PURPOSE: The purpose of this study is to explore the influence of segmentation of the upstream and downstream parent artery and hemodynamic boundary conditions (BCs) on the evaluated hemodynamic factors for the computational fluid dynamics (CFD) analysis of intracranial aneurysms. MATERIALS AND METHODS: Three dimensional patient-specific aneurysm models were analyzed by applying various combinations of inlet and outlet BCs. Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases. RESULTS: Hemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs. When the inlet length was relatively short, different inlet BCs showed different hemodynamic factors and the calculated hemodynamic factors were also dependent on the inlet length. However, when the inlet length (L) was long enough (L>20D, where D is the diameter of inlet section), the hemodynamic factors became similar regardless of the inlet BCs and lengths. The error due to different inlet BCs was negligible. The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length. CONCLUSION: Simulated hemodynamic factors are highly sensitive to inlet BCs and upstream parent artery segmentation. The results of this work can provide an insight into how to build models and to apply BCs for more accurate estimation of hemodynamic factors from CFD simulations of intracranial aneurysms.
Adult ; Arteries ; Blood Flow Velocity ; *Hemodynamics ; Humans ; Hydrodynamics ; Intracranial Aneurysm/*physiopathology ; *Models, Cardiovascular ; Stress, Mechanical

BACKGROUNDUnclippable fusiform basilar trunk aneurysm is a formidable condition for surgical treatment. The aim of this study was to establish a computational model and to investigate the hemodynamic characteristics in a fusiform basilar trunk aneurysm.

METHODSThe three-dimensional digital model of a fusiform basilar trunk aneurysm was constructed using MIMICS, ANSYS and CFX software. Different hemodynamic modalities and border conditions were assigned to the model. Thirty points were selected randomly on the wall and within the aneurysm. Wall total pressure (WTP), wall shear stress (WSS), and blood flow velocity of each point were calculated and hemodynamic status was compared between different modalities.

RESULTSThe quantitative average values of the 30 points on the wall and within the aneurysm were obtained by computational calculation point by point. The velocity and WSS in modalities A and B were different from those of the remaining 5 modalities; and the WTP in modalities A, E and F were higher than those of the remaining 4 modalities.

CONCLUSIONSThe digital model of a fusiform basilar artery aneurysm is feasible and reliable. This model could provide some important information to clinical treatment options.

Adult ; Computational Biology ; Hemodynamics ; physiology ; Humans ; Intracranial Aneurysm ; diagnostic imaging ; pathology ; physiopathology ; Male ; Radiography

OBJECTIVETo investigate the aortic elastic properties and its clinical significance in intracranial aneurysms (IAs).

METHODSOne hundred and seven IAs patients (57 with hypertension) and 108 healthy subjects were recruited. The internal aortic diameters in systole and diastole were measured by the M-mode echocardiography, the aortic elasticity indexes were calculated and compared.

RESULTSThe aortic distensibility (DIS) was lower and the aortic stiffness index (SI) was higher in IAs patients than those in controls (both P <0.001). DIS was lower and SI was higher in IAs patients with hypertension (IAs-HP) than those in IAs with no hypertension (P <0.001). Similar results were obtained when the aortic elasticity index were adjusted for body surface area and body mass index.

CONCLUSIONAbnormal aortic elasticity is a common finding in IAs patients and hypertension is closely related to the severity of aortic elasticity.

Adult ; Aged ; Aorta ; diagnostic imaging ; physiopathology ; Case-Control Studies ; Elasticity ; Female ; Humans ; Intracranial Aneurysm ; physiopathology ; Male ; Middle Aged ; Ultrasonography

BACKGROUNDAn ideal aneurysm model of cerebral aneurysm is of great importance for studying the pathogenesis of the lesion and testing new techniques for diagnosis and treatment. Several models have been created in rabbits and are now widely used in experimental studies; however, every model has certain intrinsic limitations. Here we report the development of a novel saccular aneurysm model in rabbits using an arterial pouch that is subject to in vitro pre-digestion with combined elastase and collagenase.

METHODSA segment of right common carotid artery (CCA) was dissected out and treated with elastase (60 U/ml, 20 min) followed by type I collagenase (1 mg/ml, 15 min) in vitro. The graft was anastomosed to an arterial arch built with the left CCA and the remaining right CCA, while the other end of the graft was ligated. The dimension and tissue structure of the pouch were analysed immediately, 2 or 8 weeks after operation.

FINDINGSTen terminal aneurysms were produced. The gross morphology of the aneurysm resembles the human cerebral terminal aneurysms. We have observed the following pathological changes: (1) growth of the aneurysm (mean diameter increased from (2.0+/-0.1) to (3.2+/-0.3) mm at 2 weeks, P<0.001, n=7-10); (2) thinning of the aneurysmal wall (the mean wall thickness decreased to 44% at 2 weeks), which was accompanied by significant losses of elastic fibres, collagen and the cellular component; and (3) spontaneous rupture (3 out of 9, one aneurysm ruptured 24 h after operation with the other two at 2 and 4 weeks respectively).

CONCLUSIONThis rabbit arterial pouch model mimics human cerebral aneurysms in relation to morphology and histology. In particular, this model exhibited an increased tendency of spontaneous rupture.

Animals ; Carotid Artery, Common ; drug effects ; pathology ; physiopathology ; Collagenases ; Disease Models, Animal ; In Vitro Techniques ; Intracranial Aneurysm ; chemically induced ; pathology ; physiopathology ; Pancreatic Elastase ; Rabbits

A patient received combined spinal-epidural anesthesia for a scheduled total knee arthroplasty. After an injection of spinal anesthetic and ephedrine due to a decrease in blood pressure, the patient developed a severe headache. The patient did not respond to verbal command at the completion of the operation. A brain CT scan revealed massive subarachnoid and intraventricular hemorrhages, and a CT angiogram showed a ruptured aneurysm. Severe headaches should not be overlooked in an uncontrolled hypertensive patient during spinal anesthesia because it may imply an intracranial and intraventricular hemorrhage due to the rupture of a hidden aneurysm.
Aged ; Anesthesia, Epidural/*adverse effects ; Anesthesia, Spinal/*adverse effects ; Aneurysm, Ruptured/*chemically induced/*complications ; Cerebral Ventricles/*physiopathology ; Humans ; Intracranial Hemorrhages/*etiology ; Male ; Subarachnoid Hemorrhage/*etiology

OBJECTIVETo establish an individualized fluid-solid coupled model of intracranial aneurysms based on computed tomography angiography (CTA) image data.

METHODSThe original Dicom format image data from a patient with an intracranial aneurysm were imported into Mimics software to construct the 3D model. The fluid-solid coupled model was simulated with ANSYS and CFX software, and the sensitivity of the model was analyzed. The difference between the rigid model and fluid-solid coupled model was also compared.

RESULTSThe fluid-solid coupled model of intracranial aneurysm was established successfully, which allowed direct simulation of the blood flow of the intracranial aneurysm and the deformation of the solid wall. The pressure field, stress field, and distribution of Von Mises stress and deformation of the aneurysm could be exported from the model. A small Young's modulus led to an obvious deformation of the vascular wall, and the walls with greater thicknesses had smaller deformations. The rigid model and the fluid-solid coupled model showed more differences in the wall shear stress and blood flow velocity than in pressure.

CONCLUSIONThe fluid-solid coupled model more accurately represents the actual condition of the intracranial aneurysm than the rigid model. The results of numerical simulation with the model are reliable to study the origin, growth and rupture of the aneurysms.

Blood Flow Velocity ; Computer Simulation ; Hemodynamics ; Humans ; Imaging, Three-Dimensional ; Intracranial Aneurysm ; diagnostic imaging ; physiopathology ; Models, Cardiovascular ; Software ; Tomography, X-Ray Computed

Computational fluid dynamics (CFD) was used to numerically investigate the blood flow in 3-D models of human preoperative and posteroperative of cerebral aneurysm clip, and the feasibility of surgical operation was evaluated by the calculated hemodynamics parameters. Mimics software was used to reconstruct the models from CT angiograms, and numerical simulation of blood flow at different time in a cardiac circle was performed. Comparison analysis of blood flow in three models of human preoperative and posteroperative of cerebral aneurysm clip was conducted in terms of blood velocity distribution, wall shear stress (WSS) distribution and pressure distribution. The results demonstrated that blood velocity and WSS were significantly increased, and pressure was obviously decreased.
Blood Flow Velocity ; Cerebrovascular Circulation ; Computer Simulation ; Hemodynamics ; Humans ; Imaging, Three-Dimensional ; Intracranial Aneurysm ; diagnostic imaging ; physiopathology ; surgery ; Models, Cardiovascular ; Stress, Mechanical ; Tomography, X-Ray Computed

BACKGROUNDSurgical treatment of intracranial aneurysms is often compromised by incomplete exclusion of the aneurysm or stenosis of parent vessels. Intraoperative microvascular Doppler (IMD) is an attractive, noninvasive, and inexpensive tool. The present study aimed to evaluate the usefulness and reliability of IMD for guiding clip placement in aneurysm surgery.

METHODSA total of 92 patients with 101 intracranial aneurysms were included in the study. IMD with a 1.5-mm diameter, 20-MHz microprobe was used before and after clip application to confirm aneurysm obliteration and patency of parent vessels and branching arteries. IMD findings were verified postoperatively with digital subtraction angiography (DSA) or dual energy computed tomography angiography (DE-CTA). Ninety consecutive patients, harboring 108 aneurysms, who underwent surgery without IMD was considered as the control group.

RESULTSThe microprobe detected all vessels of the Circle of Willis and their major branches. Clips were repositioned in 24 (23.8%) aneurysms on the basis of the IMD findings consistent with incomplete exclusion and/or stenosis. IMD identified persistent weak blood flow through the aneurismal sac of 11 of the 101 (10.9%) aneurysms requiring clip adjustment. Stenosis or occlusion of the parent or branching arteries as indicated by IMD necessitated immediate clip adjustment in 19 aneurysms (18.8%). The mean duration of the IMD procedure was 4.8 minutes. The frequency of clip adjustment (mean: 1.8 times per case) was associated with the size and location of the aneurysm. There were no complications related to the use of IMD, and postoperative angiograms confirmed complete aneurysm exclusion and parent vessel patency. About 8.3% (9/108) aneurysms were unexpectedly incompletely occluded, and 10.2% (11/108) aneurysms and parent vessel stenosis without IMD were detected by postoperative DSA or DE-CTA. IMD could reduce the rate of residual aneurysm and unanticipated vessel stenosis which demonstrated statistically significant advantages compared with aneurysm surgery without IMD.

CONCLUSIONIMD is a safe, easily performed, reliable, and valuable tool that is suitable for routine use in intracranial surgery, especially in complicated, large, and giant aneurysms with wide neck or without neck.

Adult ; Aged ; Angiography, Digital Subtraction ; Cerebrovascular Circulation ; Female ; Humans ; Intracranial Aneurysm ; physiopathology ; surgery ; Laser-Doppler Flowmetry ; Male ; Middle Aged ; Monitoring, Intraoperative ; methods

BACKGROUNDNeurophysiologic monitoring during surgery is to prevent permanent neurological injury resulting from surgical manipulation. To improve the accuracy and sensitivity of intraoperative neuromonitoring, combined monitoring of transcranial electrical stimulation motor evoked potentials (TES-MEPs), somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) was attempted in microsurgery for lesions adjacent to the brainstem and intracranial aneurysms.

METHODSMonitoring of combined TES-MEPs with SSEPs was attempted in 68 consecutive patients with lesions adjacent to the brainstem as well as intracranial aneurysms. Among them, 31 patients (31 operations, 28 of posterior cranial fossa tumors, 3 of posterior circulation aneurysms) were also subjected to monitoring of BAEPs. The correlation of monitoring results and clinical outcome was studied prospectively.

RESULTSCombined monitoring of evoked potentials (EPs) was done in 64 (94.1%) of the 68 patients. MEPs monitoring was impossible for 4 patients (5.9%). No complication was observed during the combined monitoring in all the patients. In 45 (66.2%) of the 68 patients, EPs were stable, and they were neurologically intact. Motor dysfunction was detected by MEPs in 8 patients, SSEPs in 5, and BAEPs in 4, respectively.

CONCLUSIONSA close relationship exists between postoperative motor function and the results of TES-MEPs monitoring. TES-MEPs are superior to SSEPs and BAEPs in detecting motor dysfunction, but combined EPs serve as a safe, effective and invasive method for intraoperative monitoring of the function of the motor nervous system. Monitoring of combined EPs during microsurgery for lesions adjacent to the brainstem and intracranial aneurysms may detect potentially hazardous maneuvers and improve the safety of subsequent procedures.

Adolescent ; Adult ; Aged ; Brain Stem ; physiopathology ; Evoked Potentials, Auditory, Brain Stem ; Evoked Potentials, Motor ; Evoked Potentials, Somatosensory ; Female ; Humans ; Intracranial Aneurysm ; physiopathology ; surgery ; Male ; Microsurgery ; Middle Aged ; Monitoring, Intraoperative ; Sensitivity and Specificity

Somatosensory evoked potential (SSEP) changes during cerebral aneurysm surgery and their relationship to postoperative neurologic complications have been studied on many occasions. However, it is still a matter of debate whether SSEP monitoring is really helpful in detecting or preventing neurologic complications. We studied 87 patients undergoing aneurysm surgery of the anterior cerebral circulation and SSEPs were monitored in 60 of these patients. All patients were grade 2 by the subarachnoid hemorrhage (SAH) grading system. Median nerve SSEP was monitored for middle cerebral or internal carotid artery aneurysms and posterior tibial nerve SSEP for anterior cerebral artery aneurysms. A decrease in the cortical amplitude of more than 50%, compared with control, was considered significant and interventions were then taken to reverse the SSEP. The pre- and postoperative neurologic deficits of each patient were evaluated immediately before and after surgery. No significant difference was found in the incidence of postoperative neurologic complications in the SSEP monitored (15% [9/60]) and unmonitored patients (22% [6/27]). In the SSEP monitored patients, the amplitudes of SSEPs decreased significantly in 14 patients and 4 of these showed neurologic complications. However, SSEP amplitudes were not significantly changed in 46 patients, and 5 of these showed neurologic complications. Significant changes in the amplitude of SSEP might represent neuronal injury, but the absence of change in the SSEP cannot guarantee patient safety. Our results suggest that SSEP monitoring may be useful for detecting the danger of neuronal injury, but that it does not reduce the incidence of neurologic complications in aneurysm surgery.
Adult ; Evoked Potentials, Somatosensory/physiology* ; Female ; Human ; Intracranial Aneurysm/surgery* ; Male ; Middle Age ; Monitoring, Physiologic* ; Nervous System Diseases/physiopathology ; Nervous System Diseases/etiology* ; Nervous System Diseases/diagnosis* ; Surgical Procedures, Operative/adverse effects*