Initial and follow-up digital subtraction angiography of a 44-year-old female patient (Table 1, #21) 8 years after bleeding.

<p><i>A</i> Right ICA angiogram (lateral view) obtained in 2005 depicting a 2 x 2 mm aneurysm of the right distal ICA <i>(arrow)</i>, which was not initially detected. <i>B</i> Pre-operative angiogram of the right ICA (lateral view) in 2013; since 2005 the morphology and extension of the distal ICA aneurysm remained stable <i>(arrow)</i>. ICA = internal carotid artery.</p

MRI follow-up eight years after nonperimesencephalic subarachnoid hemorrhage of a 73-year-old male patient (Table 1, #17).

<p>Post-hemorrhagic sulcal siderosis is indicated by arrows. <i>A-D</i> show no residuals after bleeding. <i>E</i> shows sulcal siderosis on the parietal and occipital left hemisphere. <i>F</i> depicts no aneurysm in TOF-angiography. Sequences: <i>A</i> = T2 TIRM weighted, <i>B</i> = T1-TIRM weighted, <i>C</i> = diffusion-weighted, <i>D</i> = T2 weighted, <i>E</i> = T2* weighted, <i>F</i> = time-of-flight-angiography.</p

Initially undetected aneurysm found 8 years after SAH of a 44-year-old female patient (Table 1, #21).

<p><i>A</i> CT scan at admission in 2005 revealing nSAH in the frontal interhemispheric fissure, in the premedullary cisterns and the bilateral sylvian fissures. The consecutive digital subtraction angiography was false negative. <i>B</i> Intracranial TOF-angiogram of the same patient in July 2013 demonstrating an aneurysm of the right internal carotid artery <i>(arrow)</i> which was retrospectively visible in the initial post-hemorrhagic digital subtraction angiography (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117925#pone.0117925.g003" target="_blank">Fig. 3</a>).</p