of 65%. Spetzler-Martin (SM) grade was determined for 86 patients and was: I-3 pts (3%); II-23 pts (27%); III-45 pts (52%); IV-13 pts (15%); V-2 pts (2%).Of 80 patients with follow-up imaging, 44 (55%) had documented complete responses (CR). Kaplan-Meier estimate probability for CR at 4 years was 62% (95% CI: 0.50, 0.74). Median time to CR was 3 years (95% CI: 2.08, 3.17). Multivariate analysis demonstrated the Spetzler-Martin grade (OR=0.14 for grade III vs. grade I-II; p=0.004 and OR 0.07 for grade IV-V vs. grade I-II; p=0.002) and dichotomized marginal dose > 17 Gy (OR=4.19; p=0.01) to be significantly associated with CR. This report demonstrates that for LINAC-based SRS of AVM, marginal dose and Spetzler-Martin grade are strong predictors of complete AVM obliteration.

Outcomes of surgery for resection of regions of symptomatic radiation injury after stereotactic radiosurgery for arteriovenous malformations

Outcomes of surgery for resection of regions of symptomatic radiation injury after stereotactic radiosurgery for arteriovenous malformations

Does Intensity Modulation Improve Healthy Tissue Sparing in Stereotactic Radiosurgery of Complex Arteriovenous Malformations?

This planning study evaluates the potential of intensity modulated treatment fields and inverse planning techniques in stereotactic radiosurgery to reduce healthy tissue dose. Twenty patients previously treated with stereotactic radiosurgery for arteriovenous malformation (AVM) were replanned with each of 4 techniques: circular non-coplanar arcs, dynamic arcs, static conformal fields, and intensity modulated radiosurgery (IMRS). Patients were selected having a maximum AVM dimension at least 20 mm, or volume greater than 10 cm 3. Target volumes ranged from 2.12 cm 3 to 13.87 cm 3 with a median of 6.03 cm 3. Resulting dose distributions show a statistically significant improvement in target conformality between circular arcs and all other techniques ( p ≤ 0.001), between conformal and both dynamic arcs and IMRS ( p ≤ 0.03) and with no difference between dynamic arcs and IMRS. However, for AVMs of volume greater than 5.5 cm 3, IMRS gives better conformality than dynamic arcs ( p = 0.04). IMRS showed consistently lower dose inhomogeneity compared to both dynamic arcs and conformal fields ( p < 0.001). At low dose levels, the dynamic arc technique irradiates less healthy tissue than the other techniques ( p ≤ 0.001). Both dynamic arcs and IMRS provide increased ability to conform to the AVM, with IMRS showing greater ability to control dose at the periphery.

Incidence of vascular malformations in spontaneous intra-cerebral haemorrhage in children

To assess the incidence of vascular malformations in children presenting with non-traumatic intra-cerebral haemorrhage and outline the need for radiological investigations. Between 1993 and 2002, 26 children presented with spontaneous intra-cerebral haemorrhage at a mean age of 26 months (range 1-192 months). Twenty-two children had, as first treatment, surgical removal of the haematoma and any malformation found. One patient with no evidence of vascular malformation had conservative treatment, two had embolisation and one had stereotactic radiosurgery of arteriovenous malformations (AVMs). The diagnosis of vascular malformation was confirmed histologically and/or radiologically in 16 (61%) patients. Of these 16 patients, 7 were AVMs, 1 thrombosed middle cerebral artery (MCA) aneurysm, 1 cavernous angioma, 6 aggregates of abnormal vessels, 1 vein of Galen aneurysm. Pre-operatively, 12 patients had magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) and 7 were positive for vascular malformation (1 false positive) with no false negatives. Digital subtraction angiography (DSA) was performed pre-operatively in 7 patients, 4 were positive with no false negatives. There were no re-bleeds at the follow-up period. Five (19%) patients died from the haemorrhage, 7 (27%) had severe neurological deficit and 14 (54%) had no neurological deficit. Residual malformation after surgery requiring additional treatment was found in 3 (16%) patients. All patients with confirmed malformations were followed-up with DSA. MRI/MRA has high sensitivity and specificity in identifying vascular malformations in children presenting acutely with spontaneous intra-cerebral haemorrhage. This may prove useful when pre-operative DSA is not promptly available. After acute clot evacuation, there is high incidence of residual malformation and such patients should be followed-up with DSA.

Impact of target point deviations on control and complication probabilities in stereotactic radiosurgery of AVMs and metastases

Objective Determination of the impact of inaccuracies in the determination and setup of the target point in stereotactic radiosurgery (SRS) on the expectable complication and control probabilities. Methods Two randomized samples of patients with arteriovenous malformation (AVM) ( n = 20) and with brain metastases ( n = 20) treated with SRS were formed, and the probability for complete obliteration (COP) or complete remission (CRP), the size of the 10 Gy-volume in the brain tissue (VOI10), and the probability for radiation necrosis (NTCP) were calculated. The dose–effect relations for COP and CRP were fitted to clinical data. Target point deviations were simulated through random vectors and the resulting probabilities and volumes were calculated and compared with the values of the treatment plan. Results The decrease of the relative value of the control probabilities at 1 mm target point deviation was up to 4% for AVMs and up to 10% for metastases. At 2 mm the median decrease was 5% for AVMs and 9% for metastases. The value for the target point deviation, at which COP and CRP decreased about 0.05 in 90% of the cases, was 1.3 mm. The increase of NTCP was maximally 0.0025 per mm target point deviation for AVMs and 0.0035/mm for metastases. The maximal increase of VOI10 was 0.7 cm 3/mm target point deviation in both patient groups. Conclusions The upper limit for tolerable target point deviations is at 1.3 mm. If this value cannot be achieved during the system test, a supplementary safety margin should be applied for the definition of the target volume. A better accuracy level is desirable, in order to ensure optimal chances for the success of the treatment. The target point precision is less important for the minimization of the probability of radiation necroses.