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

Trauma and arteriovenous malformation of the brain — a problem in medico-legal practice

Legal difficulties can always arise when a death, owing to a pre-existing natural disease, follows trauma. Arteriovenous malformations of the brain are well known to rupture spontaneously, causing severe and often fatal cerebral haemorrhage. When such rupture is preceded by head injury, it is necessary to consider whether the rupture was coincidental or a direct result of the physical injury sustained. The standard of evidence required for criminal conviction in such cases must be 'beyond any reasonable doubt'. The present article discusses the relationship between physical trauma and cerebral arteriovenous malformation in an adult male who died following an alteration with a colleague that resulted in his being punched in the face, falling down and hitting his head.

Control of epilepsy associated with cerebral arteriovenous malformations after radiosurgery

OBJECTIVE

To investigate the effect of radiosurgery for symptomatic epilepsy associated with cerebral arteriovenous malformations (AVMs).

METHODS

Thirty five patients with unruptured epileptogenic AVMs were studied with a mean follow up of 43.0 months. The duration of epilepsy before radiosurgery ranged from 2 months to 21 years (mean 2.8 years). Fifteen patients showed partial seizures; eight of these had associated secondary generalisation. The remaining 20 patients showed only generalised seizures without preceding focal seizures.

RESULTS

At the final follow up examination, 28 patients remained seizure free, whereas seizures continued in seven. Variables significantly associated with continuity of seizures after radiosurgery were the number of seizures before therapy (p<0.01) and duration of epilepsy (p<0.05). According to Engel's classification, the 10 patients with intractable seizures before treatment included five with grade I, four with grade III, and one with grade IV. The frequency of seizures began to decrease several months after radiosurgery; much shorter than the time required for morphological change in the AVMs.

CONCLUSIONS

Radiosurgery seems to be beneficial for seizure control in patients with unruptured epileptogenic AVM.

Early surgical treatment of intracerebral hemorrhages caused by AVM: our experience in 10 cases

Between February, 1980, and April, 1993. 10 patients with intraparenchymal hemorrhage due to the bleeding of an arteriovenous malformation (AVM) underwent emergency surgical procedures within an average time of 3 hours (min. 2-max. 7) from casualty to admission. Rapid neurological worsening and mass effect of the extensive intracerebral hemorrhage prompted early surgical treatment. Post-operative angiography was performed to confirm that the malformation had been excluded from the circulation. The aim of this study is to evaluate the role of early surgery in patients requiring emergency surgical procedures for severe neurological injury induced by extensive intracerebral hematoma produced by AVM bleeding.

Theoretical modelling of arteriovenous malformation rupture risk: a feasibility and validation study

PURPOSE

To explore the feasibility of using a theoretical computational model to simulate the risk of spontaneous arteriovenous malformation (AVM) haemorrhage.

METHODS

Data from 12 patients were collected from a prospective databank which documented the angioarchitecture and morphological characteristics of the AVM and the feeding mean arterial pressure (FMAP) measured during initial superselective angiography prior to any treatment. Using the data, a computational model of the cerebral circulation and the AVM was constructed for each patient (patient-specific model). Two model risk (Risk(model)) calculations (haemodynamic- and structural-weighted estimates) were performed by using the patient-specific models. In our previously developed method of haemodynamic-weighted estimate, Risk(model) was calculated with the simulated intranidal pressures related to its maximal and minimal values. In the method of structural-weighted estimate developed and described in this paper, the vessel mechanical properties and probability calculation were considered in more detail than in the haemodynamic-weighted estimate. Risk(model) was then compared to experimentally determined risk which was calculated using a statistical method for determining the relative risk of having initially presented with AVM haemorrhage, termed Risk(exp).

RESULTS

The Risk(model) calculated by both haemodynamic- and structural-weighted estimates correlated with experimental risks with chi2 = 6.0 and 0.64, respectively. The risks of the structural-weighted estimate were more correlated to experimental risks.

CONCLUSIONS

Using two different approaches to the calculation of AVM haemorrhage risk, we found a general agreement with independent statistical estimates of haemorrhagic risk based on patient data. Computational approaches are feasible; future work can focus on specific pathomechanistic questions. Detailed patient-specific computational models can also be developed as an adjunct to individual patient risk assessment for risk-stratification purposes.

Significance of factors contributing to surgical complications and to late outcome after elective surgery of cerebral arteriovenous malformations

OBJECTIVES

This study focuses on the relevance of size, eloquence, type of venous drainage, the Spetzler-Martin scale as a whole, and other factors, such as rupture of cerebral arteriovenous malformations (AVMs) for the prediction of neurological deficits in the context of microsurgical AVM removal.

METHODS

One hundred and fifty patients with AVMs, whose data were retrieved from a prospectively employed computerised data bank were included. Seventeen patients (11.3%) underwent preoperative embolisation. According to the Spetzler-Martin scale they were graded as follows: 22.0% grade I, 32.0% grade II, 29.3% grade III, 14.0% grade IV, and 2.7% grade V. Intracerebral haemorrhage was present in 39.0%. The AVMs were <3 cm in 52.00/0, 3-6 cm in 43.3% and >6 cm in 4.7%; 59.3% of the AVMs were eloquently located and 29.3% had deep venous drainage (DVD). Follow up information was assessed 6 months after surgery in all but one patient, who died. The applied statistical test was chi2.

RESULTS

Surgical morbidity was 15.3%. Early new deficits were noted in 39.3%, permanent new deficits in 10.6%, being significant (major) in 7.3%. The occurrence of permanent deficits correlated significantly with size, deep venous drainage, and the Spetzler-Martin scale. There was statistical evidence for a trend in risk of poor surgical outcome across the three categories non-eloquent, "less eloquent" (for example, visual cortex) and "highly eloquent" (brainstem, basal ganglia, or precentral cortex) with the last being associated with the highest risk for permanent neurological compromise.

CONCLUSION

"Eloquence" of the Spetzler-Martin scale should be divided into "highly eloquent" and "less eloquent", which is important for risk analysis of the treatment of asymptomatic and deep seated AVMs and for future trials comparing various treatment modalities. In addition, resection of eloquent AVMs v non-eloquent ones is significantly associated with higher surgical morbidity.

High-resolution venography of the brain using magnetic resonance imaging

The purpose of this study was to evaluate a non-flow related magnetic resonance imaging method to visualize small veins independent of arteries in the human brain. A long TE, high-resolution 3D gradient echo MR acquisition was used to highlight venous information. The method is based on the paramagnetic property of deoxyhemoglobin and the resulting phase difference between veins and brain parenchyma at long echo times. The MR magnitude images were masked with a phase mask filter to enhance small structure visibility. Venous information down to sub-pixel vessel diameters of several hundred microns is visible. Venous data are displayed in an angiographic manner using a minimum intensity projection algorithm. Both superficial veins and deep white matter veins are visible. The method has been successfully applied in volunteers. Preliminary results in patients with cerebral arteriovenous malformations indicate its potential in clinical applications. The proposed method is easy to implement and does not require administration of a contrast agent or application of specially designed rf pulses to highlight the veins. Rather it exploits the intrinsic magnetic properties (BOLD-effect) and the prolonged T2* of venous blood. The method may be of diagnostic potential in the assessment of arteriovenous malformations or other vascular venous lesions.

Stereotactic radiosurgery of angiographically occult vascular malformations: 14-year experience

OBJECTIVE

Radiosurgery is generally effective in obliterating true arteriovenous malformations, but less is known about its effects on angiographically occult vascular malformations (AOVMs). Since July 1983, 57 patients with surgically inaccessible AOVMs of the brain were treated using helium ion (47 patients) or linear accelerator (10 patients) radiosurgery. This study retrospectively evaluates the response of these AOVMs to treatment.

METHODS

All patients presented with previous hemorrhage. The mean patient age was 35.6 years (range, 13-71 yr). The mean AOVM volume was 2.25 cm3 (range, 0.080-15.2 cm3), treated with a mean of 18.0 Gy equivalent (physical dose x relative biological effectiveness, which is 1.3 for helium ion Bragg peak) (range, 7.0-40 Gy equivalent). The Drake scale scores before treatment were as follows: excellent (25 patients), good (26 patients), and poor (6 patients). The mean follow-up period was 7.5 years (range, 9 mo-13.8 yr).

RESULTS

Eighteen patients (32%) bled symptomatically (20 hemorrhages) after radiosurgery. Sixteen hemorrhages occurred within 36 months after radiosurgery (9.4% annual bleed rate; 16 hemorrhages/171 patient yr); 4 hemorrhages occurred more than 36 months after treatment (1.6% annual bleed rate; 4 hemorrhages/257 patient yr) (P < 0.001). Complications included symptomatic radiation edema (four patients, 7%), necrosis (one patient, 2%), and increased seizure frequency (one patient, 2%). Eight patients underwent surgical resection of their AOVMs 8 to 59 months after radiosurgery because of subsequent hemorrhage. The Drake scale scores after treatment were as follows: excellent (25 patients), good (24 patients), poor (3 patients), and dead (5 patients, 3 of whom died as a result of causes unrelated to the AOVMs or radiosurgery).

CONCLUSION

Radiosurgery may be useful for AOVMs located in surgically inaccessible regions of the brain. A significant decrease in bleed rate exists more than 3 years after treatment compared with the bleed rate within 3 years of treatment. Because current neuroradiological techniques are not able to image obliterative response in these slow-flow vascular lesions, longer term clinical follow-up is required.

Feeding artery pressure and venous drainage pattern are primary determinants of hemorrhage from cerebral arteriovenous malformations

PURPOSE

The purpose of this study was to define the influence of feeding mean arterial pressure (FMAP) in conjunction with other morphological or clinical risk factors in determining the probability of hemorrhagic presentation in patients with cerebral arteriovenous malformations (AVMs).

METHODS

Clinical and angiographic data from 340 patients with cerebral AVMs from a prospective database were reviewed. Patients were identified in whom FMAP was measured during superselective angiography. Additional variables analyzed included AVM size, location, nidus border, presence of aneurysms, and arterial supply and venous drainage patterns. The presence of arterial aneurysms was also correlated with site of bleeding on imaging studies.

RESULTS

By univariate analysis, exclusively deep venous drainage, periventricular venous drainage, posterior fossa location, and FMAP predicted hemorrhagic presentation. When we used stepwise multiple logistic regression analysis in the cohort that had FMAP measurements (n = 129), only exclusively deep venous drainage (odds ratio [OR], 3.7; 95% confidence interval [CI], 1.4 to 9.8) and FMAP (OR, 1.4 per 10 mm Hg increase; 95% CI, 1.1 to 1.8) were independent predictors (P < 0.01) of hemorrhagic presentation; size, location, and the presence of aneurysms were not independent predictors. There was also no association (P = 0.23) between the presence of arterial aneurysms and subarachnoid hemorrhage.

CONCLUSIONS

High arterial input pressure (FMAP) and venous outflow restriction (exclusively deep venous drainage) were the most powerful risk predictors for hemorrhagic AVM presentation. Our findings suggest that high intranidal pressure is more important than factors such as size, location, and the presence of arterial aneurysms in the pathophysiology of AVM hemorrhage.

Morbidity of intracranial hemorrhage in patients with cerebral arteriovenous malformation

BACKGROUND AND PURPOSE

Decisions on invasive arteriovenous malformation (AVM) treatment are currently based on natural-course risk estimates of AVM bleeding and assumptions on morbidity from cerebral hemorrhage in general. However, morbidity of AVM hemorrhage has rarely been reported. We sought to assess the morbidity of intracranial hemorrhage in patients with cerebral AVMs.

METHODS

From a prospective AVM database, 119 patients were analyzed: 115 had a hemorrhage as the diagnostic event, and 27 of them suffered a second hemorrhage during follow-up; an additional 4 patients had other diagnostic symptoms but bled during follow-up. The type (parenchymal, subarachnoid, intraventricular) and location of AVM hemorrhage were determined by CT/MR brain imaging. Disability and neurological impairment were assessed with the Barthel Index, the Rankin Scale, and the National Institutes of Health Stroke Scale, with a mean follow-up time of 16.2 months.

RESULTS

Of the 115 incident hemorrhages, 34 (30%) were subarachnoid, 27 (23%) parenchymal, 18 (16%) intraventricular, and 36 (31%) in combined locations. In 54 patients (47%; 95% confidence interval [CI], 38% to 56%) the incident hemorrhage resulted in no neurological deficit, and an additional 43 patients (37%; 95% CI, 28% to 46%) were independent in their daily activities (Rankin 1). Fifteen patients (13%; 95% CI, 7% to 19%) were moderately disabled (Rankin 2 or 3), and 3 (3%; 95% CI, 0% to 6%) were severely disabled (Rankin > or =4). Parenchymal hemorrhages were most likely to result in a neurological deficit (52%). Type and morbidity of hemorrhage during follow-up were similar to incident events. Twenty (74%) of 27 patients with both incident and follow-up hemorrhages were normal or independent (Rankin 0 or 1). None of the patients with a hemorrhage during follow-up died during the observation period.

CONCLUSIONS

Hemorrhage from cerebral AVMs appears to have a lower morbidity than currently assumed. This finding encourages a reevaluation of the risks and benefits of invasive AVM treatment.

Microsurgical treatment of arteriovenous malformations: analysis and comparison with stereotactic radiosurgery

OBJECT

To compare microsurgical and stereotactic radiosurgical treatment of arteriovenous malformations (AVMs), the authors analyzed a prospective series of 72 consecutive patients who were treated microsurgically for cerebral AVMs by one neurosurgeon. The authors then compared the results of microsurgical treatment with published results of stereotactic radiosurgical treatment of small AVMs.

METHODS

Patients were categorized by age, gender, presentation, and preoperative neurological status. The AVMs were categorized by size, location, presence of deep venous drainage, and Spetzler-Martin grade. Outcome was assessed for angiographic obliteration, hemorrhage following treatment, presence of a new, persistent postoperative neurological deficit, and Glasgow Outcome Scale (GOS) score. Ordinal logistic regression was used to model the GOS score and to predict new postoperative deficits. Generalized estimating equations were used to compare published results of microsurgical and stereotactic radiosurgical treatment of AVMs. Kaplan-Meier event-free survival plots were generated to compare the two modalities with respect to hemorrhage following treatment. Overall, six patients (8.3%) exhibited a new persistent neurological deficit postoperatively. Sixty-five patients (90.3%) had a GOS score of 5. Three patients were moderately disabled and four patients were severely disabled. No patient was observed to be in a vegetative state and there were no treatment-related deaths. Seventy-one patients (98.6%) underwent intra- or postoperative angiography. Total excision of the AVM was angiographically confirmed in 70 patients (98.6% of those who underwent angiography). To date no patient has suffered from hemorrhage since the microsurgical treatment. When analysis was confined to patients whose AVMs were smaller than 3 cm in maximum diameter, the authors found a 100% angiographic obliteration rate, no new postoperative neurological deficit, and a good recovery in all patients. An analysis of all patients with Spetzler-Martin Grades I to III resulted in a 100% rate of angiographic obliteration, one patient with a new postoperative neurological deficit, and good recovery in 93% of the patients. Size of the AVM, preoperative neurological status, and patient age are associated with GOS score (for all, p < 0.02). The Spetzler-Martin grading system as well as each component of this system are associated with the development of a new postoperative neurological deficit (for all, p < 0.01). For the entire series there were fewer postoperative hemorrhages and deaths than those mentioned in published series of small AVMs treated with stereotactic radiosurgery. When these patients and published series of patients with microsurgically treated AVMs classified as Grade I to III were compared with similar patients treated radiosurgically there were significantly fewer postoperative hemorrhages (odds ratio = 0.210, p = 0.001), fewer deaths (odds ratio = 0.659, p = 0.019), fewer new posttreatment neurological deficits (odds ratio = 0.464, p = 0.013), and a higher incidence of obliteration (odds ratio = 28.2, p = 0.001) for the microsurgical group. Lifetable analysis confirms the statistically significant difference in hemorrhage-free survival time between the two groups (p = 0.002).

CONCLUSIONS

Based on this analysis, microsurgical treatment of Grades I to III AVMs is superior to stereotactic radiosurgery.

Hypertension, small size, and deep venous drainage are associated with risk of hemorrhagic presentation of cerebral arteriovenous malformations

OBJECTIVE

To identify clinical and angiographic factors of cerebral arteriovenous malformations (AVMs) associated with hemorrhage to improve the estimation of the risks and help guide management in clinical decision making.

METHODS

We conducted a retrospective analysis of 100 consecutive adults who have presented during the past 3 years to our institution with cerebral AVMs. Angiographic and clinical parameters were evaluated using multivariate logistic regression analysis to analyze factors associated with hemorrhagic presentation.

RESULTS

The group had a mean age of 37.8 years; 53% were men, 48% presented with intracranial hemorrhage, and 40% presented with seizures. All 10 patients with cerebellar AVMs presented with hemorrhage. The following factors were independently associated with AVM hemorrhage: history of hypertension (P = 0.019; odds ratio [OR] = 5.36), nidal diameter <3 cm (P = 0.023: OR = 4.60), and deep venous drainage (P = 0.009: OR = 5.77). Dural arterial supply (P = 0.008; OR = 0.15) was independently associated with decreased risk of bleed. Location, nidal aneurysms, patient age, and smoking were not associated with increased or decreased bleeding risk.

CONCLUSION

In this study, we found small AVM size and deep venous drainage to be positively associated with AVM hemorrhage. Dural supply was associated with a decreased likelihood of hemorrhagic presentation. Hypertension was found to be the only clinical factor positively associated with hemorrhage, a finding not previously reported. Smoking, although associated with increased risk of aneurysmal subarachnoid hemorrhage, was not associated with a higher risk of AVM hemorrhage.

[Radioanatomy of cerebral arteriovenous malformations]

New imaging modalities permit detailed knowledge of the anatomy of cerebral arteriovenous malformations. Magnetic resonance imaging (MRI) provides morphological data, size and topography of the nidus, anatomic relationship, as well as dynamic information particularly with the use of MR angiography. Selective and hyperselective cerebral angiography provide information about the angioarchitecture and search for associated vascular abnormalities such as aneurysms. It is therefore possible to distinguish malformations associated with a high risk of hemorrhage and to define the indications for radiosurgery.

Results of 55 AVM Cases Treated by Embolization and/or Surgery

SUMMARY

In order to build a data base for future comparison, we summarized the treatment results of cerebral arteriovenous malformation (AVM) patients in our hospital. Fifty five AVM patients who had been treated at Nagoya University Hospital from 1988 to 1995 were enrolled in the study. The patient characteristics were nearly the same as other reported series. Trend of treatment modality was changing in this period and embolization was increasing in its role. Karnofsky score was used to follow the patients' clinical status. It was useful to assess pretreatment clinical status and post treatment status. The results showed the improvement of the embolization procedure.

Risk of spontaneous haemorrhage after diagnosis of cerebral arteriovenous malformation

BACKGROUND

A small proportion of strokes are caused by cerebral arteriovenous malformations (AVM). Treatment to prevent intracranial haemorrhage itself carries risks, and untreated AVM may in many cases have a good prognosis. We investigated the risk of subsequent symptomatic bleeding in the clinical course of AVM in patients with and without an initial haemorrhage.

METHODS

281 unselected, consecutive, prospectively enrolled patients with cerebral AVM were grouped according to their initial clinical presentation--142 presented with and 139 without haemorrhage. The frequency of AVM haemorrhages during the subsequent clinical course (before the start of endovascular, surgical, or radiation treatment) in the two groups was compared by means of Kaplan-Meier life-tables, log-rank test, and multivariate proportional-hazards regression models. Haemorrhage was defined as a clinically symptomatic event with signs of acute bleeding on computed tomography or magnetic resonance brain imaging.

FINDINGS

During mean follow-up of 8.5 months for the haemorrhage group and 11.9 months for the non-haemorrhage group, haemorrhages occurred in 18 (13%) of the former patients and in three (2%) of the latter (p=0.0002). The annual risk of haemorrhage was 17.8% and 2.2%, respectively. In the multivariate regression model, the adjusted hazard ratio for haemorrhage at initial presentation was 13.9 (95% CI 2.6-73.8; p=0.002). Deep venous drainage (hazard ratio 4.1 [1.2-14.9], p=0.029) and male sex (9.2 [2.1-41.3], p=0.004) were also significantly associated with subsequent haemorrhage, but no significant association was found for age or AVM size. The annual rate of spontaneous haemorrhage was 32.6% for men and 10.4% for women in the haemorrhage group compared with 3.3% for men and 1.3% for women in the non-haemorrhage group. Among patients with haemorrhage at initial presentation, the risk of haemorrhage fell from 32.9% in year 1 to 11.3% in subsequent years (34.2% to 31.0% in men; 31.1% to 5.5% in women).

INTERPRETATION

In AVM, patients initially presenting with haemorrhage have a higher risk of subsequent bleeding than those presenting with other symptoms. The risk is higher in men than in women.

Surgery versus stereotactic radiosurgery for small, operable cerebral arteriovenous malformations: a clinical and cost comparison

OBJECTIVE

Cerebral arteriovenous malformations (AVMs) may cause stroke and death in young patients. For small AVMs, the major curative treatment options are surgery and stereotactic radiosurgery (SR). Although the initial costs and risks of SR are less, there is a latency to cure and ultimately the success rate is lower than with surgery. Thus, these two treatment modalities were compared with respect to clinical outcomes and associated costs by means of a cost-effectiveness analysis.

METHODS

A decision analysis model was developed using Smltree software (J.P. Hollenberg, Roslyn, NY). Probability estimates for cure and complications for both therapies were derived from the literature. Utility values for minor and major stroke were measured in patients with AVMs who were treated at the University of Toronto clinic, using the standard gamble technique. Costs were obtained from several sources, including the case costing systems of several hospitals in Ontario, Canada.

RESULTS

Surgery confers a 0.98 quality-adjusted life year (QALY) advantage over SR, at an additional cost of $6937 per patient. Thus, from a societal perspective, the incremental cost-effectiveness ratio is $7100 per QALY for a patient treated surgically. The result is sensitive to only two variables: surgical morbidity and surgical mortality. However, the preferred treatment strategy changes to favor SR only at the extreme high end of the possible range for these variables, when the rate of permanent neurological morbidity resulting from surgery exceeds 12% or the surgical mortality rate exceeds 4%.

CONCLUSIONS

In the treatment of small AVMs, surgery confers a large clinical benefit over SR. The reason is that surgery protects the patient from hemorrhage earlier and with greater success than does SR. The associated cost-effectiveness ratio, $7100/QALY, is highly economically attractive. Therefore, surgery achieves important improvements in clinical outcomes and is associated with an excellent ratio of incremental costs per QALY gained.

Magnetic resonance imaging appearance of intracranial hemorrhage secondary to cerebral vascular malformation in a dog

A 14-year-old dog developed an acute onset of depression, disorientation, left hemiparesis,left hemianopia, left facial hypoesthesia, and a tendency to turn to the right. Based on these findings, a lesion affecting the right forebrain was suspected. Magnetic resonance imaging showed a mass within the right cerebral hemisphere resulting in compression of the right lateral ventricle and shifting the longitudinal fissure to the left. The lesion was hyperintense on T1-weighted images and hyperintense with focal regions of hypointensity on proton density-, and T2-weighted images, consistent with a subacute hemorrhage. At necropsy, there was a hematoma in the parietal portion of the right cerebral hemisphere. The hemorrhage was surrounded by numerous thin-walled veins, most likely a venous malformation. Magnetic resonance imaging of intracranial hemorrhage is reviewed.

Transarterial Embolisation of Cerebral Arteriovenous Malformations

Arteriovenous malformations of the brain are rare disorders. Embolisation has emerged as an effective treatment with an acceptable, low complication rate.

Previously presented results are completed with results from 1994 to 1996. Ninety-six percent of the patients were treated with no or very minor sequelae resulting in total obliteration in 32% and supplementary stereotactic radiation in 49%.

Ninety percent of all patients are in excellent or good health at follow up. These results may be jeopardised by the ongoing proliferation of endovascular treatment for AVMs.

Radiosurgery for arteriovenous malformations: the University of Toronto experience

BACKGROUND

From July 1989 to February 1996, 130 patients underwent stereotactic radiosurgery. We report the results of the first 50 patients eligible for a minimum of three years of follow-up.

METHODS

Twenty women and 30 men, (mean age: 37.5 years) were treated by dynamic rotation on a 6 MV linear accelerator. Prior treatment was embolization in seventeen, surgery in three and embolization and surgery in six. All had DSA and enhanced CT scanning, while some had MRI. Forty-seven treatments used a single isodose. Restricting eloquent normal tissue to 15 Gy, margin doses (at 50-90% isodose) were 12 Gy (one patient); 15 Gy (sixteen patients); 20 Gy (31 patients); 25 Gy (two patients). Maximum diameters were: < 1.5 cm (12 patients); < 2.0 cm (nine patients); < 2.5 cm (twelve patients); < 3.0 cm (thirteen patients; 3.0 cm (four patients).

RESULTS

Forty-five patients were evaluable at three years, with thirty-nine having angiography. Twenty-five had angiographically confirmed obliterations; two had parenchymal AVMs obliterated but with residual dural components; four had MRI evidence of obliteration (refused angiography). One patient acutely had a seizure; one patient (with hemorrhages, resection, and embolizations preceding two applications of radiosurgery, separated by 3.5 years) had worsening of memory.

CONCLUSIONS

Our uncorrected (five patients unevaluable at three years) and corrected angiographically confirmed obliteration rates are 54% and 60% respectively. Our follow-up (98% accounting of cohort; 78% angiographic rate) and explicit derivation of denominators help delineate the efficacy of radiosurgery at these doses.

Long-term outcome after surgical excision of parenchymal arteriovenous malformations in patients over 60 years of age

BACKGROUND

Age is considered an important limiting factor for surgical excision of parenchymal arteriovenous malformations (AVMs) and a more conservative therapeutic approach has been advocated in the elderly. There are no studies available investigating the long-term outcome after surgical excision of parenchymal AVMs in patients over 60 years of age.

METHODS

We report the surgical outcome after excision of an AVM in a series of 13 consecutive patients older than 60 years. Medical records were analyzed retrospectively.

RESULTS

Hemorrhage was the mode of presentation in all patients. Three patients were admitted in a comatose state. Surgery was performed within 1 week from the initial bleeding in seven cases and within 2 weeks in five cases. There were no deaths directly related to surgery in this series. However, one patient died as a result of an intracranial hemorrhage complicating preoperative embolization and another patient died 3 months after surgery from intervening medical complications. During the follow-up period (mean 46 months), three more patients had died 8, 19, and 48 months after surgery, respectively. Of the remaining eight patients, six are doing well and are independent in the activities of daily living. One patient is independent but requires supervision, and the remaining one was lost to follow-up.

CONCLUSIONS

Age alone should no longer be considered a contraindication to treatment. In selected cases, surgery can be performed safely even in the elderly patient with an AVM. After surgical excision, elderly patients have the potential for several years of active life.

A dose-response analysis of arteriovenous malformation obliteration after radiosurgery

PURPOSE

Although radiosurgery is effective in obliterating the pathologic vessels of intracranial arteriovenous malformations (AVM), the relationships of both dose and volume to obliteration have not been well defined.

METHODS AND MATERIALS

The results of radiosurgery in 197 AVM patients with 3-year angiographic follow-up were analyzed. Volume varied from 0.06-18 cc (median: 4.1 cc), and minimum target dose (Dmin) varied from 12.0-25.6 Gy (median: 20.0 Gy).

RESULTS

Follow-up angiography revealed complete AVM obliteration in 142 out of 197 patients (72%). The targeted AVM nidus failed to obliterate in 20 patients (10%), but in-field obliteration was complete in the remaining 35 patients (18%) discovered to have residual untargeted AVM nidus. Multivariate logistic regression analysis of in-field obliteration revealed a significant independent correlation with Dmin (p = 0.04), but not with volume or maximum dose. A sigmoid dose-response curve for in-field obliteration was constructed that significantly differed from the dose-volume-response relationships that would have been expected from overall obliteration data.

CONCLUSIONS

The success rate for in-field obliteration of AVM after radiosurgery depends on Dmin but does not appear to change appreciably with volume or maximum dose. Success rates for complete obliteration additionally are limited by problems defining the complete AVM nidus.

The surgical treatment of small deep intracranial ateriovenous malformations: a report of 85 cases

A series of 85 patients having what are defined as small, deep intracranial arteriovenous malformations (AVMs) is analysed in terms of presentation, investigation, treatment and outcome. This group of patients is taken from a consecutive series of 306 patients with AVM treated over a 20 year period. The anatomical distribution was as follows: cerebral hemisphere 54 patients, basal ganglia and thalamus 6 patients, brain stem and cerebellum 19 patients and deep dural 6 patients. Haemorrhage, both subarachnoid and intraparenchymal, was the predominant mode of presentation (71 of 85 cases). Other presentations were with epilepsy (5 cases), headache only (4 cases), progressive focal deficit (1 case) and mixed (4 cases). The vast majority of patients (71 of 85, 83.5%) were treated surgically: 67 by surgery only, 3 by surgery following partial embolisation and one with focussed irradiation after subtotal excision. The overall outcome in this group at 1 month was 27 (38.0%) improved (largely due to haematoma removal), 42 (59.2%) unchanged and 2 (2.8%) worse. One of the unchanged group died during the second month with pulmonary complications following prolonged impairment of consciousness. The two patients worse at 1 month (Gd I -> Gd II) returned to Gd I within 3 months. There were 3 patients treated non-surgically (2 by focussed irradiation and 1 by embolisation) while 11 patients were not treated because they declined treatment (3 cases), they died before treatment could be carried out (3 cases), or treatment was deemed inadvisable (5 cases). The results of surgical treatment in small deep AVMs are compared with those of other treatment modalities, in particular focussed irradiation. It is argued on the basis of these figures that surgery remains the best treatment for these lesions.

Embolization of cerebral arteriovenous malformations: Part I--Technique, morphology, and complications

OBJECTIVE

The aim of this two-part study is to give a full account of all patients referred for embolization of arteriovenous malformations (AVMs) from 1987 to 1993. This article (Part I of II) presents the patient study, including angiographic features and their relation to the immediate outcome of embolization.

METHODS

Of the 192 patients referred, 150 were subsequently treated. Most patients were referred by neurosurgeons, and 85% of the AVMs were Spetzler-Martin Grade > or = 3. We have accounted for the 42 patients who did not undergo embolization.

RESULTS

Occlusion from embolization alone (total embolization) was obtained in 13% of patients. Full treatment (total embolization or embolization and then stereotactic radiation or surgery) was achieved in two-thirds of all patients (n = 100, 66%), and combined treatment with stereotactic gamma radiation was the most important part of the treatment strategy. The procedural mortality was 1.3%. The total incidence of complications after embolization was high (40%), but only 6.7% of cases were labeled severe. Of all angiographic features that were considered, large size and the presence of deep feeders were predictors of failure to achieve full treatment. Thirty-four patients with AVMs < 8 cc were included in the study. These could have been irradiated as the sole treatment. In this group of small AVMs, the results of embolization were far better than in the whole group. Fourteen of the AVMs had volumes of < 4 cc, and 10 of these (71%) were totally embolized. One patient had a hemianopsia. Among AVMs 4 to 8 cc in volume (n = 20), the total embolization rate was 15%, the full treatment rate in combination with gamma treatment was 75%, and 10% of the patients were operated on after embolization. Severe complications occurred in 15% of patients, but no complications occurred after November 1990.

CONCLUSION

In a series of AVMs, most of which were regarded as unsuitable for surgical excision, two-thirds were reduced to a size suitable for gamma knife treatment or totally occluded by embolization alone. The total complication rate was high, but the combined rate of death and complications affecting lifestyle was 8.0%, equal to approximately 3.2 years of natural history.

Embolization of cerebral arteriovenous malformations: Part II--Aspects of complications and late outcome

OBJECTIVE

From 1987 through 1993, we performed embolizations on 150 patients with cerebral arteriovenous malformations (AVMs) at Sahlgrenska University Hospital. The patients ranged in age from 5 to 70 years (35.5 +/- 14.8 yr, mean +/- standard deviation) and were selected by neurosurgeons in Scandinavia. We analyzed the risk of complications and late outcome to have a better basis for the decision to perform embolization.

METHODS

The follow-up was a personal clinical examination of all surviving patients by a neurologist. Files for all patients were also studied.

RESULTS

In 34 patients, the AVMs were eliminated by embolization alone (20 patients) or by supplementary surgery (14 patients). In 66 patients, the AVMs were embolized to a size suitable for supplementary stereotactic radiation. The clinical course was stable for those 100 patients. Another group of 50 patients who had undergone embolization was only partially treated, and as a group, those patients had less favorable outcomes. The manifestations or symptoms leading to diagnosis were in concordance with other studies. Headache and epilepsy showed a positive response to treatment in patients whose AVMs had been eliminated as well as in those who received only partial treatment. A history of cerebral bleeding did not influence the prognosis of recurrent bleeding. Conversely, AVMs with feeder or nidus aneurysms were related to an increased risk of bleeding. If there was a history of bleeding in a patient with large, partially treated AVMs, the prognosis for survival was diminished.

CONCLUSION

The indication for treatment increases with the occurrence of AVMs with associated aneurysms. For patients with large AVMs, a history of bleeding justifies a more aggressive approach to treatment. The reduced risk of complications during the last years of the study also increases the indication for embolization.

Stereotactic radiosurgery for arteriovenous malformations of the brain using a standard linear accelerator: the Lyon experience

Radiosurgery (RS) was initiated in Lyon in October 1989. The technique was adapted from that described by Lutz and Saunders in Boston (BRW stereotactic frame). Irradiation is delivered with 18-MV photons produced by a LINAC. From December 1989 to December 1992, 41 patients with arteriovenous malformations were treated by RS; the median age was 33 years. The largest lesion diameter was 11.2-38.5 mm. Fifteen to 20 Gy were delivered on the 70% isodose line. Angiography was performed at 2 years post-treatment in 32 patients demonstrating an overall complete thrombosis rate of 81.3%. This incidence was significantly correlated with the Spetzler and Martin grade before RS (P = 0.0055). Two patients (4.9%) experienced haemorrhage after radiosurgical treatment and one died from an intracerebral-intraventricular haemorrhage. Four patients (9.7%) experienced permanent radiation-induced neurological complications.

Treatment of brain arteriovenous malformations by embolization and radiosurgery

Embolization was used to reduce the size of brain arteriovenous malformations (AVMs) prior to radiosurgical treatment in 125 patients who were poor surgical candidates or had refused surgery. Of these patients, 81% had suffered hemorrhage, and 22.4% had undergone treatment at another institution. According to the Spetzler-Martin scale, the AVMs were Grade II in 9.6%, Grade III in 31.2%, Grade IV in 30.4%, and Grades V to VI in 28.8% of the cases. Most embolizations were performed using cyanoacrylate delivered by flow-guided microcatheters. Radiosurgery was performed using a linear accelerator in 62 patients treated by the authors, and 34 patients were treated at other institutions using various methods. Embolization produced total occlusion in 11.2% of AVMs and reduced 76% of AVMs enough to allow radiosurgery. Radiosurgery produced total occlusion in 65% of the partially embolized AVMs (79% when the residual nidus was < 2 cm in diameter). Embolizations resulted in a mortality rate of 1.6% and a morbidity rate of 12.8%. No complications were associated with radiosurgery. The hemorrhage rate for partially embolized AVMs was 3% per year. No patient with a completely occluded AVM experienced rehemorrhage. Angiographic follow-up review of AVMs embolized with cyanoacrylate demonstrated a 11.8% revascularization rate, occurring within 1 year. It is concluded that after partial embolization with cyanoacrylate, the risk of hemorrhage from the residual nidus is comparable to the natural history of AVMs and that the residual nidus can be irradiated with results almost as good as for a native AVM of the same size.

The risk of hemorrhage after radiosurgery for arteriovenous malformations

Two hundred and one patients with arteriovenous malformations (AVMs) treated radiosurgically between May 1988 and February 1995 are analyzed in this study. Twelve patients sustained a posttreatment hemorrhage during this period. Pretreatment factors associated with increased hemorrhage risk were identified in 11 of these patients and included arterial aneurysms, venous aneurysms, venous outflow obstruction, periventricular location, prior embolization, and prior surgical treatment. A detailed statistical analysis, using both Poisson regression and parametric survival regression techniques, was undertaken to determine whether radiosurgery had any effect on the risk of hemorrhage, when compared to the natural history of the disease, in those patients in whom a complete angiographic cure was not achieved. No evidence was found to support a statistically significant departure from the natural hemorrhage rate at any time period after radiosurgical treatment. Significant risk factors for hemorrhage appeared to correlate with increasing AVM volume.

Surgical resection of large incompletely treated intracranial arteriovenous malformations following stereotactic radiosurgery

Although radiosurgery is effective in obliterating small arteriovenous malformations (AVMs), it has a lower success rate for thrombosing larger AVMs. The authors surgically resected AVMs from 33 patients ranging in age from 7 to 64 years (mean 30.4 years) 1 to 11 years after radiosurgery. Initial AVM volumes were 0.8 to 117 cm3 (mean 21.6 cm3), and doses ranged from 4.6 to 45 GyE (mean 21.2 GyE). Of 27 AVMs in eloquent or critical areas, 10 were located in language, motor, sensory, or visual cortex, 11 in the basal ganglia/thalamus, one each in the brainstem, hypothalamus, and cerebellum, and three in the corpus callosum. Venous drainage was deep in 13, superficial in 12, or both in eight lesions. Spetzler-Martin grades were II in one, III in 12, IV in 16, and V in four patients. Eight patients experienced rebleeding after radiosurgery but prior to surgery. Three patients developed radiation necrosis and 25 underwent endovascular embolization prior to surgery. At surgery the AVMs were found to be markedly less vascular, partially thrombosed, and more easily resected, compared to those seen in patients who had not undergone radiosurgery. Pathological investigation showed endothelial proliferation with hyaline and calcium in vessel walls. There was partial or complete thrombosis of some AVM vessels and evidence of vessel and brain necrosis in many cases. Complete resection was achieved in 28 patients and partial resection in five. Clinical outcome was excellent or good in 31 cases, and two patients died of rebleeding from residual AVM. Four patients' conditions worsened following microsurgical resection. Final clinical outcome was largely related to the pretreatment grade. Radiosurgery several years prior to open microsurgery may prove to be a useful adjunct in treating unusually large and complex AVMs.

Stereotactic radiosurgery for postgeniculate visual pathway arteriovenous malformations

Arteriovenous malformations (AVMs) that are located within the postgeniculate optic radiations or striate cortex are difficult to resect without creating postoperative visual defects. To reduce the risk of an AVM hemorrhage and to enhance the possibility of preserving visual function, the authors performed stereotactic radiosurgery in 34 patients with newly diagnosed or residual AVMs of the visual pathways. The mean AVM volume was 4.7 ml, and the average radiation dose to the AVM margin was 21 Gy. The median follow up was 47 months (range 16-83 months). Two (6%) of 34 patients had documented new visual field defects (central scotoma in one, and partial hemianopsia in one) after single-stage radiosurgery, but no patient developed a new permanent homonymous hemianopsia. Angiography was performed in all patients at a median of 26 months after radiosurgery: 22 (65%) had complete obliteration, 10 (29%) had a significant decrease in AVM volume, one (3%) had only a persistent early draining vein without residual nidus, and one (3%) had no change in the AVM. Thirteen (81%) of 16 patients with AVMs less of than 4 ml had complete obliteration. Five patients had second-stage stereotactic radiosurgery after angiography revealed a persistent AVM nidus; two patients eligible for follow-up angiography had complete obliteration, thereby increasing the overall series obliteration rate to 71%. The calculated annual risk of AVM bleeding (before radiographic evidence of obliteration) was 2.4%. No patient bled after angiographically confirmed obliteration. In most patients stereotactic radiosurgery obliterates visual pathway AVMs and also preserves preoperative visual function. Multimodality management (embolization, microsurgery, or staged radiosurgery) enhances AVM obliteration and visual preservation rates.

Large cerebral arteriovenous malformations: experience with 27 cases

BACKGROUND

The management of large cerebral arteriovenous malformations is difficult. Surgical excision is often attempted after embolization. Interventional neuro-radiology is available in only a few centers. If large AVMs can be safely excised without pre-operative embolizaton, then these lesions can be treated at many neurosurgical centers.

METHODS

Between January 1986 and June 1992, a total of 210 patients with cerebral AVMs were diagnosed by angiographic studies. Twenty-seven of them had large AVMs wider than 5 cm in the longest diameter. The case records of these patients were retrieved and studied.

RESULTS

Two patients were treated with Bragg peak proton beam therapy. Twelve patients were treated conservatively with no improvement. Thirteen patients underwent surgery and total AVM excision was achieved in 11. None of the patients who underwent surgery had any pre- or intra-operative embolization. All the patients had no neurological deterioration post-operatively.

CONCLUSIONS

Large cerebral AVMs can be treated by surgical excision alone with acceptable results.

Amobarbital evaluation of neurobehavioral function prior to therapeutic occlusion of brain arteriovenous malformations: a new neuropsychological procedure

Because untreated arteriovenous malformations (AVMs) frequently result in some form of permanent neurological complication, treatment of AVMs is aggressively pursued A relatively new treatment consists of sending micropellets into blood vessels supplying the AVM core to block blood flow and "shrink" the AVM When vessels supplying the AVM are thought to also irrigate vital portions of brain, evaluations of neurobehavioral function after injection of amobarbital into intracranial vessels (Wada testing) may be performed to prevent significant complications folIowing embolization This study details our preliminary experience with Wada testing and electroencephalography (EEG) prior to AVM embolization in seven patients Neurobehavioral functions were continuously monitored after injection of 50-75 mg of amobarbital into target cerebral vessels No change in sensorimotor, cognitive, or EEG functions were detected in any of the superselective Wada examinations Embolization was performed following all negative Wada evaluations The only irreversible complication after embolization was a superior quadrantanopia No other permanent neurobehavioral sequelae resulted from embolization These preliminary findings suggest that simultaneous Wada/EEG monitoring may be useful in predicting neurobehavioral complications prior to AVM embolization.

Repeat stereotactic radiosurgery of arteriovenous malformations: factors associated with incomplete obliteration

Second stereotactic radiosurgery procedures were required in 45 patients with arteriovenous malformations (AVMs) who initially had incomplete obliteration. Repeat radiosurgery was performed at a median of 39 months (range, 24-71 mo) after the first stage. The median AVM volume at the first procedure was 6.0 ml (range, 0.2-18.0 ml). Thirty-seven patients (82%) had AVMs of Spetzler-Martin Grades III through VI. A retrospective analysis revealed definite causes for incomplete obliteration after the first procedure in 33 patients (73%). Incomplete angiographic definition of the nidus was the most frequent factor (57%) associated with failed radiosurgery. Three patients (7%) had recanalization of the AVM nidus after prior embolization; four patients (9%) had incomplete nidus recognition, because AVM vessels were not visualized in the presence of a hematoma. "Radiobiological resistance" was another potential factor associated with failed radiosurgery in 17 patients (38%). Our current technique for volume determination and dose planning includes stereotactic magnetic resonance angiography, magnetic resonance imaging, and complete cerebral angiography (including superselective and external carotid artery injections, as indicated). Integrated multiplanar high-resolution imaging will likely increase the rate of AVM obliteration after stereotactic radiosurgery.

Factors that predict the bleeding risk of cerebral arteriovenous malformations

BACKGROUND AND PURPOSE

Arteriovenous malformations (AVMs) have an overall 2% to 4% annual risk of hemorrhage. The purpose of this study was to determine whether specific clinical and radiographic factors predispose AVMs to bleed and to predict the bleeding risk for individual AVM patients.

METHODS

We reviewed the clinical histories and cerebral angiograms of 315 AVM patients who underwent stereotactic radiosurgery at our center. One half of the patient data (analysis cohort) was used to determine risk factors for bleeding and to construct AVM hemorrhage risk groups. These risk groups were then tested with the second half of the patient data (test cohort).

RESULTS

The mean AVM volume was 4.0 +/- 3.4 mL (approximate maximum diameter of 2 cm). One hundred ninety-six initial hemorrhages occurred in 10,348 patient-years for an annual initial bleed rate of 1.89%; 44 of these 196 patients had a repeat bleed in 591 patient-years for an annual rebleed rate of 7.45%. The overall crude annual hemorrhage rate was 2.40%. Multivariate analysis revealed three factors associated with hemorrhage: history of a prior bleed (relative risk [RR], 9.09; 95% confidence interval [CI], 5.44 to 15.19; P < .001), a single draining vein (RR, 1.66; 95% CI, 1.13 to 2.38; P < .01), and a diffuse AVM morphology (RR, 1.64; 95% CI, 1.12 to 2.46; P < .01). Four AVM hemorrhage risk groups were constructed on the basis of the significant factors. The annual rate of bleeding was 0.99% for low-risk AVMs, 2.22% for intermediate-low-risk AVMs, 3.72% for intermediate-high-risk AVMs, and 8.94% for high-risk AVMs.

CONCLUSIONS

Analysis of a large group of AVM patients who underwent stereotactic radiosurgery demonstrated that small AVMs have an annual hemorrhage risk similar to that of the general AVM population. AVM patients have a wide variability of bleeding risk that can be predicted from their clinical presentation and the angiographic characteristics of the AVM. The management of AVM patients should be based not only on the morbidity of the proposed treatment but also those factors that predispose individual patients to either a low or high hemorrhage risk.

Cerebral arteriovenous malformations: improved nidus demarcation by means of dynamic tagging MR-angiography

Our purpose was to further improve the target volume definition for radiosurgical treatment of cerebral arteriovenous malformations (AVMs) by means of dynamic MRA (dMRA) using a blood bolus tagging sequence. We therefore compare this technique with 3D-TOF-MRA and transfemoral high resolution angiography in plain film technique. Twenty patients with angiographically proven cerebral AVMs were investigated by dMRA, TOF-MRA, and conventional angiography during the MR-assisted radiosurgical planning protocol. The patient's head was fixed in an MR-compatible stereotactic device. The different angiography techniques were evaluated by consensus of two radiologists. AVMs were characterized by the number and origin of feeding arteries, the maximum diameter of the AVM nidus, and the venous drainage pattern. Dynamic MRA was able to demonstrate the complete AVM characteristics and hemodynamics in 12 out of 20 patients. In three patients with an AVM nidus smaller than 1 cm in diameter the technique could not reliably depict the malformation. Technical problems due to steel screws and pins in the initially used stereotactic frame occurred in five patients. Due to reduced vessel overlap and the lack of disturbances caused by formations with short T1 time, dMRA was superior to TOF-MRA in the detection and the exact localization of the AVM nidus in four patients. We conclude that dMRA is able to demonstrate reliably AVM characteristics and hemodynamics in AVMs with a nidus larger than 1 cm in diameter. Because of the improved demarcation of the AVM nidus, this technique may be a valuable adjunct to radiosurgery planning of cerebral AVMs.

Decision analysis in the clinical neurosciences: a systematic review of the literature

Clinical decision analysis can be a useful scientific tool for individual patient management, for planning of clinical research and for reaching consensus about clinical problems. We systematically reviewed the decision analytic studies in the clinical neurosciences that were published between 1975 and July 1994. All studies were assessed on aspects of clinical applicability: presence of case and context description, completeness of the analysed strategies from a clinical point of view, extendibility of the analyses to different patient profiles, and up-to-date-ness. Fifty-nine decision analyses of twenty-eight different clinical problems were identified. Twenty-eight analyses were based on the theory of subjective expected utility, twelve on cost-effectiveness analysis. Four studies used ROC analysis, and fifteen were risk-, or risk-benefit analyses. At least six studies could have been improved by more elaborately disclosing the context of the clinical problem that was addressed. In eleven studies, the effect of different, yet plausible assumptions was not explored, and in eighteen studies the reader was not informed how to extend the results of the analysis to patients with (slightly) different clinical characterisitics. All studies had, by nature, the potential to promote insight into the clinical problem and focus the discussion on clinically important aspects, and gave clinically useful advice. We conclude that clinical decision analysis, as an explicit, quantitative approach to uncertainty in decision making in the clinical neurosciences will fulfill a growing need in the near future.