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The hypothesis of this study was that evaluation of radiodensity assessment beyond a carotid stenosis in arterial and/or venous phase can be used to separate near-occlusion and conventional ≥ 50% stenosis. We prospectively included participants with ≥ 50% carotid stenosis with inclusion preference for cases with extracranial internal carotid artery (ICA) asymmetry. All participants were examined with a research biphasic computed tomography angiography (CTA) protocol (arterial and venous phase). Reference diagnosis was set by interpretation on CTA and radiodensity difference between ipsilateral and contralateral ICA (c-corrected) or vertebral (v-corrected) was compared. We included 93 participants, 62 with near-occlusion and 31 with conventional ≥ 50% stenosis. Just beyond the stenosis, median c-corrected radiodensity was - 20 Hounsfield units (HU) among near-occlusions and - 1 HU among conventional ≥ 50% stenoses (p < 0.001) in the arterial phase. For the venous phase, these findings were + 17 HU and + 3 HU (p = 0.007). Similar group differences were seen for v-correction. No parameter had good diagnostic performance, area under the curve ≤ 0.82. With specificity set at ≥ 95%, detected near-occlusions were foremost those with large side-to-side differences in distal ICA-diameter. Carotid near-occlusions can have reduced radiodensity beyond the stenosis in arterial phases and increased radiodensity in venous phases compared to a reference artery-which was not clearly seen for conventional stenoses. However, these radiodensity findings are best seen in near-occlusion cases that are not diagnostically challenging, while they work poorly as additional diagnostic aids.

Introduction: The aim of this study was to assess sensitivity, specificity and interrater reliability of phase-contrast MRI (PC-MRI) for diagnosing carotid near-occlusion.

Patients and methods: Prospective cross-sectional study conducted between 2018 and 2021. We included participants with suspected 50%–100% carotid stenosis on at least one side, all were examined with CT angiography (CTA) and PC-MRI and both ICAs were analyzed. Degree of stenosis on CTA was the reference test. PC-MRI-based blood flow rates in extracranial ICA and intracranial cerebral arteries were assessed. ICA-cerebral blood flow (CBF) ratio was defined as ICA divided by sum of both ICAs and Basilar artery.

Results: We included 136 participants. The ICAs were 102 < 50% stenosis, 88 conventional ⩾50% stenosis (31 with ⩾70%), 49 near-occlusion, 12 occlusions, 20 unclear cause of small distal ICA on CTA and one excluded. For separation of near-occlusion and conventional stenoses, ICA flow rate and ICA-CBF ratio had the highest area under the curve (AUC; 0.98–0.99) for near-occlusion. ICA-CBF ratio ⩽0.225 was 90% (45/49) sensitive and 99% (188/190) specific for near-occlusion. Inter-rater reliability for this threshold was excellent (kappa 0.98). Specificity was 94% (29/31) for cases with ⩾70% stenosis. PC-MRI had modest performance for separating <50% and conventional ⩾50% stenosis (highest AUC 0.74), and eight (16%) of near-occlusions were not distinguishable from occlusion (no visible flow).

Conclusion: ICA-CBF ratio ⩽0.225 on PC-MRI is an accurate and reliable method to separate conventional ⩾50% stenosis and near-occlusion that is feasible for routine use. PC-MRI should be considered further as a potential standard method for near-occlusion detection, to be used side-by-side with established modalities as PC-MRI cannot separate other degrees of stenosis.

We aimed to validate the prognostic ability and assess interrater reliability of a recently suggested measurement-based definition of near-occlusion with full collapse (distal ICA diameter ≤ 2.0 mm and/or ICA ratio ≤ 0.42). 118 consecutive patients with symptomatic near-occlusion were prospectively included and assessed on computed tomography angiography by 2 blinded observers, 26 (22%) had full collapse. At 2 days after presenting event, the risk of preoperative stroke was 3% for without full collapse and 16% for with full collapse (p = 0.01). At 28 days, this risk was 16% for without full collapse and 22% for with full collapse (p = 0.22). Interrater reliability was perfect (kappa 1.0). Thus, near-occlusion with full collapse should be defined as distal ICA ≤ 2.0 mm and/or ICA ratio ≤ 0.42 in order to detect cases with very high risk of early stroke recurrence.

Objective: It is unclear whether ischaemic stroke among patients with symptomatic carotid near occlusion is caused by an embolic or haemodynamic mechanism. An embolic mechanism can be reflected by the occurrence of microembolic signals (MES) on transcranial Doppler. This study aimed to compare the incidence of MES between patients with symptomatic near occlusion, symptomatic conventional ≥ 50% stenosis, and asymptomatic ≥ 50% stenosis.

Methods: This cross sectional study included patients with ≥ 50% symptomatic or asymptomatic carotid stenosis. The degree of stenosis was assessed with computed tomography angiography, where near occlusion was diagnosed by feature interpretation. Symptomatic was defined as ipsilateral events within six months. Occurrence of MES was recorded bilaterally in the middle cerebral artery for 30 minutes with transcranial Doppler.

Results: A total of 109 participants with ≥ 50% carotid stenosis were included, comprising 52 with symptomatic ≥ 50% conventional stenosis, 41 symptomatic near occlusion, and 16 asymptomatic ≥ 50% stenosis. The incidence of MES was 46% (19/41; 95% confidence interval [CI] 30 – 62%) among symptomatic near occlusion, 27% (14/52; 95% CI 14 – 39%) among symptomatic ≥ 50% conventional stenosis, and 6% (1/16; 95% CI 0 – 20%) among asymptomatic ≥ 50% carotid stenosis. The incidence of MES tended to be higher among symptomatic near occlusions compared with symptomatic ≥ 50% conventional stenoses (unadjusted odds ratio [OR] 2.3, 95% CI 1.0 – 5.6; p = .054), but was statistically significantly higher after adjustments (adjusted OR 3.9, 95% CI 1.4 – 10.7; p = .009). The MES incidence was higher among symptomatic near occlusions than asymptomatic ≥ 50% stenoses (p = .005).

Conclusion: Microembolic signals appear to be more prevalent in symptomatic near occlusions compared with both symptomatic conventional ≥ 50% carotid stenoses and asymptomatic conventional ≥ 50% carotid stenoses. These findings could reflect a possible embolic mechanism behind ischaemic stroke in symptomatic carotid near occlusion patients, but do not rule out concurrent haemodynamic mechanisms. Additional studies using various markers of both embolic and haemodynamic mechanisms are warranted.

Purpose: Compare extracranial internal carotid artery flow rates and intracranial collateral use between conventional ≥ 50% carotid stenosis and carotid near-occlusion, and between symptomatic and asymptomatic carotid near-occlusion.

Methods: We included patients with ≥ 50% carotid stenosis. Degree of stenosis was diagnosed on CTA. Mean blood flow rates were assessed with four-dimensional phase-contrast MRI.

Results: We included 110 patients of which 83% were symptomatic, and 38% had near-occlusion. Near-occlusions had lower mean internal carotid artery flow (70 ml/min) than conventional ≥ 50% stenoses (203 ml/min, P <.001). Definite use of ≥ 1 collateral was found in 83% (35/42) of near-occlusions and 10% (7/68) of conventional stenoses (P <.001). However, there were no differences in total cerebral blood flow (514 ml/min vs. 519 ml/min, P =.78) or ipsilateral hemispheric blood flow (234 vs. 227 ml/min, P =.52), between near-occlusions and conventional ≥ 50% stenoses, based on phase-contrast MRI flow rates. There were no differences in total cerebral or hemispheric blood flow, or collateral use, between symptomatic and asymptomatic near-occlusions.

Conclusion: Near-occlusions have lower internal carotid artery flow rates and more collateral use, but similar total cerebral blood flow and hemispheric blood flow, compared to conventional ≥ 50% carotid stenosis.

Objective: To assess if intravenous thrombolysis (IVT) affects the risk of recurrent preoperative cerebrovascular events before carotid surgery or stenting in patients with symptomatic ≥ 50% carotid stenosis.

Methods: Three cohorts of symptomatic ≥ 50% carotid stenosis patients were merged. To make the control group relevant, we excluded patients not presenting with stroke on the day of symptom onset. The risk of preoperative cerebrovascular events up to 30 days were compared between the IVT-treated and non-IVT-treated.

Results: 316 patients were included, 64 (20%) treated with IVT. Those treated with IVT had similar risk of recurrent ipsilateral ischemic stroke or retinal artery occlusion (12% at day 7, 12% at day 30) as those not treated (9% at day 7, 15% at day 30; adjusted HR 0.9, 95%CI 0.4-2.2). There was a tendency (p=0.09) towards time-dependency in the data where the recurrence risk was higher in IVT treated at day 0 (6% in IVT-treated, 1% in non-IVT-treated, OR 5.5, 95%CI 1.2-25.4, p=0.03). This was not significant when adjusting for co-factors (adjusted OR 4.4, 95%CI 0.9-21.8, p=0.07) and was offset by a later risk decrease, with no remaining risk difference between IVT-treated and non-IVT treated at day 7.

Conclusions: IVT treatment does not seem to affect the risk of recurrent ipsilateral ischemic stroke in patients with symptomatic ≥ 50% carotid stenosis: The risk is high in both IVT-treated and non-IVT-treated. However, there might be a risk increase on the day of IVT treatment that is offset by a risk decrease during the first week.