The Underlying Mechanisms of Endovascular Exclusion of Intracranial Aneurysms by Coils. How Important is Electrothrombosis?

Abstract

Endovascular coil treatment of intracranial aneurysms is now widely accepted. We discuss some of the arguments for the relative roles of electrothrombosis, spontaneous thrombosis, mechanical filling, haemodynamic effects and surface properties in successful coil treatment. Despite an enormous body of literature, with many theories and much data, there is limited evidence for, or understanding of, the mechanisms by which coil treatment protects against aneurysm rupture. It seems likely that electrothrombosis plays no part.Dense packing is probably important in preventing recurrence. New technologies aiming to encourage endothelialisation and increased connective tissue formation appear promising.

Figure 1

Two aneurysms of the left internal carotid artery, treated by parent vessel occlusion with electrolytically detachable coils. Note that despite the electrolytic detachment of innumerable coils within both aneurysms and the parent vessel, there is persistent flow in the aneurysms and parent vessel, and no evident thrombus formation.

Figure 2

Treatment of a Vein of Galen Malformation in a four year old child, by partial filling of the varix with electrolytically detached coils. Note that despite a dense coil mass, extending into the falcine sinus, there is persistent flow and no evident thrombus. Subsequently, the choroidal arterial pedicle in which the microcatheter is evident was embolized with Histoacryl.