Influence of perianeurysmal environment on the deformation and bleb formation of the unruptured cerebral aneurysm: assessment with fusion imaging of 3D MR cisternography and 3D MR angiography.

BACKGROUND AND PURPOSE: Surface irregularity and bleb formation are anatomical factors that are associated with aneurysm rupture. The perianeurysmal environment has been proposed as one factor that may influence aneurysm morphology. We have developed a fusion imaging technique of 3D MR cisternography and angiography that allows clear visualization of an aneurysm and its environment. This technique may prove useful in further understanding of the natural history of intracranial aneurysms. METHODS: Fusion images of 3D MR cisternography and angiography were reconstructed by a perspective volume-rendering algorithm from the volume datasets of MR cisternography, obtained by a T2-weighted 3D fast spin-echo sequence, and coordinated MR angiography, by a 3D time-of-flight sequence. On the fusion images, the anatomic relationship of an aneurysm to the perianeurysmal structures was assessed, and the influence of perianeurysmal environment on the deformation and bleb formation of the aneurysm was investigated. RESULTS: Marked and minor deformation and bleb formation of the aneurysmal dome were found at the areas confronted or adjacent to a certain contact with perianeurysmal structures, including cranial nerves, brain parenchyma, cranial base bones, petroclinoidal dural folds, and dura mater. CONCLUSION: Fusion images of 3D MR cisternography and angiography can depict the contact of an aneurysm with its perianeurysmal environment; this may provide an additional parameter in consideration for the natural history of cerebral aneurysms.

[Assessment of the perianeurysmal environment of unruptured internal carotid-posterior communicating artery aneurysms with fusion imaging of three-dimensional magnetic resonance cisternography and angiography].

The anatomical relationship of an unruptured internal carotid-posterior communicating artery aneurysm and the perianeurysmal environment was investigated by using three-dimensional (3D) magnetic resonance cisternography (MRC), angiography (MRA) and newly developed fusion images of 3D MRC and 3D MRA. Contact of an aneurysm with the adjacent intra- and pericisternal structures was observed in cases with the aneurysm developing and extending beyond the capacity of the surrounding subarachnoid space. Deformation and bleb formation of the aneurysmal dome was depicted at the dome in contact with the perianeurysmal environment, including the tentorial edge, the anterior petroclinoid dural fold, the oculomotor nerve, the posterior clinoid process, the dorsum sellae and the cranial base bone. By using the fusion imaging technique of 3D MRC and 3D MRA, assessment of the contact of an unruptured cerebral aneurysm with its perianeurysmal environment can be made. Such contact gives ride to risk of deformation and bleb formation of the aneurysmal dome; and may result in cranial nerve symptoms and accelerate rupture from an unruptured cerebral aneurysm.

[Assessment of the signal intensity distribution pattern within the unruptured cerebral aneurysms using color-coded 3D MR angiography].

To evaluate the interaction between the MR signal intensity distribution pattern and bleb formation/ deformation of the aneurysmal dome, fifty cases of the unruptured cerebral aneurysms were investigated with the color-coded 3D MR angiography. Patterns were categorized into central-type, neck-type and peripheral-type according to the distribution of MR signals with low-, moderate- and high signal intensity areas. Imaging analysis revealed the significant relationship (P < 0.02) of the peripheral-type aneurysms to the bleb formation and deformation of the dome, compared with those of central- and neck-type. Additionally, peripheral-type signal intensity distribution pattern was shown with aneurysms harboring relatively large dome size and lateral-type growth including internal carotid aneurysms. Prospective analysis of intraaneurysmal flow pattern with the color-coded 3D MR angiography may provide patient-specific analysis of intraaneurysmal flow status in relation to the morphological change of the corresponding aneurysmal dome in the management of unruptured cerebral aneurysms.

Visualization of aneurysmal contours and perianeurysmal environment with conventional and transparent 3D MR cisternography.

We have developed conventional and transparent 3D MR cisternography to investigate the spatial relationship between the contours of aneurysmal complex and the perianeurysmal structures including the cranial nerves, dural fold, cranial base bone, and brain parenchyma. Volume data obtained by a T2-weighted 3D fast spin-echo sequence were reconstructed by using a perspective volume-rendering algorithm with a transluminal imaging technique. 3D MR cisternograms provide useful anatomic information in the therapeutic and follow-up management of unruptured cerebral aneurysms.

Evaluation of contour of unruptured cerebral aneurysm using three-dimensional CT cisternogram.

Angiography is gold standard technique as preoperative examination for unruptured aneurysmal surgery. Neurosurgeons have observed the unexpected irregular shape and size of the aneurysmal dome and neck in many cases of unruptured cerebral aneurysms during aneurysmal microsurgery, and known the discrepancy between the findings of angiography and operative view. We could not find out the report described the preoperative evaluation of outer-wall (contour) of aneurysm. In the present study, we attempted to evaluate the outer-wall of an unruptured cerebral aneurysm using three-dimensional CT cisternogram (3D-CTC) to provide useful preoperative information. The study was performed on three cases of unruptured cerebral aneurysm that were identified incidentally by MR angiography. We performed three-dimensional CT aniography (3D-CTA) and 3D-CTC for each patient. In the present study, we visualized the contours of vessels and aneurysms using a 3D-CTC in three cases of unruptured cerebral aneurysm. We found the discrepancy between the 3D-CTC contour image and the intra-luminal image 3D-CTA image. This method may be useful for the decision of the surgical approach and have the potential to evaluate the anatomical structure of aneurysmal dome and neck preoperatively.

[Evaluation of the contours and perianeurysmal environment of unruptured cerebral aneurysms, using three-dimensional magnetic resonance cisternogram].

To evaluate the anatomical relationship between cerebral aneurysm and the perianeurysmal environment within a cisternal space, the contours of an unruptured cerebral aneurysm and pericisternal structures were depicted on a three-dimensional (3D) MR cisternogram. By using perspective volume-rendering algorithm, the 3D MR cisternograms were reconstructed from the source axial volume data set obtained by the T2-weighted 3D fast spin-echo sequence. Those images were shown together with the coordinated 3D MR angiograms through similar visual projections, and then compared with the intraoperative findings. The outer wall configurations of cerebral aneurysms within the cisternal space were shown in conjunction with the accompanying surface veins, adjacent cranial nerves, dura mater and tentorial edge, cranial base bone, and surrounding pericisternal brain surfaces. With application of 3D MR cisternograms in the management of unruptured cerebral aneurysm, the anatomical relationship between the aneurysmal contours and the perianeurysmal environment could be evaluated the within the cisternal space. This might provide another clinical factor when considering the potential risk of growth, rupture, and symptomatic cranial nerve signs of an unruptured cerebral aneurysm.

Intraoperative evaluation of aneurysmal architecture: comparative study with transluminal images of 3D MR and CT angiograms.

BACKGROUND AND PURPOSE: When exposure and visual access in aneurysmal microsurgery are limited, exact intraoperative information must be obtained regarding the whole shape of the aneurysm, property of the aneurysmal wall, vessels hidden behind the aneurysmal sac, and surrounding bony structures of the skull base. We developed a transluminal imaging technique that uses 3D MR and CT angiograms and applied it for intraoperative transparent evaluation of the angioarchitecture of cerebral aneurysms. METHODS: Transluminal images were reconstructed from a perspective volume-rendering algorithm by selecting information on the luminal margin from the whole volume data sets of MR and CT angiograms. The images show the vessel and aneurysmal walls as a series of rings and provide direct visualization of the underlying objects through the spaces between the rings. By connecting a graphic workstation to the operative microscope, data were reconstructed intraoperatively and adjusted to coincide with the operative views by manipulating the projection and visual angle. The aneurysmal angioarchitecture could then be evaluated transparently on the reconstructed transluminal images through the operative approach. RESULTS: Transluminal images provided direct transparent visualization of the aneurysmal architecture, including orifices at the neck, dome, and bleb and the parent arteries though the vessel and aneurysmal walls. The angioarchitecture of the neck complex was evaluated intraoperatively with transluminal 3D MR and CT angiograms through the operative approach before actual aneurysmal neck clipping. CONCLUSIONS: Intraoperative exact evaluation of aneurysmal angioarchitecture with transluminal images would be a feasible and useful adjunct for aneurysmal microsurgery. Merging of data across modalities including 3D MR and CT angiography may improve preoperative or intraoperative evaluation of the angioarchitecture of cerebral aneurysms.

Visualization of intraaneurysmal flow patterns with transluminal flow images of 3D MR angiograms in conjunction with aneurysmal configurations.

BACKGROUND AND PURPOSE: How the complex flow phenomena generated within unruptured cerebral aneurysms relate to the corresponding aneurysmal geometry is unknown. To estimate the interaction between flow patterns and morphologic features of unruptured cerebral aneurysms, we developed a method to visualize intraanuerysmal flow patterns with transluminal flow imaging of 3D MR angiograms in conjunction with aneurysmal configurations. METHODS: Transluminal images of the vessel lumen were reconstructed with use of a parallel volume-rendering algorithm by selecting information on the margin of lumina from the volume data sets of 3D time-of-flight MR angiograms. Transluminal flow images were then created by superimposing flow-related intraluminal information onto transluminal images. Intraaneurysmal flow patterns were evaluated in three cases of unruptured cerebral aneurysms, based on the animated display of transluminal flow images with stepwise extracted intraluminal volume data of signal intensity, in conjunction with the corresponding aneurysmal configurations depicted on 3D MR angiograms. RESULTS: Transluminal flow images showed 3D visualization of flow-related signal intensity distribution obtained from volume data of MR angiograms, so that qualitative information regarding intraaneurysmal flow patterns could be estimated with respect to morphologic features of cerebral aneurysms. CONCLUSION: Transluminal flow images of 3D MR angiograms allowed feasible visualization of intraaneurysmal flow patterns that were studied. More work is required to validate the technique and clarify the significance of being able to visualize intraaneurysmal flow patterns.

Transcortical transchoroidal fissure approach for ruptured distal posterior cerebral artery (P2-P3 junction) aneurysm associated with packed intraventricular hemorrhage--two case reports.

A 56-year-old man with ruptured right P2-P3 junction aneurysm and a 66-year-old man with ruptured left P2-P3 junction aneurysm of the posterior cerebral artery associated with acute-stage packed intraventricular hemorrhage. The aneurysms were successfully clipped through the transcortical transchoroidal fissure approach. This approach requires less retraction of the temporal lobe, provides a wider surgical field, and the P2 segment can be easily reached. The present approach is very useful for the treatment of ruptured aneurysms at the P2-P3 junction, in particular for acute stage surgery associated with packed intraventricular hemorrhage.

Large cerebral arteriovenous malformation presenting with venous ischemia in the contralateral hemisphere. Case report.

The authors report a rare case in which a large cerebral arteriovenous malformation (AVM) located in the left parietooccipital region presented with venous ischemia in the contralateral hemisphere. A 74-year-old man was admitted to the hospital because he was experiencing a loss of appetite, disorientation, and left hemiparesis. Computerized tomography scans revealed a low-density area in the right temporal lobe. Angiography demonstrated a large AVM in the left parietooccipital lobe and dilation, stagnation, and meanders of cortical veins in the contralateral hemisphere. The authors speculated that the elevated sinus pressure caused by a huge venous return of blood from the AVM produced venous ischemia in the contralateral hemisphere.