Stereotactic radiosurgery for postgeniculate visual pathway arteriovenous malformations

Application of diffusion tensor-based tractography in treatment of brain arteriovenous malformations: a systematic review

There is no systematic review investigating the utility of Diffusion tensor-based tractography findings for treating brain arteriovenous malformations (bAVMs). This systematic review aims to investigate the outcomes following bAVM treatment when tractography data is incorporated into treatment planning. PubMed/MEDLINE, Scopus, and Cochrane Library, were searched for published studies. Prospective or retrospective studies involving at least one patient with confirmed bAVM and available data on tractography and clinical outcomes were included. A total of 16 studies were eligible for this review, consisting of 298 patients. 48.2% of patients were female. The mean age of the patients was 27.5 years (range: 5-77). Stereotactic radiosurgery (SRS) and microsurgical resection each were the treatment of choice in eight studies, respectively. Two-hundred forty-eight patients underwent SRS as the primary treatment, while microsurgery was used to resect the bAVMs in 50 patients. The corticospinal tract, optic pathway, and arcuate fasciculus were the most widely investigated white matter tracts. Tractography disruption and failure frequencies were 19.1% and 1.8%, respectively. The pooled proportions (95% CI) of obliteration rates were 88.78% (73.51-95.76) for microsurgery and 51.45% (13-17-88.10) following SRS. Treatment-related non-hemorrhagic complications rates occurred in 24.2% and 9.9% of patients who underwent microsurgical resection and SRS, respectively. Tractography findings can contribute to providing a more accurate dosimetry analysis of functional white matter tracts at risk prior to SRS and minimizing the surgical morbidity following microsurgical resection.

Highlights on Cerebral Arteriovenous Malformation Treatment Using Combined Embolization and Stereotactic Radiosurgery: Why Outcomes are Controversial?

Cerebral arteriovenous malformations (AVMs) are abnormal tangling between brain arteries and veins causing an arteriovenous shunt called nidus with an intervening network of vessels from the region of formation and spans through the brain. AVM effect is debilitating to the affected individual due to associated persistent intracerebral hemorrhage, resulting in significant occurrences of seizures and neurological damage. Recent innovative treatments involve a combination of embolization (Embo) procedures followed by stereotactic radiosurgery (SRS), designed to optimize less-invasive practice for the obliteration of the AVMs. Three groups of investigators reported different outcomes based on obliteration rates and adverse events, making the effectiveness of options for therapy, controversial. We have taken the case-oriented-approach to highlight on varying outcomes from various studies and provide insights as to why findings from different operation settings could be so conflicting. We chose 18 articles for systematic analysis based on initial electronic database selection of 40 key papers already identified for inclusion, followed by independent blinding assessment by two co-authors. Our evaluation was based first on our specific inclusion criteria, examining method quality, obliteration rates, serious adverse events (SAEs) and mortality rates. Second, we made a comparison between SRS or embo alone treatments versus combined embo/SRS procedures, relative to AVM sizes, following Spetzler-Martin (SM) method. Third, we considered publications which had concrete statistics with well-defined P-values and clarified outcomes for accurate evaluation. We found that patients with small to medium-sized AVM were susceptible to either embo alone or SRS alone treatments, yielding obliteration rates from 71%-100%. Except for one report, giant sizes AVMs were not amenable to these single treatments, subjecting patients to embo/SRS procedures, which yielded mixed results: One group reported 52%-65% obliteration rates, compared to 23%-28% embo alone treatment. A second group contradicted this apparent beneficial outcome, obtaining obliteration rates of 53% with combined treatment compared to 71% with SRS alone, four-year postoperative. A third group reported there was no difference between single and combined treatments and obtained complete obliteration of 70%-82%, ranging from three-five-years postoperative follow-up. In all the cases analyzed, obliteration rates improved with time. SAEs, such as persistent hemorrhage and permanent neurologic deficits (P-NDs), as well as mortality, were minimal during intraoperative and postoperative follow-ups. The problem of conflicting outcomes in combined treatments of AVM by EMBO/SRS exists. Previous investigators, however, have overlooked to address this issue satisfactorily. Our analysis found that the reported inconsistencies in AVM treatment outcomes are attributable to key factors making therapy unpredictable, which includes: the size of the AVM, nidus localization and accessibility of either Embo or radiation dose applied, certain Embo materials lowering obliteration rates by masking radioactive effect on the nidus during SRS and follow-up timing for obtaining obliteration rates determine the extent of obliteration. We have indicated critical factors which require consideration when planning strategies for treatment of AVM patients and have made suggestions of how to overcome such hurdles.

Visual Field Preservation in Surgery of Occipital Arteriovenous Malformations: A Prospective Study

OBJECTIVE

We reviewed our prospective study of patients with occipital arteriovenous malformations (AVMs) to assess whether the display of optic radiation diffusion tensor imaging (DTI) during neuronavigation-guided surgery can reduce the severity of postoperative visual field deficits (VFDs) and to evaluate the factors associated with visual field preservation.

METHODS

Forty-six consecutive patients with occipital AVMs were randomized in our study. DTI of the optic radiation was displayed during neuronavigation surgery in 24 patients. The other 22 patients were treated surgically without neuronavigation. Modified Rankin Scale (mRS) scores and visual fields were evaluated preoperatively, immediately after surgery, and at the last follow-up.

RESULTS

The patients' baseline characteristics and AVM features were statistically similar between the 2 surgical groups. The postoperative obliteration rate was 100%. The postoperative mRS scores did not differ between the 2 groups (P > 0.05). Preexisting VFDs were more common (P = 0.00004) in patients who bled than in those with unruptured AVMs. The application of DTI-incorporated neuronavigation reduced the frequency and severity of postoperative VFDs (P = 0.013 and 0.001, respectively). Visual fields were more likely to be preserved in patients with an AVM >5 mm from the optic radiation (P = 0.025).

CONCLUSIONS

A history of hemorrhage is an independent risk factor for VFDs associated with occipital AVMs. Although not showing superiority in postoperative mRS, functional MRI navigation-guided surgery may help to radically resect occipital AVMs and preserve patient visual fields. A 5-mm distance from the optic radiation may be a suitable safety margin for visual field preservation.

Stereotactic radiosurgery for arteriovenous malformations of the postgeniculate visual pathway

OBJECT

A visual field deficit resulting from the management of an arteriovenous malformation (AVM) significantly impacts a patient's quality of life. The present study was designed to investigate the clinical and radiological outcomes of stereotactic radiosurgery (SRS) performed for AVMs involving the postgeniculate visual pathway.

METHODS

In this retrospective single-institution analysis, the authors reviewed their experience with Gamma Knife surgery for postgeniculate visual pathway AVMs performed during the period between 1987 and 2009.

RESULTS

During the study interval, 171 patients underwent SRS for AVMs in this region. Forty-one patients (24%) had a visual deficit prior to SRS. The median target volume was 6.0 cm3 (range 0.4–22 cm3), and 19 Gy (range 14–25 Gy) was the median margin dose. Obliteration of the AVM was confirmed in 80 patients after a single SRS procedure at a median follow-up of 74 months (range 5–297 months). The actuarial rate of total obliteration was 67% at 4 years. Arteriovenous malformations with a volume < 5 cm3 had obliteration rates of 60% at 3 years and 79% at 4 years. The delivered margin dose proved significant given that 82% of patients receiving ≥ 22 Gy had complete obliteration. The AVM was completely obliterated in an additional 18 patients after they underwent repeat SRS. At a median of 25 months (range 11–107 months) after SRS, 9 patients developed new or worsened visual field deficits. One patient developed a complete homonymous hemianopia, and 8 patients developed quadrantanopias. The actuarial risk of sustaining a new visual deficit was 3% at 3 years, 5% at 5 years, and 8% at 10 years. Fifteen patients had hemorrhage during the latency period, resulting in death in 9 of the patients. The annual hemorrhage rate during the latency interval was 2%, and no hemorrhages occurred after confirmed obliteration.

CONCLUSIONS

Despite an overall treatment mortality of 5%, related to latency interval hemorrhage, SRS was associated with only a 5.6% risk of new visual deficit and a final obliteration rate close to 80% in patients with AVMs of the postgeniculate visual pathway.

Embolization and radiosurgery for arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) requires a multidisciplinary management including microsurgery, endovascular embolization, and stereotactic radiosurgery (SRS). This article reviews the recent advancements in the multimodality treatment of patients with AVMs using endovascular neurosurgery and SRS. We describe the natural history of AVMs and the role of endovascular and radiosurgical treatment as well as their interplay in the management of these complex vascular lesions. Also, we present some representative cases treated at our institution.

Pretreatment predictors of adverse radiation effects after radiosurgery for arteriovenous malformation

PURPOSE

To identify vascular and dosimetric predictors of symptomatic T2 signal change and adverse radiation effects after radiosurgery for arteriovenous malformation, in order to define and validate preexisting risk models.

METHODS AND MATERIALS

A total of 125 patients with arteriovenous malformations (AVM) were treated at our institution between 2005 and 2009. Eighty-five patients have at least 12 months of clinical and radiological follow-up. Any new-onset headaches, new or worsening seizures, or neurological deficit were considered adverse events. Follow-up magnetic resonance images were assessed for new onset T2 signal change and the volume calculated. Pretreatment characteristics and dosimetric variables were analyzed to identify predictors of adverse radiation effects.

RESULTS

There were 19 children and 66 adults in the study cohort, with a mean age of 34 (range 6-74). Twenty-three (27%) patients suffered adverse radiation effects (ARE), 9 patients with permanent neurological deficit (10.6%). Of these, 5 developed fixed visual field deficits. Target volume and 12 Gy volume were the most significant predictors of adverse radiation effects on univariate analysis (p < 0.001). Location and cortical eloquence were not significantly associated with the development of adverse events (p = 0.12). No additional vascular parameters were identified as predictive of ARE. There was a significant target volume threshold of 4 cm(3), above which the rate of ARE increased dramatically. Multivariate analysis target volume and the absence of prior hemorrhage are the only significant predictors of ARE. The volume of T2 signal change correlates to ARE, but only target volume is predictive of a higher volume of T2 signal change.

CONCLUSIONS

Target volume and the absence of prior hemorrhage is the most accurate predictor of adverse radiation effects and complications after radiosurgery for AVMs. A high percentage of permanent visual field defects in this series suggest the optic radiation is a critical radiosensitive structure.

The place for surgical treatment for AVM involving the temporal lobe

OBJECTIVE

The objective of this study was to analyze preoperative symptoms and late clinical outcomes in patients who underwent surgical treatment of arterio-venous malformations (AVMs) of the temporal lobe, including those involving the Sylvian fissure (SF) and the lateral wall of the inferior ventricular horns-with special respect to postoperative hemiparesis and visual field defects (VFD).

METHODS

Between 1990 and 2007, 44 patients (n = 22 women, n = 22 men) with a mean age of 41 (12-67) years were operated on an AVM of the temporal lobe. All data had been collected prospectively. Patients' charts, as well as surgical reports and outpatient files, were analyzed. Thirteen patients showed an involvement of the SF, and six were localized partially in the lateral wall of the temporal horn. Eight AVMs were located in the temporo-mesial region. Fourteen patients had an AVM located mainly within the visual pathway. In 24 cases, the AVM was located in the dominant hemisphere. The AVMs were classified by the Spetzler-Martin grading system (SM). Visual fields were assessed in all patients pre- and postoperatively by independent ophthalmological examiners.

RESULTS

The initial symptoms leading to the diagnosis of the AVM were seizures in 20 cases (45%), headache without hemorrhage in six cases (14%), incidental finding in five cases (11%), and tinnitus in two cases (5%). Hemorrhage had occurred in 15 cases (34%). Based on SM, 7 AVMs were grade I, 17 grade II, 17 grade III, and 3 grade IV. Preoperatively, seven patients presented with a VFD and two with a hemiparesis. Postoperatively, 8 of 44 (18%) patients presented with a new hemiparesis, remaining permanent in 3 of 44 (7%). In two of these patients, the AVMs were localized temporo-mesially (n = 2/8, 25%). Seven patients (19%) showed a new significant postoperative VFD, and in addition, three patients had worsening of their preexisting VFD (3/7, 43%). Postoperative angiography verified complete AVM occlusion in 43 of 44 (98%) cases. One patient needed reoperation for residual AVM; hence, in all patients, complete occlusion before discharge was achieved.

CONCLUSION

Treatment of temporal lobe AVMs is demanding due to their close spatio-anatomical relationship with important neurovascular structures and the optic radiation. In this surgically treated series, morbidity for a new permanent hemiparesis was 7% and preservation of the visual field could be achieved in almost 90% of all cases. This is a calculable risk for most patients that renders microsurgical resection a justifiable option, even in light of other treatment modalities. The risk for new permanent motor deficits is elevated in temporo-mesial AVMs, and these patients have to be advised accordingly for surgical treatment.

Multidisciplinary care of occipital arteriovenous malformations: effect on nonhemorrhagic headache, vision, and outcome in a series of 135 patients

Object

In this study, the authors evaluated how an appropriate allocation of patients with occipital arteriovenous malformations (AVMs) who were treated according to different strategies would affect nonhemorrhagic headache, visual function, and hemorrhage risk levels.

Methods

Of the 712 patients with brain AVMs in the Toronto Western Hospital prospective database, 135 had occipital AVMs. The treatment decision was based on patients' characteristics, presentation, and morphology of the AVM. The management modalities were correlated with their outcomes.

Results

The mean follow-up period was 6.78 years. Nonhemorrhagic headache was the most frequent symptom (82 [61%] of 135 patients). Ninety-four patients underwent treatment with one or a combination of embolization, surgery, or radiosurgery, and 41 were simply observed. Of the 40 nontreated patients with nonhemorrhagic headache, only 12 (30%) showed improvement. In the observation group 2 patients (22%) had worsening of visual symptoms, and 2 experienced hemorrhage, for an annual hemorrhage rate of 0.7% per year; 1 patient died. In the treatment group, the improvement in nonhemorrhagic headache in 35 patients (83%) was significant (p < 0.0001). Visual deficit at presentation worsened in 2 (8%), and there were 8 new visual field deficits (9%). The visual worsening was not significantly different. There were 2 other neurological deficits (2%) and 2 deaths (2%) related to the AVM treatment. One AVM hemorrhaged. The annual hemorrhage rate was 0.1% per year. The hemorrhage risk in the observation and treatment groups was lower than the observed hemorrhage risk of all patients with AVMs (4.6%) at the authors' institution.

Conclusions

Appropriate selection of patients with occipital AVMs for one or a combination of treatment modalities yields a significant decrease in nonhemorrhagic headache without significant visual worsening. The multidisciplinary care of occipital AVMs can aim for an apparent decrease in hemorrhage risk.

Radiosurgical considerations in the treatment of large cerebral arteriovenous malformations

OBJECTIVE

In order to establish the role of Gamma Knife radiosurgery (GKS) in large intracranial arteriovenous malformations (AVMs), we analyzed clinical characteristics, radiological features, and radiosurgical outcomes.

METHODS

Between March 1992 and March 2005, 28 of 33 patients with large AVMs (> 10 cm(3) in nidus-volume) who were treated with GKS underwent single session radiosurgery (RS), and the other 5 patients underwent staged volumetric RS. Retrospectively collected data were available in 23 cases. We analyzed treatment outcomes in each subdivided groups and according to the AVM sizes. We compared the estimated volume, defined as primarily estimated nidus volume using MR images, with real target volume after excluding draining veins and feeding arteries embedded into the nidus.

RESULTS

Regarding those patients who underwent single session RS, 44.4% (8/18) had complete obliteration; regarding staged volumetric RS, the obliteration rate was 40% (2/5). The complete obliteration rate was 60% (6/10) in the smaller nidus group (10-15 cm(3) size), and 25% (2/8) in the larger nidus group (over 15 cm(3) size). One case of cerebral edema and two cases (8.7%) of hemorrhage were seen during the latent period. The mean real target volume for 18 single sessions of RS was 17.1 cm(3) (10.1-38.4 cm(3)), in contrast with the mean estimated volume of 20.9 cm(3) (12.0-45.0 cm(3)).

CONCLUSION

The radiosurgical treatment outcomes of large AVMs are generally poor. However, we presume that the recent development in planning software and imaging devices aid more accurate measurement of the nidus volume, therefore improving the treatment outcome.

Optic radiation tractography integrated into simulated treatment planning for Gamma Knife surgery

OBJECT

No definitive method of preventing visual field deficits after stereotactic radiosurgery for lesions near the optic radiation (OR) has been available so far. The authors report the results of integrating OR tractography based on diffusion tensor (DT) magnetic resonance imaging into simulated treatment planning for Gamma Knife surgery (GKS).

METHODS

Data from imaging studies performed in 10 patients who underwent GKS for treatment of arteriovenous malformations (AVMs) located adjacent to the OR were used for the simulated treatment planning. Diffusion tensor images performed without the patient's head being secured by a stereotactic frame were used for DT tractography, and the OR was visualized by means of software developed by the authors. Data from stereotactic 3D imaging studies performed after frame fixation were coregistered with the data from DT tractography. The combined images were transferred to a GKS treatment-planning workstation. Delivered doses and distances between the treated lesions and the OR were analyzed and correlated with posttreatment neurological changes.

RESULTS

In patients presenting with migraine with visual aura or occipital lobe epilepsy, the OR was located within 11 mm from AVMs. In a patient who developed new quadrantanopia after GKS, the OR had received 32 Gy. A maximum dose to the OR of less than 12 Gy did not cause new visual field deficits. A maximum dose to the OR of 8 Gy or more was significantly related to neurological change (p < 0.05), including visual field deficits and development or improvement of migraine.

CONCLUSIONS

Integration of OR tractography into GKS represents a promising tool for preventing GKS-induced visual disturbances and headaches. Single-session irradiation at a dose of 8 Gy or more was associated with neurological change.

Stereotactic Radiosurgery of the Rete Mirabile in Swine: A Longitudinal Study of Histopathological Changes

OBJECTIVE:

Stereotactic radiosurgery is an established, effective treatment for brain arteriovenous malformations. The mechanisms of vessel occlusion in arteriovenous malformations has not been extensively evaluated. To better understand these mechanisms, we report histopathological changes in the swine rete mirabile after stereotactic radiosurgery.

METHODS:

Thirty-five swine were used, 15 as nonradiated controls and 20 as radiated. Two in the control group and five in the radiated group were sacrificed before the study endpoint. Tissue was obtained from 13 nonradiated (4 at 3 mo, 5 at 6 mo, 4 at 9 mo) and 15 radiated swine (2 at 3 mo, 3 at 6 mo, 10 at 9 mo) for histological, immunohistochemical, and morphometric analysis.

RESULTS:

Radiated vessels showed increasing intimal hyperplasia over the follow-up period. Histometrical analysis confirmed this with evidence of progressive luminal narrowing over the follow-up period. Immunohistochemical analysis showed intimal cells to be proliferating smooth muscle cells with surrounding extracellular collagen Type IV. Adventitial fibrosis composed of collagen Type IV was also seen with smooth muscle cells interspersed within the collagen matrix. The nonradiated animals showed no intimal hyperplasia or change in the appearance or size of the vessels over the same follow-up period. Adventitial fibrosis was minimal in the nonradiated animals.

CONCLUSION:

The vessels show an intimal response to radiation with progressive occlusion caused by migrating, proliferating smooth muscle cells, a likely source of the extracellular collagen in the intima. Cytokine mediated pathways likely produce these morphological changes. Future studies will be directed toward elucidating these underlying molecular mechanisms.

Natural history, evaluation, and management of intracranial vascular malformations

Intracranial vascular malformations are seen increasingly in clinical practice, primarily because of advances in cross-sectional brain and spinal cord imaging. Commonly encountered lesion types include arteriovenous malformations, cavernous malformations, venous malformations, dural arteriovenous fistulas, and capillary telangiectasias. Patients can experience various symptoms and signs at presentation. The natural history of vascular malformations depends on lesion type, location, size, and overall hemodynamics. The natural history for each lesion subtype is reviewed, with special consideration of the risk of hemorrhage or other adverse outcomes after the lesion is detected and any known predictors of hemorrhage or other outcomes. In practice, these data are compared with the risk of available treatment options as the optimal management is clarified. A multidisciplinary approach including neurosurgery, radiosurgery, interventional neuroradiology, and vascular neurology is most useful in determining the best management strategy.

Headaches in patients with radiosurgically treated occipital arteriovenous malformations

OBJECT

The goal of this study was to determine the prevalence, characteristics, and radiosurgical outcomes of headaches associated with occipital arteriovenous malformations (AVMs).

METHODS

The authors reviewed the medical records of 37 consecutive patients with occipital AVMs who had been treated by radiosurgery to identify the radiological features of the AVMs before and after treatment and the clinical features and outcomes of headaches described in accordance with the criteria of the International Headache Society (IHS). Thirty-six patients (97.3%) were followed for a mean period of 46.6 months. The median volume of the AVMs was 1.9 cm3, to which a mean radiation dose of 21.6 Gy was delivered. In the entire study group, periodic headaches were found in 17 patients (45.9%), of whom seven (18.9%) suffered from migraines with the characteristic visual aura. Migraine was predominantly found in patients with right-sided (p = 0.038) or laterally located (p = 0.025) AVMs. Factors associated with a higher incidence of any type of headache included larger nidus volume (p = 0.02), tortuous change of feeding artery (p = 0.036), and cortical drainage with reflux in the superior sagittal sinus (p = 0.032). The actuarial rate of angiographic obliteration was 71.6% at 3 years. Headaches resolved or improved in 12 (70.6%) of 17 patients, including six (85.7%) of seven with migraine. The outcome of headache closely correlated with the obliteration results of the AVM (p = 0.002).

CONCLUSIONS

A portion of occipital AVMs do cause headaches that satisfy the current IHS criteria for migraine, and the prevalence varies by the topography of the lesion. Radiosurgery can resolve headaches in the majority of treated patients.

Stereotactic radiosurgical pallidotomy and thalamotomy with the gamma knife: MR imaging findings with clinical correlation--preliminary experience

PURPOSE

To evaluate the temporal evolution and appearance of a radiosurgical lesion at magnetic resonance (MR) imaging and the clinical response in patients undergoing stereotactic radiosurgical pallidotomy or thalamotomy with the gamma knife.

MATERIALS AND METHODS

Seventeen patients with medically refractory movement disorders underwent stereotactic radiosurgical pallidotomy (n = 2) or thalamotomy (n = 15). A single dose of 120-140 Gy was administered to a target in the globus pallidus interna or ventralis intermedius thalamic nucleus. Postprocedure gadolinium-enhanced MR imaging and clinical assessment were performed at 1 month and 3 months.

RESULTS

At 3 months, the radiosurgical lesion most commonly (n = 11) appeared as a ring-enhancing focus 5 mm or less in diameter surrounded by vasogenic edema that extended less than 7 mm in radius beyond the target. Five patients had ring-enhancing lesions 7 mm or more in diameter; four of these developed symptomatic perilesional edema at 3 (n = 2) or 8 (n = 2) months after the procedure. Onset of therapeutic effect began approximately 4 weeks after treatment. In the 15 patients with tremor, there was a mean decline of 2.1 on the Tremor Rating Scale.

CONCLUSION

Findings in this pilot study suggest that radiosurgical thalamotomy is a promising treatment for medically refractory tremor. Three-month follow-up MR studies show a ring-enhancing lesion surrounded by a variable amount of vasogenic edema. Visualization of the radiosurgical lesion and the clinical response are delayed compared to that with radio-frequency procedures.

[Arteriovenous malformations of the central nervous system. Analysis of 53 cases]

Fifty-three patients with arteriovenous malformation (AVM) were studied. The mean age at the time of diagnosis was 32.5 +/- 11.5 years (range 3 to 56 years); the sex ratio was male 1.9:1 female. The most common clinical presentation was intracranial hemorrhage, followed by focal neurological signs, headache, epilepsy, and acute deep coma. Fourty-three (82%) out of the total number of AVM were supratentorial and had the following distribution: 10 temporal lobe, 9 pariental lobe, 6 frontal lobe, 3 occipital lobe, 3 frontotemporal, 4 corpus callosum/pericalosal, 1 temporo-occipital, 1 temporoparieto-occipital, 6 deep-located (3 thalamic, 3 basal ganglia). Spetzler-Martin grade II was seen in 17 cases (32%), grade III in 21 cases (39%), and grade IV in 10 cases (19%). AVM-associated aneurysms were detected in 3 patients (5.6%). All three cases were middle artery aneurysms ipsilateral to AVM. Twelve (32%) out of 37 operated patients were submitted to embolization prior to surgery. AVM was totally removed in all cases except one. Embolization without posterior surgery was used in 11 patients; in 3 of them, embolization was partial. Two patients were neither embolized nor operated on. Three patients were, submitted to radiosurgery because they were poor candidates to embolization and/or surgery. Mortality rate was 1.8%. All patients returned to their normal life function after a period of recovery. Associated or isolated therapies should be individualized to each patient with AVM and is likely to provide results better than the expected outcome without any treatment.

The Mayo Clinic gamma knife experience: indications and initial results

OBJECTIVE

To review the results and expectations of contemporary stereotactic radiosurgery.

MATERIAL AND METHODS

We conducted a retrospective analysis of 1,033 consecutive patients who underwent gamma knife radiosurgery at Mayo Clinic Rochester between January 1990 and January 1998.

RESULTS

The number of patients undergoing radiosurgery increased from 57 in 1990 to 216 in 1997. Of 97 patients with arteriovenous malformations who underwent follow-up angiography 2 years or more after a single radiosurgical procedure, 72 (74%) had complete obliteration of the vascular malformation. Of 209 patients who underwent radiosurgery for benign tumors (schwannomas, meningiomas, or pituitary adenomas) and had radiologic studies after 2 years or more of follow-up, tumor growth control was noted in 200 (96%). Tumor growth was also controlled in 90% of brain metastatic lesions at a median of 7 months after radiosurgery. Of 20 patients with trigeminal neuralgia and follow-up for more than 2 months, 14 (70%) were free of pain after radiosurgery.

CONCLUSION

Radiosurgery is a safe and effective management strategy for a wide variety of intracranial disorders. Use of radiosurgical treatment should continue to increase as more data become available on the long-term results of this procedure.

Occipital lobe vascular malformations: prevalence of visual field deficits and prognosis after therapeutic intervention

BACKGROUND

The prevalence of visual field (VF) deficits in association with vascular malformations of the occipital lobe is not known, and the prognosis of the VF after therapeutic intervention has not been systematically documented.

METHODS

We reviewed the clinical records of 23 consecutive patients who were managed at a single institution during a 3-year period with intracranial vascular malformations extending within the anatomic borders of the occipital lobe. Lesion location and treatment rendered were correlated with formal VF testing performed before and after therapeutic intervention.

RESULTS

Twenty-one of the 23 patients underwent treatment of their lesions. Treatment included resection after preoperative embolization (12 patients), resection alone (2 patients with arteriovenous malformations and 3 patients with cavernous malformations), and stereotactic radiosurgery (4 patients; preceded by embolization in 3 of the 4). One patient was followed expectantly, and another died as a result of hemorrhage soon after undergoing endovascular embolization. The VFs were assessed before and after therapeutic intervention (follow-up assessment, 2-29 mo). New VF deficits or worsening of preexisting VF deficits were documented in 5 of the 21 treated patients (24%), but only 2 of these patients (9.5%) had persistent deficits at the time of their follow-up examinations. Among the 10 patients with pretreatment VF deficits, 5 improved and the other 5 were unchanged after treatment.

CONCLUSION

Patients with occipital lobe vascular malformations frequently present with associated VF deficits. Surgical resection or stereotactic radiosurgery (with or without previous embolization) of these lesions can be performed with little risk of causing new VF deficits or worsening of preexisting ones. Many VF deficits can be expected to improve or resolve after therapy.

[Radiosurgery of cerebral arteriovenous malformations. Therapeutic strategies]

Modalities of management of arterio-venous malformations are discussed according to natural history and size of lesion, patient clinical status, and potential side effects of available techniques (microsurgery, radiosurgery, ambolization). Clinical cases illustrate this discussion.