Abstract
Background:
While CT angiography is the standard tool to identify the site of large vessel occlusion (LVO) in acute ischemic stroke (AIS), CTP may be confirmatory or facilitate identification of the occluded vessel especially in distal LVOs. This study aims to examine the utility of CTP in localizing the site of intracranial large vessel occlusions (LVOs).
Method:
We reviewed our prospective database of all patients between January 2017 and July 2019 who underwent CTP for suspected AIS. Vascular territories with perfusion abnormalities were recorded. Reference standard for occlusion was defined as confirmed LVO by CTA or digital substraction angiogram (DSA). CTP results were deemed true positive when the identified area with perfusion abnormality was the same as or overlapped with the territory of the occluded vessel on CTA/DSA.
Result:
We identified 280 stroke alert patients with median NIHSS 11. LVOs were confirmed in 155 patients, of whom 146 showed corresponding perfusion abnormality (sensitivity 94.2%), and 129 with ischemic penumbra. CT perfusion was highly sensitive for occlusions in the MCA (sensitivity 95.7%, 111/116), ICA (100%, 21/21), and PCA (100%, 10/10). CTP only identified 2 of 5 (40%) basilar artery occlusions. CTP sensitivity was 97.2% (69/71), 97.5% (39/40), and 60% (3/5) for occlusions at M1, M2, and M3, respectively. Of the 125 patients who did not have LVO, 54 had falsely positive CT perfusion studies (41 with penumbra) due to stenotic processes, microvascular ischemia, chronic infarcts, or artifacts. In this cohort, 90 patients underwent mechanical thrombectomy, all with confirmed LVOs. 86/90 thrombectomy recipients (95.6%) had perfusion penumbra on initial imaging. Of the remaining 4 thrombectomy recipients who did not demonstrate perfusion mismatch on CTP, 3 had basilar occlusions.
Conclusion:
CTP is highly sensitive for identifying the site of LVO in the ICA, MCA, and PCA and may be particularly useful in cases of difficult to detect LVOs particularly in M2 and PCA vessels. However, the low specificity of CTP continues to emphasize the importance of correlation with CTA and clinical findings.