Objective To explore the causes

prevention

and management of the complications during intra-cranial aneurysm embolization with controllable coils （mechanical detachable spiral

MDS; and Guglielmi detachable coil

GDC）. Methods Retrospective review of 120 cases with 125 intracranial aneurysms embolized with con-trollable coils from March 1995 to July 1999 was conducted. The 20 accidents（in 18 cases） including aneurysm rupture

over-embolization

protrusion of coil end into the parent artery

and thrombosis of the parent artery were analyzed. Results Among the 20 accidents

there were 6 aneurysm ruptures

6 over-embolizations （in 5 cases）

6 coil protrusions

and 2 thromboses （one was secondary to coil protrusion）. The embolization-related mortality was 3.33% （4/120）

the permanent neurological deficit was 1.67% （2/120）

and the transitory neurological deficit was 3.33%（4/120）. The occurrence and outcome of the complications were related to the embolizing technique

the pattern of aneurysm and its parent artery

the imperfection of embolic materials

and the observation and management during embolization. Conclusion Skilled embolizing technique

better understanding of the angio-anatomy of an aneurysm and its parent artery

correct judgement and management during embolization

and improvement of embolic materials are beneficial to the reduction of complications and to the melioration of the outcome of complications.