DIAGNOSTIC NEURORADIOLOGY Frequency and appearance of hemosiderin depositions after aneurysmal subarachnoid hemorrhage treated by endovascular therapy Bernhard Falter 1 & Martin Wiesmann 1 & Jessica Freiherr 1 & Omid Nikoubashman 1 & Michael Mull 1 Received: 17 May 2015 /Accepted: 1 July 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Introduction It is still unclear how often subarachnoid hemor- rhage (SAH) leads to chronic hemosiderin depositions. In this study, we aimed to determine the frequency of chronic hemo- siderin depositions after aneurysmal SAH in patients who did not undergo surgery. Furthermore, we analyzed typical MRI patterns of chronic SAH and sought to obtain information on the temporal course of MRI signal changes. Methods We retrospectively analyzed 90 patients who had undergone endovascular treatment for acute aneurysmal SAH. In all patients, initial CT studies and at least one T2*- weighted MRI obtained 6 months or later after SAH were analyzed for the presence and anatomical distribution of SAH or chronic hemosiderin depositions. In total, 185 T2*- weighted MRI studies obtained between 2 days and 148 months after SAH were evaluated (mean follow-up 30.2 months). Results On MRI studies obtained later than 6 months after SAH, subpial hemosiderin depositions were found in 50 pa- tients (55.5 %). Most frequent localizations were the paren- chyma adjacent to the frontal and parietal sulci and the insular cisterns. While the appearance of hemosiderin depositions was dynamic within the first 3 months, no changes were found during subsequent follow-up. MR signal changes were not only conclusive with subarachnoid hemosiderin depositions but in many cases also resembled those that have been asso- ciated with cortical hemosiderosis. Conclusions T2*-weighted MRI is an effective means of di- agnosing prior SAH. Our study suggests that chronic hemo- siderin depositions can be found in a considerable number of patients after a single event of subarachnoid hemorrhage. Keywords Hemosiderin . Endovascular therapy . T2*w magnetic resonance imaging . Subarachnoid hemorrhage . Aneurysm Introduction Gradient-echo T2*-weighted MRI has been shown to reliably detect hemosiderin degradation products [1–5]. This method can be used to diagnose both acute and chronic intracranial hemorrhage [5–8]. T2*-weighted imaging has therefore be- come a routine tool in the diagnosis of, e.g., cerebral cavernomas, amyloid angiopathy, or superficial siderosis. In patients with intracranial aneurysms, the decision wheth- er to treat the aneurysm or not may depend on knowledge that the aneurysm has ruptured. In some cases, however, subarach- noid hemorrhage (SAH) can be hard to detect. Small hemor- rhages can be almost asymptomatic. The sensitivity of CT in the detection of SAH decreases from 85 % in the first day to 50 % after 1 week, and 30 % only after 2 weeks [9]. Cerebro- spinal fluid (CSF) examination has a higher sensitivity but will also fail after a few months [10]. It has been shown that hemosiderin depositions (HD) can be detected on T2*- weighted MRI years after an intracranial hemorrhage, possi- bly even after decades [5, 7]. However, it is still unclear how often SAH leads to chronic HD. To the best of our knowledge, only two studies have looked systematically into the frequen- cy of HD after SAH [11, 12]. Imaizumi et al. found HD in 72.4 % of their patients. However, only patients who had undergone surgical clipping of their aneurysms were included. * Michael Mull mmull@ukaachen.de 1 Department of Neuroradiology, University Hospital Aachen RWTH, Pauwelsstr. 30, 52074 Aachen, Germany Neuroradiology DOI 10.1007/s00234-015-1559-8