ORIGINAL ARTICLE Subarachnoid hemorrhage and negative angiography: clinical course and long-term follow-up Marco Fontanella & Innocenzo Rainero & Pier Paolo Panciani & Bawarjan Schatlo & Chiara Benevello & Diego Garbossa & Christian Carlino & Walter Valfrè & Federico Griva & Gianni Boris Bradac & Alessandro Ducati Received: 18 November 2010 / Revised: 1 March 2011 / Accepted: 6 March 2011 # Springer-Verlag 2011 Abstract The aim of this study was to investigate the long- term natural history of nontraumatic angiogram-negative subarachnoid hemorrhage with typical pretruncal (P-SAH) and diffuse (D-SAH) pattern of hemorrhage. A retrospective review of 102 patients who experienced angiographically negative SAH at our institution was undertaken (11.6% of 882 spontaneous SAH). Follow-ups were obtained at 7.9 to 16 years. In the D-SAH group, 11 patients (13.9%) out of 79 had an aneurysm, and four (5.1%) had rebleeding episodes. In the P-SAH group, the second angiography was negative in all of the 23 cases, and no rebleeding episodes were recorded. The long-term follow-up confirms that P-SAH is a benign disease. A second angiography could not be necessary. D-SAH is probably due to an aneurysm that thrombose early after the bleeding. At short-term follow-up, the sack could frequently recanalize and rebleed, whereas a late follow-up shows that rebleeding is very rare. Keywords Negative angiography . Pretruncal subarachnoid hemorrhage . Intracranial aneurysms . Subarachnoid hemorrhage of unknown cause . Angiogram-negative subarachnoid hemorrhage Introduction A considerable improvement in neurodiagnostic techniques has increased our ability to detect intracranial aneurysms with angiography and Angio-CT. However, angiogram- negative subarachnoid hemorrhage (SAH) still accounts for 2–24% of the cases of SAH [3, 18]. Jung et al. analyzed over 3,000 patients with SAH. In their series, 4.4% (143) showed no evidence and found that 18 patients showed an aneurysm on a repeat angiography exam. Of these 18 patients, all but one had a blood distribution on CT which was sylvian, interhemispheric, diffuse, or tentorial suggesting an aneurysm [18]. The pattern of blood distribution in the subarachnoid cisterns on the computed tomography scan (CT) at SAH onset is thus very important for predicting the possible negative result of cerebral angiographic examination [17, 31]. In particular, subarachnoid blood which is limited to the prepontine, pretruncal region, as reported in the literature [27, 28, 30, 31], is associated with good outcome and a lower risk of rebleeding. On the other hand, a diffuse SAH may be due to the presence of an intracranial aneurysm. The long-term follow-up and in particular the long-term risk of rebleeding in perimesencephalic and diffuse subarachnoid hemorrhage are not clear and require further study. In the present study, we considered initial angiogram- negative SAH patients with diffuse SAH and pretruncal SAH. Our aim was to study (1) the clinical course and the outcome at discharge, (2) the percentage of intracranial M. Fontanella (*) : P. P. Panciani : C. Benevello : D. Garbossa : C. Carlino : F. Griva : A. Ducati Division of Neurosurgery, Department of Neuroscience, University of Torino, Via Cherasco 15, 10126 Torino, Italy e-mail: marco.fontanella@tin.it I. Rainero : W. Valfrè Division of Neurology, Department of Neuroscience, University of Torino, Torino, Italy B. Schatlo Department of Neurosurgery, University Hospital Geneva, Geneva, Switzerland G. B. Bradac Division of Neuroradiology, Department of Neuroscience, University of Torino, Torino, Italy Neurosurg Rev DOI 10.1007/s10143-011-0323-8