General discussion 153 conclusion that CTA should be used as the primary imaging modality in patients presenting with a SAH, and that MRA should be the imaging modality of choice in the follow-up of coiled aneurysms. In Chapter 1 we noted that most cost-effectiveness studies in patients with intracranial aneurysms focused on treatment of the aneurysms, and few on screening for unruptured aneurysms. Wermer et al. assessed the yield of screening for new aneurysms after treatment for SAH, with the Markov model,84 and in a later paper these same authors assessed the cost-effectiveness of screening patients using CTA every five years after being clipped for a ruptured intracranial aneurysm.85 For this patient population in general, screening for new aneurysms did not lead to an increase in QALY’s, nor was it cost-effective. Screening was found to save costs and increase QALYs in patients with a relatively high risk of both aneurysm formation and rupture, however, and to increase QALYs at acceptable costs in patients with a higher risk of recurrence.85 There have been no cost-effectiveness studies published on the follow-up of coiled aneurysms. In view of our proposal 8 above, that prolonged follow-up is not recommended in patients with an adequately occluded aneurysm at six months after coiling, it would be interesting to see whether a cost-effectiveness study would support this. Future research Many aspects of imaging in patients presenting with SAH have been addressed in the past, as described in Chapter 1, and are still being addressed in on-going research. For detection of aneurysms as well as for follow-up of treated aneurysms, most diagnostic modalities have been tested on all levels necessary for proper evaluation of a diagnostic test.86,87 However, this thesis has shown the necessity for several studies to be carried out in the near future: • A systematic review and meta-analysis of MRA for the detection of intracranial aneurysms based on recent literature, with separate analyses for CEMRA and TOF-MRA and for ruptured and unruptured aneurysms. • Confirmation or rejection of our proposal that the three-point R&R classification can be reduced to a two-point classification: adequately or inadequately occluded. This should ideally be done in a prospective study. However, if existing studies have used the R&R classification correctly, a retrospective analysis of these data could be useful, as the one we carried out on the LOTUS data. • Cost-effectiveness studies of different follow-up strategies are required in order to define the optimal timing of follow-up, and clarify whether prolonged follow-up of all coiled aneurysms with MRA is cost-effective. • The yield of ultra-long follow-up (>10 yrs) has yet to be assessed. Plans for such a study (LOTUS III) have been made. Preferably, all the above studies should meet the Standards for Reporting of Diagnostic Accuracy (STARD) criteria,88 as this will improve and simplify the comparison and pooling of data. References 1 Holmes, T. Aneurysms of the internal carotid artery in the cavernous sinus. Trans Pathol Soc London 12, 61, (1860). 2 Bederson, J. B. et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke 40, 994-1025, (2009).
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