Imagerie vasculaire non invasive et malformations artérioveineuses cérébrales

Current and Future Applications of Arterial Spin Labeling MRI in Cerebral Arteriovenous Malformations

Arterial spin labeling (ASL) has emerged as a promising noninvasive tool for the evaluation of both pediatric and adult arteriovenous malformations (AVMs). This paper reviews the advantages and challenges associated with the use of ASL in AVM assessment. An assessment of the diagnostic workup of AVMs and their variants in both adult and pediatric populations is proposed. Evaluation after treatments, whether endovascular or microsurgical, was similarly examined. ASL, with its endogenous tracer and favorable safety profile, offers functional assessment and arterial feeder identification. ASL has demonstrated strong performance in identifying feeder arteries and detecting arteriovenous shunting, although some studies report inferior performance compared with digital subtraction angiography (DSA) in delineating venous drainage. Challenges include uncertainties in sensitivity for specific AVM features. Detecting AVMs in challenging locations, such as the apical cranial convexity, is further complicated, demanding careful consideration due to the risk of underestimating total blood flow. Navigating these challenges, ASL provides a noninvasive avenue with undeniable merits, but a balanced approach considering its limitations is crucial. Larger-scale prospective studies are needed to comprehensively evaluate the diagnostic performance of ASL in AVM assessment.

Spontaneous occlusion of cerebral arteriovenous malformation following partial embolization with Onyx

Management options for brain arteriovenous malformations (AVMs) are surgery, radiosurgery, and endovascular embolization. The aim of partial embolization in endovascular treatment is to make total resection possible. However, increased risk of bleeding in partial embolization creates some controversies about treatment options. Spontaneous total occlusion of cerebral AVMs following partial obliteration with embolization agents is a rarely seen condition. We present a case with an AVM vanishing from right posterior cerebral artery which spontaneously occluded following partial embolization with Onyx liquid agent.

Hydrocephalus caused by a venous varix

INTRODUCTION

Vascular malformations are uncommon causes of aqueductal obstruction. To our concern, only one case of hydrocephalus caused by a venous varix draining an unruptured arteriovenous malformation has been described in the literature.

CASE REPORT

We report the case of a 70-year-old woman presenting with progressive cognitive impairment, gait disturbance and urinary incontinence. Magnetic resonance imaging and magnetic resonance angiography revealed a large venous varix draining an unruptured arteriovenous malformation causing hydrocephalus.

CONCLUSION

Although uncommon, it is necessary to consider the presence of a vascular malformation in adults who presented with signs of aqueductal obstruction.

Delineation of brain AVMs on MR-Angiography for the purpose of stereotactic radiosurgery

PURPOSE

To assess the dosimetric consequences of brain arteriovenous malformation (bAVM) delineation on magnetic resonance angiography (MRA) for the purpose of stereotactic radiosurgery.

METHODS AND MATERIALS

Three observers contoured a bAVM in 20 patients, using digital subtraction angiography (V(DSA)) and three-dimensional time-of-flight MRA (V(MRA)). Displacement between contours was calculated. Agreement and differences between observers and imaging modalities were assessed. A standardized treatment plan with dynamic conformal arcs was generated and dosimetric coverage of all contours and the volume of normal brain tissue within the high dose region was determined.

RESULTS

The generalized reliability coefficient was "fair" for target volume (0.79), but "poor" for displacement (0.35). V(MRA) was larger than V(DSA) (5.0 vs. 4.0 mL, p = 0.001). No difference in displacement was found (2.8 vs. 2.5 mm, p = 0.156). Dosimetric coverage of V(MRA) was 62.9% (95% CI, 56.9-68.8) when V(DSA) was used as planning target volume, and coverage of V(DSA) was 83.5% (95% CI, 78.1-88.8) when V(MRA) was used for planning (p < 0.001). The mean volume of normal brain within the 80% isodose was larger when the bAVM was delineated on MRA (0.7 vs. 1.0 mL (p = 0.02) for targets < or =3 mL and 3.7 vs. 7.0 mL (p = 0.01) for targets >3 mL).

CONCLUSIONS

Brain arteriovenous malformations delineated on MRA are larger and more randomly displaced. However, for bAVMs < or =3 mL, the difference in volume of normal brain tissue within the high-dose region does not seem to be clinically relevant. Therefore, MRA-images might be used as the sole imaging modality for the radiosurgical treatment of bAVMs < or =3 mL when the bAVM is located in a noneloquent position.

ROLE OF RADIOSURGERY IN THE MANAGEMENT OF CEREBRAL ARTERIOVENOUS MALFORMATIONS IN THE PEDIATRIC AGE GROUP

OBJECTIVE

To assess the safety and efficacy of radiosurgery for the management of arteriovenous malformations (AVMs) in the pediatric age group.

METHODS

We reviewed data from 100 children (44 girls and 56 boys) presenting a total of 103 AVMs treated by linear accelerator radiosurgery between December 1988 and May 2002. The median patient age was 12 years (range, 2–16 yr). Sixty-seven AVMs (65%) were in functional locations and 30% were inoperable. The mean AVM volume was 2.8 cm3 (range, 0.9–21.3 cm3). The mean marginal dose was 23 Gy (range, 15–25 Gy) and required between one and four isocenters. Fifty patients received multimodal treatments with embolization and/or surgery before and/or after radiosurgery. Given that 16 patients underwent two sessions of radiosurgery and one patient received three sessions, a total of 119 radiosurgical treatments were delivered. We maintained our clinical and angiographic follow-up for at least 36 months after irradiation or until the complete obliteration of the AVM was confirmed by angiography (our sole end point for judging clinical efficacy). Univariate and multivariate analysis were performed to determine predictive factors for obliteration.

RESULTS

Complete obliteration was achieved for 72 AVMs (70%). The permanent neurological deficit rate was 5%. One patient died because of rebleeding. None of our patients presented bleeding after an angiographically verified AVM obliteration. The main predictive factors for obliteration were low AVM volume and no previous embolization. Moreover, the younger the patient, the more effective the radiosurgery seemed to be.

CONCLUSION

Radiosurgery is a safe and effective treatment for AVMs in the pediatric age group. One criterion for success was the use of a prescription dose similar to that used with adult populations.

[Neuroimaging characteristics of intracerebral haematoma]

The objective of brain imaging is to identify the hematoma according to its different stages and to find a potential underlying cause because of the risk of recurrence and the possibilities of treatment. In emergency, the diagnosis of hematoma is often obtained by CT scan, however today MRI has proved to be more accurate than CT to detect hemorrhage and to identify an underlying etiology. In some cases, according to the patient age, the medical history and the location of the hematoma, it may be necessary to perform a conventional angiography in order to exclude an intracranial vascular malformation. The aim of this review is to detail the different aspects of intracerebral hemorrhages according to the sequences and the temporal evolution, and to describe special findings which can help to identify an underlying etiology.