Early irradiation effects observed on magnetic resonance imaging and angiography, and positron emission tomography for arteriovenous malformations treated by Gamma Knife radiosurgery

Safety of the APOLLO Onyx delivery microcatheter for embolization of brain arteriovenous malformations: results from a prospective post-market study

BACKGROUND

Catheter retention and difficulty in retrieval have been observed during embolization of brain arteriovenous malformations (bAVMs) with the Onyx liquid embolic system (Onyx). The Apollo Onyx delivery microcatheter (Apollo) is a single lumen catheter designed for controlled delivery of Onyx into the neurovasculature, with a detachable distal tip to aid catheter retrieval. This study evaluates the safety of the Apollo for delivery of Onyx during embolization of bAVMs.

METHODS

This was a prospective, non-randomized, single-arm, multicenter, post-market study of patients with a bAVM who underwent Onyx embolization with the Apollo between May 2015 and February 2018. The primary endpoint was any catheter-related adverse event (AE) at 30 days, such as unintentional tip detachment or malfunction with clinical sequelae, or retained catheter. Procedure-related AEs (untoward medical occurrence, disease, injury, or clinical signs) and serious AEs (life threatening illness or injury, permanent physiological impairment, hospitalization, or requiring intervention) were also recorded.

RESULTS

A total of 112 patients were enrolled (mean age 44.1±17.6 years, 56.3% men), and 201 Apollo devices were used in 142 embolization procedures. The mean Spetzler-Martin grade was 2.38. The primary endpoint was not observed (0/112, 0%). The catheter tip detached during 83 (58.5%) procedures, of which 2 (2.4%) were unintentional and did not result in clinical sequelae. At 30 days, procedure related AEs occurred in 26 (23.2%) patients, and procedure-related serious AEs in 12 (10.7%). At 12 months, there were 3 (2.7%) mortalities, including 2 (1.8%) neurological deaths, none of which were device-related.

CONCLUSION

This study demonstrates the safety of Apollo for Onyx embolization of bAVMs.

CLINICAL TRIAL REGISTRATION

CNCT02378883.

Cerebral arteriovenous malformations in the era of embolization for angiographic cure: a single-center experience in Egypt

Background

Embolization for cerebral arteriovenous malformations (AVMs) has evolved in the last decade with evolution in both equipment and material. Embolization targets have expanded to include angiographic cure.

Methods

To discuss the technical and management outcomes of our first cerebral AVM case series treated with embolization. The clinical, angiographic, treatment, and outcome variables of consecutive cerebral arteriovenous malformation cases, treated with curative embolization, between January 2011 and June 2017 in one regional center, were retrospectively analyzed.

Results

In 21 patients, 21 AVMs were identified, and 13 patients (61.9%) were males. The mean of the age was 34.24 ± 12.99. Fifteen patients (71.4%) had a history of intracranial hemorrhage, and 10 (47.6%) patients had seizures. Sixteen patients (76.2%) were at grade 1 of modified Rankin Scale (mRS) at admission. The median for modal Spetzler-Martin grade was 2. The average number of arterial feeders was 3. Direct arteriovenous fistulas were found in 4 cases (19.0%). Venous aneurysms were found in 4 cases (19.0%). Seventeen AVMs (80.9%) were considered high bleeding risk lesions. Forty-three embolization sessions were done. Early hemorrhage occurred in 3 sessions (7.0%). Vessel perforation occurred 1 session (2.3%). Poor outcome occurred in 1 patient that was discharged at grade 3 mRS. Angiographic cure was achieved in 9 patients (42.9%). The average size reduction was 65%.

Conclusions

Onyx embolization could serve as a curative option for AVM treatment with accepted morbidity and mortality.

The Diagnosis and Management of Brain Arteriovenous Malformations in a Single Regional Center

BACKGROUND

Cerebral arteriovenous malformations are vascular abnormalities in which arteriovenous shunting occurs through an abnormal vascular network (nidus) in the parenchyma. These lesions typically present by the third decade of life with cerebral bleeding, seizures, headache, or neurologic deficits; however, they are sometimes found incidentally.

METHODS

A retrospective analysis of intracranial AVMs referred to a single regional center, over a 7-year period, was performed to review the clinical presentation, pathologic features and management outcomes from January 2005 to December 2012.

RESULTS

We identified 142 patients (56% female, age range 4-69 years). Emergency referrals accounted for 87% of the cohort with the most frequent presentation being headache and/or hemorrhage. More than half (52%) of the cases were observed to have a neurologic deficit on examination. The modal Spetzler-Martin Grade was 3 with 76% of lesions located in areas of eloquent brain and 57% of cases in the dominant hemisphere. Half of the cases had multiple feeder vessels, and 29% were associated with aneurysms. The nidus was obliterated in 91% of cases actively managed. Two thirds of patients were successfully treated with a single modality, the most common being embolization. Only 8% of cases were managed conservatively. Additionally, 93% of aneurysms identified were treated successfully. The complication rate was 7% with 2% of reported infection.

CONCLUSIONS

The burden of AVM management is significantly enhanced by the number of emergency referrals. Interestingly, complication rates are higher in the unruptured cohort. Surgical management is the most effective modality, but it carries the highest complication rate. This accompanied by the challenges of AVM anatomy and associated pathology argue for expert service provision in a single center.

Arterial spin labeling perfusion-weighted MRI for long-term follow-up of a cerebral arteriovenous malformation after stereotactic radiosurgery

We present a longitudinal series of arterial spin-labeling magnetic resonance imaging (ASL-MRI) in a patient with cerebral arteriovenous malformations (AVMs) treated by stereotactic radiosurgery (SRS). Pretreatment ASL-MRI showed high signal intensity in both the nidus and draining veins, and the latter signal abnormality gradually moved proximally by 14 months after SRS. At 24 months, the signal abnormalities finally disappeared, indicating complete obliteration of the nidus. The hemodynamic changes in the AVM were clearly visualized in the longitudinal ASL-MRI series, thus this non-invasive MR method may be useful not only for detecting AVMs but also for assessment of their response after SRS.

Territorial and microvascular perfusion impairment in brain arteriovenous malformations

BACKGROUND AND PURPOSE

Both the existence and clinical relevance of a steal phenomenon in brain arteriovenous malformations (AVMs) remains a matter of debate. This study aimed to assess perfusion in the brain adjacent to brain AVMs and to relate these to macrovascular blood flow in a single measurement.

MATERIALS AND METHODS

Twenty consecutive patients with AVMs with a median age of 37 years were evaluated by 3T MR imaging by using 3D time-resolved MR angiography to determine blood flow and perfusion patterns. Cerebral perfusion was estimated by using an arterial spin-labeling technique in vascular territories around the nidus and in symmetric regions of interest in the ipsilateral and contralateral hemispheres. Mapping of concentric shells around the nidus was used to define the immediate and adjacent brain and relative perfusion reductions >20% of baseline, termed perinidal dip (PND).

RESULTS

A significant reduction in perfusion ratios between ipsilateral and contralateral hemispheres remote to the AVMs was demonstrated in the middle and posterior cerebral artery territories. PND was detected in 5 patients, and 17 patients overall showed reduced perfusion in the perinidal region on visual inspection. There was a negative correlation of the hemispheric territorial perfusion with the affected/nonaffected inflow time ratio (R = -0.402, P = .015).

CONCLUSIONS

The perfusion impairment in vascular territories adjacent to brain AVMs that we identified as PND may reflect the existence of 2 levels of perfusion impairment: a territorial and a microvascular perfusion disturbance. Although the hemispheric asymmetry in territorial perfusion seems the result of arterioarterial redistribution, the PND was inhomogeneously distributed within a single vascular territory and thus might result from low perfusion pressure in small arteries and arterioles.

Neurovascular radiosurgery

SUMMARY

This article focuses on the treatment of neurovascular diseases, in particular brain arteriovenous malformations (BAVMs), with radiosurgery. The target group for this review is physicians who manage patients with neurovascular diseases, but are not actively engaged in radiosurgery. Radiosurgery for BAVMs is an established treatment with clearly defined risks and benefits. The efficacy of radiosurgery for dural arteriovenous shunts (DAVSs) is probably similar but the treatment has not yet gained the same acceptance. Radiosurgical treatment of cavernomas (cavernous hemangiomas) remains controversial. Well founded predictive models for BAVM radiosurgery show: * The probability of obliteration depends on the dose of radiation given to the periphery of the BAVM. * The risk of adverse radiation effects depends on the total dose of radiation, i.e. the amount of energy imparted into the tissue. The risk is greater in centrally located lesions. The risk of damage to brainstem nucleii and cranial nerves must be added to the risk predicted from current outcome models. * The risk of hemorrhage during the time span before obliteration depends on the BAVM volume, the dose of radiation to the periphery of the lesion and the age of the patient. Central location is a probably also a risk factor.

The Impact of Arteriovenous Malformation Radiosurgery on the Brain: From Morphology and Perfusion to Neurocognition

The therapeutic aims of brain arteriovenous malformation (AVM) radiosurgery are multiple. Protecting patients from rebleeding is the prime goal. Among the others, hemodynamics, perfusion and neurocognition recovery are interesting and important. Anatomically AVM contains an abnormal cluster of vascular networks (nidus) between arteries and veins. Hemodynamically the nidus contains a low resistance and causes high-flow transnidal shunts between both sides of the nidus. The shunts cause hypotension in the neighboring arteries and diversion of blood from the adjacent brain tissues. The diversion disturbs brain hemodynamics. Radiosurgery, by eliminating the nidus, reconstitutes normal brain hemodynamics. From the early stage after radiosurgery, the abnormal transnidal flows gradually decrease, and the adjacent hemodynamics recovers toward normal. For nonhemorrhagic AVM, improvement of seizure control and stable or improved neurological status are observed clinically. The radiosurgical effects are also reflected in the recovery of metabolism in the adjacent brain and neurocognitive function paralleling the hemodynamic normalization. Morphological cure of AVM and the associated recovery of brain hemodynamics, metabolism and neurocognitive function form the therapeutic rationale of AVM radiosurgery.

Cognitive function in patients with cerebral arteriovenous malformations after radiosurgery: prospective long-term follow-up

PURPOSE

To evaluate the long-term cognitive function of patients with cerebral arteriovenous malformations (AVMs) after radiosurgery.

METHODS AND MATERIALS

The data of 95 AVM patients were prospectively assessed up to 3 years after radiosurgery. Of these patients, 39 had a follow-up of at least 2 years. Radiosurgery was performed using a modified linear accelerator (minimal doses to the target volume 15-22 Gy, median dose 20). The neuropsychological evaluation included testing of intelligence, attention, and memory. The effect of a preexisting intracranial hemorrhage, as well as AVM occlusion, on cognitive functions was analyzed after 1 and 2 years.

RESULTS

No cognitive declines were observed during follow-up. Instead significant improvements occurred in intelligence (1 year, +6.1 IQ points; 2 years, +5.1 IQ points), memory (1 year, +18.3 percentile score; 2 years, +12.2 percentile score), and attention (1 year, +19 percentile score; 2 years, +18 percentile score). Patients without previous intracranial hemorrhage improved more than patients with intracranial hemorrhage, although this difference was not statistically significant. The role of AVM occlusion on cognitive function is not clear at present.

CONCLUSION

Radiosurgery does not induce measurable deterioration of cognitive function in patients with cerebral AVMs.

Integration of the metabolic data of positron emission tomography in the dosimetry planning of radiosurgery with the Leksell gamma knife: early experience with brain tumors

✓ The purpose of this study was to assess the use of positron emission tomography (PET) as a stereotactic planning modality for gamma knife radiosurgery (GKS).

The authors developed and validated a technique for fiducial marker imaging, importation, and handling of PET data for integration into GammaPlan planning software. The clinical feasibility in applying this approach to a selected group of patients presenting with recurrent glial tumors or metastases was evaluated.

Positron emission tomography data can be integrated into GammaPlan, allowing a high spatial accuracy, as validated using a phantom. Positron emission tomography data were successfully combined with magnetic resonance (MR) images to define the target volume for the radiosurgical treatment of patients with recurrent glioma or metastasis. This approach may contribute to optimizing target selection for infiltrating or ill-defined brain lesions. Because PET is also useful for the pretreatment and follow-up evaluation, the use of stereotactic PET in these patients can enable an accurate comparison of PET-based metabolic data with MR-based anatomical data. This could give a better understanding of the metabolic changes following radiosurgery.

The ability to use PET data in GKS represents a crucial step toward further developments in radiosurgery, as this approach provides additional information that may open new perspectives for the optimization of the treatment of brain tumors.

[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.

Application of MR in stereotactic radiosurgery

Radiosurgery, a bladeless brain surgery without opening skull, requires higher imaging accuracy as compared to microsurgery. Accordingly, we must refine the ways we use the MR scanner and interpret the obtained images. A well tuned and regularly calibrated MR scanner provides excellent images, which allow us to define detailed intracranial structures without distortion. This enables us to obtain a reliable imaging diagnosis despite the fact that pathologic diagnosis is not available in many radiosurgical patients. Due to its three-dimensional imaging and excellence in tissue and spatial contrast, MR is important in exploring new radiosurgical indications. Large arteriovenous malformations (AVM), dural AVM of cavernous sinus and trigeminal neuralgia are some of the successful examples. By using MR, longitudinal investigation of radiosurgical effects becomes feasible. For tumors, the longitudinal studies are important in optimization of dose selection. For AVM, MR is reliable in verification of radiosurgical result. The reliability is comparable to conventional x-ray angiography. Application of MR enhances the essence of noninvasiveness of radiosurgery.