Successful obliteration of a ruptured partially thrombosed giant M1 fusiform aneurysm with coil embolization at distal M1 after extracranial-intracranial bypass

Proximal occlusion or trapping combined with EC-IC bypass is usually employed as a definite treatment for a giant fusiform aneurysm in cases where it is impossible to apply clips and do vascular reconstruction. Endovascular treatment is very important as an alternative or combined technique if direct surgery is impossible. The authors report a young male who presented with a 2^nd episode of intracranial bleeding in basal ganglion and subarachnoid hemorrhage with mild right hemiparesis. His 3D-CT scan revealed left ruptured partially thrombosed giant M1 fusiform aneurysm and left unruptured C3 saccular aneurysm. He underwent STA-MCA bypass with attempted M1 reconstruction and a week later attempted total occlusion of the M1 aneurysm with coils. But only a ruptured point at the distal M1 was occluded which, however, resulted in temporary mild right hemiparesis and aphasia. A month later when he was supposed to have his 2^nd coiling procedure his angiogram demonstrated spontaneous and complete obliteration of both the M1 and C3 aneurysms without any new neurological deficit, so no further endovascular procedure was attempted. The discussion is based on this case and previous reports regarding difficult giant M1 fusiform aneurysms, its treatment and spontaneous thrombosis of aneurysmal sac after bypass and distal occlusion. Conclusions are drawn that 1) spontaneous thrombosis of M1 and C3 aneurysms should be the result of hemodynamic alteration in both aneurysms due to a lower flow velocity induced by distal bypass and distal occlusion of M1, 2) combined distal bypass and endovascular obliteration of the aneurysmal sac with coils is a good alternative if vascular reconstruction is difficult or impossible.