Aneurysm treatment apparatus includes a steerable catheter assembly having a catheter with a steerable distal end. A pouch is disposed over the distal end of the catheter so as to be in co-axial overlying relationship therewith. A constraining sheath is disposed over a major portion of the pouch and has a proximal sheath portion which is bonded to the catheter. The sheath terminates short of the distal end of the catheter, so as to leave a distal end of the pouch exposed. The steerable catheter can be steered into an aneurysm sac and filler material fed through the catheter in order to fill chamber of the pouch. The pouch will expand from its distal end with filler material and gradually slide off the sheath as it fills the aneurysm sac. The sheath prevents the pouch from expanding proximally, and potentially adversely affecting the filling process.
