Reply
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* Nick Bryan
* John Mathis
* Daniele Rigamonti

Dr. Byrne's letter emphasizes a critical factor necessary for the final determination of GDC coil effectiveness for the treatment of intracranial aneurysms; that is, the long-term biological response to coil implants. Our previous commentary on the endovascular coil treatment of aneurysms addresses the persisting uncertainty of long-term outcomes of such therapy as compared with conventional surgical clipping, but Dr. Byrne more elegantly poses specific questions related to long-term outcome. The biological tolerance to the coils and their induction (direct versus indirect) of stable clot and fibrosis will indeed be determining factors in successful treatment. This critical information remains lacking, and we concur with Dr. Byrne's plea for more basic and clinical investigation of these topics.

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