CASE SERIES Admission CT perfusion may overestimate initial infarct core: the ghost infarct core concept Sandra Boned, 1,2 Marina Padroni, 3 Marta Rubiera, 1,2 Alejandro Tomasello, 4 Pilar Coscojuela, 4 Nicolás Romero, 4 Marián Muchada, 1,2 David Rodríguez-Luna, 1,2 Alan Flores, 1,2 Noelia Rodríguez, 1,2 Jesús Juega, 1,2 Jorge Pagola, 1,2 José Alvarez-Sabin, 1,2 Carlos A Molina, 1,2 Marc Ribó 1,2 1 Stroke Unit, Department of Neurology, Vall d’Hebron University Hospital, Vall d’Hebron Research Institute, Barcelona, Spain 2 Departament de Medicina, Universitat Autónoma de Barcelona, Barcelona, Spain 3 Università di Ferrara, Sezione di Clinica Neurologica, Ferrara, Italia 4 Department of Neuroradiology, Vall d’Hebron University Hospital, Barcelona, Spain Correspondence to Dr Marc Ribo, Unitat d’Ictus, Servei de Neurologia, Hospital Vall d’Hebron, Passeig de la Vall d’Hebron, Barcelona 119-129, Spain; marcriboj@hotmail.com Received 1 May 2016 Revised 30 July 2016 Accepted 5 August 2016 Published Online First 26 August 2016 To cite: Boned S, Padroni M, Rubiera M, et al. J NeuroIntervent Surg 2017;9:66–69. ABSTRACT Background Identifying infarct core on admission is essential to establish the amount of salvageable tissue and indicate reperfusion therapies. Infarct core is established on CT perfusion (CTP) as the severely hypoperfused area, however the correlation between hypoperfusion and infarct core may be time-dependent as it is not a direct indicator of tissue damage. This study aims to characterize those cases in which the admission core lesion on CTP does not reflect an infarct on follow-up imaging. Methods We studied patients with cerebral large vessel occlusion who underwent CTP on admission but received endovascular thrombectomy based on a non- contrast CT Alberta Stroke Program Early CT Score (ASPECTS) >6. Admission infarct core was measured on initial cerebral blood volume (CBV) CTP and final infarct on follow-up CT. We defined ghost infarct core (GIC) as initial core minus final infarct >10 mL. Results 79 patients were studied. Median National Institutes of Health Stroke Scale (NIHSS) score was 17 (11–20), median time from symptoms to CTP was 215 (87–327) min, and recanalization rate (TICI 2b–3) was 77%. Thirty patients (38%) presented with a GIC >10 mL. GIC >10 mL was associated with recanalization (TICI 2b–3: 90% vs 68%; p=0.026), admission glycemia (<185 mg/dL: 42% vs 0%; p=0.028), and time to CTP (<185 min: 51% vs >185 min: 26%; p=0.033). An adjusted logistic regression model identified time from symptom to CTP imaging <185 min as the only predictor of GIC >10 mL (OR 2.89, 95% CI 1.04 to 8.09). At 24 hours, clinical improvement was more frequent in patients with GIC >10 mL (66.6% vs 39%; p=0.017). Conclusions CT perfusion may overestimate final infarct core, especially in the early time window. Selecting patients for reperfusion therapies based on the CTP mismatch concept may deny treatment to patients who might still benefit from reperfusion. INTRODUCTION The early restoration of cerebral blood flow (CBF) within the ischemic tissue is the only therapy of proven benefit in reducing infarct growth and pro- moting clinical improvement in ischemic stroke. In the last few years the management of acute ischemic stroke has changed, after studies con- firmed the efficacy of reperfusion therapies. At first, IV tissue-type plasminogen activator (tPA) proved to reduce disability after acute ischemic stroke, 12 and in the last year clinical trials have shown the efficacy of endovascular therapy in treating patients with acute anterior circulation ischemic stroke. 3–7 Selection of candidates for these procedures may require identifying infarct core or irreversible infarct on admission in order to establish the amount of salvageable tissue. 8 Ideal candidates will present with a small ischemic core and a large pen- umbra. 9 Theoretically, a timely reperfusion at this point will stop the progression of the irreversibly damaged core and lead to functional recovery of the remaining penumbral tissue at risk. In this context, multimodal imaging techniques based on MRI 89 or CT 10 11 help identify target large vessel occlusions and can provide information about immediate time-dependent changes that follow the occlusion of a large cerebral vessel. In recent years, multimodal imaging has been used to select patients with acute ischemic stroke for endovascular reperfusion therapies in clinical trials; EXTEND-IA 4 and SWIFT PRIME 7 12 demonstrated the effectiveness of mechanical thrombectomy in patients with large vessel occlu- sion and salvageable tissue defined as the mismatch between the infarct core and the hypoperfused area. The infarct core area is typically depicted by dif- fusion sequences on MRI 89 or by cerebral blood volume (CBV) 13 14 or CBF 15 16 on CT perfusion (CTP) studies. While diffusion-weighted imaging (DWI) abnormalities reflect actual histological changes that occur as a consequence of cerebral ischemia, the CTP abnormalities that are inter- preted as infarct core solely represent the absence of contrast arrival into the severely hypoperfused brain regions. The definition of these areas as irre- versible lesions comes from studies showing that CBV maps reliably predict the final infarct on follow-up imaging. 13 15–17 These studies were done under specific time from onset to imaging and time from imaging to reperfusion conditions. Recent therapeutic, technical, and organizational advances are leading to significant decreases in these time frames, creating a scenario in which the value of CTP as a marker of infarct core is not validated. We aim to describe the value of CBV in different time frames as a predictor of infarct core and to characterize those cases in which the admission core lesion on CTP does not reflect an infarct on follow-up imaging. Boned S, et al. J NeuroIntervent Surg 2017;9:66–69. doi:10.1136/neurintsurg-2016-012494 1 of 5 Neuroimaging