Falsely normal CT perfusion ischemic core readings are common and often associated with deep infarcts

Proper identification of infarct extent is crucial for thrombectomy and prognostication. We sought to study the frequency and topographic aspects of those cases in which CT perfusion (CTP) misses a core lesion that is present on initial non-contrast CT (NCCT).

A review was carried out of a prospectively collected database of endovascular patients with anterior circulation large vessel occlusion strokes from January 2014 to November 2018. Patients with an e-ASPECTS <10 and adequate CTP maps were included. Total missed ischemic core (TMC) was defined as a CTP core lesion (relative cerebral blood flow <30%) <1 mL with a visualized hypodensity on NCCT.

In total, 629 patients were analyzed of which 161 (25.6%) had a TMC. On univariate analysis, TMC was associated with isolated deep middle cerebral artery (MCA) strokes (77.6% vs 56.6%, p<0.001), lower National Institutes of Health Stroke Scale (NIHSS) score (9 (15-20) vs 17 (13-21), p=0.007) and longer times to treatment (452 (288-652) min vs 355 (236-655) min, p=0.03). After adjusting for identifiable confounders, isolated deep MCA stroke was an independent predictor of TMC (OR 2.49 (95% CI 1.63 to 3.8), p<0.001). There were no differences between patients presenting with a TMC and those not with good outcomes (modified Rankin Scale 0-2) (50.8% vs 47.6%, p=0.53) or 90-day mortality (23% vs 17.6%, p=0.17). However, TMC was associated with lower rates of any parenchymal hematomas (5.2% vs 14.6%, p=0.02; aOR 0.11 (95% CI 0.01 to 0.91), p=0.04) and smaller final infarct volumes (20.5 (11.3-42.9) mL vs 47.5 (20.3-85) mL, p<0.001).

CTP may completely fail to detect ischemic core in as many as 25% of cases, especially in isolated deep MCA strokes. Technical refinements of the post-processing algorithms are therefore warranted. TMC infarcts may have a lower risk of reperfusion hemorrhage, potentially due to greater preservation of the neurovascular unit structure in face of delayed recovery of cerebral blood flow.