Incidence of Orbital Infarction Syndrome Following Anterior Circulation Endovascular Thrombectomy.

Background: Orbital infarction syndrome (OIS) is a rare entity defined as acute ischemia of intraorbital structures. Its occurrence requires interruption of the rich collateral supply to the orbit from both the ophthalmic artery (OA) and branches of the external carotid artery. Three case reports have recently been published of OIS occurring after endovascular thrombectomy (EVT). The goal of this study was to determine the true incidence of post-EVT OIS and to identify associated imaging findings on computed tomography angiography and digital subtraction angiography (DSA). Methods: A retrospective cohort study was performed at our comprehensive stroke center, including all patients who underwent EVT for anterior circulation strokes in 2019 and 2020. Patient charts were reviewed up to 24 hours after EVT for the presence of acute painful vision loss, ophthalmoplegia, chemosis, and proptosis. Patients with any combination of these symptoms in the absence of a carotid-cavernous fistula were defined as having OIS. Pre-EVT computed tomography angiography, pre-EVT DSA, and post-EVT DSA images were reviewed to determine the sensitivity and specificity of absent OA opacification, nonopacified external carotid artery, and absent choroid blush (CB) for post-EVT OIS. Patients were excluded from sensitivity and specificity analysis for each finding that was objectively impossible to assess on their images, either because it was outside the field of view or not tested during the procedure. Findings were deemed indeterminate if motion artifact or contrast timing led to uncertainty about their presence. Sensitivity and specificity calculations were performed on a worst-case-scenario basis, with all indeterminate findings assumed to be false positives or false negatives. Results: Of 217 patients with anterior circulation EVT (male:female, 107:110; median age, 73 [21-98] years), 4 cases of OIS were discovered (male:female, 1:3; median age, 71 [66-80] years; incidence, 1.7%). The number of patients excluded from sensitivity and specificity analysis for each imaging finding was as follows: 34 for pre-EVT CB, 45 for post-EVT CB, 7 for pre-EVT OA, and 19 for post-EVT OA. CB was deemed indeterminate in 47 patients on pre-EVT DSA and 36 patients on post-EVT DSA. All indeterminate cases occurred in non-OIS patients and were counted as false negatives. Absent OA opacification was 50% sensitive and 91% specific for OIS on both pre-EVT computed tomography angiography and pre-EVT DSA, and 0% sensitive and 97% specific on post-EVT DSA. Absent CB was 33% sensitive and 65% specific for OIS on pre-EVT DSA, and 100% sensitive and 73% specific on post-EVT DSA. Conclusion: Post-EVT OIS is rare, with an incidence of 1.7%. Absent OA opacification is 91% specific for OIS on pre-EVT computed tomography angiography and 97% specific for OIS on post-EVT DSA. Absent post-EVT CB is 100% sensitive for OIS, with a worst-case scenario specificity of 73%. These findings may help alert clinicians to potential OIS cases as well as determine the underlying cause of OIS.