Abstract TP137: Characteristics of Perfusion Profiles in Patients With Chronic Internal Carotid Artery Occlusion

Abstract

Introduction: Internal carotid artery (ICA) occlusion may cause an acute stroke or may remain asymptomatic for years. Differences in the perfusion characteristics between patients with acute symptomatic ICA occlusions and those with chronic ICA occlusions have not been defined. The aim of this study is to identify the characteristics of the relatively “benign” perfusion pattern associated with chronic asymptomatic ICA occlusions and to determine if this pattern can be differentiated from the pattern observed in acutely symptomatic cases. Methods: We included 31 chronic ICA patients who had no history of a cerebral ischemic event for at least 1 year at the time of imaging and 20 patients with acute ischemic stroke caused by ICA occlusions from DEFUSE 2. All patients underwent MRI with perfusion. Perfusion parameters, including Tmax lesion volumes, hypoperfusion index (Tmax10/Tmax6), and CBV index (rCBV in Tmax6) were calculated by RAPID software. The status of the CBV, CBF, and MTT in the ischemic hemisphere was also rated by visual inspection on a 3-point scale (unchanged, reduced or increased). Differences were assessed by Mann-Whitney and Fisher’s exact tests. Results: The average age was 65.0±9.9 years in chronic vs. 64.7±14.2 years in acute ICA occlusion group ( p =0.90). Most of the chronic ICA patients had no territory with Tmax>10s (29/31) or Tmax>8s (24/31) in the ischemic hemisphere. The average Tmax lesion volumes were lower in the chronic ICA group (Tmax>6 of 14 ml and Tmax>4 of 81 ml) than in the acute ICA occlusion group (Tmax>6 of 131 ml and Tmax>4 of 220 ml, p <0.0001 for both, Figure). CBV was unchanged in all chronic occlusion cases. In the acute occlusion group, there were 12 out of 20 cases (60%) with decreased CBV ( p <0.0001). CBF was decreased in 1 (3%) patient with a chronic occlusion and 17 cases (85%) with acute occlusions ( p <0.0001). MTT prolonged in 7 cases (22%) with chronic occlusions vs. all cases (100%) with acute occlusions ( p <0.0001). Conclusions: Several features on perfusion MRI distinguish chronic ICA occlusions from acute occlusions. Patients with chronic ICA occlusions tend to have none or a minimal volume of tissue with Tmax>8s or >10s delay, smaller volumes of tissue with Tmax>4s and >6s delay, and normal appearing CBV and CBF maps.