Evaluating performance of the spetzler-martin supplemented model in selecting patients with brain arteriovenous malformation for surgery

Microsurgery alone versus preoperative embolisation: A meta-analysis of outcomes in brain AVMs by Spetzler-Martin grade

Preoperative embolisation is frequently used an adjunct to microsurgery for brain arteriovenous malformations (AVMs), yet high-level evidence supporting its routine use remains limited. This meta-analysis compares outcomes of microsurgery alone versus combined microsurgery and preoperative embolisation, stratified by Spetzler-Martin (SM) grade. A systematic review of Embase, Medline, Scopus, Emcare, and the Cochrane Library identified 43 studies encompassing 3916 patients, equally divided between microsurgery alone (n = 1958) and combination therapy (n = 1958). Primary endpoints included functional dependence (modified Rankin Scale score > 2), angiographic obliteration, haemorrhagic complications, and intraoperative blood loss. Pooled analyses demonstrated no significant differences in functional dependence (OR 0.65, 95 % CI 0.32-1.32, p = 0.21), obliteration rates (OR 1.15, 95 % CI 0.60-2.19, p = 0.63), haemorrhagic complications (OR 1.67, 95 % CI 0.71-3.95, p = 0.20), or intraoperative blood loss (MD -98.90 mL, 95 % CI -417.38-219.57, p = 0.44). Subgroup analysis for SM grade I-II and III-V AVMs found no significant differences in outcomes between treatment modalities. For SM grade III AVMs, angiographic cure rates were comparable, though data scarcity precluded a robust assessment of functional dependence, postoperative haemorrhage, and intraoperative blood loss. While theoretical advantages exist for preoperative embolisation in higher-grade or high-flow AVMs, current evidence does not demonstrate consistent benefits in outcomes or complication rates. Further studies, particularly for SM grade III AVMs, are needed to determine whether combination therapy provides a meaningful advantage over microsurgery alone.

Is Supplemented Spetzler-Martin grading Superior? A comparative study in AVM microsurgery risk stratification

The Spetzler-Martin (SM) grading system remains the most widely adopted classification for brain arteriovenous malformations (AVMs). The Supplemented Spetzler-Martin (Supp-SM) system was developed to improve surgical risk stratification by incorporating patient age, rupture status, and nidus diffuseness. However, data comparing its predictive validity remain limited. This study investigates the predictive relevance of SM and Supp-SM grading for postoperative neurological morbidity following AVM microsurgery at a single tertiary cerebrovascular centre. A retrospective review identified 96 patients who underwent AVM microsurgical resection, with or without preoperative embolisation, between 2015 and 2024. Postoperative morbidity was defined as worsened modified Rankin Scale (mRS) score at 90 days. Predictive accuracy was analysed using ROC curves, correlation with postoperative mRS scores, and Supp-SM risk threshold. Postoperative morbidity occurred in 9 patients (9.4 %). ROC analysis revealed no significant difference between SM (AUROC 0.717; 95 % CI 0.55-0.88) and Supp-SM (AUROC 0.667; 95 % CI 0.46-0.88) scores, p = 0.3899. However, Supp-SM scores demonstrated a stronger correlation with postoperative mRS changes (Spearman's ρ = 0.269, p = 0.008) than SM grades (Spearman's ρ = 0.144, p = 0.161). Patients with Supp-SM grades < 6 had a 3.2 % morbidity risk, compared with a 20.6 % risk for scores ≥ 6 (p = 0.009). A Supp-SM threshold of 6 demonstrated the highest discriminative accuracy in differentiating high- and low-risk surgical candidates. While no significant predictive difference was found between SM and Supp-SM grading, a Supp-SM score of ≥ 6 was associated with substantially higher morbidity. These findings support the adjunctive use of Supp-SM grading for surgical risk assessment in AVM patients.

Stereotactic Radiosurgery for Spetzler-Martin Grade I and II Arteriovenous Malformations: International Society of Stereotactic Radiosurgery (ISRS) Practice Guideline

BACKGROUND

No guidelines have been published regarding stereotactic radiosurgery (SRS) in the management of Spetzler-Martin grade I and II arteriovenous malformations (AVMs).

OBJECTIVE

To establish SRS practice guidelines for grade I-II AVMs on the basis of a systematic literature review.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant search of Medline, Embase, and Scopus, 1986-2018, for publications reporting post-SRS outcomes in ≥10 grade I-II AVMs with a follow-up of ≥24 mo. Primary endpoints were obliteration and hemorrhage; secondary outcomes included Spetzler-Martin parameters, dosimetric variables, and “excellent” outcomes (defined as total obliteration without new post-SRS deficit).

RESULTS

Of 447 abstracts screened, 8 were included (n = 1, level 2 evidence; n = 7, level 4 evidence), representing 1102 AVMs, of which 836 (76%) were grade II. Obliteration was achieved in 884 (80%) at a median of 37 mo; 66 hemorrhages (6%) occurred during a median follow-up of 68 mo. Total obliteration without hemorrhage was achieved in 78%. Of 836 grade II AVMs, Spetzler-Martin parameters were reported in 680: 377 were eloquent brain and 178 had deep venous drainage, totaling 555/680 (82%) high-risk SRS-treated grade II AVMs.

CONCLUSION

The literature regarding SRS for grade I-II AVM is low quality, limiting interpretation. Cautiously, we observed that SRS appears to be a safe, effective treatment for grade I-II AVM and may be considered a front-line treatment, particularly for lesions in deep or eloquent locations. Preceding publications may be influenced by selection bias, with favorable AVMs undergoing resection, whereas those at increased risk of complications and nonobliteration are disproportionately referred for SRS.

Management of Unruptured Cerebral Aneurysms and Arteriovenous Malformations

PURPOSE OF REVIEW

Unruptured intracranial aneurysms and brain arteriovenous malformations (AVMs) may be detected as incidental findings on cranial imaging. This article provides a practical approach to the management of unruptured intracranial aneurysms and unruptured brain AVMs and reviews the risk of rupture, risk factors for rupture, preventive treatment options with their associated risks, and the approach of treatment versus observation for both types of vascular malformations.

RECENT FINDINGS

For unruptured intracranial aneurysms, scoring systems on the risk of rupture can help with choosing preventive treatment or observation with follow-up imaging. Although the literature provides detailed information on the complication risks of preventive treatment of unruptured intracranial aneurysms, individualized predictions of these procedural complication risks are not yet available. With observation with imaging, growth of unruptured intracranial aneurysms can be monitored, and prediction scores for growth can help determine the optimal timing of monitoring. The past years have revealed more about the risk of complications of the different treatment modalities for brain AVMs. A randomized clinical trial and prospective follow-up data have shown that preventive interventional therapy in patients with brain AVMs is associated with a higher rate of neurologic morbidity and mortality compared with observation.

SUMMARY

The risk of hemorrhage from both unruptured intracranial aneurysms and brain AVMs varies depending on the number of risk factors associated with hemorrhage. For both types of vascular malformations, different preventive treatment options are available, and all carry risks of complications. For unruptured intracranial aneurysms, the consideration of preventive treatment versus observation is complex, and several factors should be included in the decision making. Overall, it is recommended that patients with unruptured asymptomatic brain AVMs should be observed.

Surgical selection and outcomes among elderly patients with brain arteriovenous malformations

OBJECTIVE

Studies of resection of brain arteriovenous malformations (AVMs) in the elderly population are scarce. This study examined factors influencing patient selection and surgical outcome among elderly patients.

METHODS

Patients 65 years of age and older who underwent resection of an unruptured or ruptured brain AVM treated by two surgeons at two centers were identified. Patient demographic characteristics, AVM characteristics, clinical presentation, and outcomes measured using the modified Rankin Scale (mRS) were analyzed. For subgroup analyses, patients were dichotomized into two age groups (group 1, 65-69 years old; group 2, ≥ 70 years old).

RESULTS

Overall, 112 patients were included in this study (group 1, n = 61; group 2, n = 51). Most of the patients presented with hemorrhage (71%), a small nidus (< 3 cm, 79%), and a low Spetzler-Martin (SM) grade (grade I or II, 63%) and were favorable surgical candidates according to the supplemented SM grade (supplemented SM grade < 7, 79%). A smaller AVM nidus was statistically significantly more likely to be present in patients with infratentorial AVMs (p = 0.006) and with a compact AVM nidus structure (p = 0.02). A larger AVM nidus was more likely to be treated with preoperative embolization (p < 0.001). Overall outcome was favorable (mRS scores 0-3) in 71% of the patients and was statistically independent from age group or AVM grading. Patients with ruptured AVMs at presentation had significantly better preoperative mRS scores (p < 0.001) and more favorable mRS scores at the last follow-up (p = 0.04) than patients with unruptured AVMs.

CONCLUSIONS

Outcomes were favorable after AVM resection in both groups of patients. Elderly patients with brain AVMs treated microsurgically were notable for small nidus size, AVM rupture, and low SM grades. Microsurgical resection is an important treatment modality for elderly patients with AVMs, and supplemented SM grading is a useful tool for the selection of patients who are most likely to achieve good neurological outcomes after resection.

ABBREVIATIONS

AVM = arteriovenous malformation; BNI = Barrow Neurological Institute; LY = Lawton-Young; mRS = modified Rankin Scale; SM = Spetzler-Martin; supp-SM = supplemented SM; UCSF = University of California, San Francisco.

Utilidad de las Escalas de Gradación en el Tratamiento Quirúrgico de Malformaciones Arteriovenosas Cerebrales

Introducción:

Las malformaciones arteriovenosas (MAVs) cerebrales comprenden una compleja pato-logía responsable de hasta el 38% de las hemorragias en pacientes de entre 15-45 años, acarreando cada episodio de sangrado un 25-50% de morbilidad y un 10-20% de mortalidad. La decisión terapéu-tica en un paciente con una MAV debe tener en cuenta la comparación entre los riesgos propios de la intervención y los de la historia natural de esta enfermedad.

Objetivo:

Evaluar la utilidad de predecir riesgo quirúrgico de diferentes escalas de gradación de MAV cerebrales según nuestra experiencia en una serie de casos.

Material y Métodos:

Se realizó un análisis bibliográfico de escalas de gradación de riesgo quirúrgico de MAV cerebrales utilizando como motor de búsqueda Pubmed incluyendo como palabras clave “malformación arteriovenosa cerebral”y “scala de gradación” (brain arteriovenous and malfor- mation grading scale). Se analizaron de forma retrospectiva aquellos pacientes intervenidos quirúrgi-camente por MAV en este hospital público, se las clasificó acorde a las escalas analizadas y se compa-raron los resultados obtenidos con los previstos en ellas.

Resultados:

Se analizaron 90 pacientes intervenidos quirúrgicamente por MAV, sin tratamiento coad-yuvante. De forma retrospectiva se los agrupó acorde a las escalas de Spetzler Martin (SM), Spetzler-Ponce (SP) y suplementaria de Lawton. Las MAV grado 3 se subclasificaron según las escalas de Lawton y de de Oliveira. Considerando buenos resultados aquellos con Rankin modificado (mRs) igual o menor a 2. Con un rango de seguimiento de 12 a 48 meses, encontramos buenos resultados en el 100% de MAV SM grado 1, 91.7% de las grado 2, 80% en grado 3 y 42.9% en grado 4. Utilizando la escala SP, 93.7% de buenos resultados en tipo A, 80% en tipo B y 42.9% en tipo C. Subclasifican-do las MAV SM 3 acorde a las escalas de de Oliveira y Lawton, 84% de buenos resultados en el tipo 3A, 71.3% en las 3B, 92% en MAV tipo 3-, 72.1% en el tipo 3+, 60% en tipo 3. Utilizando la escala suplementaria de Lawton combinada con SM, buen resultado en 100% grados II y III, 85,7% grado IV, 87,6 grado V, 80% grado VI, 75% grado VII y 66,6% grado VIII.

Conclusión:

Reafirmamos en esta serie, la utilidad de estimar riesgo quirúrgico con las escalas SM, SP, y la subclasificación de las MAV grado 3 propuesta por Lawton. Y principalmente el utilizar la escala suplementaria de Lawton-Young al considerar el tratamiento quirúrgico de los pacientes con MAV que sangraron.

A proposed classification for assessing rupture risk in patients with intracranial arteriovenous malformations

Background:

Whether cerebral arteriovenous malformations (AVMs) should be treated remains an ongoing debate. Nevertheless, there is a need for predictive factors that assist in labelling lesions as low or high risk for future rupture. Our aim was to design a new classification that would consider hemodynamic and anatomic factors in the rapid assessment of rupture risk in patients with AVMs.

Methods:

This was a retrospective study that included 639 patients with ruptured and unruptured AVMs. We proposed a new classification score (1–4 points) for AVM rupture risk using three factors: feeding artery mean velocity (Vm), nidus size, and type of venous drainage. We employed descriptive statistics and logistic regression analysis.

Results:

A total of 639 patients with cerebral AVMs, 388 (60%) had unruptured AVMs and 251 (40%) had ruptured AVMs. Logistic regression analysis revealed a significant effect of Vm, nidus size, and venous drainage type in accounting for the variability of rupture odds (P = 0.0001, R² = 0.437) for patients with AVMs. Based in the odds ratios, grades 1 and 2 of the proposed classification were corresponded to low risk of hemorrhage, while grades 3 and 4 were associated with hemorrhage: 1 point OR = (0.107 95% CI; 0.061–0.188), 2 point OR = (0.227 95% CI; 0.153–0.338), 3 point OR = (3.292 95% CI; 2.325–4.661), and 4 point OR = (23.304 95% CI; 11.077–49.027).

Conclusion:

This classification is useful and easy to use, and it may allow for the individualisation of each cerebral AVM and the assessment of rupture risk based on a model of categorisation.

Intraoperative neuromonitoring during brain arteriovenous malformation microsurgeries and postoperative dysfunction: A retrospective follow-up study

To evaluate the effectiveness of intraoperative neuromonitoring (IONM) during arteriovenous malformation (AVM) surgery, we retrospectively analyzed neurologic dysfunction in patients who underwent AVM surgery with (IONM group) and without IONM (non-IONM group). The sensitivity and specificity of short-term neurologic dysfunction were calculated in the IONM group. IONM parameters were obtained in all patients. There was no significant difference in neurologic dysfunction between patients in the IONM and non-IONM groups. The short-term hemiplegia ratio among grade III patients in the IONM group was significantly lower than the non-IONM group. The sensitivity of IONM for predicting short-term neurologic dysfunction in the IONM group was 86.7% with a specificity of 100%. Of the different parameters monitored intraoperatively, the somatosensory-evoked potential (SEP), maximum expiratory pressure (MEP), and brain auditory-evoked potential (BAEP) may be beneficial in grade III and IV patients. The BAEP complemented the SEP and MEP. Electromyography and the visual-evoked potential have promise in preserving cranial nerve and visual function. For grades I and II patients, no SEP monitoring was safe. For grade V patients, further investigation is required to prevent neurologic dysfunction because of highly related risks for disability and postoperative complications. Moreover, a larger sample size is required to demonstrate the usefulness of IONM during awake craniotomies.

Microsurgery for intracranial arteriovenous malformation: Long-term outcomes in 445 patients

BACKGROUND

The management of intracranial arteriovenous malformations(AVMs) poses challenges to the cerebrovascular specialists.

OBJECTIVE

To review the long-term outcomes of intracranial AVMs treated with microsurgical resections.

METHODS

We performed a retrospective review of 445 patients with intracranial AVMs treated in our hospital from January 1st, 2008 to December 31st, 2014. The extracted data included demographic characteristics, clinical presentations, Spetzler-Martin (SM) grades, Supplemented Spetzler-Martin (SM-Supp) Grades, treatment modalities, long-term outcomes, and obliteration rates. Outcome was assessed with a post-operative modified Rankin Scale (mRS) score at the last follow-up visit.

RESULTS

Of the 445 patients treated with microsurgery, 298 (67.0%) patients initially presented with hemorrhage. Based on the SM grading system, the patients were graded as follows: 83(18.6%) Grade I, 156(35.1%) Grade II, 132(29.7%) Grade III, 61(13.7%) Grade IV and 13(2.9%) Grade V. Overall, 344(77.3%) patients had a favorable outcome (mRS score of 0-2). The favorable outcome for Grade I and II were 92.8% and 85.9%, respectively, sharply reducing to 52.5% in patients with Grade IV and 15.4% in patients with Grade V AVMs. 388(87.2%) patients achieved complete obliteration of the AVMs. 63(14.2%) patients experienced recurrent hemorrhage, and the frequency of rehemorrhage was highest in Grade V patients (77.0%), dropping to 3.6% and 3.8% in patients with Grade I and II lesions, respectively. Permanent neurological deficits occurred in 66(14.8%) patients and death in 35(7.9%) patients. There was no difference of AUROC values between SM grading system and SM-supp grading system (0.726 and 0.734, respectively, p = .715).

CONCLUSION

The Spetzler-Martin grading system is a simple and effective method to estimate the risk of surgery and to evaluate the prognosis. Microsurgical resection for AVMs depends on the SM grades, and the morbidity-mortality rate increases with an increasing SM grade.

Interobserver Agreement on Arteriovenous Malformation Diffuseness Using Digital Subtraction Angiography

BACKGROUND

Arteriovenous malformation (AVM) diffuseness has been shown to be prognostic of treatment outcomes. We assessed interobserver agreement of AVM diffuseness among physicians of different specialty and training backgrounds using digital subtraction angiography (DSA).

METHODS

All research protocols were approved by the institutional review board for this retrospective chart review. In a single-blinded setting, 2 attending neurosurgeons, 1 attending interventional neuroradiologist, and 1 senior neurosurgical resident rated 80 DSA views of 36 AVMs as either compact or diffuse. Individual interobserver agreement and subgroup agreement were analyzed using κ agreement and intraclass correlation coefficient.

RESULTS

Disagreement regarding AVM diffuseness occurred in 43.8% of all DSA views (n = 80). Interobserver κ agreement on AVM diffuseness using DSA views among 4 physicians ranged from fair (κ = 0.40 [95% confidence interval (CI) = 0.22-0.58]) to substantial (κ = 0.65 [95% CI = 0.48-0.81]), whereas total intraclass correlation coefficient was 0.81 (95% CI = 0.73-0.87). For the 36 AVMs, κ agreement ranged from fair (κ = 0.36 [95% CI = 0.13-0.60]) to moderate (κ = 0.57 [95% CI = 0.35-0.79]), whereas intraclass correlation coefficient among all 4 physicians was 0.68 (95% CI = 0.47-0.82). Moderate agreement on AVM diffuseness (n = 80) was found between attending and resident assessments (κ = 0.57 [95% CI = 0.39-0.75]) and between neurosurgeon and interventional neuroradiologist assessments (κ = 0.55 [95% CI = 0.37-0.73]).

CONCLUSIONS

Agreement of individual physicians on AVM diffuseness varies from fair to substantial. Objective and three-dimensional measures of AVM diffuseness should be developed for consistent clinical application.

Therapeutic management of cerebral arteriovenous malformations: a review

The therapeutic management of cerebral arteriovenous malformations has undergone significant change over the past 40 years. Embolization, radiosurgery, advanced imaging modalities, neuropsychological testing and advances in surgical technique has both significantly improved our ability to treat patients, as well as confounding the landscape as to what constitutes best medical practice. Variability in natural history provides additional challenges in that it is challenging to determine an accurate estimate of the risk of hemorrhage, morbidity and mortality. It is clear that the complexity of the treatment of these lesions demands a multidisciplinary approach. The need for a team of neurosurgeons, interventional and diagnostic neuroradiologists, neurologists, radiation oncologists and neuropsychologists will improve outcomes and aid in determining best therapy for patients.

Validation of the supplemented Spetzler-Martin grading system for brain arteriovenous malformations in a multicenter cohort of 1009 surgical patients

BACKGROUND

The supplementary grading system for brain arteriovenous malformations (AVMs) was introduced in 2010 as a tool for improving preoperative risk prediction and selecting surgical patients.

OBJECTIVE

To demonstrate in this multicenter validation study that supplemented Spetzler-Martin (SM-Supp) grades have greater predictive accuracy than Spetzler-Martin (SM) grades alone.

METHODS

Data collected from 1009 AVM patients who underwent AVM resection were used to compare the predictive powers of SM and SM-Supp grades. Patients included the original 300 University of California, San Francisco patients plus those treated thereafter (n = 117) and an additional 592 patients from 3 other centers.

RESULTS

In the combined cohort, the SM-Supp system performed better than SM system alone: area under the receiver-operating characteristics curve (AUROC) = 0.75 (95% confidence interval, 0.71-0.78) for SM-Supp and AUROC = 0.69 (95% confidence interval, 0.65-0.73) for SM (P < .001). Stratified analysis fitting models within 3 different follow-up groupings (<6 months, 6 months-2 years, and >2 years) demonstrated that the SM-Supp system performed better than SM system for both medium (AUROC = 0.71 vs 0.62; P = .003) and long (AUROC = 0.69 vs 0.58; P = .001) follow-up. Patients with SM-Supp grades ≤6 had acceptably low surgical risks (0%-24%), with a significant increase in risk for grades >6 (39%-63%).

CONCLUSION

This study validates the predictive accuracy of the SM-Supp system in a multicenter cohort. An SM-Supp grade of 6 is a cutoff or boundary for AVM operability. Supplemented grading is currently the best method of estimating neurological outcomes after AVM surgery, and we recommend it as a starting point in the evaluation of AVM operability.

Brain arteriovenous malformations

An arteriovenous malformation is a tangle of dysplastic vessels (nidus) fed by arteries and drained by veins without intervening capillaries, forming a high-flow, low-resistance shunt between the arterial and venous systems. Arteriovenous malformations in the brain have a low estimated prevalence but are an important cause of intracerebral haemorrhage in young adults. For previously unruptured malformations, bleeding rates are approximately 1% per year. Once ruptured, the subsequent risk increases fivefold, depending on associated aneurysms, deep locations, deep drainage and increasing age. Recent findings from novel animal models and genetic studies suggest that arteriovenous malformations, which were long considered congenital, arise from aberrant vasculogenesis, genetic mutations and/or angiogenesis after injury. The phenotypical characteristics of arteriovenous malformations differ among age groups, with fistulous lesions in children and nidal lesions in adults. Diagnosis mainly involves imaging techniques, including CT, MRI and angiography. Management includes observation, microsurgical resection, endovascular embolization and stereotactic radiosurgery, alone or in any combination. There is little consensus on how to manage patients with unruptured malformations; recent studies have shown that patients managed medically fared better than those with intervention at short-term follow-up. By contrast, interventional treatment is preferred following a ruptured malformation to prevent rehaemorrhage. Management continues to evolve as new mechanistic discoveries and reliable animal models raise the possibility of developing drugs that might prevent the formation of arteriovenous malformations, induce obliteration and/or stabilize vessels to reduce rupture risk. For an illustrated summary of this Primer, visit: http://go.nature.com/TMoAdn.

Treatment and outcomes of ARUBA-eligible patients with unruptured brain arteriovenous malformations at a single institution

OBJECT

Management of unruptured arteriovenous malformations (AVMs) is controversial. In the first randomized trial of unruptured AVMs (A Randomized Trial of Unruptured Brain Arteriovenous Malformations [ARUBA]), medically managed patients had a significantly lower risk of death or stroke and had better outcomes. The University of California, San Francisco (UCSF) was one of the participating ARUBA sites. While 473 patients were screened for eligibility, only 4 patients were enrolled in ARUBA. The purpose of this study is to report the treatment and outcomes of all ARUBA-eligible patients at UCSF.

METHODS

The authors compared the treatment and outcomes of ARUBA-eligible patients using prospectively collected data from the UCSF brain AVM registry. Similar to ARUBA, they compared the rate of stroke or death in observed and treated patients and used the modified Rankin Scale to grade outcomes.

RESULTS

Of 74 patients, 61 received an intervention and 13 were observed. Most treated patients had resection with or without preoperative embolization (43 [70.5%] of 61 patients). One of the 13 observed patients died after AVM hemorrhage. Nine of the 61 treated patients had a stroke or died. There was no significant difference in the rate of stroke or death (HR 1.34, 95% CI 0.12-14.53, p = 0.81) or clinical impairment (Fisher's exact test, p > 0.99) between observed and treated patients.

CONCLUSIONS

The risk of stroke or death and degree of clinical impairment among treated patients was lower than reported in ARUBA. The authors found no significant difference in outcomes between observed and treated ARUBA-eligible patients at UCSF. Results in ARUBA-eligible patients managed outside that trial led to an entirely different conclusion about AVM intervention, due to the primary role of surgery, judicious surgical selection with established outcome predictors, and technical expertise developed at high-volume AVM centers.

Intraoperative arteriovenous malformation rupture: causes, management techniques, outcomes, and the effect of neurosurgeon experience

OBJECT

Intraoperative rupture can transform an arteriovenous malformation (AVM) resection. Blood suffuses the field and visualization is lost; suction must clear the field and the hand holding the suction device is immobilized; the resection stalls while hemostasis is being reestablished; the cause and site of the bleeding may be unclear; bleeding may force technical errors and morbidity from chasing the source into eloquent white matter; and AVM bleeding can be so brisk that it overwhelms the neurosurgeon. The authors reviewed their experience with this dangerous complication to examine its causes, management, and outcomes.

METHODS

From a cohort of 591 patients with AVMs treated surgically during a 15-year period, 32 patients (5%) experienced intraoperative AVM rupture. Their prospective data and medical records were reviewed.

RESULTS

Intraoperative AVM rupture was not correlated with presenting hemorrhage, but had a slightly higher incidence infratentorially (7%) than supratentorially (5%). Rupture was due to arterial bleeding in 18 patients (56%), premature occlusion of a major draining vein in 10 (31%), and nidal penetration in 4 (13%). In 14 cases (44%), bleeding control was abandoned and the AVM was removed immediately ("commando resection"). The incidence of intraoperative rupture was highest during the initial 5-year period (9%) and dropped to 3% and 4% in the second and third 5-year periods, respectively. Ruptures due to premature venous occlusion and nidal penetration diminished with experience, whereas those due to arterial bleeding remained steady. Despite intraoperative rupture, 90% of AVMs were completely resected initially and all of them ultimately. Intraoperative rupture negatively impacted outcome, with significantly higher final modified Rankin Scale scores (mean 2.8) than in the overall cohort (mean 1.5; p < 0.001).

CONCLUSIONS

Intraoperative AVM rupture is an uncommon complication caused by pathological arterial anatomy and by technical mistakes in judging the dissection distance from the AVM margin and in mishandling or misinterpreting the draining veins. The decrease in intraoperative rupture rate over time suggests the existence of a learning curve. In contrast, intraoperative rupture due to arterial bleeding reflects the difficulty with dysplastic feeding vessels and deep perforator anatomy rather than neurosurgeon experience. The results demonstrate that intraoperative AVM rupture negatively impacts patient outcome, and that skills in managing this catastrophe are critical.

Diagnosis and evaluation of intracranial arteriovenous malformations

BACKGROUND

Ideal management of intracranial arteriovenous malformations (AVMs) remains poorly defined. Decisions regarding management of AVMs are based on the expected natural history of the lesion and risk prediction for peritreatment morbidity. Microsurgical resection, stereotactic radiosurgery, and endovascular embolization alone or in combination are all viable treatment options, each with different risks. The authors attempt to clarify the existing literature's understanding of the natural history of intracranial AVMs, and risk-assessment grading scales for each of the three treatment modalities.

METHODS

The authors conducted a literature review of the existing AVM natural history studies and studies that clarify the utility of existing grading scales available for the assessment of peritreatment risk for all three treatment modalities.

RESULTS

The authors systematically outline the diagnosis and evaluation of patients with intracranial AVMs and clarify estimation of the expected natural history and predicted risk of treatment for intracranial AVMs.

CONCLUSION

AVMs are a heterogenous pathology with three different options for treatment. Accurate assessment of risk of observation and risk of treatment is essential for achieving the best outcome for each patient.

Hemorrhage rates and risk factors in the natural history course of brain arteriovenous malformations

Brain arteriovenous malformations (AVMs) are abnormal connections of arteries and veins, resulting in arteriovenous shunting of blood. Primary medical therapy is lacking; treatment options include surgery, radiosurgery, and embolization, often in combination. Judicious selection of AVM patients for treatment requires balancing risk of treatment complications against the risk of hemorrhage in the natural history course. This review focuses on the epidemiology, hemorrhage risk, and factors influencing risk of hemorrhage in the untreated natural course associated with sporadic brain AVM.