Abstract

Since its introduction in 1991 by Guglielmi, the principle of endovascular therapy with platinum coils has been well-established as an alternative method to neurosurgical clip-ping. This therapy option has especially proven itself in the case of aneurysms, which are difficult to treat with neurosurgery. The location, size and shape of the aneurysm play an important role in deciding between clipping and coiling. In some cases, it is quite difficult to treat very small and wide-necked aneurysms by coiling. However, the currently available data does not indicate which the better treatment method is. In par-ticular, questions concerning the treatment and complications of aneurysms = 3 mm are not adequately answered, since these were the subject of only a few studies. It is there-fore necessary to carry out investigations with this focus in order to adequately assess risk and benefit.

In the present study, 637 endovascular interventions were performed at the Institute for Neuroradiology of the Johann Wolfgang Goethe University Hospital between February 1999 and March 2011. In this study period of 12 years, 47 patients with an aneurysm = 3 mm were included. The study is based on retrospective data collections of patient records, radiological findings and angiography documentation protocols. The character-istics of the patient cohort, like age and gender, are broadly consistent with the litera-ture. Average age was 55 years. 85 % of the patients were women. In contrast to other studies there was a different frequency of aneurysms in certain vascular localizations. In similar studies, the majority of the aneurysms were found at the internal carotid artery, whereas in the present study the anterior communicating artery was most frequently af-fected, followed by the internal carotid artery. 

There is little agreement in literature concerning complication rates. In the present study, it was not possible to complete the coiling in 17 % of cases. A complete aneurysm occlusion was archived in 55 % of the cases, while 28 % of the patients had a minimal neck remnant after intervention. 

The general complication rate was 12.8 %. Intra-procedural rupture occurred in two cases (4.3 %). This falls within the range of rates provided by recent literature (0 % to 11.7 %).

The availability of follow-up studies plays an important role in assessing the success of therapy. In the present study, follow-ups were available in 87 % of patients, which cor-responds to the results in literature. The overall re-treatment rate of 4.3 % was compara-tively low. The formation of a recurrent aneurysm was found in one case.
 
59 % of patients showed a preoperative Hunt and Hess grade of 0 to 2, while other studies presented a Hunt and Hess grade of 0 to 2 in 87 % of cases. Hunt and Hess Grade 3 and 4 was presented in 15 % of patients and 11 % had a grade of 5. In terms of patient welfare, 55.3 % were able to manage their daily life without assistance, which corresponds to a modified Rankin Scale (mRS) 0, 1 and 2. However, 34.0 % of the patients needed help from others and 10.9 % died due to the subarachnoid hemorrhage. This is in contrast to other studies, which achieved a mRS of 0-2 in more than 75%. This reinforces the assumption that an initial low Hunt and Hess grade could be associated with a better outcome while a higher Hunt and Hess grade probably correlates with a poorer clinical outcome.

Due to the small size of the patient cohort, as well as the retrospective data collection of the present work, it is not possible to derive generally reliable, valid treatment recom-mendations. A detailed analysis of our patients’ results was performed and the results were compared to similar publications. Further, it is recommended to conduct prospec-tively planned studies.

In general, it can be concluded that coiling very small aneurysms is a relatively safe treatment method when sufficiently experienced neuroradiologists are involved. In addition to the experience of the interventional neuroradiologist, technical improvement of the used materials, such as coils, stents, balloons and micro catheters, can help minimize the complication risk.