Devices and methods for treating vascular malformations

A method of filling an aneurysm, comprising the steps of:

• advancing a device through a patient's vascular system to an aneurysm, the device being a closed mesh structure formed of a plurality of flexible filaments, the device having a proximal collar and a distal collar with the flexible filaments extending therebetween, the closed mesh structure being movable from a collapsed configuration to an expanded configuration, the closed mesh structure forming a tubular structure in the collapsed configuration, the closed mesh structure further having a first expandable section and a second expandable section, the first expandable section being coupled to the proximal collar and the second expandable section being coupled to the distal collar, the first expandable section being less permeable to fluid than the second expandable section;
• and
• positioning the device in the expanded position within the aneurysm, the proximal collar being positioned adjacent a neck of the aneurysm and the distal collar being positioned adjacent a dome of the aneurysm, the positioning step also being carried out with the first expandable section being positioned adjacent the neck of the aneurysm and the second expandable section being positioned adjacent the dome of the aneurysm.