70 Chapter 3 endovascular treatment were to be undertaken. These patients will be referred to the neurosurgeon for clipping of the aneurysm. The percentage of aneurysms that are coiled in our department has increased from less than 50% ten years ago to more than 70% at present. In the present study 36 of the 65 aneurysms appeared to be suitable for endovascular treatment on the basis of the DSA findings in the diagnostic phase. In two of these patients an endovascular procedure was initiated, but during the procedure it proved that coiling was not possible. The procedure was aborted and the patients were referred for surgery. In our analysis these aneurysms are considered as not suitable for endovascular treatment, reflecting the findings during the endovascular procedure. Thus 34 of the 65 aneurysms (52.3%) were treated by endovascular coiling, which is less than average in our general population of patients with an aneurysmal SAH (see Chapter 5).23 If there is doubt about the coilability of an aneurysm on the basis of the CTA findings, diagnostic DSA is performed. In some of the cases presented to the neurosurgeon for clipping on the basis of the CTA findings, an additional DSA study is requested by the neurosurgeon. If CEMRA were to perform better than CTA in the selection of aneurysms suitable for coiling or clipping, then this might prevent a number of additional diagnostic DSA studies with their inherent risks and costs.24 There are hardly any reports in the literature describing the accuracy of noninvasive techniques in deciding whether endovascular treatment of an aneurysm will be possible. In one study that used CTA as the only pretreatment modality for detection and treatment planning, the authors state that in only 18% (41/223) of patients with an aneurysm was an additional DSA study needed for treatment planning.5 The report does not mention however whether all these decisions on treatment selection made on the basis of CTA were correct. A second study reports the results of a strategy in which CTA was the primary modality to select the appropriate mode of treatment.8 Only in cases in which CTA findings left room for doubt, was a diagnostic DSA study performed. This was the case in in 31 of 224 patients (13.8%). In two of these cases a reversal of the initial treatment decision, which had been based on the CTA findings, took place. In this study there is no direct comparison however with a gold standard (DSA or intra operative findings) in all cases. Other studies report strategies using CTA as a pretreatment modality,25-29 but none specify the accuracy of CTA in assessing the feasibility of endovascular treatment of an intracranial aneurysm The decision whether an aneurysm can be treated by endovascular coiling depends on many factors such as the configuration of the aneurysm, dome to neck ratio and presence of vessels emerging from the base of the aneurysm. Even using these criteria however the decision is largely subjective, depending on the insights and experience of the observer. To investigate this aspect we asked two experienced neurointerventionists from two different hospitals to give their opinion on the feasibility of endovascular treatment on the basis of the DSA findings in our patients with an aneurysm. The Kappa value for interobserver agreement was only 0.41. Of the 65 aneurysms evaluated, the first observer considered 46 aneurysms to be suitable for endovascular coiling, while the second observer agreed with this verdict in only 33 aneurysms (table 3). This indicates that an aspect of the standard of reference - the DSA findings in the cases in which endovascular treatment was considered not possible- depends significantly on subjective criteria.
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