Thrombosed giant aneurysm (TGA) possesses a high growth potential. In patients with TGAs, clinical symptoms evolve most commonly from its mass effect. Surgical interventions are therefore required to prevent TGA growth. We analyze the clinical characteristics and histopathological findings of TGAs, and discuss possible mechanisms underlying their growth. We have treated 30 cases of TGA during the last 10 years. Of these, 10 underwent direct surgery and 20 were treated by endovascular surgery. Endovascular obliteration of TGAs frequently fails to terminate their growth when contrast-enhancement of the aneurysmal wall is demonstrated on CT or MRI. Incomplete endovascular obliteration of TGAs does not appear to reduce their growth potential. Complete thrombosis of TGAs, induced either spontaneously or by surgical modification of the blood flow, does not necessarily indicate termination of their growth.
The growth of TGAs can be terminated when both the aneurysmal lumen and vascular channels of the aneurysmal wall are physically isolated from the blood flow through direct surgery: neck clipping or trapping. Together with the histopathological findings of TGAs, the above-mentioned characteristics suggest that 2 mechanisms may underlie their growth: intraluminal thrombus accumulation, and proliferation of vascular channels of the aneurysmal wall. Radical surgery to isolate TGAs from the blood flow, before they become too large to be operated on safely, may be advisable.