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Endovascular coiling of intracranial aneurysms using bioactive coils

Endovascular treatment (EVT) of intracranial aneurysms by using Guglielmi Detachable Coils (GDC) was introduced in 1991 (1). The GDC is made of platinum and enables controllable coil detachment from the deploying wire by electrolysis. This novel technique spread rapidly throughout the world and became an acceptable alternative to surgery (2, 4). Since its introduction, coil technology has taken huge steps forward. Already in the 1990s, new modifications of the GDC were developed, including 2Dand 3D-shaped coils as well as soft and ultrasoft coils. Later, competitive platinum coils with different detachment technologies also became available. The feasibility, safety, and efficacy of EVT using platinum coils has been proven in several clinical series (2, 4). The most significant drawbacks of this technique, however, were the inability to treat widenecked aneurysms and aneurysm recanalization after treatment. Currently, the limitations associated with wide aneurysm neck can be solved on most occasions by the balloon remodeling technique (5) or by intracranial stents (3). However, the problem of long-term durability of the treatment, i.e., aneurysm recanalization, has remained unsolved and is the main limitation of EVT compared to surgery. The recanalization rate has varied between 13% and 34% in previous studies (7). With the aim of preventing recanalization, several types of second-generation coils with surface modifications have been under investigation. The first coated coil available for clinical use was coated with bioactive copolymer consisting of polyglycolic/ polylactic acid (PGLA). Despite promising initial results in experimental aneurysm models (6), only a few clinical series have so far been published with regard to the safety and efficacy of this device. A recent prospective multicenter study from France included 261 patients. Patients with giant aneurysms or poor clinical condition (Glasgow Coma Scale v10) were excluded, and selection bias could not be totally avoided. Clinical analysis was conducted in 236 patients having 244 aneurysms. Complete occlusion and neck remnant were achieved in 102 (44%) and 58 (25%) aneurysms, respectively. Technical and clinical complications related to the procedure were encountered in 43 patients (18.2%). Postoperative modification of clinical status was observed in 12 patients (5.1%). Treatment-related mortality and permanent morbidity were 0.8% and 2.5%, respectively. The authors concluded that the method is feasible, and demonstrated initial angiographic results and overall morbidity and mortality rates that are within the ranges found in the literature in the use of bare platinum coils (7). In this issue of Acta Radiologica, Rossitti describes a single-center experience with this coil. One hundred eighteen aneurysms in 104 patients (73 with subarachnoid hemorrhage) were embolized with PGLA coil alone (n552) or combined with bare platinum coils (n566). Complete obliteration was achieved in 45 aneurysms (38.1%), residual neck in 44 (37.3%), and residual aneurysm in 29 (24.6%). Procedure-related mortality and morbidity were 1.0% and 4.8%, respectively. Imaging follow-up of 73 aneurysms showed complete obliteration in 64.4%, residual neck in 24.7%, and residual aneurysm in 10.9%. Recanalization occurred in 11 (15.1%), and four (5.5%) aneurysms required retreatment. The author concludes that the method has a satisfactory safety profile and aneurysm obliteration rates were similar to those reported with bare platinum coils (8). The results of this study, however, are to be interpreted with caution, given the complexity of aneurysmal lesions, selection bias, and the short follow-up period. The biologic response of intracranial aneurysms to bare platinum coils and PGLA-coated coils is complex, requiring stability of the initial occlusion for a significant length of time for treatment to be considered durable. Also, the classification of aneurysm occlusion is difficult and subjective (2, 7). The real benefits of aneurysm occlusion with PGLA-coated coils compared to occlusion with bare platinum coils are still unknown, and a prospective randomized study will yield the most accurate answer to this question. The article by Rossitti is an important contribution in its field and highly recommended reading.