The natural history of symptomatic arteriovenous malformations of the brain: a 24-year follow-up assessment

Decision analysis for small, asymptomatic intracranial arteriovenous malformations

Object

Asymptomatic intracranial arteriovenous malformations (AVMs) represent a clinically challenging problem because of the complex decision making that must be undertaken prior to beginning any type of treatment. In addition, the relative infrequency of these lesions means that there is relatively little experience reported in the literature. The authors use a decision-analysis technique to model the considerations that go into determining the treatment of these lesions in an effort to quantify the various risks and overall benefits conferred by the following three treatment strategies: observation/natural history, microsurgery, and stereotactic radiosurgery.

Methods

The authors conducted a thorough literature search to elucidate the risks and outcomes associated with each treatment option. These values were used to build and run a comprehensive Markov model to determine a base-case analysis. All of the input variables were also subjected to sensitivity analysis to identify the most influential input variables and the crossover points in which favored strategies changed.

The base-case analysis suggested that microsurgery was the favored treatment option because this hypothetical cohort accumulated 21.53 quality-adjusted life years (QALYs) over the course of the model compared with the 16.97 QALYs and 16.40 QALYs for stereotctic radiosurgery and observation, respectively. Sensitivity analysis demonstrated that overall major neurological morbidity and mortality were the most influential input variables both perioperatively and during the radiosurgical “latent” period (that is, up to 2 years posttreatment). The maximum acceptable perioperative combined major neurological morbidity and mortality rate was 6.8%. The latent period combined major neurological morbidity and mortality would need to be 0.7% to make radiosurgery favorable in this analysis.

Conclusions

Results of this decision analysis model suggest that microsurgery in the hands of experienced cerebrovascular surgeons, who can expect a less than 6.8% combined rate of major neurological morbidity and mortality, offers patients a greater overall quality of life over time.

Epidemiology and natural history of arteriovenous malformations

The epidemiology and natural history of cerebral arteriovenous malformations (AVMs) remains incompletely elucidated. Several factors are responsible. With regard to the incidence and prevalence of AVMs, the results of prior studies have suffered because of the retrospective design, the use of nonspecific ICD-9 codes, and a focus on small genetically isolated populations. Recent data from the New York Islands AVM Hemorrhage Study, an ongoing, prospective, population-based survey determining the incidence of AVM-related hemorrhage and the associated rates of morbidity and mortality in a zip code–defined population of 10 million people, suggests that the AVM detection rate is 1.21/100,000 person-years (95% confidence interval [CI] 1.02–1.42) and the incidence of AVM-hemorrhage is 0.42/100,000 person-years (95% CI 0.32–0.55). Contemporaneous data from the Northern Manhattan Stroke Study, a prospective, longitudinal population-based study of nearly 150,000 patients in which the focus is to define the incidence of stroke, suggest the crude incidence for first-ever AVM-related hemorrhage to be 0.55/100,000 person-years (95% CI 0.11–1.61). Efforts are ongoing to study the natural history of both ruptured and unruptured AVMs in these datasets to examine the relevance of prior studies of patients selected for conservative follow up in Finland. In addition, data are being gathered to determine whether risk factors for future hemorrhage, which have previously been established in small case series, are valid when applied to whole populations. Together, these data should help inform therapeutic decisionmaking.

Population-based analysis of arteriovenous malformation treatment

OBJECT

The author sought to describe overall management data on cerebral arteriovenous malformations (AVMs) and to focus the actuarial need for different treatment modalities on a population-based scale. Such data would seem important in the planning of regional or national multimodality strategies for the treatment of AVMs. This analysis of a nonselected, consecutive series of patients representing every diagnosed case of cerebral AVM in a population of 1,000,000 over one decade may serve to shed some light on these treatment aspects.

METHODS

During the 11-year period from 1989 to 1999, data from every patient harboring a cerebral AVM that was presented clinically or discovered incidentally in a strictly defined population of 986,000 people were collected prospectively. No patient was lost to follow up. There were 12.4 de novo diagnosed AVMs per 1,000,000 population per year (135 AVMs). Large high-grade AVMs (Spetzler-Martin classification) were rare, and Grade 1 to 3 lesions represented 85% of the caseload. Hemorrhage was the initial manifestation of AVM in 69.6% of the cases. lntracerebral hematoma was the most common hemorrhagic manifestation occurring in 78 patients. There were 4.4 cases per 1,000,000 population per year of hematomas needing expedient surgical evacuation. In the remaining patients who did not require hematoma surgery, small, critically located Grade 3 and Grade 4 lesions amounted to 1.6 cases per 1,000,000 population per year. There were 5.8 cases per 1,000,000 population per year of Grade 1 to 2 and larger noncritically located Grade 3 malformations. There were 0.5 cases per 1,000,000 population per year of Grade 5 AVMs. The overall outcome in 135 patients was classified as good according to the Glasgow Outcome Scale (Score 5) in 61% of the cases, and the overall mortality rate was 9%.

CONCLUSIONS

In centers with population-based referral, AVM of the brain is predominantly a disease related to intracranial bleeding. and parenchymal clots have a profound impact on overall management outcome. The rupture of an AVM is as devastating as that of an aneurysm. Aneurysm ruptures are more lethal, whereas AVM rupture tends to result in more neurological disability due to the high occurrence of lobar intracerebral hematoma. In an attempt to quantify the need for different modalities of AVM treatment based on a population of 1,000,000 people, figures for surgeries performed range from six to 10 operations per year and embolization as well as gamma knife surgery procedures range from two to seven per year, depending on the strategy at hand. When using nonsurgical approaches to Grade 1 to 3 lesions, the number of patients requiring treatment with more than one method for obliteration increases drastically as does the potential risk for procedure-related complications.

The Göteborg cohort of embolized cerebral arteriovenous malformations: a 6-year follow-up

OBJECTIVE

To present a follow-up of the results after endovascular treatment of cerebral arteriovenous malformations (AVMs) with acrylic glue. An initial follow-up was published in 1996.

METHODS

A cohort of 150 patients with cerebral AVMs underwent embolization between 1987 and 1993. Fifty-seven patients had supplemental stereotactic irradiation, and 13 had subsequent surgery. The follow-up was carried out clinically and radiologically.

RESULTS

The mean follow-up time was 6.2 years. Only four patients were lost to follow-up. If at least 90% of the AVM had been obliterated, the clinical course was stable and there were no new manifestations from the AVM. No recanalization occurred in any AVM that had been totally obliterated with glue. For patients in whom it was not possible to totally obliterate the AVM either with glue alone or glue supplemented with stereotactic irradiation or surgery, the long-term outcome was discouraging.

CONCLUSION

Obliteration of an AVM with acrylic glue seems to offer stability. If the AVM is totally obliterated, the patient had a stable clinical course. Patients with large AVMs with minor occlusion after embolization may have a worse clinical outcome than expected.

Endothelial proliferation, neoangiogenesis, and potential de novo generation of cerebrovascular malformations

OBJECT

To date, both arteriovenous malformations (AVMs) and cavernomas have been considered to be congenital malformations. A recent survey of the literature has shown the potential for de novo generation of both familial and sporadic cavernomas as well as AVMs. Therefore, it was of interest to determine the biological behavior of these lesions in detail.

METHODS

The proliferative and angiogenic capacities of the endothelium of 13 cavernomas and 25 AVMs obtained in patients recently treated (1997-1998) at one institution were studied. Immunohistochemical staining for proliferating cell nuclear antigen (PCNA), MIB-1, and vascular endothelial growth factor (VEGF) and its receptor Flk-1 was performed using standard staining procedures. Positive immunostaining of the nuclei of endothelial cells was observed in specimens of both AVMs and cavernomas for PCNA (80% of AVMs and 85% of cavernomas), and Flk-1 (80% of AVMs and 31% of cavernomas). Endothelial expression of VEGF in the 18 incompletely embolized AVMs was found in 72% of cases but only in 28% of the seven cases in which patients did not undergo endovascular treatment: it was found in 38% of cavernomas. Endothelial expression of MIB-1 was found in 12% of AVMs but in no cavernomas.

CONCLUSIONS

These results indicate that there is endothelial proliferation as well as neoangiogenesis in cerebral cavernomas and AVMs. The increased level of angiogenesis in only partially obliterated AVMs underscores the need for radical and complete occlusion of cerebral AVMs to avoid recurrences and further risks of morbidity.

Reporting terminology for brain arteriovenous malformation clinical and radiographic features for use in clinical trials

“If you wish to converse with me,” said Voltaire, “define your terms.” How many a debate would have been deflated into a paragraph if the disputants had dared to define their terms!

Will Durant: The Story of Philosophy

Palliative embolisation of brain arteriovenous malformations presenting with progressive neurological deficit

SUMMARY

Large arteriovenous malformations (AVMs) located in eloquent areas of the brain are generally considered incurable because of the high morbidity and mortality associated with their treatment. When these patients develop a progressive neurological deficit they in time often become severely disabled. This report presents the results of palliative embolisation in this subgroup of patients. Analysis of our data-base of 714 patients with known brain AVMs revealed 17 patients who presented with progressive neurological deficit and who underwent palliative embolisation as the therapeutic modality of choice for management of their AVM. One patient was excluded due to lack of follow-up and two were excluded because they later received radiation therapy. Following embolisation 43% had improvement of their neurological deficit, 50% stabilized and 7% continued to deteriorate and these clinical results persisted for an average of more than 2 years follow-up. Transient neurological morbidity associated with embolisation treatment was 7% and there was no permanent morbidity and no mortality. Palliative embolisation of brain AVMs presenting with progressive neurological deficits arrested deterioration in more than 90% of patients and was associated with low morbidity and no mortality.

Seizures in cerebral arteriovenous malformations: type, clinical course, and medical management

SUMMARY

We investigated the type and early clinical course of seizure disorders in cerebral arteriovenous malformations (AVMs). Decisions on invasive treatment for AVMs depend on detailed knowledge of the natural course and prognosis of neurologic sequelae. Among 328 patients of a prospective cerebral AVM databank 92 (28%) presented with seizures unrelated to haemorrhage. Under a median observation time of 2.2 years (mean 3.8 years) the 92 patients received 454 follow-up examinations (median time interval 4.6 months). All patients were treated with anticonvulsant medication. During the observation period sixty (65%) patients received staged endovascular glue embolisation. The effect of staged embolisation on seizure recurrence was tested univariately by comparing patients undergoing embolisation versus those without endovascular treatment. At the time of enrolment in the database, elementary (motor or sensory) and partial complex seizures were described in twenty (22 %) and one (1%) patients, respectively. Generalized seizures without focal initiation were reported in sixty (65%) and with focal initiation in 11 (12%) patients. 57 (62%) cases had suffered a seizure as a first single event, ten (11%) had weekly, 17 (19%) monthly, and eight (9%) patients had seizures once per year. In the following clinical course, complete cessation of seizure activity was seen in 69 (75%). Ten (11%) patients continued to have seizures at a rate of once per year or less. 13 (14%) cases continued to have weekly to monthly events with only four (4%) of them showing (monthly) grand mal. An early beneficial effect of staged embolisation on seizure recurrence was not observed. Seizure disorders in cerebral AVMs show a benign early course, leaving few patients with insufficient seizure control. The differential longterm effect of invasive AVM treatment on seizure control should be subject to clinical trials.

Embolisation of Small (< 3 cm) Brain Arteriovenous Malformations. Correlation of Angiographic Results to a Proposed Angioarchitecture Grading System

SUMMARY

The role of embolisation in the treatment of small < 3cm) brain arteriovenous malformations (AVMs) has not been elucidated. We reviewed our experience using embolisation in the treatment of small AVMs and correlated a proposed grading system based on the angioarchitecture to the percentage obliteration achieved by embolisation. Eighty-one small AVMs in 80 patients were embolised from 1984 to 1999. The age range was from 3 to 72 years. The AVMs were given a score from 0 to 6 based on the angioarchitecture. The assigned scores were as follows: nidus (fistula = 0, < 1 cm = 1, 1-3 cm = 2), type offeeding arteries (cortical = 0, perforator or choroidal = 1), number of feeding arteries (single = 0, multiple = 2) and number of draining veins (single = 0, multiple = 1). Angiographic results based on percentage obliteration were grouped into three categories: complete, 66-99%, and 0-65%. The goal of embolisation was cure in 27 AVMs, pre-surgical in 23, pre-radiosurgery in 26, and elimination of an aneurysm in five. Embolisation achieved complete obliteration in 22 (27%) of the 81 AVMs. In the AVMs where the goal was cure, 19 (70%) of 27 were completely obliterated. In the AVMs with angioarchitecture scores of 0-2, 12 (86%) of 14 were cured, with scores of 3-4, 8 (34%) of 24 were cured and with scores of 5-6, 2 (4%) of 44 were cured. Embolisation resulted in transient morbidity of 5.0%, permanent morbidity of 2.5%, and mortality of 1.2%. There were no complications in AVMs with scores of 0-2. Embolisation is an effective treatment of small AVMs when the angioarchitecture is favourable (scores 0-2). This includes pure fistulas and AVMs with a single, pial, feeding artery.

Cerebral Arteriovenous Malformations: Comparison of Novel Magnetic Resonance Angiographic Techniques and Conventional Catheter Angiography

OBJECTIVE

To investigate the potential of novel magnetic resonance (MR) angiographic techniques for the assessment of cerebral arteriovenous malformations.

METHODS

Forty patients who were about to undergo stereotactic radiosurgery were prospectively recruited. Three-dimensional, sliding-slab interleaved ky (SLINKY), time-of-flight acquisition was performed, as was a dynamic MR digital subtraction angiography (DSA) procedure in which single thick slices (6–10 cm) were obtained using a radiofrequency spoiled Fourier-acquired steady-state sequence (1 image/s). Sixty images were acquired, in two or three projections, during passage of a 6- to 10-ml bolus of gadolinium chelate. Subtraction and postprocessing were performed, and images were viewed in an inverted cine mode. SLINKY time-of-flight acquisition was repeated after the administration of gadolinium. Routine stereotactic conventional catheter angiography was performed after MR imaging. All images were assessed (in a blinded randomized manner) for Spetzler-Martin grading and determination of associated vascular pathological features.

RESULTS

Forty-one arteriovenous malformations were assessed in 40 patients. Contrast-enhanced (CE) SLINKY MR angiography was the most consistent MR imaging technique, yielding a 95% correlation with the Spetzler-Martin classification defined by conventional catheter angiography; MR DSA exhibited 90% agreement, and SLINKY MR angiography exhibited 81% agreement. CE SLINKY MR angiography provided improved nidus delineation, compared with non-CE SLINKY MR angiography. Dynamic information from MR DSA significantly improved the observation of early-draining veins and associated aneurysms.

CONCLUSION

CE SLINKY MR angiographic assessment of cerebral arteriovenous malformations offers significant advantages, compared with the use of non-CE SLINKY MR angiography, including improved nidus demonstration. MR DSA shows promise as a noninvasive method for dynamic angiography but is presently restricted by limitations in both temporal and spatial resolution.

Cerebrovascular manifestations in 321 cases of hereditary hemorrhagic telangiectasia

BACKGROUND AND PURPOSE

Patients with hereditary hemorrhagic telangiectasia (HHT) are at risk for developing cerebral vascular malformations and pulmonary arteriovenous fistulae. We assessed the risk of neurological dysfunction from these malformations and fistulae.

METHODS

Three hundred twenty-one consecutive patients with HHT seen at a single institution over a 20-year period were studied. Any evidence of prior neurological symptoms or presence of an intracranial vascular malformation was recorded. All cases of possible cerebral arteriovenous malformation were confirmed by conventional arteriography.

RESULTS

Twelve patients (3.7%) had a history of cerebral vascular malformations. Ten patients had arteriovenous malformations, 1 had a dural arteriovenous fistula, and 1 had a cavernous malformation. Seven patients (2.1%) presented with intracranial hemorrhage, 2 presented with seizures alone, and 3 were discovered incidentally. The average age at the time of symptomatic intracranial hemorrhage was 25.4 years. All patients with a history of intracranial hemorrhage were classified as Rankin grade I or II at a mean follow-up interval of 6.0 years. A history of cerebral infarction or transient ischemic attack was found in 29.6% of patients with HHT and a pulmonary arteriovenous fistula.

CONCLUSIONS

The risk of intracranial hemorrhage is low among people with HHT. Furthermore, a majority of these patients have a good functional outcome after hemorrhage. The data do not suggest a compelling indication for routine screening of patients with HHT for asymptomatic cerebral vascular malformations. By comparison, pulmonary arteriovenous fistulae are a much more frequent cause of neurological symptoms in this population.

Risk for hemorrhage during the 2-year latency period following gamma knife radiosurgery for arteriovenous malformations

PURPOSE

Radiosurgery does not immediately obliterate an arteriovenous malformation (AVM), and the risk for hemorrhage still persists until the AVM is occluded. There is controversy about whether this risk is altered after as compared to before radiosurgery. The aim of this paper is to study this topic further and to suggest a model to predict the risk for posttreatment hemorrhage.

METHODS AND MATERIALS

The incidence of hemorrhages within the first 24 months following Gamma Knife radiosurgery was studied retrospectively among 1593 AVM patients, and was related to patient, AVM, and treatment parameters.

RESULTS

Fifty-six patients experienced a hemorrhage in the latency period, representing an average annual incidence of 1.8%. The incidence of posttreatment hemorrhage was related to the patient's age, AVM volume, minimum dose, and average dose delivered to the AVM nidus. Based on these observations, an equation was defined that could quantify the probability for a posttreatment hemorrhage to occur.

CONCLUSION

A model that can predict the probability for a hemorrhage within the first 24 months after radiosurgery is presented. The risk is higher for larger AVMs and for older patients, and it is lower when higher doses of radiation are used.

Stereotactic radiosurgery for motor cortex region arteriovenous malformations

OBJECTIVE

The optimal management of arteriovenous malformations (AVMs) in critical brain locations remains controversial. To reduce the risk of an AVM hemorrhage and to enhance the possibility of preserving neurological function, stereotactic radiosurgery was performed in 33 patients with newly diagnosed or residual AVMs located within the motor cortex. The role of embolization also was examined.

METHODS

During a 9-year study period, 33 patients with AVMs located primarily in the motor cortex region were treated with stereotactic radiosurgery. These patients were followed up radiographically for a minimum of 36 months, or less if obliteration was documented before 36 months had elapsed. Of the 33 patients, 9 underwent embolization and 1 underwent microsurgery before radiosurgery. Nine patients required a second radiosurgery. The mean AVM target volume was 4.35 cc, and the average radiation dose to the AVM margin was 20 Gy. The median follow-up was 36 months (range, 10-91 mo), and angiographic follow-up of eligible patients was performed 24 or 36 months after radiosurgery.

RESULTS

Results were stratified by radiosurgical target volumes: less than 3 cc (Group 1), 3 to 10 cc (Group 2), and greater than 10 cc (Group 3). Overall (including second radiosurgery), 13 (87%) of 15 patients in Group 1 had complete obliteration confirmed by angiography. Nine (64%) of 14 patients in Group 2 exhibited nidus obliteration, and one (25%) of four patients in Group 3 demonstrated obliteration on a magnetic resonance imaging scan. Eight patients (24%) underwent second-stage radiosurgery after angiography revealed a persistent AVM nidus; three patients demonstrated complete obliteration on follow-up angiography. The obliteration rate was higher (87%) for AVMs with less than 3 cc target volume and lower (56%) for those with target volumes larger than 3 cc. One patient experienced worsening neurological function after radiosurgery, and one died from delayed AVM hemorrhage during the latency period. No patient bled after angiographically confirmed AVM obliteration.

CONCLUSION

Stereotactic radiosurgery is a successful and safe management option for patients with motor cortex AVMs. The obliteration of AVMs and the attendant low morbidity rates indicate a primary role for radiosurgery in these patients. Staged radiosurgery may be necessary to increase obliteration rates for larger AVMs or for those that are not obliterated after the first procedure.

Gamma knife radiosurgery as a single treatment modality for large cerebral arteriovenous malformations

Object. A consecutive series of 240 patients with arteriovenous malformations (AVMs) treated by gamma knife radiosurgery (GKS) between March 1993 and March 1999 was evaluated to assess the efficacy and safety of radiosurgery for cerebral AVMs larger than 10 cm3 in volume.

Methods. Seventy-six patients (32%) had AVM nidus volumes of more than 10 cm3. During radiosurgery, targeting and delineation of AVM nidi were based on integrated stereotactic magnetic resonance (MR) imaging and x-ray angiography. The radiation treatment was performed using multiple small isocenters to improve conformity of the treatment volume. The mean dose inside the nidus was kept between 20 Gy and 24 Gy. The margin dose ranged between 15 to 18 Gy placed at the 55 to 60% isodose centers. Follow up ranged from 12 to 73 months.

There was complete obliteration in 24 patients with an AVM volume of more than 10 cm3 and in 91 patients with an AVM volume of less than 10 cm3. The latency for complete obliteration in larger-volume AVMs was significantly longer. In Kaplan—Meier analysis, the complete obliteration rate in 40 months was 77% in AVMs with volumes between 10 to 15 cm3, as compared with 25% for AVMs with a volume of more than 15 cm3. In the latter, the obliteration rate had increased to 58% at 50 months. The follow-up MR images revealed that large-volume AVMs had higher incidences of postradiosurgical edema, petechiae, and hemorrhage. The bleeding rate before cure was 9.2% (seven of 76) for AVMs with a volume exceeding 10 cm3, and 1.8% (three of 164) for AVMs with a volume less than 10 cm3. Although focal edema was more frequently found in large AVMs, most of the cases were reversible. Permanent neurological complications were found in 3.9% (three of 76) of the patients with an AVM volume of more than 10 cm3, 3.8% (three of 80) of those with AVM volume of 3 to 10 cm3, and 2.4% (two of 84) of those with an AVM volume less than 3 cm3. These differences in complications rate were not significant.

Conclusions. Recent improvement of radiosurgery in conjunction with stereotactic MR targeting and multiplanar dose planning has permitted the treatment of larger AVMs. It is suggested that gamma knife radiosurgery is effective for treating AVMs as large as 30 cm3 in volume with an acceptable risk.

Arteriovenous malformations: assessment of gliotic and ischemic changes with fluid-attenuated inversion-recovery MRI

RATIONALE AND OBJECTIVES

To evaluate the diagnostic potential of fluid-attenuated inversion-recovery (FLAIR) MRI in the assessment of patients with cerebral arteriovenous malformations (AVMs) and to correlate the MR findings with clinical symptoms, in particular, perilesional gliosis and ischemic changes.

METHODS

Forty-five patients with cerebral AVMs were examined with FLAIR and conventional T1- and T2-weighted MRI by using identical slice parameters. Images were assessed in a two-reader study for detection and delineation of gliotic and ischemic tissue. Also, the extent of the flow void phenomenon and image artifacts were evaluated.

RESULTS

FLAIR MRI was rated superior to the conventional T2-weighted fast spin-echo imaging in the assessment of intralesional and perilesional gliosis. The superior delineation was a result of the suppression of cerebrospinal fluid, mild T1 weighting, and the more pronounced flow void phenomenon. There was no significant correlation between the extent of gliosis and the clinical symptoms. However, larger AVMs had more extensive signal changes.

CONCLUSIONS

FLAIR is a valuable MRI technique to assess gliotic and ischemic changes in or close to cerebral AVMs. Because gliotic and ischemic changes are common findings and are known to be associated with epilepsy, in the assessment of these patients FLAIR is clinically useful and may guide decisions about treatment-for instance, the extent of surgical resection of the potential epileptogenic focus.

Risk factors for poor outcome of untreated arteriovenous malformation

This study was conducted to determine risk factors for poor outcome in the natural history of arteriovenous malformation (AVM). We statistically analysed the correlation between clinical or angiographical findings and clinical outcomes for 55 cases of untreated AVM. Subsequent haemorrhage from AVMs was the only significant risk factor for poor outcome (P< 0.0001). The odds ratio was 44.56 with a 95% confidence interval (CI) from 4.80 to 413.90. Risk factors for subsequent haemorrhage from AVMs were also determined. The size (P = 0.0483) and location (P = 0.0147) of an AVM were significant risk factors for subsequent haemorrhage. The odds ratios were 3.97 with a 95% CI from 1.18 to 13.33 and 3.89 with a 95% CI from 1.10 to 13.72, respectively. AVMs of more than 60 mm, and deep or infratentorial AVMs had more chance of subsequent haemorrhage, and hence of a poor outcome. We propose using an aggressive multidisciplinary approach to treating these AVMs.

Functional and topographical considerations in the surgical management of cerebral vascular malformations

Cerebral vascular malformations with potential surgical consequences mainly consist of arteriovenous malformations (AVM) and cavernous malformations. The standard preoperative workup of these lesions includes basic neuroradiological investigation, such as computed tomography, magnetic resonance imaging (MRI), and magnetic resonance angiography, and conventional angiography, to assess the exact neurotopographical relationships of the nidus, arterial feeding pedicles, and venous drainage. In cases where lesions are located near or within eloquent areas, precise documentation of the anatomy can be obtained using various functional tests including functional MRI, activated positron emission tomoqraphy, and magnetoencephalography (MEG), which may then be integrated into a neuronavigational system allowing for selective, image-guided surgery, thus potentially reducing surgical morbidity. Preoperative embolization may in certain cases improve the surqical excision by reducinq blood flow throuqh the AVM. Cavernous malformations may also be removed with minimally invasive and highly selective techniques.

Radiosurgery for childhood intracranial arteriovenous malformations

OBJECTIVE

The optimal management of intracranial arteriovenous malformations (AVMs) in children remains controversial. Children with intracranial AVMs present a special challenge in therapeutic decision-making because of the early recognition of their future life-long risks of hemorrhage if they are treated conservatively. The goals of radiosurgery are to achieve complete AVM obliteration and to preserve neurological function. We present long-term outcomes for a series of children treated using radiosurgery.

METHODS

The findings for 53 consecutive children who underwent at least 36 months of imaging follow-up monitoring after radiosurgery were reviewed. The median age at the time of treatment was 12 years (range, 2-17 yr). Thirty-one children (58%) presented after their first intracranial hemorrhaging episodes, two (4%) after their second hemorrhaging episodes, and one (2%) after five hemorrhaging episodes. Nineteen children (36%) presented with unruptured AVMs, and a total of 25 children (47%) exhibited neurological deficits. AVMs were graded as Spetzler-Martin Grade I (2%), Grade II (23%), Grade III (36%), Grade IV (9%), or Grade VI (30%). The median AVM volume was 1.7 ml (range, 0.11-10.2 ml). The median marginal dose was 20 Gy (range, 15-25 Gy).

RESULTS

Results were stratified according to AVM volumes (Group 1, < or =3 ml; Group 2, >3 ml to < or =10 ml; Group 3, >10 ml). Twenty-eight patients (80%) in Group 1 and 11 (64.7%) in Group 2 achieved complete obliteration. The only patient in Group 3 did not achieve obliteration. Complications included brainstem edema (n = 1) and transient pulmonary edema (n = 1). Four patients experienced hemorrhaging episodes, 30, 40, 84, and 96 months after radiosurgery. Multivariate logistic regression analysis demonstrated that only volume was significantly correlated with obliteration rates (P = 0.0109).

CONCLUSION

Radiosurgery is safe and efficacious for selected children with AVMs. The obliteration rates and the attendant low morbidity rates suggest a primary role for stereotactic radiosurgery for pediatric AVMs.

Resectability of Spetzler-Martin grade IV and V cerebral arteriovenous malformations

This study retrospectively analysed treatment modalities and outcomes in 63 cases of high grade cerebral arteriovenous malformations (Spetzler-Martin's classification grade IV 51, V 12) who were admitted to this institute between January 1986 and April 1998. Twenty-seven of 37 cases with haemorrhagic onset received surgical resection with or without pre-operative embolisation. Total extirpation was achieved in 23 cases, and small residual nidus was treated by postoperative radiosurgery in two of four subtotally resected cases. Another 6 of 37 haemorrhagic cases received radiosurgery with or without preradiosurgical embolisation. Four cases with haemorrhagic onset received partial embolisation. Finally, 29 of 37 haemorrhagic cases obtained complete disappearance of nidus. On the other hand, 4 of 26 non-haemorrhagic cases received surgical total resection, 5 radiosurgery, 9 partial embolisation and 8 observation without treatment. Microsurgical morbidity was 9% and mortality was 0%. Post-treatment haemorrhage was seen in 11 cases (1 after subtotal resection, 4 after radiosurgery, 6 after partial embolisation) and was fatal in 3 cases. Surgical resection can be achieved with acceptable morbidity, and complete obliteration of nidus should be accomplished in any treatment modality to avoid post-treatment haemorrhage.

Selection of treatment modalities for cerebral arteriovenous malformations: a retrospective analysis of 348 consecutive cases

The objective was to establish the selection criteria for the optimal management modalities for cerebral arteriovenous malformations. We analysed the complications and late outcomes in 348 consecutive cases (132 microsurgical resections, 202 stereotactic radiosurgeries, 8 embolisations only, 6 combined treatments) managed at Yonsei University Hospital from 1988 to 1997. Files for all patients were analysed. The outcome was classified into good for the patients who returned to their previous job with or without neurological deficits, fair for the patients who were unable to return to work but performed daily activities independently with minor deficits, and poor for the patients who were performing dependent daily activities with major deficits. The outcome of microsurgery was considered good in 108 patients (81.8%), fair in 18 (13.6%), poor in 4 (3.1%), and 2 (1.5%) patients died. Initial insults and haemodynamic complications were the major cause of an unfavourable outcome. The cumulative occlusion rate of the nidus after radiosurgery was 10.2% within 12 months, 75.3% within 24 months, and 89.8% within 36 months. Perilesional imaging changes with neurological deficits (4 permanent and 6 transient, 4.8%) and haemorrhage (16 patients, 7.7%) during the latent interval were the major cause of an unfavourable outcome (1 poor, 4 dead after radiosurgery). Postradiosurgery bleeding occurred frequently within 6 months (6 patients), and between 13 and 24 months (8 patients). In conclusion, selection of treatment modality for cerebral AVMs depends on the preoperative evaluation of the risk/benefit ratio in each case. Microsurgical removal, which eliminates the risk of bleeding immediately, is preferred for lesions in non-eloquent areas. Radiosurgery is an effective treatment modality for small lesions in eloquent areas, but has a substantial risk of haemorrhage during the latency period. Results of this study suggest that microsurgical removal should be considered for lesions in eloquent areas with high haemorrhage risk, such as prior haemorrhage, medium to large size lesion, and single deep venous drainage.

Multimodality treatment of nongalenic arteriovenous malformations in pediatric patients

OBJECTIVE

Previously reported series of arteriovenous malformations (AVMs) in pediatric patients have primarily used a single-modality treatment approach of either surgery, radiosurgery, or embolization, with significant treatment-related morbidity and mortality. At our institution, we have used a combined multidisciplinary team approach of all three treatment modalities, alone or in combination, to minimize complications and to maximize efficacy in the management of these lesions.

METHODS

We retrospectively reviewed 40 consecutive pediatric patients with AVMs seen at our institution from 1991 to 1999. A multidisciplinary team planned the treatment for each AVM. The treatment modality consisted of the following approaches: surgery alone in 14 patients, a combination of endovascular embolization and surgery in 6 patients, radiosurgery alone in 11 patients, a combination of endovascular embolization and radiosurgery in 2 patients, and a combination of radiosurgery and surgery in 2 patients. Four patients are receiving ongoing multistaged treatment for reduction of the nidus size for eventual surgical resection or radiosurgical obliteration of large, complex lesions. In one patient, no treatment was recommended.

RESULTS

The clinical outcomes for the overall series were 95.0% excellent or good (Glasgow Outcome Scale score 5 or 4), 2.5% fair (Glasgow Outcome Scale score 3), and 2.5% dead. Radiographic efficacy in the patients who have completed treatment was 92.9% complete obliteration of their AVMs and 7.1% incomplete obliteration. Of the 10 patients who had seizures, 9 are seizure-free.

CONCLUSION

A combined multimodality approach of surgery, radiosurgery, and embolization in managing AVMs in pediatric patients can improve outcomes and minimize morbidity and mortality.

The epidemiology of brain arteriovenous malformations

OBJECTIVE

Common estimates of the prevalence rate for pial arteriovenous malformations (AVMs) of the brain vary widely, and their accuracy is questionable. Our objective was to critically review the original sources from which these rates were derived and to establish best estimates for both the incidence and prevalence of the disease.

METHODS

We reviewed all of the relevant original literature: autopsy series, the Cooperative Study of Intracranial Aneurysms and Subarachnoid Hemorrhage and related analyses, and other population-based studies. We also modeled the confidence intervals of estimates for a process of low prevalence such as AVMs.

RESULTS

Many of the prevalence estimates (500-600/100,000 population) were based on autopsy data, a source that is inherently biased. Other estimates (140/100,000 population) originated from an inappropriate analysis of data from the Cooperative Study. The most reliable information comes from a population-based study of Olmsted County, MN, but prevalence data specific to AVMs was not found in that study.

CONCLUSION

The estimates for AVM prevalence that are published in the medical literature are unfounded. Because of the rarity of the disease and the existence of asymptomatic patients, establishing a true prevalence rate is not feasible. Owing to variation in the detection rate of asymptomatic AVMs, the most reliable estimate for the occurrence of the disease is the detection rate for symptomatic lesions: 0.94 per 100,000 person-years (95% confidence interval, 0.57-1.30/100,000 person-years). This figure is derived from a single population-based study, but it is supported by a reanalysis of other data sources. The prevalence of detected, active (at risk) AVM disease is unknown, but it can be inferred from incidence data to be lower than 10.3 per 100,000 population.

Bleeding risk of cerebrovascular malformations in hereditary hemorrhagic telangiectasia

OBJECT

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal-dominant vascular dysplasia with a high prevalence of cerebrovascular malformations (CVMs), mostly manifested as arteriovenous malformations (AVMs). The natural history and bleeding risk of these CVMs is unknown. The authors investigated the risk of bleeding in conjunction with clinical and radiological features in patients with HHT and proven CVMs.

METHODS

Intravenous digital subtraction (DS) angiography was used to screen 196 patients with HHT for the presence of CVMs. Patients with abnormal results on DS angiography were asked to undergo a conventional cerebral angiographic study. All patients with a proven CVM were assessed by a neurologist. The bleeding risk was retrospectively and prospectively calculated for patients with AVMs only, as well as for the whole cohort of patients with CVMs. Twenty-four patients (12.2%; 16 female and eight male), aged 14 to 66 years (mean 35.4 years) with one or more CVMs were identified. Fifteen patients (62.5%) had a CVM and a pulmonary AVM. Eleven patients (45.8%) exhibited no neurological signs of their CVM; six (25%) had headache or migraine; four (16.7%) had seizures; and three (12.5%) had an intracranial hemorrhage. Twenty-two patients had at least one AVM (with a total of 28 AVMs), whereas two patients only had telangiectases. Twenty-seven AVMs were small (96%), 36% were located in eloquent areas of the brain, and 82% had superficial venous drainage. One third of the patients had multiple CVMs. The bleeding risk for patients with at least one AVM ranged from 0.41 to 0.72% per year, and for the whole cohort the range was 0.38 to 0.69% per year. Calculation of the bleeding risk as determined by lesion-years ranged from 0.36 to 0.56% per year for patients with AVMs and from 0.27 to 0.46% per year for all patients with CVMs.

CONCLUSIONS

Patients with HHT have a high risk of harboring a CVM, especially in the presence of a pulmonary AVM. These CVMs are mostly low-grade AVMs (Spetzler-Martin Grade I or II), are frequently multiple, and have a lower risk of bleeding than that associated with sporadic AVMs. Female patients are more often affected than male patients. The inherent low sensitivity of DS angiography screening for CVMs may yield false negative results.

Postoperative seizure outcome in a series of 114 patients with supratentorial arteriovenous malformations

The incidence of de novo and ongoing postoperative seizures and factors implicated in an increased likelihood of seizures following supratentorial cerebral arteriovenous malformation (AVM) resection remain controversial. We investigated the frequency, severity and variables associated with postoperative seizures in 114 consecutive patients who underwent complete surgical excision of supratentorial AVMs at our institution. The minimal follow up period was 24 months. The incidence of seizures post-AVM surgery was 21% (less than half that found preoperatively). The incidence of postoperative seizures first manifesting >12 months post-AVM resection was 6.3%. A history of preoperative seizures was associated with an increased likelihood of multiple (> or =4) seizures >1 month post-AVM resection (chi2 = 4.38, P = 0.04). Poor functional neurological outcome at 12 months was also a risk factor for the development of > or =1 postoperative seizure using logistic regression analysis (P = 0.04, odds ratio 1.52, 95% CI 1.01-2.28). Cessation of AED therapy in all patients who remain seizure-free at 12 months post-AVM resection is appropriate due to a low risk of new seizure onset or seizure recurrence.

Posttreatment sequelae of palliatively treated cerebral arteriovenous malformations

OBJECTIVE

Posttreatment sequelae of palliatively treated cerebral arteriovenous malformations (AVMs) were studied to evaluate the significance of these nonradical treatments.

METHODS

Between 1987 and 1997, 46 patients with cerebral AVMs were managed with treatments such as partial embolization, radiosurgery, subtotal resection, or feeder ligation alone. Their AVMs were not radically resected because of difficulties in radical treatment, hesitance to treat eloquent area lesions, or residual nidi after subtotal obliteration. The patients' posttreatment sequelae were evaluated. The duration of follow-up ranged from 0.5 to 169 months (mean, 49.4+/-39.8 mo).

RESULTS

Twenty-six bleeding episodes from AVMs were documented in 18 patients. The annual risk of bleeding in this palliatively treated group was 14.6%. Persistent progressive neurological deficit was observed in one patient. Major neurological deficits occurred in 10 patients (23.3%), and the mortality rate was 9.3%.

CONCLUSION

Palliative treatments cannot prevent bleeding and may even worsen the posttreatment course compared with the natural history of cerebral AVMs. A more conservative indication is required in recommending palliative treatment alone.

Volume rendering quantification algorithm for reconstruction of CT volume-rendered structures: Part I. Cerebral arteriovenous malformations

Volume rendering is a visualization technique that has important applications in diagnostic radiology and in radiotherapy but has not achieved widespread use due, in part, to the lack of volumetric analysis tools for comparison of volume rendering to conventional visualization techniques. The volume rendering quantification algorithm (VRQA), a technique for three-dimensional (3-D) reconstruction of a structure identified on six principal volume-rendered views, is introduced and described. VRQA involves three major steps: 1) preprocessing of the partial surfaces constructed from each of six volume-rendered images; 2) merging these processed partial surfaces to define the boundaries of a volume; and 3) computation of the volume of the structure from this boundary information. After testing on phantoms, VRQA was applied to CT data of patients with cerebral arteriovenous malformations (AVM's). Because volumetric visualization of the cerebral AVM is relatively insensitive to operator dependencies, such as the choice of opacity transfer function, and because precise volumetric definition of the AVM is necessary for radiosurgical treatment planning, it is representative of a class of structures that is ideal for testing and calibration of VRQA. AVM volumes obtained using VRQA are intermediate to those obtained using axial contouring and those obtained using CT-correlated biplanar angiography (two routinely used visualization techniques for treatment planning for AVM's). Applications and potential expansions of VRQA are discussed.

High-resolution MR venography of cerebral arteriovenous malformations

The purpose of this study was to evaluate the diagnostic potential of a high-resolution magnetic resonance (MR) venography technique in patients with cerebral arteriovenous malformations (AVMs). A high-resolution 3D gradient echo sequence was used with a long echo time TE to obtain venous information down to sub-pixel sized vessel diameters of several hundred microns. The method is based on the paramagnetic property of deoxyhemoglobin, and the resulting developing phase difference between veins and brain parenchyma at long echo times which leads to signal cancellation. The reconstructed venograms were compared with time-of-flight (TOF)-MR angiography using qualitative and quantitative criteria with the conventional digital subtraction angiography serving as the reference gold standard. In 17 patients with angiographically proven cerebral AVMs, the method indicates its potential in clinical applications. Venography was able to detect all AVMs whereas TOF-MRA failed in three patients. In the delineation of venous drainage patterns MR venography was superior to TOF-MRA, however, the method failed in the detection of about half of the main feeding arteries, as expected. Due to susceptibility artifacts at air/tissue boundaries and interference with paramagnetic hemosiderin, venography was limited with respect to the delineation of the exact nidus sizes and shapes in ten patients with AVMs located close to the skull base or having suffered from previous bleeding. Although the visualization of draining veins represents an important prerequisite in the surgical and radiosurgical treatment planning of cerebral AVMs, application of high resolution MR venography may be limited in the diagnostic work-up in some of these patients. On the other hand, it may be of special importance in the early detection and assessment of small AVMs that are difficult to diagnose with other MR methods.

Two-step presurgical endovascular treatment of five arteriovenous malformations partially fed by single vessels en passage

PURPOSE

To describe a method for the preoperative embolization of arteriovenous malformations (AVM) containing vessels en passage (VeP). First, before embolization of the primary AVM, the distal portion of the VeP beyond the AVM, which supplies the parenchymal compartment, is blocked through placement of an endovascular ligature (fibered coils). This protects the post lesional parenchymal tissue and isolates malformational compartments before embolization. Thus the proximal AVM-supplying segment of the VeP can be safely embolized.

PATIENTS AND METHODS

Five of 204 AVM patients admitted for preoperative embolization between 1989 and 1997 fulfilled the following treatment criteria for the placement of an endovascular ligature in a VeP before embolization: 1. The diameter of the distal portion of the VeP behind the AVM was large whereas the parenchymal blush was poor; 2. The VeP fed a large portion of the AVM; 3. The VeP was judged to be accessible only late in the surgical procedure; 4. The VeP and its off branches were an integral part of the AVM periphery and thus not suitable for microdissection.

RESULTS

In all five cases the leptomeningeal collateral perfusion (the arterial supply to parenchymal brain areas) served to supply brain areas distal to the AVM after primary blockage of a VeP by endovascular ligature with fibered coils. Embolization and complete surgical dissection of the AVM was then achieved in all cases. No neurological deficits occurred.

CONCLUSION

Experience with our five cases indicates that a preparatory endovascular ligature of a VeP between parenchyma and the malformational compartment followed by embolization of the AVM can serve as an alternative to open surgical dissection of a vessel en passage and that it safely allows effective preoperative embolization.

[Arteriovenous malformations of the central nervous system. Analysis of 53 cases]

Fifty-three patients with arteriovenous malformation (AVM) were studied. The mean age at the time of diagnosis was 32.5 +/- 11.5 years (range 3 to 56 years); the sex ratio was male 1.9:1 female. The most common clinical presentation was intracranial hemorrhage, followed by focal neurological signs, headache, epilepsy, and acute deep coma. Fourty-three (82%) out of the total number of AVM were supratentorial and had the following distribution: 10 temporal lobe, 9 pariental lobe, 6 frontal lobe, 3 occipital lobe, 3 frontotemporal, 4 corpus callosum/pericalosal, 1 temporo-occipital, 1 temporoparieto-occipital, 6 deep-located (3 thalamic, 3 basal ganglia). Spetzler-Martin grade II was seen in 17 cases (32%), grade III in 21 cases (39%), and grade IV in 10 cases (19%). AVM-associated aneurysms were detected in 3 patients (5.6%). All three cases were middle artery aneurysms ipsilateral to AVM. Twelve (32%) out of 37 operated patients were submitted to embolization prior to surgery. AVM was totally removed in all cases except one. Embolization without posterior surgery was used in 11 patients; in 3 of them, embolization was partial. Two patients were neither embolized nor operated on. Three patients were, submitted to radiosurgery because they were poor candidates to embolization and/or surgery. Mortality rate was 1.8%. All patients returned to their normal life function after a period of recovery. Associated or isolated therapies should be individualized to each patient with AVM and is likely to provide results better than the expected outcome without any treatment.

A simple relationship between radiological arteriovenous malformation hemodynamics and clinical presentation: a prospective, blinded analysis of 31 cases

OBJECT

The authors sought to establish prospectively whether there is a simple relationship between radiological features of brain arteriovenous malformation (AVM) hemodynamics and a patient's clinical presentation.

METHODS

Thirty-one consecutive patients with AVMs underwent cerebral angiography at 3.8 frames/second during each standardized injection of contrast material. Contrast dilution curves were derived from the image sequences by using regions of interest (ROIs) traced on arteries feeding and veins draining the AVM nidus. Angiographic parameters were then analyzed in a blinded fashion. These parameters included the times required to reach the peak contrast density, the contrast decay time, and fractions thereof, in the ROI for each vessel. The authors determined whether these parameters, the arteriovenous transit time, and/or AVM size were related to patients' presentation with hemorrhage (11 patients), seizure (11 patients), or other clinical symptoms (nine patients). Statistically significant results were found only in analyses of arterial phase times to reach peak contrast density. Analyses of venous parameters, AVM size, and nidus transit time showed trends but no statistical significance. Arterial filling with contrast material was significantly slower in patients presenting with hemorrhage (mean 50%, 80%, and 100% of time to peak +/- standard error [SE] = 1.19+/-0.13, 1.97+/-0.18, and 3.04+/-0.34 seconds, respectively) compared with patients presenting with seizures (mean 50%, 80%, and 100% of time to peak +/- SE = 0.80+/-0.12, 1.32+/-0.18, and 1.95+/-0.29 seconds, respectively) according to analysis of variance (p<0.05) and post-hoc t-tests (p<0.05) for each parameter. Patients who presented with other symptoms had intermediate arterial filling times.

CONCLUSIONS

These simple hemodynamic parameters, which can be obtained without added risk to the patient, may help identify a subset of individuals in whom AVMs pose a higher risk of future hemorrhage and who may therefore warrant more expeditious treatment.

Theoretical comparison of surgery and radiosurgery in cerebral arteriovenous malformations

OBJECT

Management of patients with cerebral arteriovenous malformations (AVMs) is controversial. Excellent surgical results are obtained in patients with low Spetzler-Martin grades, whereas radiosurgery offers a good alternative with its high obliteration rate. In the absence of randomized studies, physicians must choose a treatment plan based on the currently available data. To support this decision-making process, a mathematical model designed to describe patient survival rates after each treatment option was developed.

METHODS

The theoretical survival curve in patients undergoing conventional surgery, radiosurgery, or observation was calculated. Theoretical life expectancies in patients with AVMs who presented at various initial ages were calculated for each treatment strategy. A systematic method was also developed to compare the estimated risks of various treatment combinations.

CONCLUSIONS

Conventional surgery and radiosurgery definitely produced better survival rates than observation. In the comparison of surgery with radiosurgery, radiosurgery was equivalent to surgery with a combined morbidity and mortality rate of approximately 7% for a 20-year-old patient with an unruptured cerebral AVM. Data for other patient ages and treatment combinations are tabulated for use in determining the best treatment strategy. The authors believe that their analysis will provide logical support for the decision-making process involved in the treatment of patients with cerebral AVMs.

The endovascular treatment of brain arteriovenous malformations

Advances in superselective microcatheterization techniques, which took place in the past decade, established superselective endovascular exploration as an integral and indispensable tool in the pretherapeutic evaluation of brain AVMs. The strict and routine application of superselective angiography furthered our knowledge on the angioarchitecture of brain AVMs, including vascular composition of the nidus, types of feeding arteries and types and patterns of venous drainage. In addition, various types of weak angioarchitectural elements, such as flow-related aneurysms, intranidal vascular cavities and varix formation proximal to high-grade stenosis of draining veins, could be identified as factors predisposing for AVM rupture. A wide spectrum of secondary angiomorphological changes induced by the arteriovenous shunt of the nidus and occurring up- and downstream of the nidus have been identified as manifestations of high-flow angiopathy. These data help to better predict the natural history, understand the widely variable clinical presentation and to define therapeutic targets of brain AVMs. Correlation of the topography of the AVM as demonstrated by MR with the angioarchitecture as demonstrated by superselective angiography provided a system for topographic-vascular classification of brain AVMs, which proved very useful for patient selection and definition of therapeutic goals. This study showed, that 40% of patients with brain AVMs can be cured by embolization alone with a severe morbidity of 1.3% and a mortality of 1.3%. Part of theses patients can, however, be cured equally effective by microsurgery or radiosurgery. Which modality will be chosen for a particular patient will mainly depend on the locally available expertise and experience, but also on the preference of the patient following its comprehensive information about the chances for cure and the risks associated with each of these therapeutic modalities. Embolization has a significant role in the multimodality treatment of brain AVMs, by either enabling or facilitating subsequent microsurgical or radiosurgical treatment. Appropriately targeted embolization in otherwise untreatable AVMs represents a reasonable form of palliative treatment of either ameliorating the clinical condition of the patient or reducing the potential risk of hemorrhage. Regarding the practical aspects of the endovascular treatment the following conclusions could be drawn from the experience obtained with this series of 387 patients with a brain AVM: (1) The goal of endovascular treatment should be defined prior to the procedure. This does not preclude a change in the goal, if additional information obtained during the procedure make this necessary. (2) The result of endovascular treatment of a brain AVM in terms of the degree of obliteration achieved and complication rate depends mainly on the endovascular strategy developed and the technique applied. These depend on the specific angioarchitecture and topography of the individual AVM, on the past history and clinical presentation of the patient and on the predefined goal of embolization. The strategy should include the definition of embolization targets, the selection of the most appropriate approach for endovascular navigation, the determination of the sequence of catheterization of individual feeding arteries, the selection of the type of catheters and microcatheters, the selection of the appropriate embolic materials as well as the site and mode of their delivery. Thereafter, every endovascular move should be, as in a chess game, the result of a logical plan. (3) Atraumatic superselective microcatheterization is a key point in the endovascular treatment of brain AVMs. It requires manual skills, knowledge of anatomy and respect for the vascular wall. (4) All locations of brain AVMs should be regarded as eloquent, and no distinction should be made between eloquent and non-eloquent areas of the brain when deciding on the execution of embolizatio