The endovascular treatment of brain arteriovenous malformations

PREOPERATIVE EMBOLIZATION OF INTRACRANIAL ARTERIOVENOUS MALFORMATIONS WITH ONYX

OBJECTIVE

Preoperative embolization in accordance with multimodal therapies for cerebral arteriovenous malformations (AVMs) is generally the first step in treatment and may result in complete obliteration. The Onyx liquid embolic system (Micro Therapeutics, Inc., Irvine, CA) may offer advantages for intranidal targeted embolization and microsurgical resection. We present our experience in the combined treatment of intracranial AVMs using Onyx embolization and neurosurgical resection.

METHODS

We treated a total of 47 patients for compact intracranial AVMs that were located in the frontal or frontoparietal area (16 patients); temporal, temporoparietal, or temporo-occipital regions (12 patients); parietal or parieto-occipital areas (8 patients); occipital regions (8 patients); had basal ganglia involvement (2 patients); and was cerebellar (1 patient). The Spetzler-Martin grading scale values were as follows: 25 patients were Grades I or II, 10 patients were Grade III, and 12 patients were Grades IV or V. Twenty-three AVMs were located in eloquent brain regions.

RESULTS

After we performed final embolizations, the mean nidus reduction was 84%. Seven patients had new, nondisabling neurological deficits, and four patients had new, disabling neurological deficits after embolization. Periprocedurally, five vessel perforations and four stuck microcatheters were encountered without clinical deficits. In two patients, delayed hemorrhage after embolization occurred with good clinical outcome. We completely resected 46 AVMs; in one patient, we detected an AVM on postoperative angiography. The mean operative time was 4.7 hours, and the mean blood loss was 455 mL. Clinical status worsened postoperatively in 14 patients. Angiographic and clinical follow-up examinations were available for 42 patients (89%); the average follow-up period was 13 months. We found no relapse of arteriovenous shunt. Fourteen patients improved clinically after discharge. Of the 42 patients followed up, 23 individuals had no neurological deficit, 16 had a nondisabling deficit, and three had a disabling deficit.

CONCLUSION

Preoperative use of the Onyx liquid embolic system in cerebral AVM treatment allows profound occlusion by targeted embolization and provides a basis for safe neurosurgical resection.

Targeting cerebral arteriovenous malformations for minimally invasive therapy

OBJECTIVE

Cerebral arteriovenous malformation (AVM) embolization has been performed for nearly 40 years to reduce the risk of hemorrhage, to reduce symptomatic arteriovenous shunting, and to pretreat patients for surgical excision or radiosurgery. In some cases, embolization alone may be able to angiographically cure an AVM, although this is a small percentage of all AVMs.

METHODS

This report reviews the current limitations of embolic therapy of cerebral AVMs from the standpoint of AVM angioarchitecture and the physical limitations of current embolic materials. In addition, it seeks to identify the areas in which embolization therapy may make advancements both as a pretreatment and as a sole therapy.

RESULTS

Currently, liquid embolic agents, ethylene vinyl alcohol, and n-butylcyanoacrylate seem to provide the greatest resistance to recanalization in AVM embolization. These agents, however, elicit only a weak, nonspecific, bioactive inflammatory response by histopathology.

CONCLUSION

The further evaluation and understanding of the vascular biology of AVM vessels and the endothelium cell wall biology will help us devise more bioactive material solutions to AVM nidus obliteration. Targeting specific receptors in AVMs with the embolic material delivered may additionally enhance the effects of radiosurgery in these patients.

The endovascular operating room as an extension of the intensive care unit: changing strategies in the management of neurovascular disease

Technological advances within the field of endovascular neurosurgery have influenced the management of the neurovascular patient within the intensive care unit (ICU). The endovascular operating room has, in fact, become an extension of the ICU in certain cases. Given the rapid development of new endovascular technologies, it is more important than ever for neurosurgeons to remain intimately involved with the care of their patients within the ICU. This article offers an overview of the evolution in ICU management of neurovascular disease and provides a framework for the incorporation of the endovascular operating room in the intensive care management of patients with this disease.

Therapy of brain arteriovenous malformations: multimodality treatment from a balanced standpoint

The three therapeutic modalities for arteriovenous malformation (AVM) treatment (surgery, embolization, and radiotherapy) developed in the past years with specific tools, each tool with its own qualities. Soon after the implementation of embolization for treatment of AVMs, this technique was used in combination with microsurgery; since the development of radiosurgery, treatment algorithms combining embolization with surgery and eventual subsequent radiosurgery, embolization with radiosurgery, or surgery with subsequent radiosurgery have been reported. These different combinations have been in use under the term multimodality treatment for many years, but the algorithms regarding the combination of tools, which tool has priority, and how the risk levels of each tool are assessed shows great variability among institutions. Centers with a surgical background see embolization as a technique to increase surgical feasibility and radiosurgery as a tool to complete subtotal AVM excision. Institutions with an endovascular background embolize AVMs with the aim of maximal occlusion rates and view surgery or radiosurgery as a technique to be used if the goal of total endovascular occlusion cannot be achieved. Radiosurgeons receive patients after incomplete embolization or surgical extirpation or a combination of both.

EMBOLIZATION BEFORE RADIOSURGERY REDUCES THE OBLITERATION RATE OF ARTERIOVENOUS MALFORMATIONS

OBJECTIVE

To evaluate the arteriovenous malformation (AVM) obliteration rate and the clinical outcome after radiosurgery in patients with and without previous embolization.

METHODS

Of 244 patients who underwent linear accelerator radiosurgery for AVMs at the Sunnybrook Health Sciences Centre between 1989 and 2000, 61 patients had embolization before radiosurgery and complete follow-up for at least 3 years. For 47 of these 61 patients (Group A, embolization plus radiosurgery), we were able to find 47 matching patients without previous embolization (Group B, radiosurgery alone). This group of matching patients had the same AVM volume (after embolization in Group A), location, and marginal dose. The radiosurgery-based AVM score and the obliteration prediction index were calculated.

RESULTS

The median follow-up period was 44 months. Nidus obliteration was achieved in 22 patients in Group A (47%) and 33 patients in Group B (70%, P = 0.036). Permanent deficit related to hemorrhage or radiation occurred in three patients (6%) in Group A and three patients (6%) in Group B. During the first 3 years after radiosurgery, two patients (4%) in Group A experienced hemorrhage; in Group B, five patients (11%) experienced hemorrhage (P = 0.2). In Group B, two patients (4%) died and two patients (4%) had their AVM surgically removed. Both deaths were related to hemorrhage during the latency period. The excellent outcome (obliteration plus no deficit) in Group A was 47% compared with 64% in Group B (P = 0.146). There was no difference in the obliteration prediction index and the radiosurgery-based AVM score between Groups A and B. The predicted rates of obliteration and excellent outcome were 55 and 62.5%, respectively, according to the obliteration prediction index and the radiosurgery-based AVM score.

CONCLUSION

Embolization before radiosurgery significantly decreases the obliteration rate, even in AVMs with the same volume, location, and marginal dose. Although an excellent outcome rate was higher in the group without embolization, this was not statistically significant.

Brain aneurysms and arteriovenous malformations: advancements and emerging treatments in endovascular embolization

BACKGROUND AND PURPOSE

Brain aneurysms and vascular malformations can cause cerebral hemorrhages, with devastating consequences for the patients and their families. Since the development of microcatheters and materials used for endovascular embolization, we have witnessed a rapid advancement in the technology and in the number or patients treated with this approach. The aim of this review is to survey recent data relevant to new technologies and emerging treatment strategies in these areas.

SUMMARY OF REVIEW

Clinical trials assessing the safety and efficacy of coil embolization for cerebral aneurysms were based on the use of bare platinum, helical coils. Since then, endovascular operators have been testing and using new materials such as bioactive coils, expandable coils, and complex-shaped coils. Based on the data so far obtained, third and fourth generation coil designs are rapidly emerging and will be ready for clinical application in the near future. Balloon- and stent-assisted coil embolization is enabling the treatment of complex, large-neck aneurysms and the vascular reconstruction of lesions previously considered not treatable. New open- and closed-cell designs allow the navigation and deployment of stents in extremely tortuous vessels. With regards to the embolization of vascular malformations, it is possible to safely navigate microcatheters and microwires through very small arteries previously considered not accessible. In addition, embolization materials such as n-butyl cyanoacrylate and ethylene-vinyl alcohol copolymer are now routinely injected to safely reduce or obliterate large and complex arteriovenous malformations and fistulae.

CONCLUSIONS

Advancements in technology are rapidly improving the endovascular approach to the treatment of cerebral aneurysms and arteriovenous malformations.

Trapped Microcatheter from Vessel Spasm: Safe Removal after Double Microcatheter Technique and Local Papaverine Infusion

In a child undergoing combined transarterial and direct percutaneous puncture embolization of an extensive and complex facial arteriovenous malformation, severe arterial spasm fixed a flow-directed microcatheter in an ethmoidal branch of the left ophthalmic artery. Multiple traction attempts failed to remove the microcatheter. After catheterization of the distal, post central retinal artery part of the same ophthalmic artery, with a second flow-directed microcatheter and following intraarterial papaverine injection through this second microcatheter, the fixed microcatheter could be removed without complication. This case demonstrates a technique that can be attempted before deciding to leave the microcatheter in the patient or to remove it surgically.

Complications of embolization of arteriovenous malformations of the brain

Object

The goal of this study was to determine the rates of mortality and morbidity associated with the embolization of arteriovenous malformations (AVMs) of the brain and to analyze the factors related to embolization-related complications.

Methods

The University of Toronto Brain Vascular Malformation Study Group database was reviewed. Three hundred six patients underwent 513 embolization sessions between November 1984 and September 2002. The combined rate of death and any permanent disabling neurological deficit was 3.9% per patient. Location of the AVM in an eloquent part of the brain, presence of a fistula, and a venous deposition of glue were related to complications. A clinically important reduction in the rate of death and disabling morbidity occurred in the second half of the study period.

Conclusions

Embolization of AVMs in the brain is associated with low overall rates of mortality and disabling morbidity.

Surgical Treatment of Non-ruptured Giant Occipital Arteriovenous Malformations With Frequent Migraine-Like Headache-Two Case Reports-

Two patients with giant occipital arteriovenous malformation (AVM) underwent microsurgical treatment among 294 patients with intracranial AVM treated between 1981 and 2004. The patients were aged 52 and 65 years and showed common symptoms consisting of long-term frequent migraine-like headaches with visual aura and recent homonymous hemianopia. Common neuroimaging findings were abundant dural feeders plus feeders from the posterior, middle, and anterior cerebral arteries, and deep drainers to the galenic system. Both patients underwent preoperative staged embolization and total microsurgical removal of the nidus with a neuronavigation system. Both patients returned to ordinary life without the need for assistance. These findings emphasize that giant occipital AVM, even if unruptured, is surgically treatable with acceptable morbidity.

Endovascular treatment of cerebral arteriovenous malformations with emphasis on the curative role of embolisation

SUMMARY

Valavanis A, Pangalu A, Tanaka M. Endovascular treatment of cerebral arteriovenous malformations with emphasis on the curative role of embolisation. Schweiz Arch Neurol Psychiatr 2004;155:341-7. Cerebral arteriovenous malformations are complex and only partially understood vascular lesions of the central nervous system with a natural history characterised by significant morbidity and mortality mainly due to an increased hemorrhagic risk, Microneurosurgical removal, radiosurgical obliteration and neuroendovascular embolisation are the principal therapeutic modalities applied individually or in various combinations according to varying selection criteria for the treatment of cerebral arteriovenous malformations. In this context embolisation plays a central role cither as a complementary or as the sole treatment technique. This report summarises the evolutive 18 years of continuous experience of the senior author with the neuroradiological evaluation and endovascular treatment of 644 patients with a cerebral arteriovenous malformation. Special emphasis is given to the underlying concepts and specific endovascular techniques developed for the complete, i.e. curative embolisation of cerebral arteriovenous malformations. Precise angiographic analysis of the vascular composition and intrinsic angioarchitecture of the nidus of the arteriovenous malformation by super-selective microcatheterisation is required to identify the types of feeding arteries and patterns of their supply, the number and vascular connections of nidal compartments, the types of arteriovenous shunts, the morphology of the vascular spaces composing the nidus and the number and exit patterns of draining veins. Complete angiographic investigation for recognition of secondarily induced phenomena of the cerebral vasculature, such as arterial and venous high-flow angiopathy and so-called perinidal angiogenesis is essential for a comprehensive evaluation and assessment of the associated haemorrhagic risk. Based on a precise topographic classification, detailed angioarchitectural analysis, application of superselective multimicrocatheterisation techniques along with a controlled intranidal injection of non-absorbable liquid embolic materials, nearly 40% of cerebral arteriovenous malformations can be completely and stably obliterated and therefore curatively treated by single session or multistaged embolisation with a morbidity of 1.3% and a mortality of 13%. which arc lower than the known natural history of this disease.

Complication analysis of 469 brain arteriovenous malformations treated with N-butyl cyanoacrylate

SUMMARY

We independently assessed the frequency, severity and determinants of neurological deficits after endovascular embolization with NBCA of brain arteriovenous malformations (BAVMs) to have a better basis for making treatment decisions. All the charts of 469 BAVMs patients who underwent embolization with NBCA were reviewed. We analyzed the complications and their relation to angiographic features. The 469 patients were treated with 1108 endovascular procedures. Each met one to eight times, average 2.3 times. Eleven patients showed treatment-related complications, including four haemorrhagic and seven ischemic complications. Of these 11 cases, two died, two had persistent disabling deficits, and another seven suffered transient neurological deficits. Our finding suggests a low rate of disabling treatment complications for embolization of brain AVMs with NBCA in this center. The management of AVM patients who have high risk of embolization therapy should be treated by special strategy.

Brain AVM Embolization with Onyx(R): Analysis of Treatment in 34 Patients

SUMMARY

The endovascular approach to arteriovenous malformations (AVM) using different embolizing agents is a well-established treatment option. This report assesses the results of our experience using a non "glueing" embolic material available for several years, commercially known as Onyx(R). We used Onyx to treat 34 consecutive patients in the last four years. All patients were treated in the same department by the same neuroradiological team, with a strictly repetitive technical strategy and procedural protocol. All our patients presented AVMs with Spetzler Grade 3 or more, because in our Institution Grade 1 or 2 AVMs are directly treated by surgical approach. We adopt a multidisciplinary treatment approach (embolization, surgery, radiotherapy) by which embolization is construed as work in progress offering definitive treatment of AVMs without severe risks. Embolization is mainly undertaken as the first step before surgery, to reduce flow and size of the AVM by a "targeted" technique. In addition to reducing lesion size, endovascular treatment aims to seal off AVM areas anatomically or haemodynamically complex for surgical treatment. Occasionally, the reduction in size allows a radiosurgical approach. Embolization seldom results in a definitive cure of AVMs. At the end of multimodal approach, we obtained the complete and definitive cure of AVM in 21/34 patients (two complete obliteration with interventional technique, 19 in combination with surgery); to these were added 5/34 patients who received radiosurgical therapy. No major complications arose during endovascular treatment. One patient had transitory (36 hour) impaired right arm pronation. The CT scan disclosed an asymptomatic mild SAH in the left sylvian fissure but no ischaemic areas. One patient still in treatment died from fatal rebleeding (the clinical onset had been with haemorrhage two weeks before the session) 12 days after the embolization. Excellent or good clinical outcome was obtained in 23/26 patients who completed the therapeutic protocol. Outcome was conditioned by focal symptoms present on admission in three patients due to haemorrhagic onset, but only one patient presented a severe disability on discharge. In our view, the main problem of Onyx is that the apparently easier approach will probably lead to a wider diffusion of these procedures. AVMs are extremely difficult and dangerous to treat: this is not affected by the quality of the embolizing agents used and must be kept in mind at all times.

Endovascular Treatment of Cerebral Arteriovenous Malformations

The modern management of cerebral arteriovenous malformations (AVMs) is based on three therapeutic modalities: microneurosurgery, endovascular embolization, and stereotactic radiosurgery. Embolization facilitates subsequent radiosurgery by reducing the volume of the nidus, prepares the resection of surgically accessible AVMs, and immediately addresses the risks related to associated intra/extranidal aneurysms and arteriovenous fistulas. We discuss in this article the current state of AVM endovascular therapy.

Ventricular/paraventricular small arteriovenous malformations: role of embolisation with cyanoacrylate

Arteriovenous malformations (AVMs) located in or near to ventricles have proven difficult to treat. We report the safety and efficacy of embolisation of these deep central lesions and describe the contribution of embolisation to multimodality treatment. Fourteen consecutive patients with small (less than 3 cm) ventricular/paraventricular AVMs arranged for possible embolisation to their nidi. All patients presented with intracranial haemorrhage. The AVMs ranged in size from 10 to 30 mm (average, 17 mm). Embolisations were performed using liquid adhesive (cyanoacrylate and iodised oil mixture at a ratio of less than 1:4) delivered by flow-guided microcatheters with the patient under general anaesthesia. One patient (7.1%) was considered unsuitable for embolisation, and another (7.1%) was not able to undergo embolisation because of the morphological features of the AVM feeders, while the remaining 12 could be embolised successfully. Six of 12 patients who underwent embolisation achieved complete occlusion of their AVMs (overall occlusion rate, 42.9%), while the remaining 6 were embolised partially with a 60-95% (mean = 80%) size reduction. One (8%) permanent neurological deficit resulted from embolisation. Endovascular therapy seems to make a significant contribution to the multimodality treatment of small AVMs located in the ventricle or paraventricular deep area. Embolisation alone permits complete cure in a large number of patients. It results in obliteration of a significant volume of the nidus in most of the remaining patients, which makes those nidi more vulnerable to subsequent multimodal therapy.

Surgical results in pediatric Spetzler-Martin grades I-III intracranial arteriovenous malformations

OBJECTS

The goal of cerebral arteriovenous malformation (AVM) therapy in pediatric patients should be complete resection or obliteration of the AVM to eliminate subsequent hemorrhage, because of high mortality and morbidity rates related to hemorrhage in addition to the longer life expectation. Despite advances in Gamma knife radiosurgery and in endovascular embolization, surgical resection is still the gold standard for treating cerebral AVMs.

METHODS

Between 1986 and 2003, 20 children were surgically treated for cerebral AVMs. The AVMs were graded I, II, and III using the Spetzler-Martin (S-M) Grading Scale. Good recovery was achieved in 18 out of 20 patients (90%) and only 1 patient was moderately disabled (5%). There was one mortality (5%) related to the preoperative deep comatose state of the patient. The total obliteration rate was 89% (17 out of 19).

CONCLUSION

For S-M grade I-III AVMs, surgical resection is the treatment of choice, considering its high cure rate and low morbidity and mortality rates.

Complications of embolization for cerebral arteriovenous malformations

SUMMARY

Embolization is recognized as an important adjunct in the treatment of cerebral arteriovenous malformations (AVMs). We reviewed our results of embolizations for AVMs and discussed procedure-related complications. Eleven complications were recorded in 68 consecutive patients (16%). Of these, four were technical problems including a glued catheter, inability to withdraw the catheter, vessel perforation by the microcatheter, and coil migration. Other complications included three cases of ischemic symptoms due to retrograde thrombosis, two cases of asymptomatic cerebral infarction, one case of asymptomatic small haemorrhage due to venous occlusion, and one case of post-embolization haemorrhage of unknown etiology. Our morbidity rate was 7%, mortality rate was 0%, and asymptomatic complication rate was 9%, retorospectively. Further improvements to endovascular techniques and devices are required.

Glubran 2: a new acrylic glue for neuroradiological endovascular use. Experimental study on animals

SUMMARY

A new acrylic glue, Glubran 2, is now available on the European market. It bears the CE mark with several surgical indications and the specific indication for neuroradiological endovascular use. Despite this approval, to our knowledge its use is still limited to surgery and no injections have been made in human patients. This study was designed to evaluate the behavior of Glubran 2 in endovascular injection in a simulation of brain AVM. Six sheep were operated on opening a fistula between the right common carotid artery and the jugular vein. This fistula modifies blood flow in the skull base rete mirabilis, which then functions as an AVM. In two sheep, the rete mirabilis was occluded by injection of 1.5 ml of Histoacryl diluted 1:1 and 1:3 with Lipiodol. In two sheep, the rete was embolized by injection of 1.5 ml of Glubran 2 diluted 1:1 with Lipiodol. The last two sheep were embolized by injection of Glubran 2 diluted 1:3 with Lipiodol. The procedures were documented by DSA angiographic acquisitions and by fluoroscopic VHS. The sheep were killed immediately after the procedures and the rete mirabilis isolated for histologic examination. Embolization was obtained with both kinds of glue. Glubran 2 diffuses in a very similar way to Histoacryl with an apparently more complete diffusion. Reflux in the ascending pharyngeal artery showed that Glubran 2 tended not to produce bubbles but diffused more homogeneously. The subjective conclusion of this work is that Glubran 2 can be used in endovascular embolizations. Before approaching brain AVMs, a further study will investigate embolization of the external carotid territory.

Functional Magnetic Resonance Imaging and Optical Imaging for Dominant-hemisphere Perisylvian Arteriovenous Malformations

OBJECTIVE:

In this study, we developed an a priori system to stratify surgical intervention of perisylvian arteriovenous malformations (AVMs) in 20 patients. We stratified the patients into three categories based on preoperative functional magnetic resonance imaging (fMRI) language activation pattern and relative location of the AVM.

METHODS:

In Group I (minimal risk), the AVM was at least one gyrus removed from language activation, and patients subsequently underwent asleep resection. In Group II (high risk), the AVM and language activation were intimately associated. Because the risk of postoperative language deficit was high, these patients were then referred to radiosurgery. In Group III (indeterminate risk), the AVM and language were adjacent to each other. The risk of language deficit could not be predicted on the basis of the fMRI alone. These patients underwent awake craniotomy with electrocortical stimulation mapping and optical imaging of intrinsic signals for language mapping.

RESULTS:

All patients from Group I (minimal risk) underwent asleep resection without deficit. All Group II (high-risk) patients tolerated radiosurgery without complication. In Group III (indeterminate risk), three patients underwent successful resection, whereas two underwent aborted resection after intracranial mapping.

CONCLUSION:

We advocate the use of fMRI to assist in the preoperative determination of operability by asleep versus awake craniotomy versus radiosurgery referral. In addition, we advocate the use of all three functional mapping (fMRI, electrocortical stimulation mapping, and optical imaging of intrinsic signals) techniques to clarify the eloquence score of the Spetzler-Martin system before definitive treatment (anesthetized resection versus radiosurgery versus intraoperative resection versus intraoperative closure and radiosurgery referral).

Emergency craniotomy for intraparenchymal massive hematoma after embolization of supratentorial arteriovenous malformations

OBJECTIVE

We sought to evaluate the efficacy of emergency craniotomy for patients with massive hematoma secondary to endovascular embolization of supratentorial arteriovenous malformations (AVMs) and to investigate relevant factors affecting outcome.

METHODS

Within the past 15 years, 605 patients with intracranial AVMs have undergone 1066 endovascular embolizations at our institution. Of these, 24 patients experienced intracranial hemorrhage during or after the procedure. Fourteen patients were demonstrated to have massive intraparenchymal hematomas and deteriorated to a comatose state (Glasgow Come Scale score < or =6). Twelve patients underwent craniotomy within 170 minutes of being diagnosed with intraparenchymal hemorrhage. The surgical procedures performed were hematoma evacuation with total (6 patients) or partial (2 patients) resection of the AVM or hematoma evacuation only (4 patients). The clinical records of these 12 patients were analyzed retrospectively.

RESULTS

Nine patients recovered to a favorable condition (good recovery, four patients; moderately disabled, five patients), one patient remained in a persistent vegetative state, and two patients died. The interval between hemorrhage and emergency craniotomy was significantly shorter in patients with favorable outcomes than in those with poor clinical outcomes. Advanced age and a larger volume of intraoperative blood loss were the factors relevant to poor outcome. Temporal lobe location of the AVM and incomplete embolization tended to correlate to poor clinical outcome, but this correlation was not statistically significant. The sizes of the AVM and the hematoma did not correlate to patient outcome. There was no difference in outcomes with regard to the surgical procedure performed.

CONCLUSION

In patients with massive postembolization hematomas, emergency craniotomy should be performed as soon as possible to achieve a favorable outcome. Cooperation among interventional neuroradiologists, intensive care physicians, and neurosurgeons is essential to manage AVM patients with critical postembolization hemorrhage. There is no need to persist in performing simultaneous total resection of the AVM at the emergency craniotomy.

Management of patients with brain arteriovenous malformations

Arteriovenous malformations (AVMs) of the brain, which are probably genetically determined, are errors in the development of the vasculature that, together with the effects of blood flow, may lead to a focal arteriovenous shunt. Clinically, the adult patient may present with acute or chronic neurological symptoms-fixed or unstable-such as deficits, seizures or headache. Sometimes the lesion is an incidental finding. In about half of the patients, the revealing event is an intracranial haemorrhage. The prevalence of AVM in the western world is probably <0.01% and the detection rate is about one per 100,000 person-years. Most AVMs are revealed in patients 20-40 years of age. Therefore, the risk of developing neurological symptoms from an AVM, usually because of haemorrhage, increases with patient age. In the young adult population, AVMs are significant risk factors for hemorrhagic stroke. This risk increases with AVM volume and is higher in centrally located AVMs. Almost all patients with AVM are subjected to treatment, either by surgery, radiosurgery or embolisation, with the functional aim of reducing the risk of haemorrhage or to alleviate neurological symptoms with an acceptable treatment risk. Few neurocentres have physicians highly skilled in all treatment modalities. Therefore, the prescribed treatment may not be defined from an objective assessment of what is optimal for each individual patient, but rather from local expertise. In this context, more and better data about the natural history and the outcome of different treatments, as well as predictive models, would be valuable to help to optimise the management. Management strategies obviously differ according to local preferences, but results presented in the literature suggest the following strategy: (I) cortically located AVMs with a nidus volume <10 ml could be operated, with or without presurgical embolisation, unless there is a single feeder that can easily be catheterised and embolised for obliteration or other obvious target for embolisation, such as pseudoaneurysms or large fistulae; (II) centrally located AVMs with a nidus volume <10 ml should be treated by radiosurgery, unless suitable for embolisation as indicated above; (III) patients harbouring AVMs with a nidus volume >10 ml could benefit from targeted partial embolisation followed by radiosurgery or surgery, depending on the angioarchitecture; and (IV) AVMs >20 ml nidus volume usually have a high treatment risk with any treatment modality and are not obvious targets for treatment at all.

Role of superselective angiography in the detection and endovascular treatment of ruptured occult arteriovenous malformations

SUMMARY

Three cases of occult micro-arteriovenous malformations not identified by cerebral angiography or other imaging modalities were detected by superselective angiography. The first case had a small intracerebral hemorrhage in the superior colliculus, the second had a perimesencephalic subarachnoid hemorrhage, and the third presented with intracerebral hemorrhage combined with massive intraventricular hematoma. While repeated selective cerebral angiography (four-vessel study) was negative, superselective angiography clearly demonstrated each lesion with small early venous filling in accordance with the location of hematoma. Successful superselective embolization with polyvinyl alcohol particles was performed in each micro-arteriovenous malformation by flow-guided microcatheter without postoperative complications. Our experience suggests that superselective angiography is necessary to visualize micro-arteriovenous malformations in patients with cerebral hemorrhage and negative four-vessel angiography. Furthermore, the superselective endovascular approach has the advantage of offering immediate obliteration of the micro-shunt, thereby reducing or eliminating the risk of further hemorrhage.

Expression of vascular endothelial growth factors and their receptors in and around intracranial arteriovenous malformations

OBJECTIVE

The precise mechanisms responsible for the development and growth of intracranial arteriovenous malformations (AVMs) remain unclear, but it has been hypothesized that vascular endothelial growth factors (VEGFs) might be involved in their pathogenesis. The aim of this study was to examine immunohistochemically the presence of the VEGF family (VEGF-A to -D) and their receptors (Flt-1, Flk-1, and Flt-4) in the surgically resected AVM nidus.

METHODS

The AVM nidus was surgically obtained from 31 patients with AVMs (mean age, 40.5 yr, range 13-73 yr). The mean size of the nidus was 31.6 mm (range, 15-60 mm). Formalin-fixed, paraffin-embedded specimens were stained immunohistochemically by the labeled streptavidin-biotin method with antibodies against VEGF-A to -D, as well as Flt-1, Flk-1, and Flt-4.

RESULTS

Positive staining for VEGF-A to -D was observed in the endothelial cells of the abnormal vessels involved in the AVM nidus and in the cytoplasm of astroglia surrounding it. Samples from 30 (96.8%) of 31 patients stained positive for VEGF-A, 4 (9.7%) for VEGF-B, 17 (54.5%) for VEGF-C, and 16 (51.6%) for VEGF-D. Flt-1, Flk-1, and Flt-4 were also positive chiefly, but not exclusively, in the cytoplasm of vascular endothelium and smooth muscle cells of the vascular wall. With regard to VEGF receptors, it was found that among the 31 patients studied, 19 (61.3%) were immunohistochemically positive for Flt-1, 6 (19.4%) for Flk-1, and 19 (61.3%) for Flt-4. A comparison of mean nidus size and average age at operation revealed significant differences between patients positive for VEGF-C, VEGF-D, Flt-1, or Flt-4. In contrast, there were no significant differences in nidus size and age in patients positive for VEGF-A, VEGF-B, and Flk-1.

CONCLUSION

These results strongly suggest a possible contribution of the VEGF-VEGF receptor system to the growth of intracranial AVMs.

Palliative embolisation of brain arteriovenous malformations presenting with progressive neurological deficit

SUMMARY

Large arteriovenous malformations (AVMs) located in eloquent areas of the brain are generally considered incurable because of the high morbidity and mortality associated with their treatment. When these patients develop a progressive neurological deficit they in time often become severely disabled. This report presents the results of palliative embolisation in this subgroup of patients. Analysis of our data-base of 714 patients with known brain AVMs revealed 17 patients who presented with progressive neurological deficit and who underwent palliative embolisation as the therapeutic modality of choice for management of their AVM. One patient was excluded due to lack of follow-up and two were excluded because they later received radiation therapy. Following embolisation 43% had improvement of their neurological deficit, 50% stabilized and 7% continued to deteriorate and these clinical results persisted for an average of more than 2 years follow-up. Transient neurological morbidity associated with embolisation treatment was 7% and there was no permanent morbidity and no mortality. Palliative embolisation of brain AVMs presenting with progressive neurological deficits arrested deterioration in more than 90% of patients and was associated with low morbidity and no mortality.

Embolisation of Small (< 3 cm) Brain Arteriovenous Malformations. Correlation of Angiographic Results to a Proposed Angioarchitecture Grading System

SUMMARY

The role of embolisation in the treatment of small < 3cm) brain arteriovenous malformations (AVMs) has not been elucidated. We reviewed our experience using embolisation in the treatment of small AVMs and correlated a proposed grading system based on the angioarchitecture to the percentage obliteration achieved by embolisation. Eighty-one small AVMs in 80 patients were embolised from 1984 to 1999. The age range was from 3 to 72 years. The AVMs were given a score from 0 to 6 based on the angioarchitecture. The assigned scores were as follows: nidus (fistula = 0, < 1 cm = 1, 1-3 cm = 2), type offeeding arteries (cortical = 0, perforator or choroidal = 1), number of feeding arteries (single = 0, multiple = 2) and number of draining veins (single = 0, multiple = 1). Angiographic results based on percentage obliteration were grouped into three categories: complete, 66-99%, and 0-65%. The goal of embolisation was cure in 27 AVMs, pre-surgical in 23, pre-radiosurgery in 26, and elimination of an aneurysm in five. Embolisation achieved complete obliteration in 22 (27%) of the 81 AVMs. In the AVMs where the goal was cure, 19 (70%) of 27 were completely obliterated. In the AVMs with angioarchitecture scores of 0-2, 12 (86%) of 14 were cured, with scores of 3-4, 8 (34%) of 24 were cured and with scores of 5-6, 2 (4%) of 44 were cured. Embolisation resulted in transient morbidity of 5.0%, permanent morbidity of 2.5%, and mortality of 1.2%. There were no complications in AVMs with scores of 0-2. Embolisation is an effective treatment of small AVMs when the angioarchitecture is favourable (scores 0-2). This includes pure fistulas and AVMs with a single, pial, feeding artery.

Strategic embolisation for successful resection of a large cerebral arteriovenous malformation

The risks accompanied by the treatment of cerebral arteriovenous malformation (AVM) are still cumulative despite recent progress in available treatment options. Pre-operative embolisation is one such option, however, it seldom makes the surgical resection difficult. The excessive embolised nidus makes the surgical resection difficult because it cannot be compressed during the resection surgery and embolised nidus as a 'glue ball' with marginal hypervascular territory is most difficult to remove. The aim of pre-operative embolisation for successful surgical resection is to put glue into the marginal part of the nidus so as to make a cleavage between the surrounding normal tissues. Remaining feedings via the dilatated leptomeningeal anastomoses from surrounding normal cortical arteries do not interfere with the resection and can be eliminated easily by coagulating the pia matter around the nidus. Strategic planning with regard to the systemic course of treatment, including the manner of resection, is important for effective pre-operative embolisation.

Anaesthesia for interventional neuroradiology

Neuroradiologists have extended their treatment modalities in the field of vascular neurosurgery. The rapidly emerging and re-engineered neuroradiological techniques confront the anaesthetist with an increasing number of patients with severe neurological disease. More of these patients will need general anaesthesia in order to facilitate the endovascular procedure, including catheter placement, deposition of embolic material, and improved imaging. Anaesthetists are challenged by additional anaesthesiological aspects previously not encountered in neuroanaesthesia. A safe anaesthetic management is based on a broad understanding of pathophysiological and technical issues that arise with the endovascular treatment of cerebral vasculopathy.