Clinical practice. Arteriovenous malformations of the brain

Speech Reorganization after an AVM Bleed Cured by Embolization. A Case Report and Review of the Literature

SUMMARY

Intracerebral arteriovenous malformations (AVMs) are defined as the direct communication of arteries to abnormal veins without interposing capillaries. Although AVMs can have various clinical presentations due to their dynamic nature, the most common presenting sign is intracerebral hemorrhage. Whenever an AVM is discovered, the therapeutic choice is often not obvious and it is influenced not only by the hemodynamic features of the AVM, but also by considerations of the extent of intervention-related morbidity and mortality. A patient with a left frontal AVM is described. He bled three years after gamma knife radiosurgery and developed aphasia. The complete obliteration of the AVM was later achieved by embolization. Functional compensatory brain reorganization and plasticity is discussed, since our patient presented with a fast recovery from aphasia and unexpected contralateral redistribution of the speech function and with preference for his second spoken language.

Endovascular treatment of epistaxis

Epistaxis is a common condition that can be managed conservatively in most cases. When these measures, including anterior and posterior packing of the nasal cavity, are unsuccessful at controlling the bleeding, interruption of the blood supply to the sinonasal area can be performed, either by surgical ligation or by transarterial embolization. Embolization should be preceded by thorough diagnostic angiography. Aside from aiding with subsequent selective catheterization and embolization, such angiography may reveal significant anatomic anomalies, anastomoses, or an unsuspected cause of epistaxis. Taking these findings into account, the interventionalist may decide to refrain from embolization or adjust the technique to minimize the risk of adverse events, which are mostly related to inadvertent embolization of the internal carotid artery or ophthalmic artery. We present a review of the various causes of epistaxis and the treatment options, with emphasis on endovascular embolization. We also describe the protocol of our institution for endovascular management of this condition.

Endothelial Notch signaling is upregulated in human brain arteriovenous malformations and a mouse model of the disease

Brain arteriovenous malformations (BAVMs) can cause lethal hemorrhagic stroke and have no effective treatment. The cellular and molecular basis for this disease is largely unknown. We have previously shown that expression of constitutively-active Notch4 receptor in the endothelium elicits and maintains the hallmarks of BAVM in mice, thus establishing a mouse model of the disease. Our work suggested that Notch pathway could be a critical molecular mediator of BAVM pathogenesis. Here, we investigated the hypothesis that upregulated Notch activation contributes to the pathogenesis of human BAVM. We examined the expression of the canonical Notch downstream target Hes1 in the endothelium of human BAVMs by immunofluorescence, and showed increased levels relative to either autopsy or surgical biopsy controls. We then analyzed receptor activity using an antibody to the activated form of the Notch1 receptor, and found increased levels of activity. These findings suggest that Notch activation may promote the development and even maintenance of BAVM. We also detected increases in Hes1 and activated Notch1 expression in our mouse model of BAVM induced by constitutively active Notch4, demonstrating molecular similarity between the mouse model and the human disease. Our work suggests that activation of Notch signaling is an important molecular candidate in BAVM pathogenesis and further validates that our animal model provides a platform to study the progression as well as the regression of the disease.

Simulation of the human intracranial arterial tree

High-resolution unsteady three-dimensional flow simulations in large intracranial arterial networks of a healthy subject and a patient with hydrocephalus have been performed. The large size of the computational domains requires the use of thousands of computer processors and solution of the flow equations with approximately one billion degrees of freedom. We have developed and implemented a two-level domain decomposition method, and a new type of outflow boundary condition to control flow rates at tens of terminal vessels of the arterial network. In this paper, we demonstrate the flow patterns in the normal and abnormal intracranial arterial networks using patient-specific data.

Radiosurgery facilitates resection of brain arteriovenous malformations and reduces surgical morbidity

OBJECTIVE

Stereotactic radiosurgery makes brain arteriovenous malformations (AVM) more manageable during their microsurgical resection. To better characterize these effects, we compared results of microsurgical resection of radiated (RS) and nonradiated (RS) AVMs to demonstrate that previous radiosurgery facilitates surgery and decreases operative morbidity.

METHODS

From our series of 344 patients who underwent AVM resections at the University of California, San Francisco (1997-2007), 21 RS patients were matched with 21 RS patients based on pretreatment clinical and AVM characteristics. Matching was blinded to outcomes, which were assessed with the modified Rankin Scale.

RESULTS

Mean AVM volume was reduced by 78% (P < 0.01), and Spetzler-Martin grades were reduced in 52% of RS patients (P < 0.001). Preoperative embolization was used less in RS than in RS patients (P < 0.001). Mean operative time (P < 0.01), blood loss (P < 0.05), and length of hospital stay (P < 0.05) were lower in the RS group. Surgical morbidity was 14% higher in RS patients, and they demonstrated significant worsening in modified Rankin Scale scores after surgery, whereas RS patients did not (P < 0.01). RS patients deteriorated between AVM diagnosis and surgery owing to hemorrhages during the latency period (P < 0.05).

CONCLUSION

Previous radiosurgery facilitates AVM microsurgery and decreases operative morbidity. Radiosurgery is recommended for unruptured AVMs that are not favorable for microsurgical resection. Microsurgical resection is recommended for radiated AVMs that are not completely obliterated after the 3-year latency period but are altered favorably for surgery, even in asymptomatic patients. Prompt resection of persistent AVMs should be considered to avoid the risk of postlatency hemorrhage and to optimize patient outcomes.

Long-term excess mortality in 623 patients with brain arteriovenous malformations

OBJECTIVE

Long-term follow-up studies in patients with brain arteriovenous malformations (AVM) have been scarce and without proper statistical estimates of mortality. We performed a retrospective survival study in 623 consecutive patients with AVMs admitted to the Department of Neurosurgery in Helsinki University Hospital between 1951 and 2005.

METHODS

Patients were followed from admission until death or the end of 2005. Patient survival was estimated using the relative survival ratio, which provides a measure of the excess mortality experienced by the patients compared with the general Finnish population matched by age, sex, and calendar time.

RESULTS

Median follow-up was 11.9 years, and total follow-up was 10,165 person-years. Treatment was conservative in 155 patients. Total AVM occlusion was attained in 356 patients, and partial occlusion was obtained in 94 patients. Overall, 206 deaths were observed. Of these, 100 were related to AVMs. Diagnosis of AVM was associated with significant long-term excess mortality, with cumulative relative survival ratios of 0.85 (95% confidence interval, 0.81-0.88) and 0.69 (95% confidence interval, 0.62-0.75) at 10 and 30 years after admission, respectively. Men had higher excess mortality than women. The excess in mortality was highest in conservatively treated patients, intermediate in patients with partially occluded AVMs, and lowest in those with totally occluded AVMs. The subgroup with the best outcome consisted of those with totally occluded unruptured AVMs, which did not demonstrate excess mortality after the first year.

CONCLUSION

AVMs are associated with long-term excess mortality that may be reduced by active, even partial, treatment. Male patients have a higher excess mortality rate than female patients.

Intraventricular thrombolysis for massive intraventricular hemorrhage due to periventricular arteriovenous malformations: no absolute contraindications as rescue therapy prior to surgical repair or embolization?

Intraventricular hemorrhage (IVH) after bleeding from a cerebral aneurysm or an arteriovenous malformation (AVM) results in a high mortality. A limited number of publications have shown that intraventricular thrombolysis with e.g. recombinant tissue plasminogen activator (rt-PA) can be a therapeutic option in IVH. However, this treatment is considered as an absolute contraindication prior to the treatment of the bleeding source. We report the successful use of low-dose intraventricular thrombolysis (rt-PA) in two cases of life-threatening intraventricular hemorrhage due to periventricular AVMs as rescue therapy, even prior to source control of the bleeding. Our observations, together with nine comparable published cases, illustrate that this treatment might be useful to clear the intraventricular blood and lower intracranial pressure. It might also improve neurological outcome and mortality in these selected patients. This suggests that hemorrhage from a periventricular AVM, even before surgical resection or endovascular embolization, is not necessarily an absolute contraindication for intraventricular thrombolysis in patients with massive IVH.

The control of vascular integrity by endothelial cell junctions: molecular basis and pathological implications

Human pathologies such as vascular malformations, hemorrhagic stroke, and edema have been associated with defects in the organization of endothelial cell junctions. Understanding the molecular basis of these diseases requires different integrated approaches which include basic cell biology, clinical studies, and studies in animal models such as mice and zebrafish. In this review we discuss recent findings derived from these approaches and their possible integration in a common picture.

Extensive white matter changes after stereotactic radiosurgery for brain arteriovenous malformations: a prognostic sign for obliteration?

OBJECTIVE

Perinidal high-signal-intensity changes on T2-weighted magnetic resonance imaging can be seen surrounding radiosurgically treated brain arteriovenous malformations (AVM). Occasionally, these signal intensity changes develop far beyond the irradiated volume. A retrospective analysis of both the pre- and postradiosurgery magnetic resonance imaging and angiographic studies was performed to analyze the cause of these extensive perinidal white matter changes.

METHODS

The pre- and postradiosurgical magnetic resonance imaging and angiographic studies of 30 patients with T2 high-signal-intensity changes surrounding a brain AVM were analyzed retrospectively. Patients were divided into 2 groups on the basis of the extension of the signal intensity changes within or beyond the 10-Gy isodose area. The angiographic analysis was focused on the venous drainage pattern (deep versus superficial), venous stenosis, and the number of draining veins before and after radiosurgery. In addition, the obliteration rate was determined for the 2 subgroups.

RESULTS

Fourteen patients (47%) showed high-signal-intensity changes far beyond the 10-Gy isodose area. A single draining vein was more often present in these patients with extensive T2 hyperintensity signal changes than in the other group. Obliteration was achieved in 12 (88%) of 14 patients with extensive signal intensity changes, as opposed to 8 (50%) of 16 patients in the other group.

CONCLUSION

High-signal-intensity changes after radiosurgery for brain AVMs, far beyond the 10-Gy isodose area on T2-weighted images, are especially seen in brain AVMs draining through a single vein. The higher occlusion rate of brain AVMs under these circumstances is well appreciated.

Treatment of arteriovenous malformations using Gamma Knife surgery: the experience at the University of Washington from 2000 to 2005

Object

The purpose of this study was to examine the efficacy and toxicity of treating arteriovenous malformations (AVMs) with the model 3C Gamma Knife at the University of Washington Medical Center.

Methods

Ninety-five evaluable patients with 99 treatable AVMs were treated at the University of Washington Medical Center from April 2000 through June 2005. The median patient age at the time of treatment was 40 years (range 6–68 years). The male to female patient ratio was 0.98:1. The median AVM volume treated was 3.8 cm3 (range 0.12–32 cm3). Forty-four percent of the patients had hemorrhaged prior to treatment. The median peripheral Gamma Knife surgery dose was 20 Gy with a median of 12 isocenters treated. The median follow-up duration was 38 months (range 3–91 months). Eighty-one percent of the patients had no previous stereotactic radiosurgery (SRS), whereas the remaining 19% had previously been treated with linear accelerator–based SRS.

Results

The Kaplan–Meier estimated 6-year AVM obliteration rate for the entire cohort was 71.4%. The Kaplan–Meier estimated 6-year obliteration rate was 72% for patients having no prior SRS and 54.5% for those undergoing repeat SRS. The median time to AVM obliteration was 47 months, with 90% of the obliterations occurring between 24 and 58 months. Eight patients (7.4%) experienced late toxicities. There were 2 fatal bleeds and 13 (13.8%) nonfatal bleeds after Gamma Knife surgery.

Conclusions

Gamma Knife surgery is an effective treatment for AVMs, resulting in an excellent obliteration rate with acceptable toxicity.

NATURAL HISTORY OF BRAIN ARTERIOVENOUS MALFORMATIONS

OBJECTIVE

Long-term follow-up studies in patients with brain arteriovenous malformations (AVM) have yielded contradictory results regarding both risk factors for rupture and annual rupture rate. We performed a long-term follow-up study in an unselected, consecutive patient population with AVMs admitted to the Department of Neurosurgery at Helsinki University Central Hospital between 1942 and 2005.

METHODS

Patients with untreated AVMs were followed from admission until death, occurrence of AVM rupture, initiation of treatment, or until the end of 2005. Patients with at least 1 month of follow-up were included in further analysis. Annual and cumulative incidence rates of AVM rupture as well as several potential risk factors for rupture were analyzed using Kaplan-Meier life table analyses and Cox proportional hazards regression models.

RESULTS

We identified 238 patients with a mean follow-up period of 13.5 years (range, 1 month–53.1 years). The average annual risk of hemorrhage from AVMs was 2.4%. The risk was highest during the first 5 years after diagnosis, decreasing thereafter. Risk factors predicting subsequent AVM hemorrhage in univariate analysis were young age, previous rupture, deep and infratentorial locations, and exclusively deep venous drainage. Previous rupture, large AVM size, and infratentorial and deep locations were independent risk factors according to multivariate models.

CONCLUSION

According to this long-term follow-up study, AVMs with previous rupture and large size, as well as with infratentorial and deep locations have the highest risk of subsequent hemorrhage. This risk is highest during the first few years after diagnosis but remains significant for decades.

Patterns of brain arteriovenous malformation treatment: prospective, population-based study

BACKGROUND AND PURPOSE

The extent of variation in the interventional treatment of brain arteriovenous malformations (AVMs) is unknown, so we explored patterns of treatment at 4 neuroscience centers in one European country.

METHODS

We included every participant with an AVM in a prospective, population-based cohort study of adults aged >or=16 years residing in Scotland at the time of AVM diagnosis in 1999 to 2003.

RESULTS

Only 11 (5%) of the 229 adults were not managed at a neuroscience center. Adults who received interventional treatment were younger (median, 43 versus 54 years), more likely to have presented with hemorrhage (OR, 2.8; 95% CI, 1.6 to 4.9), and had smaller AVMs (median nidus diameter, 2 cm versus 3 cm; P=0.003) than those who did not. Adults seen at the 4 centers only differed in AVM Spetzler-Martin grade (P=0.04). The 4 centers did not differ in the proportion of adults with AVMs who received interventional treatment (P=0.16), but they differed in the Spetzler-Martin grade of the AVMs they treated (Grades III to IV, P=0.01) and the interventional treatments used (P=0.004). The 2 largest centers differed from each other in the likelihood of surgical resection (OR, 0.2; 95% CI, 0.1 to 0.6) and stereotactic radiosurgery (OR, 2.8; 95% CI, 1.3 to 6.1), and the choice of modality varied within some Spetzler-Martin grades.

CONCLUSIONS

Patient characteristics and patterns of AVM interventional treatment differ between neuroscience centers in the same population necessitating careful consideration of these factors when comparing one hospital's outcome with another.

Endothelial Notch4 signaling induces hallmarks of brain arteriovenous malformations in mice

Brain arteriovenous malformations (BAVMs) can cause devastating stroke in young people and contribute to half of all hemorrhagic stroke in children. Unfortunately, the pathogenesis of BAVMs is unknown. In this article we show that activation of Notch signaling in the endothelium during brain development causes BAVM in mice. We turned on constitutively active Notch4 (int3) expression in endothelial cells from birth by using the tetracycline-regulatable system. All mutants developed hallmarks of BAVMs, including cerebral arteriovenous shunting and vessel enlargement, by 3 weeks of age and died by 5 weeks of age. Twenty-five percent of the mutants showed signs of neurological dysfunction, including ataxia and seizure. Affected mice exhibited hemorrhage and neuronal cell death within the cerebral cortex and cerebellum. Strikingly, int3 repression resolved ataxia and reversed the disease progression, demonstrating that int3 is not only sufficient to induce, but also required to sustain the disease. We show that int3 expression results in widespread enlargement of the microvasculature, which coincided with a reduction in capillary density, linking vessel enlargement to Notch's known function of inhibiting vessel sprouting. Our data suggest that the Notch pathway is a molecular regulator of BAVM pathogenesis in mice, and offer hope that their regression might be possible by targeting the causal molecular lesion.