NEUROSURGERY VOLUME 65 | NUMBER 2 | AUGUST 2009 | 311 CLINICAL STUDIES Andrew J. Ringer, M.D. Department of Neurosurgery, University of Cincinnati Neuroscience Institute, University of Cincinnati College of Medicine, and Mayfield Clinic, Cincinnati, Ohio Rafael Rodriguez-Mercado, M.D. Department of Neurosurgery, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico Erol Veznedaroglu, M.D. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania Elad I. Levy, M.D. Department of Neurosurgery, University at Buffalo, The State University of New York, Buffalo, New York Ricardo A. Hanel, M.D., Ph.D. Department of Neurosurgery, University at Buffalo, The State University of New York, Buffalo, New York Robert A. Mericle, M.D. Department of Neurosurgery, Vanderbilt University, Nashville, Tennessee Demetrius K. Lopes, M.D. Department of Neurosurgery, Rush University Medical Center, Chicago, Illinois Giuseppe Lanzino, M.D. Department of Neurosurgery, Illinois Neurological Institute, University of Illinois College of Medicine at Peoria, Peoria, Illinois Alan S. Boulos, M.D. Department of Neurosurgery, University at Albany, The State University of New York, Albany, New York Reprint requests: Andrew J. Ringer, M.D., c/o Editorial Office, Department of Neurosurgery, University of Cincinnati College of Medicine, PO Box 670515, Cincinnati, OH 45267-0515. Email: editor@mayfieldclinic.com Received, August 29, 2008. Accepted, April 1, 2009. Copyright © 2009 by the Congress of Neurological Surgeons E ndovascular therapy of intracranial aneu- rysms was initially approved by the Food and Drug Administration as a treatment option for aneurysms considered high risk for surgery. Endovascular therapy has now become a popular alternative to surgical repair and is con- sidered a first-line treatment in many patients. Although recent clinical trials have demonstrated that short-term outcomes are better after endovas- cular coiling than after surgical clipping, aneu- rysm recurrence remains a major concern for these endovascular patients (11, 12, 17). Most practitioners recommend regular sur- veillance imaging after coiling because of the small but real risk of subarachnoid hemorrhage caused by an incompletely treated or recurrent aneurysm (3). Although recurrences of small aneurysms (e.g., 2 mm on angiography) are simply observed, retreatment is typically rec- ommended for larger recurrent aneurysms (6, 8). However, for endovascular coiling to be pre- ferred to surgical management, the estimated risk of treatment for angiographic recurrences or residuals must not exceed the expected risk of subsequent subarachnoid hemorrhage. In this multicenter study, we quantified this risk of retreatment for angiographic recurrences or residuals, thus providing practitioners with quantitative evidence on which to base their treatment determinations. PATIENTS AND METHODS The Endovascular Neurosurgery Research Group (ENRG) is a collaboration of cerebrovascular neuro- ABBREVIATIONS: ENRG, Endovascular Neurosurgery Research Group DEFINING THE RISK OF RETREATMENT FOR ANEURYSM RECURRENCE OR RESIDUAL AFTER INITIAL TREATMENT BY ENDOVASCULAR COILING: A MULTICENTER STUDY OBJECTIVE: Endovascular treatment of intracranial aneurysms is less invasive than sur- gical repair but poses a higher risk for aneurysm recurrence, which may necessitate retreatment, thus adding to the long-term risk. Cerebrovascular neurosurgeons from 8 institutions in the United States and Puerto Rico collaborated to assess the risk of retreatment for residual or recurrent aneurysms after the initial endovascular coiling. METHODS: Data were prospectively recorded for 311 patients with coiled intracranial aneurysms who underwent 352 retreatment procedures after angiographic or clinical recurrence (hemorrhage after initial coiling). Results analyzed included procedural com- plications and procedure-related morbidity. Morbidity was classified as major (modified Rankin scale score  3) or minor, and temporary (30 days) or permanent (30 days). RESULTS: Retreatment mortality was 0.85% per procedure and 0.96% per patient. Treatment-related rates were 0.32% per patient (0.28% per procedure) for permanent or temporary major disability; 1.29% for permanent minor disability (1.14% per proce- dure); and 1.61% for temporary minor disability (1.42% per procedure). Total risk for death or permanent major disability was 1.28% per patient and 1.13% per procedure. CONCLUSION: Retreatment poses a low risk for patients with recurrences of intracra- nial aneurysms after initial coiling; this risk is smaller than that posed by the initial endovascular therapy. The risk of disability associated with retreatment for aneurysm recurrence after coiling must be considered prospectively in the choice of treatment but with the recognition that its effects are low in the overall management risk. KEY WORDS: Aneurysm, Angiography, Coiling, Recurrence, Residual Neurosurgery 65:311–315, 2009 DOI: 10.1227/01.NEU.0000349922.05350.96 www.neurosurgery-online.com