Changes of MR Images in Arteriovenous Malformations of Brain after Gamma-knife Radiosurgery

PURPOSE: To evaluate the changes in arteriovenous malformation(AVM) of the brain revealed by follow-up MR images after gamma-knife surgery. MATERIALS AND METHODS: In 25 patients with AVM of the brain who had undergone gamma-knife radiosurgery, 39 MR images were obtained during follow-up between 6 and 46 months later, and were reviewed. We evaluated changes volume of the nidus and in its enhancement patterns, changes in T1- and T2-weighted images of the regions in which the nidus had disappeared, and changes in adjacent brain. Conventional follow-up cerebral angiography was performed in seven patients, and the results were correlated with those obtained by M-RI. RESULT: On the MR images obtained as described, disappearance of signal void lesion within the nidus was observed in 16 of the 25 patients. In five of 16, the nidus was obliterated within 1 year of gamma-kinfe radio-surgery, and in the remaining 11 patients this happened after 1 year. In nine cases in which the nidus remained and 16 in which it was obliterated, follow-up examination of MR images revealed spot and mixed spot-nodular enhancement, with signal void lesion. Within the nidus, serial follow-up MR images showed increased enhancement, which was nodule-like. As seen on T1-weighted images, the lesions of obliterated nidus showed slightly lower or iso- signal intensity to gray matter in all 25 cases, while T2-weighted images revealed high signal intensity in 21 cases and iso-signal intensity in four. Abnormal high signal intensity adjacent to the brain was seen on T2 weighted images in nine of 25 cases. In six of seven cases in which cerebral angiography was performed, AVM was obliterated on both MRI and angiography. In one case, however, MR imaging showed that a signal void lesion remained. Cerebral angiography in this case revealed arteriovenous shunting. CONCLUSION: After gamma-knife surgery, early follow-up revealed that in AVM of the brain, a spot and mixed spot and nodular enhancement pattern was visible, with a reduced volume of signal void lesions. During later follow-up, an enhanced nodular pattern was revealed. Nodular enhancement without signal void lesion probably indicates complete regression of the nidus of AVM.

Radiologic Evaluation of the Therapeutic Effect of Gamma Knife Radiosurgery in Cerebral Vasular Malformation

PURPOSE: To evaluate the therapeutic effect of gamma knife radiosurgery in cerebral vascular malformationusing a radiologic imaging method such as MRI or angiography. MATERIALS AND METHODS: We retrospectively reviewedMRIs, Ct scans and angiograms of 29 cases of arteriovenous malformation and 15 of cavernous malformation beforeand after gamma knife radiosurgery. The patients underwent follow-up radiologic studies for between 6 and 35months after radiosurgery. No patient underwent ofter surgery of embolization. Radiological imaging analysisfocused on changes in the volume of the nidus or central core. Other findings of edema, cystic change, hemorrhage,signal intensity, enhancement and distributional vascular markings were also studied. The volume of the AVM niduswas measured and assigned ot one of four groups : 4-10cc and> 10cc. RESULTS: In arteriovenousmalformation cases, the volume of the nidus decreased by mean 60.2%; reduction was greatest(68.1%) in the 1-4ccgroup. Three cases showed complete loss of the nidus at 9, 12 and 25 months after radiosurgery, respectively. Innine cases, dereased caliber or loss of draining vein was noted. High signal intensity on T2-weighted MR images,suggesting either edema or demyelination, was observed in four cases. In cavernous angioma cases, core volume wasreduced by 36.8%. Transient cerebral edema and presumed radiation necrosis were observed in two cases and one,respectively. CONCLUSION: Gamma knife suregery was effective in nearly all cases of arteriovenous malformationand some cases of cavernous malformation. More than two years follow-up involving radiologic imaging such as MRIis needed for the evaluation of therapeutic effect and diagnosis of complications.

Analysis of Angiographic Findings in Arteriovenous Malformations (AVM) of Brain According to PresentingClinical Manifestations

PURPOSE: To evaluate the different angio-architectures of brain arteriovenour malformatigns (AVMs) accordingto the presence of non-hemorrhagic symptoms or intracerebral (ICH) and/or intraventricular hemorrhage(IVH). MATERIALS AND METHODS: The results of complete cerebral angiography obtained in 215 patients with AVM between1989 and 1994 were retrospectively reviewed. The M:F ratio was 136:78 and their mean age was 29 (ranged 4 - 66)years. On the based of clincal presentation, CT and/or MR images, they were divided into hemorrhagic andnon-hemorrhagic groups. Angiograms were analyzed by two radiologists for the size and location of nidus; thenumber of feeding arteries and the extent of aneurysm, stenosis, dural supply, and angiomatous change; the numberof draining veins and the extent of deep or superficial drainage, stenosis, ectasia, kinking, and stasis. Thestandard chi-square test was used for statistical analysis. RESULTS: Hemorrhage was noted in 140 patients(65%),and no hemorrhage in 75(35%). Hemorrhage was more common in AVM with deep-seated and callosal locations, a nidusof less than 2cm, single feeder and single venous drainage, and deep venous drainage only (p < 0.05 - 0.001).Non-hemorrhagic presentations were more common in AVM with cortical and subcortical location, a nidus of more than5cm, angiomatous change, dural supply, both superficial and deep venous drainage, kinking, and stasis (p <0.05-0.001). CONCLUSION: The angio-architechture of AVM with hemorrhage correlated with clinical symptomaticpresentation. Analysis of the patterns of angioarchitectureis useful for prognosis and in deeiding the direetionof freatment.