Simulation of therapeutic parent artery occlusion for basilar head aneurysms. Hemodynamic effect of occlusion sites and diameters of collateral arteries

Radical surgical treatment for recurrent giant fusiform thrombosed vertebral artery aneurysm previously coiled

Background:

Fusiform aneurysms are rare (<1%) and the underlying pathophysiology is not well known. Endovascular coiling is the standard of treatment; however, a surgical procedure with vascular reconstruction by excluding the pathological segment of the vessel and restoring the blood flow, seems to be the most effective and definitive treatment.

Case Description:

We report a patient who presented a fusiform vertebral artery aneurysm previously coiled which developed a giant enlargement and a new contralateral fusiform aneurysm. Hemodynamic changes resulting in the formation of contralateral aneurysm might be the result of aneurysm occlusion without revascularization. In addition, continued blood flow to the aneurysmal wall through the vasa vasorum might result in aneurysm recanalization or regrowth. In order to account for these possible sources of complications, we performed a vascular reconstruction with high and low flow bypasses after trapping the aneurysm.

Conclusions:

We hypothesize that, in this and similar cases, surgical vascular reconstruction should be the first and definitive treatment under experienced cerebrovascular surgeons.

Model analysis of coil embolization of cerebral aneurysms: prediction of thrombus formation in aneurysms based on the coil embolization rate

OBJECTIVES

Intra-aneurysmal coil embolization has been established as a common method for the intravascular treatment of cerebral aneurysms, but few studies have evaluated its long-term results. Because there is no sufficient objective landmark of complete embolization, determination of its application depends on a surgeon's experience.

METHODS

A glass cerebral aneurysm model was produced, and the changes in intra-aneurysmal hemodynamics were examined. Nylon thread with a diameter of 0.33 mm, resembling the coils clinically used for embolization, was used to fill in the model. After perfusion of glycerin solution to represent human blood, the half life of a dye injected into the aneurysm was optically measured, and the relationship between the half life and the volume embolization rate (VER) of nylon thread in the aneurysm was examined.

RESULTS

The maximal VER obtained by filling nylon thread in the aneurysm was 41.7+/- 2.9%. The half life of the dye increased with the VER and was significantly increased at VER>30%.

DISCUSSION

The half life of the dye in the aneurysm reflected stagnation of intra-aneurysmal hemodynamics, suggesting that the prolongation of the half life enhances thrombus formation. The results of this study suggested that VER>30% is sufficient for effective coil embolization.

Combined surgical and endovascular techniques of flow alteration to treat fusiform and complex wide-necked intracranial aneurysms that are unsuitable for clipping or coil embolization

OBJECT

Certain intracranial aneurysms, because of their fusiform or complex wide-necked structure, giant size, or involvement with critical perforating or branch vessels. are unamenable to direct surgical clipping or endovascular coil treatment. Management of such lesions requires alternative or novel treatment strategies. Proximal and distal occlusion (trapping) is the most effective strategy. In lesions that cannot be trapped, alteration in blood flow to the "inflow zone," the site most vulnerable to aneurysm growth and rupture, is used.

METHODS

From 1991 to 1999 the combined neurosurgical-neuroendovascular team at the Massachusetts General Hospital (MGH) managed 48 intracranial aneurysms that could not be clipped or occluded. Intracavernous internal carotid artery aneurysms were excluded from this analysis. By applying a previously described aneurysm rupture risk classification system (MGH Grades 0-5) based on the age of the patient, aneurysm size, Hunt and Hess grade, Fisher grade, and whether the aneurysm was a giant lesion located in the posterior circulation, the authors found that a significant number of patients were at moderate risk (MGH Grade 2; 31.3% of patients) and at high risk (MGH Grades 3 or 4; 22.9%) for treatment-related morbidity. The lesions were treated using a variety of strategies--surgical, endovascular, or a combination of modalities. Aneurysms that could not be trapped or occluded were treated using a paradigm of flow alteration, with flow redirected from either native collateral networks or from a surgically performed vascular bypass. Overall clinical outcomes were determined using the Glasgow Outcome Scale (GOS). A GOS score of 5 or 4 was achieved in 77.1%, a GOS score of 3 or 2 in 8.3%, and death (GOS 1) occurred in 14.6% of the patients. Procedure-related complications occurred in 27.1% of cases; the major morbidity rate was 6.3% and the mortality rate was 10.4%. Three patients experienced aneurysmal hemorrhage posttreatment; in two patients this event proved to be fatal. Aneurysms with MGH Grades 0, 1, 2, 3, and 4 were associated with favorable outcomes (GOS scores of 5 or 4) in 100%, 92.8%, 71.4%, 50%, and 0% of instances, respectively.

CONCLUSIONS

Despite a high incidence of transient complications, intracranial aneurysms that cannot be clipped or occluded require alternative surgical and endovascular treatment strategies. In those aneurysms that cannot safely be trapped or occluded, one approach is the treatment strategy of flow alteration.