The non-enhancing peritumoral area (NEPA) is defined as the hyperintense region in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images surrounding a brain tumor. The NEPA corresponds to different pathological processes, including vasogenic edema and infiltrative edema. The analysis of the NEPA with conventional and advanced magnetic resonance imaging (MRI) was proposed in the differential diagnosis of solid brain tumors, showing higher accuracy than MRI evaluation of the enhancing part of the tumor. In particular, MRI assessment of the NEPA was demonstrated to be a promising tool for distinguishing high-grade gliomas from primary lymphoma and brain metastases. Additionally, the MRI characteristics of the NEPA were found to correlate with prognosis and treatment response. The purpose of this narrative review was to describe MRI features of the NEPA obtained with conventional and advanced MRI techniques to better understand their potential in identifying the different characteristics of high-grade gliomas, primary lymphoma and brain metastases and in predicting clinical outcome and response to surgery and chemo-irradiation. Diffusion and perfusion techniques, such as diffusion tensor imaging (DTI), diffusional kurtosis imaging (DKI), dynamic susceptibility contrast-enhanced (DSC) perfusion imaging, dynamic contrast-enhanced (DCE) perfusion imaging, arterial spin labeling (ASL), spectroscopy and amide proton transfer (APT), were the advanced MRI procedures we reviewed.

Background: CT perfusion (CTP) overestimation of core volume >10 mL compared to the final infarct volume (FIV) size is the current definition of the ghost infarct core (GIC) phenomenon. However, subsequent infarct growth might influence FIV. We aimed to report a more reliable assessment of GIC occurrence, defined as no evidence of infarct at 24 h follow-up imaging, compared to CTP core volume at admission. This phenomenon was named absolute GIC (aGIC), and we investigated its prevalence and predictors. Methods: A total of 652 consecutive stroke patients with large vessel occlusion who achieved successful recanalization (mTICI 2b-3) after endovascular treatment (EVT) and non-contrast CT (NCCT) follow-up imaging at 24 h were retrospectively analyzed. Ischemic core volume was automatically generated from CTP, and FIV was manually determined on follow-up NCCT. Multivariable logistic regression was used to explore aGIC predictors. Results: We included 652 patients (53.3% female, median age 75 years), of whom 35 (5.3%) had an aGIC. The aGIC group showed higher ASPECTS (p < 0.001), shorter (<3 h) onset-to-imaging time (p < 0.016), poorer collaterals (p < 0.001), and higher hypoperfusion intensity ratio (p < 0.001) compared to the non-aGIC group. In multivariate analysis, ASPECTS (odds ratio (OR), 2.37; p <0.001), onset-to-imaging time (OR, 0.99; p = 0.034), collateral score (OR, 0.24; p < 0.001), and hypoperfusion intensity ratio (OR, 23.2; p < 0.001) were independently associated with aGIC. Conclusions: aGIC is a more reliable evaluation of infarct core volume overestimation assessed on admission CTP and represents a rare phenomenon, associated with ultra-early presentation and poor collaterals.

Background: Deep medullary vein (DMV) drainage has been suggested as a new biomarker for predicting clinical outcomes in patients with acute ischemic stroke (AIS). We evaluated this hypothesis in patients who received endovascular treatment (EVT) within 24 h of symptom onset. Methods: We performed a retrospective study of consecutive AIS patients at a single institution treated with EVT achieving successful recanalization (final mTICI score ≥2b). DMV drainage was graded on a three-point scale (0-1-2) during the second peak venous phase of mCTA by assessing contrast filling, with grade 2 indicating a favorable DMV profile. Our primary outcomes were functional independence, defined as a modified Rankin Scale (mRS) score of 0–2 at 90 days, and ordinal mRS shift at 90 days. Secondary outcomes were excellent clinical status (mRS 0–1 at 90 days), hemorrhagic transformation, and symptomatic intracranial hemorrhage. We investigated independent associations using multivariable logistic and ordinal regression analyses as appropriate, adjusting for age, sex, baseline mRS, NIHSS at onset, occlusion site, intravenous thrombolysis, onset-to-CT time, and ASPECTS. Results: We included 506 patients; the mean age was 76 years. A favorable DMV profile was present in 394 (78%) patients. We found that DMV doubled the odds of achieving functional independence (OR = 2.22; 95% CI = 1.28–3.85) and was associated with a shift towards better functional outcomes in ordinal regression analysis (cOR = 1.93; 95% CI = 1.24–3.02), whereas we did not find any association between a favorable DMV profile and secondary outcomes. Conclusions: In AIS patients successfully recanalized with EVT, a favorable DMV profile was associated with better functional outcomes. Further investigations may clarify the clinical use and predictive ability of this novel radiological marker.