Imaging after direct and indirect extracranial-intracranial bypass surgery

Case report of intracranial large vessel occlusion in glioblastoma multiforme patient after radiation therapy

INTRODUCTION

Vasculopathy of the large arteries is a prominent complication of radiotherapy. Radiation-induced cerebral vasculopathy can cause arterial stenosis/occlusion, cerebral hemorrhage, and aneurysm formation. We report a cases of glioblastoma multiforme (GBM) with occlusive radiation vasculopathy (ORV).

CASE PRESENTATION

This 28-year-old patient who suffered from GBM had surgery for cytoreduction and received postoperative CCRT. We adopted the radiotherapy and oncology group radiation guideline. This patient had cerebrovascular accident episodes without any known risk. Therefore, ORV was highly suspected and vascular stenosis was confirmed using magnetic resonance angiography (MRA) or digital subtraction angiography. Extracranial-intracranial bypass was performed and patency was confirmed. The patient had not suffered from recurrent symptoms of transient ischemic attack or ischemic stroke for 1.5 years.

DISCUSSION

This is the first article to report bypass surgery for GBM patients. Although the median survival rate of GBM is approximately 15 months, the short survival time may be sufficient for occlusive vasculopathy to occur. Regular follow-up magnetic resonance imaging assessments are recommended, as is MRA as a screening tool for the early diagnosis of ORV.The Stenting versus Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial focused on atherosclerotic intracranial arterial stenosis, revealing that aggressive medical management was superior to stenting for secondary stroke prevention; however, it did not mention radiation-induced vasculopathy. Bypass surgery has yielded some positive outcomes. In the absence of contraindications, antiplatelet or anticoagulation agents could be added, and bypass surgery could be performed because there was no stent in the distal intracranial arteries.

CONCLUSION

MRA is a potential screening tool for ORV in GBM patients and bypass surgery could be performed to improve brain perfusion. Bypass surgery could help patient with occlusive radiation vasculopathy.

Imaging of the pial arterial vasculature of the human brain in vivo using high-resolution 7T time-of-flight angiography

The pial arterial vasculature of the human brain is the only blood supply to the neocortex, but quantitative data on the morphology and topology of these mesoscopic arteries (diameter 50–300 µm) remains scarce. Because it is commonly assumed that blood flow velocities in these vessels are prohibitively slow, non-invasive time-of-flight magnetic resonance angiography (TOF-MRA)—which is well suited to high 3D imaging resolutions—has not been applied to imaging the pial arteries. Here, we provide a theoretical framework that outlines how TOF-MRA can visualize small pial arteries in vivo, by employing extremely small voxels at the size of individual vessels. We then provide evidence for this theory by imaging the pial arteries at 140 µm isotropic resolution using a 7 Tesla (T) magnetic resonance imaging (MRI) scanner and prospective motion correction, and show that pial arteries one voxel width in diameter can be detected. We conclude that imaging pial arteries is not limited by slow blood flow, but instead by achievable image resolution. This study represents the first targeted, comprehensive account of imaging pial arteries in vivo in the human brain. This ultra-high-resolution angiography will enable the characterization of pial vascular anatomy across the brain to investigate patterns of blood supply and relationships between vascular and functional architecture.

[Methods to assess competence of indirect cerebral revascularization in children]

The use of catheterization cerebral angiography (CCA) to assess collateral blood flow through an indirect anastomosis is traumatic for children, uses a high radiation dose, and requires anesthetic care in most cases.

AIM

we aimed to compare the capabilities of triplex ultrasound (TU) of vessels, magnetic resonance angiography (MRA), computed tomography angiography (CTA), and CCA in assessing the competence of indirect cerebral revascularization (ICR) in children.

MATERIAL AND METHODS

ICR was performed in 18 children in 24 hemispheres (24 operations). The results were evaluated by Matsushima classification-based comparison of the data of preoperative and postoperative clinical examinations, TU of the superficial temporal artery, magnetic resonance imaging (MRI) and computed tomography (CT) of vessels, and selective cerebral angiography.

RESULTS

After surgery, improvements in the neurological and neuropsychological status were assessed. Matsushima grade A collaterals were found in 12 (50%) cases, grade B collaterals were present in 3 (13%) cases, grade C collaterals were present in 7 (29%) cases, and grade D collaterals were detected in 1 (4%) case; in 1 (4%) case, the superficial temporal artery was not enhanced. MR angiography visualized 18 (75%) indirect anastomoses, CT angiography revealed 4 indirect anastomoses, and TU visualized 4 indirect anastomoses. Comparison of preoperative and postoperative TU data for the superficial temporal artery revealed significant changes in blood flow in the form of increased rate indices and a decreased resistance index; mean values of indices for each angiographic class of revascularization and significant differences in pre- and postoperative observations were calculated.

CONCLUSION

Examination of ICR competence using CCA is necessary in the presence of persistent clinical signs of chronic cerebral circulatory insufficiency, absence of increased blood flow and decreased peripheral resistance in the superficial temporal artery, and lack of anastomosis according to MRA. The most optimal techniques for postoperative examination are MRA with perfusion and diffusion maps and TU.

Evaluation of Encephaloduroarteriosynangiosis Efficacy Using Probabilistic Independent Component Analysis Applied to Dynamic Susceptibility Contrast Perfusion MRI

BACKGROUND AND PURPOSE

Indirect cerebral revascularization has been successfully used for treatment in Moyamoya disease and symptomatic intracranial atherosclerosis. While angiographic neovascularization has been demonstrated after surgery, measurements of local tissue perfusion are scarce and may not reflect the reported successful clinical outcomes. We investigated probabilistic independent component analysis and conventional perfusion parameters from DSC-MR imaging to measure postsurgical changes in tissue perfusion.

MATERIALS AND METHODS

In this prospective study, 13 patients underwent unilateral indirect cerebral revascularization and DSC-MR imaging before and after surgery. Conventional perfusion parameters (relative cerebral blood volume, relative cerebral blood flow, and TTP) and probabilistic independent components that reflect the relative contributions of DSC signals consistent with arterial, capillary, and venous hemodynamics were calculated and examined for significant changes after surgery. Results were compared with postsurgical DSA studies to determine whether changes in tissue perfusion were due to postsurgical neovascularization.

RESULTS

Before surgery, tissue within the affected hemisphere demonstrated a high probability for hemodynamics consistent with venous flow and a low probability for hemodynamics consistent with arterial flow, whereas the contralateral control hemisphere demonstrated the reverse. Consistent with symptomatic improvement, the probability for venous hemodynamics within the affected hemisphere decreased with time after surgery (P = .002). No other perfusion parameters demonstrated this association. Postsurgical DSA revealed an association between an increased preoperative venous probability in the symptomatic hemisphere and neovascularization after surgery.

CONCLUSIONS

Probabilistic independent component analysis yielded sensitive measurements of changes in local tissue perfusion that may be associated with newly formed vasculature after indirect cerebral revascularization surgery.