Clinical outcome of radiosurgery for cerebral arteriovenous malformations

Radiosurgery in the treatment of cerebral AVMs

Radiosurgery of AVM's is gaining in popularity and is advocated by many for the treatment of lesions less than 3 cm in diameter. During a 17 month period 33 patients with cerebral AVM's were treated with radiosurgery. All regions of the brain were represented in the series including brain stem. A mean follow-up of 10.8 months revealed a 6% rebleed rate and a 9% total complication rate. Multimodality therapy including embolization and surgery is recommended for the treatment of AVM's and radiosurgery is seen as an important adjunctive treatment option.

Stereotactic radiotherapy for AVMs: the University of Toronto experience

Since July 1989, 66 patients have received stereotactic radiosurgery for arteriovenous malformations of the brain. All cases were reviewed by our multidisciplinary group. As result of our treatment algorithms these patients underwent stereotactic radiosurgery, either as the sole therapy or as part of combined modality treatment. Using a 6 MV linear accelerator, we have usually employed doses of either 15 or 20 Gy to the edge of the lesion, ensuring that critical normal structures do not receive a dose in excess of 15 Gy. Of the initial 24 patients followed for a minimum of 2 years, 12 have complete obliteration documented by angiography; 8 have > 90% obliteration (several have deferred further angiographic follow-up which may show progression to complete obliteration); 3 have had the nidus diminish; and one has had no change. Within this cohort, one patient experienced a transient acute effect; one patient has developed a minor late effect; one suffered a fatal hemorrhage despite ongoing response to radiosurgery; one has recently undergone retreatment.

Clinical and radiological evaluation of long-term results of stereotactic proton beam radiosurgery in patients with cerebral arteriovenous malformations

Within a period of nearly 10 years, from October, 1980, to May, 1990, a total of 68 patients with a cerebral arteriovenous malformation (AVM) were referred to a radiosurgical center in the United States for stereotactic Bragg peak proton beam therapy. Radiosurgery was chosen as an alternative treatment, either because the AVM was considered to be of high surgical risk due to its size and/or location, or because the patient refused surgery. In 63 patients (92.6%), complete clinical and radiological follow-up examinations were available. Clinical and radiological long-term results were correlated to size and to the Spetzler-Martin scale of the AVM. With increasing size or higher grade on the Spetzler-Martin scale, the clinical results of proton beam therapy became progressively worse. Of 37 patients with an AVM between 3 and 6 cm in diameter, only one-third showed amelioration of their clinical symptoms, and two-thirds remained the same or even deteriorated after radiation treatment. The same results apply to patients with very large AVM's, of whom only one-third profited from proton beam therapy. Although 85.7% of the patients in Spetzler-Martin Grades I and II showed postirradiation amelioration of their clinical symptoms, this compares to only 54.2% of the patients in Grade III, and only 24% in Grade IV. In regard to the radiological results of proton beam therapy, complete obliteration during long-term observation was only detectable in 10 patients or 15.9%, which is less than one-sixth of the whole group of 63 patients. All of these obliterated AVM's were smaller than 3 cm. Almost 85% of the patients treated using stereotactic proton beam therapy did not show any angiographic change in the radiological appearance of their AVM. The results reported here indicate that radiosurgery using stereotactic proton beam therapy is ineffective for the treatment of medium- or large-sized AVM's and should not be recommended for patients harboring an AVM larger than 3 cm. If proton beam treatment is contemplated, it should be restricted to AVM's that are less than 3 cm in size and whose location makes them easily accessible only for proton beam therapy.

The role of high-dose, single-fraction irradiation in small and large intracranial arteriovenous malformations

PURPOSE

Radiosurgery with external beam irradiation is an accepted treatment for small intracranial vascular malformations. It has been proven effective and safe for lesions with volumes of less than 4 cc. However, there is only some limited clinical data for malformations of grade 4 and grade 5, according to Spetzler and Martin.

METHODS AND MATERIALS

At the Heidelberg radiosurgery facility equipped with a linear accelerator, 212 patients with cerebral arteriovenous malformations have been treated since 1984. Thirty-eight percent of the arteriovenous malformations treated were classified inoperable, 14% grade 5, 19% grade 4, and 29% grades 1-3. Radiation doses between 10 and 29 Gy were applied to the 80% isodose contour.

RESULTS

Above a threshold dose of 18 Gy, the overall obliteration rate was 72%. After 3 years, the obliteration rates were 83% with volumes of less than 4.2 cc, 75% with volumes of up to 33.5 cc, and 50% with volumes of up to 113 cc. Of the patients presenting with seizures and paresis, 83% and 56%, respectively, showed improvement, which correlated with the degree of obliteration. After a follow-up period of up to 9 years, the rate of radiation-induced severe late complications was 4.3%. In grade 5 lesions, the risk of side effects was 10%. No serious complications occurred if a maximum dose of less than 25 Gy was applied to treatment volumes of less than 33.5 cc.

CONCLUSION

The success of stereotactic high-dose irradiation of arteriovenous malformations depends on the dose applied. The incidence of radiation-induced side effects increased with the applied dose and treatment volumes. From our experience, doses of less than 25 Gy and treatment volumes of up to 33.5 cc are safe and effective. In the future, new techniques of radiosurgery with linear accelerators and dynamically reshaped beams will allow us to apply homogenous dose distributions. Additional use of magnetic resonance angiography for 3D treatment planning will help to identify the nidus more easily.

Arteriovenous malformations in elderly patients

This article discusses the presentation, natural history, and management of arteriovenous malformations (AVMs) in elderly patients, based on our experience at the Dartmouth-Hitchcock Medical Center. We also present a review of the literature. In our series of 50 patients with AVMs who were operated on by one surgeon, six patients were 65 years old or older at the time of presentation. All six patients presented with intracerebral hemorrhage, and one patient had developed a seizure disorder 2 months before hemorrhaging. In three patients, the clinical course was consistent with the occurrence of two hemorrhages within a 48-hour period. The patients' preoperative neurological status varied from intact to moribund. In two patients, the diagnosis of AVM was made intraoperatively. Preoperative angiography revealed the diagnosis in the remaining patients. All the patients underwent surgical excision of their AVMs. Despite concurrent medical illnesses, all patients tolerated the procedure well with no new, persistent neurological deficits. At follow-up, all patients showed sufficient neurological recovery to return to the community and four of the patients were neurologically intact. Based on this experience and a review of the literature, we conclude that AVMs in elderly patients are not benign lesions and that surgical excision should be considered among the management options for these patients.

Angiographic characteristics of dural arteriovenous malformations that present with intracranial hemorrhage

Dural arteriovenous malformations (dAVMs) are uncommon lesions that constitute about 12% of all the arteriovenous malformations. Depending on the location and the hemodynamics of the lesion, bruit, focal neurological deficit, and visual symptoms represent the more common presentation modalities. Although uncommon, intracranial hemorrhage can occur. In the present study, we report six patients with dural arteriovenous malformation that presented with intracranial hemorrhage. In five cases the hemorrhage was intraparenchymal (localized to the parietooccipital area in three), while it was confined to the subarachnoid space in the remaining one. The dAVM involved the transverse sinus in three cases, was based along the tentorial incisura in two, and was at the level of the torcular Herophili in one. Leptomeningeal drainage was present in all the cases. Aneurysmal dilatation of the draining vein(s) was identified in three. Sinus stenosis/occlusion was identified in two of the four patients with a dAVM draining into a major dural sinus. Four patients underwent pre-operative embolization, and all patients had surgical resection of their lesions. Anatomical cure, as defined by absence of any residual dAVM on postoperative angiogram, was achieved in all six patients. We conclude that several findings such as leptomeningeal drainage, location outside a major venous sinus, variceal dilatation, sinus stenosis/occlusion increase the risk of bleeding and are frequently observed in those dAVMs that present with intracranial hemorrhage. Recognition of these angiographic features is critical in planning a therapeutic approach tailored to the characteristics of the individual case. When these angiographic findings are present, prompt and definitive treatment is mandatory.(ABSTRACT TRUNCATED AT 250 WORDS)

Patient outcomes after stereotactic radiosurgery for "operable" arteriovenous malformations

To define the outcomes after stereotactic radiosurgery performed for smaller volume arteriovenous malformations (AVMs) that are potentially suitable for surgical removal, we retrospectively reviewed our 4-year experience in 65 patients who declined microsurgery. All 65 patients had Spetzler-Martin Grade I or II AVMs and a minimum follow-up of 24 months (median, 29 mo). Symptomatic improvement after radiosurgery occurred in 52% of patients with seizures and in 63% of patients with headaches. The annual risk of AVM hemorrhage during the latency interval after radiosurgery was 3.7%. Five patients (7.7%) had a subsequent hemorrhage (all within 8 mo of radiosurgery); two died, and three recovered (one after hematoma evacuation and two with conservative management). Forty-seven patients (72%) returned to their previous employment status or activity level within 1 week of radiosurgery (92% within 1 yr). No patient suffered radiation-related complications. Twenty-seven (84%) of 32 patients evaluated by postradiosurgical angiography had complete AVM obliteration. Radiosurgery is an effective and less invasive management strategy for Grade I or II AVM patients who are either medically unsuitable for or unwilling to undergo surgical removal. The risk of AVM hemorrhage during the latency interval until obliteration occurs appears to be no different than the natural history of untreated AVMs. These results (including hemorrhage prevention and symptom amelioration) indicate that the conservative management of small AVMs can rarely be justified.

Vascular malformations of the brain in hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease)

Six patients with vascular malformation of the brain in hereditary hemorrhagic telangiectasia (HHT) were reviewed to determine clinical and radiographic characteristics of these lesions. There were two patients with arteriovenous fistula (AVF), three with arteriovenous malformation (AVM), and one with multiple AVMs associated with AVF. Seizures were the most common presenting symptom (seen in three patients), and two of them had intracerebral hematomas (ICH). In the remainder, the malformations were incidentally found in the course of evaluation of other diseases. Their locations were variable, but the majority was superficially confined to the cerebral cortex. Arterial supply was from mostly one feeding artery that was a cortical branch of either anterior, middle, or posterior cerebral artery. In six of nine malformations, the venous drainage was through a superficial cerebral vein into either the superior sagittal sinus or transverse sinus. Direct surgery was done on two patients with ICH, artificial embolization on one, and stereotactic radiosurgery on one. The cerebral vascular malformations in HHT are not infrequent, and in particular the importance of computed tomography and cerebral angiography should be recognized in patients with pulmonary AVF associated with HHT.

Treatment of cerebral arteriovenous malformations by neuroradiological intervention and surgical resection

We present the results of a series of 105 patients with cerebral arteriovenous malformations (AVMs) who were treated by a combined protocol including endovascular occlusive measures and open surgical resection. 25 patients were treated only by surgical intervention, 72 patients underwent preoperative endovascular embolization and 8 patients were treated only by embolization, seven of which were only treated for palliation. After superselective angiography the vascular territories suitable for endovascular or microsurgical approach were defined, and in most cases these territories were complementary to each other. In 56 cases, only one embolization was necessary and due to an advantageous co-localization of the departments the whole combined endovascular/neurosurgical procedure was done in one anesthesia. If several endovascular sessions were necessary (16 patients), the resection was mostly carried out immediately after the last neuroradiological session in the same anesthesia with total time of such combined procedure now averaging about 7 hours. According to the proposed grading system by Spetzler we treated 25 grade 1, 24 grade 2, 40 grade 3, 11 grade 4, and 5 grade 5 lesions. The overall success rate defined as complete resection without additional permanent neurological deficit was 89.6% (87 out of 97 surgical cases). The benefits of such combined approach to cerebral AVMs become apparent in shortened and safer surgical procedures as well as in a low complication rate.

Radiosurgery of epilepsy. Long-term results

Based on experimental research, since 1982 until 1991 a series of 11 patients diagnosed as suffering from idiopathic focal epilepsy have been treated with stereotactic radiosurgery. Focus location was determined with cortical electrodes and confirmed by stereotactically placed deep electrodes. Stereotactic radiosurgery was performed with photons from a cobalt source with a dose of 10 to 20 Gy, except in two cases in whom a betatron was used. The results were: complete cessation of seizures in four cases and a significant reduction in the number of seizures in five additional cases. Seizures began to decrease gradually after a period of three months of one year, except in two cases in whom there was an immediate response after treatment. In two cases there was no change. No complication related to the irradiation was recorded. The gradual and delayed effect, obtained with low doses, may favour the hypothesis that non-descructive permanent structural changes, possibly related to the neuronal plasticity phenomenon, constitute the mechanism underlying these facts. Although the number of cases so far is too small, the absence of side-effects may make this bloodless method the one of choice specially in those cases in whom eloquent areas are involved.

Linear accelerator radiosurgery of cerebral arteriovenous malformations: current status

228 patients affected by cerebral arteriovenous malformations (AVMs) underwent linear accelerator radiosurgery. Follow-up ranges from 1 to 100 months (mean 42 months). Complete angiographic obliteration was achieved in 47% of treated patients at one year and 80% at 2 years. 17 haemorrhages were observed after treatment and 6 patients died from them. No bleeding took place after complete angiographic obliteration. 11 patients suffered for radionecrosis. In 6 patients complete recovery was obtained with corticoid medication. The aim of this study is to present our results and to evaluate the effect of irradiation on the risk of bleeding after radiosurgery. Patients were considered at risk in the time lapse after irradiation and before angiographic obliteration or other definitive treatment or death. Patients were followed from the date of radiosurgery and the number of haemorrhages were recorded every six months. In our series the bleeding risk in patients harbouring incompletely obliterated AVMs decreases from 8% in the first year after radiosurgery to 0% starting from the 24th month of the follow-up.

A joint protocol for the neurosurgical and neuroradiologic treatment of cerebral arteriovenous malformations: indications, technique, and results in 76 cases

We report on a group of 76 patients who had been treated during a period in which preoperative embolization using interventional neuroradiologic technique was standard procedure. During this time, 20 consecutive patients were operated on without embolization, eight patients were treated with embolization only, and 48 patients were operated on after embolization. In 35 cases surgery immediately followed the last embolization procedure. All arteriovenous malformations (AVMs) were classified and the outcome analyzed according to Spetzler [J Neurosurg 1986; 65: 476-83]. Those lesions treated with a combination of embolization and surgery had higher Spetzler grading than those that had been operated without previous embolization. The overall recovery rate was 82.9%. In 7.9% of the cases the AVMs were not totally extirpated. The overall complication rate was 9.2%. It is concluded that preoperative embolization facilitates surgery and reduces the risk of severe morbidity and mortality, especially in high-grade lesions. In addition to the clinical results, the application and usefulness of Ethibloc as an embolizing agent is reported.

The combined management of cerebral arteriovenous malformations. Experience with 100 cases and review of the literature

A series of 100 patients treated for a cerebral arteriovenous malformation (AVM) is presented. Patients were admitted between 1985 and April 1992. Two groups are considered: the first group including 52 patients treated before the availability of radiosurgery (1985-1988), and the second group including 48 patients treated after the availability of radiosurgery (1989-1992). AVM's were classified in five grades according to the Spetzler's Grading System. Three techniques of treatment were used: surgical resection, intravascular embolization (with cyanoacrylate), and radiosurgery (linear accelerator). These three techniques were used either alone or in association, giving four types of management: surgical resection alone, embolization and resection, embolization alone, and radiosurgery (alone, or after embolization, or after surgical resection). From 1989 on, the availability of radiosurgery was responsible for the decrease of the "embolization and resection" group, which until then was predominantly used as well for low-grade (I, II, III) as for high-grade AVM's (IV, V). Overall, for the low-grade AVM's, the treatment of choice was surgical resection (79% of cases), with pre-operative embolization in one-half of these cases; the other low-grade AVM's were irradiated, with various combinations. For the high-grade AVM's, the treatment of choice was intravascular embolization (95% of cases), either alone, or followed by resection (45%) or radiosurgery (9%). Results were evaluated in terms of deterioration following treatment, in five groups: no deterioration (59%), minor deterioration (20%), long-lasting deficit (10%), major deterioration (5%), and death (6%). Overall, results improved after 1989: favourable outcome (no deterioration and minor deterioration) increased from 67% to 90%. Results were not related to the patients' age. More favourable results were obtained for low-grade AVM's (93%) than for high-grade AVM's (60%). For the low-grade AVM's the evolution from 1989 on (favourable outcomes increasing from 89% to 96%) occurred with the lowering of the mortality rate. For the high-grade AVM's, the evolution from 1989 onwards (favourable outcome increasing from 46% to 78%) occurred with the decrease of the cases with deficits. The angiographic results were strongly related to the management: 95% of complete eradication after surgical resection and 5% only after embolization alone. Concerning the results in irradiated cases, the follow-up is not long enough. The review of the neurosurgical literature since 1972 demonstrates progressive modifications in the therapeutic attitude as regards AVM's. The surgical management which was predominantly used at the beginning gave way progressively to a combined management, with a combination of embolization, surgery, and lately radiosurgery.(ABSTRACT TRUNCATED AT 400 WORDS)

Successful radiosurgical treatment of a dural arteriovenous malformation: case report

An anterior fossa dural arteriovenous malformation was treated with radiosurgery. The lesion was irradiated with 3000 cGy to the 80% isodose line of an 18-mm collimator. Angiography revealed complete thrombosis 3 years after treatment. The case is described in detail, and the pertinent literature is reviewed.

The future of therapy for glioblastoma

Effective therapy for malignant gliomas has centered on traditional approaches such as surgery and radiation therapy. Over the past two decades, more innovative approaches involving the use of chemotherapy and immunotherapy have been developed. Although these techniques have improved the quality of survival for many patients, the median survival following diagnosis and adjuvant treatment still remains only about a year. Recently, genetically engineered viruses for gene transduction and targeted cell killing have been used successfully in the experimental treatment of glioblastoma multiforme. We provide a review of the current and possible future therapies for malignant glioma with the belief that molecular biologic and genetic techniques offer the greatest hope of significantly altering the course of disease.

Gamma knife surgery of cerebral arteriovenous malformations: serial MR imaging studies after radiosurgery

PURPOSE

To investigate the temporal sequence of post radiosurgery magnetic resonance imaging changes in cerebral arteriovenous malformations.

METHODS AND MATERIALS

Eighteen patients were regularly followed up after gamma knife surgery. The follow-up intervals ranged from one day to 44 months. High signal lesion in or around arteriovenous malformations on T2-weighted magnetic resonance images corresponding to the treatment volume and developing after radiosurgery were defined as the adverse reaction of the irradiation. This high signal and the regression of arteriovenous malformations nidus after radiosurgery were evaluated.

RESULTS

Adverse reaction of irradiation was observed in nine cases. Seven of them were symptomatic. The reactions presented as focal high signal in three cases and focal high signal with extension along the neural tracts in six cases. The reactions were seen either immediately after treatment (one case), between 3 and 14 months (seven cases), and 40 months after treatment (one case). The regression of the adverse reaction was observed to start 5 +/- 3 months after its appearance. Regression of the arteriovenous malformations' nidus was found in 16 cases. In two cases the AVMs became invisible on magnetic resonance images but the angiogram still demonstrated abnormal shunts. In another one case with angiogram showing total obliteration, the nidus was erroneously interpreted as incomplete obliteration on magnetic resonance images.

CONCLUSION

It is concluded that magnetic resonance imaging is a sensitive in vivo method for detecting cerebral radiation injury. Magnetic resonance imaging offers a method for evaluating the regression of arteriovenous malformations' nidus, but the diagnosis of complete obliteration of the nidus after radiosurgery still relies on the angiogram.