Diagnostic separation of conventional ⩾50% carotid stenosis and near-occlusion with phase-contrast MRI

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.

Quantifying Carotid Stenosis: History, Current Applications, Limitations, and Potential: How Imaging Is Changing the Scenario

Carotid artery stenosis is a major cause of morbidity and mortality. The journey to understanding carotid disease has developed over time and radiology has a pivotal role in diagnosis, risk stratification and therapeutic management. This paper reviews the history of diagnostic imaging in carotid disease, its evolution towards its current applications in the clinical and research fields, and the potential of new technologies to aid clinicians in identifying the disease and tailoring medical and surgical treatment.

[Ct-angiography in assessment of critical occlusive carotid artery disease]

BACKGROUND

Occlusive carotid artery disease is still one of the major causes of ischemic stroke in the world. Progression of severe carotid stenosis may lead to critical stenosis and vascular occlusion. Nevertheless, there is still no pure definition of the concept of critical occlusive carotid artery disease.

OBJECTIVE

To define the role of CT-angiography in assessment of critical occlusive carotid artery disease.

MATERIAL AND METHODS

We analyzed data of 405 patients who underwent preoperative precise assessment of carotid arteries and subsequent surgical treatment for the period from 2016 to 2019. Contrast-enhanced CT-angiography (Philips Ict scanner, 256 slices) was made after previous ultrasound. Contrast agent injection rate was 4-5 ml/sec. CT angiography data were assessed according to a specialized protocol.

RESULTS

Critical occlusive carotid artery disease was observed in 128 (31.6%) cases including critical stenosis (24.94%), near-occlusion (5.92%) and local occlusion (0.74%). Critical stenosis was characterized by local narrowing ≥90% and normal diameter of distal arterial segment. In case of near-occlusion, local critical stenosis was accompanied by narrowing of distal arterial segment. In case of local occlusion, distal collateral supply of internal carotid artery occurred through atypically originating ascending pharyngeal artery. Patients with near-occlusion and local occlusion of internal carotid artery had no signs of ICA hypoplasia and intracranial stenoses. All elements of circle of Willis were observed in 70% of patients.

CONCLUSION

State of distal segment of internal carotid artery can be considered as a differential diagnostic criterion for critical occlusive carotid disease variants. CT-angiography provides all necessary data and can be recommended for precise preoperative assessment.

Carotid near-occlusion can be identified with ultrasound by low flow velocity distal to the stenosis

BACKGROUND

Most carotid near-occlusions are indistinguishable from conventional ≥ 50% stenosis on ultrasound, demonstrating high peak systolic velocity (PSV) in the stenosis.

PURPOSE

To study whether the velocity distal to the stenosis can separate high PSV near-occlusion from conventional ≥ 50% stenosis.

MATERIAL AND METHODS

We included patients with ≥ 50% carotid stenosis with high PSV (≥125 cm/s), examined with both computed tomography angiography (CTA) and ultrasound within 30 days, and a distal velocity measurement was performed. Based on CTA, cases were divided into three groups: conventional stenosis; near-occlusion without full collapse (NwoC; normal-appearing albeit small distal artery); and near-occlusion with full collapse (NwC; threadlike distal artery). Distal Doppler ultrasound flow velocities were compared between these groups.

RESULTS

Sixty patients were included: 33 patients with conventional stenosis; 20 patients with NwoC; and seven patients with NwC. Mean distal PSV was 93, 63, and 21 cm/s ( P < 0.001) and mean distal end-diastolic velocity was 30, 24, and 5 cm/s ( P < 0.001), respectively. A distal PSV < 50 cm/s was 63% sensitive and 94% specific for separating both types of near-occlusion from conventional stenosis.

CONCLUSION

In high PSV carotid stenoses, the distal velocity was lower in near-occlusions than conventional carotid stenosis. Distal velocities warrant further investigation in diagnostic studies.

Carotid Near-Occlusion Stent Experiences

Introduction

Treatment strategy for near-occlusions (NO) of the internal carotid artery (ICA) is still controversial. In this study, we aimed to present the clinical results of stent placement in 50 patients with carotid artery (NO) stenosis that presented to our center, and upon which revascularization will be performed.

Methods

Between 2014 and 2017, 50 patients with (NO) from 180 patients who had stents in the Interventional Vascular Neurology clinic were retrospectively studied. All the patients whether using or not using the proximal and distal protection device during the procedure were included. Patients had clinical neurologic evaluation, and underwent carotid artery radiologic imaging before the carotid artery stent (CAS) procedure. Balloon dilatation was applied before the stent procedure for patients that had advanced stenosis. Post-dilatation was applied with a balloon of appropriate size in case of residual narrowing. Findings such as bradycardia, hypotension, reperfusion hemorrhage during and after the stent placement procedure, as well as patients that developed restenosis within 12 months were recorded.

Results

This study includes 50 (30 males, 20 females) patients that underwent carotid stent placement. The mean age of patients was 65 (28-81). Reperfusion hemorrhage was seen in 1 (2%) patient and the patient died in week 3. Ten (20%) patients complained of chills and tremor lasting less than 3 hours after the procedure. One (2%) patient had encephalopathy and agitation for less than 24 hours. Two (4%) patients had hypotension, and 15 (30%) patients had a headache for less than 24 hours. Three patients developed local hematoma at the site of the sheath, and were treated by applying compression. Restenosis signs in the stent site was observed in 6 patients (12%) in color Doppler ultrasonography of the carotid performed in the 6th and 12th months.

Conclusion

Although the innate process of ICA NO is not well known, it might be more frequent than currently considered. Especially after the diagnosis of ICA stenosis, it is important to make the right diagnosis in patients that have new ipsilateral symptoms. After the diagnosis is made, CAS, when performed by an experienced neuro-interventional team, seems beneficial with low complication rates.