CLINICAL ARTICLE W ithin the frst 72 hours after aneurysm rupture multiple pathways are activated, leading to im- pairment of microcirculation, autoregulation, and cerebral perfusion associated with brain edema for - mation. These pathophysiological changes are summa- rized as early brain injury (EBI). 2,8,9,11,15,17,24,25,27 Although the exact pathophysiology of EBI is still not completely elucidated, it is assumed that EBI might have an impact on the incidence of delayed complications as well as on clini- cal outcome after aneurysmal subarachnoid hemorrhage (aSAH). 24,26 Therefore, addressing EBI as a diagnostic and therapeutic target might have the potential to prevent sec- ondary brain injury and to improve outcome. Blood-brain barrier (BBB) disruption with increased tissue permeabil- ity (PMB) is deemed to be an integral part of EBI after aSAH presenting with global or focal cerebral edema. 10,18,22 Although cerebral perfusion was evaluated in most previ- ously published aSAH studies, the assessment of BBB in- tegrity is currently underrepresented. Recently, 2 studies have been published on BBB function and EBI. 1,3 Choi et ABBREVIATIONS aSAH = aneurysmal subarachnoid hemorrhage; BBB = blood-brain barrier; BFV = blood flow velocity; CTP = CT perfusion; DCI = delayed cerebral ischemia; EBI = early brain injury; mRS = modified Rankin Scale; NPV = negative predictive value; PMB = permeability; PPV = positive predictive value; SEBES = Sub- arachnoid Hemorrhage Early Brain Edema Score; VOI = volume of interest. SUBMITTED March 17, 2019. ACCEPTED May 30, 2019. INCLUDE WHEN CITING Published online August 23, 2019; DOI: 10.3171/2019.5.JNS19765. * M.N.P. and D.M. contributed equally to this work and share senior authorship. Assessment of tissue permeability by early CT perfusion as a surrogate parameter for early brain injury after subarachnoid hemorrhage *Vesna Malinova, MD, 1 Bogdan Iliev, 1 Ioannis Tsogkas, 2 Veit Rohde, MD, 1 Marios-Nikos Psychogios, MD, 2,3 and Dorothee Mielke, MD 1 Departments of 1 Neurosurgery and 2 Neuroradiology, Georg-August-University, Göttingen, Germany; and 3 Department of Neuroradiology, University Hospital Basel, Switzerland OBJECTIVE The severity of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (aSAH) correlates with delayed cerebral ischemia (DCI) and outcome. A disruption of the blood-brain barrier is part of EBI pathophysiology. The aim of this study was to assess tissue permeability (PMB) by CT perfusion (CTP) in the acute phase after aSAH and its impact on DCI and outcome. METHODS CTP was performed on day 3 after aSAH. Qualitative and quantitative analyses of all CTP parameters, including PMB, were performed. The areas with increased PMB were documented. The value of an early PMB increase as a predictor of DCI and outcome according to the modifed Rankin Scale (mRS) grade 3 to 24 months after aSAH was assessed. Possible associations of increased PMB with the Subarachnoid Hemorrhage Early Brain Edema Score (SEBES) and with early perfusion defcits, as radiographic EBI markers, were evaluated. RESULTS A total of 69 patients were enrolled in the study. An increased PMB on early CTP was detected in 10.1% (7/69) of all patients. A favorable outcome (mRS grade ≤ 2) occurred in 40.6% (28/69) of all patients. DCI was detected in 25% (17/69) of all patients. An increased PMB was a predictor of DCI (logistic regression, p = 0.03) but not of outcome (logistic regression, p = 0.40). The detection of increased PMB predicted DCI with a sensitivity of 25%, a specifcity of 94%, a positive predictive value of 57%, and a negative predictive value of 79% (chi-square test p = 0.03). Early perfu- sion defcits were seen in 68.1% (47/69) of the patients, a fnding that correlated with DCI (p = 0.005) but not with the outcome. No correlation was found between the SEBES and increased PMB. CONCLUSIONS Changes in PMB can be detected by early CTP after aSAH, which correlates with DCI. Future studies are needed to evaluate the time course of PMB changes and their interaction with therapeutic measures. https://thejns.org/doi/abs/10.3171/2019.5.JNS19765 KEYWORDS subarachnoid hemorrhage; delayed cerebral ischemia; CT perfusion; vascular disorders J Neurosurg August 23, 2019 1 ©AANS 2019, except where prohibited by US copyright law