Ultrastructural changes in arteriovenous malformations after gamma knife surgery: an electron microscopic study

2005 ◽  
Vol 102 ◽  
pp. 289-292 ◽  
Author(s):  
György T. Szeifert ◽  
Ottó Major ◽  
Andras A. Kemeny
Keyword(s):  
Electron Microscopy ◽  
Gamma Knife ◽  
Cell Population ◽  
Arteriovenous Malformations ◽  
Spindle Cell ◽  
Gamma Knife Surgery ◽  
Ultrastructural Changes ◽  
Electron Microscopic ◽  
Content Type ◽  
Fine Print

Object.The authors analyzed morphological alterations at the subcellular level by undertaking transmission electron microscopy in arteriovenous malformations (AVMs) after gamma knife surgery (GKS).Methods.Histological, immunohistochemical, and electron microscopic investigations were performed in a series of pathological specimens obtained in seven patients. The patients harbored cerebral AVMs that had been previously treated with GKS and had suffered subsequent bleeding 10 to 52 months after treatment.Histological studies revealed spindle cell proliferation in the connective tissue stroma and in the subendothelial region of the irradiated AVM vessels. Electron microscopy demonstrated different ultrastructural characteristics of this spindle cell population. There were cells with a smooth-edged oval nuclei surrounded by massive bundles of collagen fibers in the extracellular matrix. Other cells with the same nuclear morphology contained abundant intracytoplasmic filaments. Nuclear deformation was connected to a fibrillary system developed within the cytoplasm, and peripheral attachment sites were related to an extracellular layer of basement membrane—like material arranged parallel to the cell border. Also present were cells containing well-developed cisterns of rough endoplasmic reticulum and dense bodies at the periphery of the cytoplasm with folded, irregular nuclei.Conclusions.The ultrastructural and histological characteristics of the spindle cell population in the GKS-treated AVMs are similar to those designated as myofibroblasts in wound healing processes and pathological fibromatoses. Because similar cell modifications have not been demonstrated in control nonirradiated AVM specimens, these myofibroblasts may contribute to the shrinking process and final occlusion of AVMs after radiosurgery.

Ultrastructural changes in arteriovenous malformations after gamma knife surgery: an electron microscopic study

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 289-292 ◽  
Author(s):  
György T. Szeifert ◽  
Ottó Major ◽  
Andras A. Kemeny
Keyword(s):  
Electron Microscopy ◽  
Gamma Knife ◽  
Cell Population ◽  
Arteriovenous Malformations ◽  
Spindle Cell ◽  
Gamma Knife Surgery ◽  
Ultrastructural Changes ◽  
Electron Microscopic ◽  
Content Type ◽  
Fine Print

Object. The authors analyzed morphological alterations at the subcellular level by undertaking transmission electron microscopy in arteriovenous malformations (AVMs) after gamma knife surgery (GKS). Methods. Histological, immunohistochemical, and electron microscopic investigations were performed in a series of pathological specimens obtained in seven patients. The patients harbored cerebral AVMs that had been previously treated with GKS and had suffered subsequent bleeding 10 to 52 months after treatment. Histological studies revealed spindle cell proliferation in the connective tissue stroma and in the subendothelial region of the irradiated AVM vessels. Electron microscopy demonstrated different ultrastructural characteristics of this spindle cell population. There were cells with a smooth-edged oval nuclei surrounded by massive bundles of collagen fibers in the extracellular matrix. Other cells with the same nuclear morphology contained abundant intracytoplasmic filaments. Nuclear deformation was connected to a fibrillary system developed within the cytoplasm, and peripheral attachment sites were related to an extracellular layer of basement membrane—like material arranged parallel to the cell border. Also present were cells containing well-developed cisterns of rough endoplasmic reticulum and dense bodies at the periphery of the cytoplasm with folded, irregular nuclei. Conclusions. The ultrastructural and histological characteristics of the spindle cell population in the GKS-treated AVMs are similar to those designated as myofibroblasts in wound healing processes and pathological fibromatoses. Because similar cell modifications have not been demonstrated in control nonirradiated AVM specimens, these myofibroblasts may contribute to the shrinking process and final occlusion of AVMs after radiosurgery.

Long-term complications after gamma knife surgery for arteriovenous malformations

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 34-37 ◽  
Author(s):  
Masahiro Izawa ◽  
Motohiro Hayashi ◽  
Mikhail Chernov ◽  
Koutarou Nakaya ◽  
Taku Ochiai ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Cyst Formation ◽  
Gamma Knife Surgery ◽  
Content Type ◽  
Delayed Hemorrhage ◽  
Complete Obliteration ◽  
Risk Of Hemorrhage ◽  
Fine Print

Object. The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs). Methods. Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05). Conclusions. Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

Late cyst formation following gamma knife surgery of arteriovenous malformations

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 124-127 ◽  
Author(s):  
Hung-Chuan Pan ◽  
Jason Sheehan ◽  
Matei Stroila ◽  
Melita Steiner ◽  
Ladislau Steiner
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Cox Regression ◽  
Cyst Formation ◽  
Senior Author ◽  
Gamma Knife Surgery ◽  
Content Type ◽  
Lost To Follow Up ◽  
Fine Print

Object. The authors present data concerning the development of cysts following gamma knife surgery (GKS) in 1203 consecutive patients with arteriovenous malformations (AVMs) treated by the senior author (L.S.). The cyst was defined as a fluid-filled cavity at the site of a treated AVM. Cases involving regions corresponding to previous hematoma cavities were excluded. The incidence of cyst formation was assessed using magnetic resonance imaging studies performed in 196 cases with more than 10 years of follow up, in 332 cases with 5 to 10 years of follow up, and in 675 cases with less than 5 years of follow up. One hundred five cases were lost to follow-up study. The Cox regression method was used to analyze the factors related to cyst formation. Methods. The incidence of cyst formation in the entire patient population was 1.6 and 3.6% in those undergoing follow-up examination for more than 5 years. Ten of 20 cysts developed between 10 to 23 years, nine between 5 to 10 years, and one in less than 5 years following the treatment. Cyst fluid aspiration, cystoperitoneal shunt placement, or craniotomy were used in three symptomatic cases. Analysis of age, sex, and treatment parameters yielded no significant relationship with cyst formation; however, radiation-induced tissue change following GKS (p = 0.027) and prior embolization (p = 0.011) were related to cyst formation. Conclusions. Overall, the incidence of cyst formation in patients who underwent GKS for AVM was 1.6%. The development of the cyst was related to the duration of the follow-up period. When cysts are symptomatic, surgical intervention should be performed.

Gamma knife surgery for arteriovenous malformations involving the corpus callosum

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 49-52 ◽  
Author(s):  
Keisuke Maruyama ◽  
Masahiro Shin ◽  
Masao Tago ◽  
Hiroki Kurita ◽  
Shunsuke Kawamoto ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Surgery ◽  
Low Risk ◽  
Patient Age ◽  
Content Type ◽  
Patient Âgé ◽  
Vascular Structures ◽  
Fine Print

Object. The purpose of this study was to evaluate the safety and efficacy of gamma knife surgery (GKS) for the treatment of arteriovenous malformations (AVMs) involving the corpus callosum. Methods. Thirty-two patients aged from 7 to 65 years (median 25 years) with AVMs of the corpus callosum underwent GKS between 1990 and 2002. The maximum AVM diameter was more than 3 cm in 11 patients (34%). The AVM volume ranged from 0.1 to 19.1 cm3 (median 1.6 cm3). The median dose to the AVM margin was 20 Gy (range 17–28 Gy). Patients were followed for 1 to 12 years (median 9 years). The angiographically confirmed actuarial obliteration rate was 64% and 74% at 4 and 6 years, respectively. Younger patient age (p < 0.05) and lower radiosurgery-based grading score (calculated from the patient age and AVM volume; p < 0.01) were the significant factors affecting successful AVM obliteration. No patient suffered a hemorrhage after GKS, although 28 patients (88%) had a history of hemorrhage from their AVMs. Radiation-induced neurological deficit was observed only in one patient (3%) who had undergone previous radiotherapy (50 Gy). No patient experienced complications of occlusion or stenosis of the normal vascular structures adjacent to the AVM. Conclusions. Gamma knife surgery is a safe and effective treatment for selected patients with AVMs involving the corpus callosum, and it carries a low risk of damaging adjacent critical vascular structures. Even ruptured AVMs with relatively large diameter can be successfully treated, especially in younger patients, with minimal morbidity and a low risk of repeated hemorrhage.

Analysis of nidus obliteration rates after gamma knife surgery for arteriovenous malformations based on long-term follow-up data: the University of Tokyo experience

2004 ◽  
Vol 101 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Masahiro Shin ◽  
Keisuke Maruyama ◽  
Hiroki Kurita ◽  
Shunsuke Kawamoto ◽  
Masao Tago ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Imaging Modality ◽  
Gamma Knife Surgery ◽  
Imaging Data ◽  
Mr Images ◽  
Content Type ◽  
Dose Planning ◽  
Fine Print

Object. A large number of clinical studies have been made on treatment outcomes of radiosurgery for arteriovenous malformations (AVMs), but the reported obliteration rates following this treatment vary significantly, perhaps reflecting the different methods and timings of the imaging studies used. Methods. The authors retrospectively analyzed their experience with gamma knife surgery in 400 patients with AVMs (follow-up period 1–135 months, median 65 months), with special reference to the imaging modality used in each case. The calculated obliteration rates varied from 68.2 to 92%, depending on imaging modality and timing of evaluation. When only unquestionable imaging data such as demonstrations of a residual nidus on computerized tomography (CT) or magnetic resonance (MR) images or findings on angiograms were used in the calculation, the obliteration rates were 72% at 3 years and 87.3% at 5 years. Factors leading to a better obliteration rate were previous hemorrhage (p = 0.0084), smaller nidus (p = 0.0023), and higher radiation dose to the lesion's margin (p = 0.0495), as determined in a multivariate analysis. Factors leading to an earlier obliteration of the nidus were male sex (p = 0.0001), previous hemorrhage (p = 0.0039), smaller nidus diameter (p = 0.0006), and dose planning using angiography alone (p = 0.0201). Conclusions. After the introduction of CT and MR images into dose planning, the conformity and selectivity of dosimetry improved remarkably, although the latency intervals until obliteration were prolonged. Imaging outcomes for AVMs should be evaluated using data provided by longer follow-up periods. The timing of additional treatments for residual AVMs should be decided cautiously, considering the size of the AVM, the patient age and sex, and the history of hemorrhage before radiosurgery.

Long-term complications after gamma knife surgery for arteriovenous malformations

2005 ◽  
Vol 102 ◽  
pp. 34-37 ◽  
Author(s):  
Masahiro Izawa ◽  
Motohiro Hayashi ◽  
Mikhail Chernov ◽  
Koutarou Nakaya ◽  
Taku Ochiai ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Cyst Formation ◽  
Gamma Knife Surgery ◽  
Content Type ◽  
Delayed Hemorrhage ◽  
Complete Obliteration ◽  
Risk Of Hemorrhage ◽  
Fine Print

Object. The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs). Methods. Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05). Conclusions. Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

Gamma knife surgery for arteriovenous malformations involving the corpus callosum

2005 ◽  
Vol 102 ◽  
pp. 49-52 ◽  
Author(s):  
Keisuke Maruyama ◽  
Masahiro Shin ◽  
Masao Tago ◽  
Hiroki Kurita ◽  
Shunsuke Kawamoto ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Surgery ◽  
Low Risk ◽  
Patient Age ◽  
Content Type ◽  
Patient Âgé ◽  
Vascular Structures ◽  
Fine Print

Object. The purpose of this study was to evaluate the safety and efficacy of gamma knife surgery (GKS) for the treatment of arteriovenous malformations (AVMs) involving the corpus callosum. Methods. Thirty-two patients aged from 7 to 65 years (median 25 years) with AVMs of the corpus callosum underwent GKS between 1990 and 2002. The maximum AVM diameter was more than 3 cm in 11 patients (34%). The AVM volume ranged from 0.1 to 19.1 cm3 (median 1.6 cm3). The median dose to the AVM margin was 20 Gy (range 17–28 Gy). Patients were followed for 1 to 12 years (median 9 years). The angiographically confirmed actuarial obliteration rate was 64% and 74% at 4 and 6 years, respectively. Younger patient age (p < 0.05) and lower radiosurgery-based grading score (calculated from the patient age and AVM volume; p < 0.01) were the significant factors affecting successful AVM obliteration. No patient suffered a hemorrhage after GKS, although 28 patients (88%) had a history of hemorrhage from their AVMs. Radiation-induced neurological deficit was observed only in one patient (3%) who had undergone previous radiotherapy (50 Gy). No patient experienced complications of occlusion or stenosis of the normal vascular structures adjacent to the AVM. Conclusions. Gamma knife surgery is a safe and effective treatment for selected patients with AVMs involving the corpus callosum, and it carries a low risk of damaging adjacent critical vascular structures. Even ruptured AVMs with relatively large diameter can be successfully treated, especially in younger patients, with minimal morbidity and a low risk of repeated hemorrhage.

Late cyst formation following gamma knife surgery of arteriovenous malformations

2005 ◽  
Vol 102 ◽  
pp. 124-127 ◽  
Author(s):  
Hung-Chuan Pan ◽  
Jason Sheehan ◽  
Matei Stroila ◽  
Melita Steiner ◽  
Ladislau Steiner
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Cox Regression ◽  
Cyst Formation ◽  
Senior Author ◽  
Gamma Knife Surgery ◽  
Content Type ◽  
Lost To Follow Up ◽  
Fine Print

Object.The authors present data concerning the development of cysts following gamma knife surgery (GKS) in 1203 consecutive patients with arteriovenous malformations (AVMs) treated by the senior author (L.S.). The cyst was defined as a fluid-filled cavity at the site of a treated AVM. Cases involving regions corresponding to previous hematoma cavities were excluded. The incidence of cyst formation was assessed using magnetic resonance imaging studies performed in 196 cases with more than 10 years of follow up, in 332 cases with 5 to 10 years of follow up, and in 675 cases with less than 5 years of follow up. One hundred five cases were lost to follow-up study. The Cox regression method was used to analyze the factors related to cyst formation.Methods.The incidence of cyst formation in the entire patient population was 1.6 and 3.6% in those undergoing follow-up examination for more than 5 years. Ten of 20 cysts developed between 10 to 23 years, nine between 5 to 10 years, and one in less than 5 years following the treatment. Cyst fluid aspiration, cystoperitoneal shunt placement, or craniotomy were used in three symptomatic cases. Analysis of age, sex, and treatment parameters yielded no significant relationship with cyst formation; however, radiation-induced tissue change following GKS (p = 0.027) and prior embolization (p = 0.011) were related to cyst formation.Conclusions.Overall, the incidence of cyst formation in patients who underwent GKS for AVM was 1.6%. The development of the cyst was related to the duration of the follow-up period. When cysts are symptomatic, surgical intervention should be performed.

Gamma knife radiosurgery as a single treatment modality for large cerebral arteriovenous malformations

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 113-119 ◽  
Author(s):  
D. Hung-Chi Pan ◽  
Wan-Yuo Guo ◽  
Wen-Yuh Chung ◽  
Cheng-Ying Shiau ◽  
Yue-Cune Chang ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Radiation Treatment ◽  
Gamma Knife Radiosurgery ◽  
Consecutive Series ◽  
Content Type ◽  
Obliteration Rate ◽  
Complete Obliteration ◽  
Fine Print

Object. A consecutive series of 240 patients with arteriovenous malformations (AVMs) treated by gamma knife radiosurgery (GKS) between March 1993 and March 1999 was evaluated to assess the efficacy and safety of radiosurgery for cerebral AVMs larger than 10 cm3 in volume. Methods. Seventy-six patients (32%) had AVM nidus volumes of more than 10 cm3. During radiosurgery, targeting and delineation of AVM nidi were based on integrated stereotactic magnetic resonance (MR) imaging and x-ray angiography. The radiation treatment was performed using multiple small isocenters to improve conformity of the treatment volume. The mean dose inside the nidus was kept between 20 Gy and 24 Gy. The margin dose ranged between 15 to 18 Gy placed at the 55 to 60% isodose centers. Follow up ranged from 12 to 73 months. There was complete obliteration in 24 patients with an AVM volume of more than 10 cm3 and in 91 patients with an AVM volume of less than 10 cm3. The latency for complete obliteration in larger-volume AVMs was significantly longer. In Kaplan—Meier analysis, the complete obliteration rate in 40 months was 77% in AVMs with volumes between 10 to 15 cm3, as compared with 25% for AVMs with a volume of more than 15 cm3. In the latter, the obliteration rate had increased to 58% at 50 months. The follow-up MR images revealed that large-volume AVMs had higher incidences of postradiosurgical edema, petechiae, and hemorrhage. The bleeding rate before cure was 9.2% (seven of 76) for AVMs with a volume exceeding 10 cm3, and 1.8% (three of 164) for AVMs with a volume less than 10 cm3. Although focal edema was more frequently found in large AVMs, most of the cases were reversible. Permanent neurological complications were found in 3.9% (three of 76) of the patients with an AVM volume of more than 10 cm3, 3.8% (three of 80) of those with AVM volume of 3 to 10 cm3, and 2.4% (two of 84) of those with an AVM volume less than 3 cm3. These differences in complications rate were not significant. Conclusions. Recent improvement of radiosurgery in conjunction with stereotactic MR targeting and multiplanar dose planning has permitted the treatment of larger AVMs. It is suggested that gamma knife radiosurgery is effective for treating AVMs as large as 30 cm3 in volume with an acceptable risk.

Factors related to complete occlusion of arteriovenous malformations after gamma knife radiosurgery

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 96-101 ◽  
Author(s):  
Jong Hee Chang ◽  
Jin Woo Chang ◽  
Yong Gou Park ◽  
Sang Sup Chung
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Radiosurgery ◽  
Maximum Diameter ◽  
Content Type ◽  
Complete Occlusion ◽  
Factors Associated ◽  
Martin Grade ◽  
Fine Print

Object. The authors sought to evaluate the effects of gamma knife radiosurgery (GKS) on cerebral arteriovenous malformations (AVMs) and the factors associated with complete occlusion. Methods. A total of 301 radiosurgical procedures for 277 cerebral AVMs were performed between December 1988 and December 1999. Two hundred seventy-eight lesions in 254 patients who were treated with GKS from May 1992 to December 1999 were analyzed. Several clinical and radiological parameters were evaluated. Conclusions. The total obliteration rate for the cases with an adequate radiological follow up of more than 2 years was 78.9%. In multivariate analysis, maximum diameter, angiographically delineated shape of the AVM nidus, and the number of draining veins significantly influenced the result of radiosurgery. In addition, margin radiation dose, Spetzler—Martin grade, and the flow pattern of the AVM nidus also had some influence on the outcome. In addition to the size, topography, and radiosurgical parameters of AVMs, it would seem to be necessary to consider the angioarchitectural and hemodynamic aspects to select proper candidates for radiosurgery.

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