Intracranial artery dissection (IAD) is a pathological dissection of the arterial wall [1, 2]. It involves the arterial intima, forming subintimal hematoma and expands between the arterial intima and arterial media [3]. IAD can occur in any part of the intracranial artery, mainly in the latter circulation in Asia, but mainly in the former circulation in Western countries [4]. It has been reported that the incidence of IAD in European population is less than 10% of carotid artery dissection. However, IAD accounts for 67% to 90% of all CAD in East Asian populations [5]. There are more male patients with IAD than females, with an average age of 50.4 years. The site of IAD is more common in the posterior circulation than the anterior circulation, with the V4 segment of the vertebral artery the most common site. IAD in the posterior circulation usually causes subarachnoid hemorrhage, which is accompanied by headache and neck pain, while patients with IAD in anterior circulation mostly have symptoms of ischemia [6, 7]. Until now, very little is known about the etiology of IAD. Hypertension, diabetes, hyperlipidemia, moyamoya disease, oral contraceptives, migraine and recent history of infection are considered to be predisposing factors for IAD [8, 9].

Due to the lack of specificity of clinical manifestations, the diagnosis of IAD mainly depends on imaging examination. The diameter of the intracranial artery is thin and the aisle is also tortuous. Low spatial resolution of intracranial artery therefore limits effective inspection methods, increasing the difficulty of diagnosis. Digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography angiography (CTA) are common imaging methods for IAD [10, 11]. With the advantages of fast imaging and the ability to provide clinicians with dynamic vascular luminal conditions throughout its course, DAS currently provides the best methodology for the clinical diagnosis of IAD. However, it should be noted that DSA is an invasive inspection method, which may cause trauma to subjects during the implementation process. Further, the risk of complications with DSA is relatively high, which is not conducive to the active acceptance and cooperation of the examination. The characteristic imaging signs of IAD with DSA are the intimal flap and double lumen, but they are only seen in a low number of patients [12]. Additionally, DSA cannot directly show the wall of the involved artery, so patients with no significant changes in the diameter of the artery may be missed. For this reason, fusiform expansion or gradual stenosis shown on DSA should be distinguished from atherosclerotic disease.

Craniocerebral MRI better reveals blood vessel wall, lumen and intramural hematoma than DSA. High-resolution MRI (HR-MRI) is a clinical imaging evaluation technology that has emerged in recent years. Compared with conventional MRI, HR-MRI mainly uses black blood sequence based on fast spin echo sequence and bright blood sequence based on gradient echo sequence [13, 14]. Black blood technology eliminates the signals of blood, extraluminal cerebrospinal fluid and perivascular fat, while achieving high-resolution images of the vascular wall. Bright blood technology clearly shows the boundary between blood and the vascular wall and assists with observation of the fine structure of the lumen and vascular wall lesions, so as to assist analysis of the etiology. HR-MRI is a technique that can effectively inhibit the signals of flowing blood in vessels, thereby providing the operator with a static tissue image of the vessel wall This is helpful for evaluating the pathological shape of the arterial vessel wall [15]. Further, by reducing the layer thickness and voxel size, HR-MRI provides high spatial resolution images for more accurate evaluation. However, HR-MRI has rarely been applied for the analysis of patients with IAD, so this study aimed to show the morphological features and imaging characteristics of IAD patients by use of HR-MRI and demonstrate the clinical value of HR-MRI for IAD patients.

IAD, including dissection and dissection aneurysm, is a primary cause of stroke in young and middle-aged people [19]. IAD can lead to severe cerebral ischemia or cerebral hemorrhage, so early diagnosis is particularly important. However, it is difficult to show the abnormal lumen structure of lesions by CTA and DSA, so the diagnosis of IAD remains a considerable challenge.

The application of HR-MRI in vascular-related diseases has attracted increasing attention in recent years. With the advantages of being non-invasive, high repeatability, high spatial resolution and providing multi-parameter imaging, HR-MRI has been used in previous studies for evaluating atherosclerotic diseases, ischemic stroke and moyamoya disease [20, 21, 22]. This technology provides information not only on the lumen, but also on the morphology and composition of the tube wall. In this study, it was shown that HR-MRI significantly assisted the visualization and characterization of IAD, which was also helpful in providing a greater in-depth understanding of IAD and its differentiation from other intracranial artery diseases.

Several characteristic patterns of HR-MRI in artery disease have been described. In unilateral middle cerebral artery inflammatory stenosis, HR-MRI has accurately determined the degree of intracranial artery stenosis and provided important diagnostic information for arterial inflammatory stenosis [23]. Additionally, the HR-MRI results of middle cerebral artery occlusion caused by intracranial atherosclerosis primarily manifested as eccentric involvement of the vessel wall with uneven signal intensity, while patients with moyamoya disease typically exhibited concentric involvement of the vessel wall with relatively uniform signal intensity [24, 25]. HR-MRI was also considered to be a useful future tool for the differential diagnosis of moyamoya disease due to its value in assessing the pathological changes of blood vessel walls and understanding the fundamental mechanisms of the disease. A previous study detected the abnormal signal of the third cranial nerve in patients with giant cell arteritis by using HR-MRI [26]. It was found that the sensitivity, specificity, positive and negative predictive values of the abnormal signal were 0.88, 1, 1 and 0.99, respectively, indicating high diagnostic significance for HR-MRI in patients with this condition. According to the correlation between HR-MRI abnormalities and clinical manifestations in patients with ischemic stroke, the hypothesis that positive remodeling was an unsafe remodeling that can easily cause acute ischemic stroke had been corroborated [27]. It was also proposed that HR-MRI might be a promising tool for detecting characteristics of the intracranial artery wall and revealing the relationship between ischemic stroke and the remodeling pattern after atherosclerosis. Further, HR-MRI confirmed that six months of high-dose statin treatment effectively stabilized symptomatic intracranial atherosclerotic plaques and improved the degree of vascular stenosis [28]. Based on the foregoing, we believe that HR-MRI has high application value in vascular diseases.

The typical imaging signs of IAD in HR-MRI include double lumen, intimal flap, luminal morphological changes and intermural hematoma [29]. The double lumen is a direct sign for diagnosis of IAD. The true cavity is generally narrow and accompanied by high-velocity blood flow. This presents a low signal on a MR black blood image sequence and a high signal on the bright blood sequence. However, a false cavity is generally wider and the blood flow rate is much slower. It is easy to form turbulence on a false cavity, thus showing an uneven signal on HR-MRI. The morphology of the true and false cavity shown by HR-MRI allows IAD to be distinguished from other cerebrovascular diseases. Intimal flap is another direct manifestation of the arterial interlayer, which can be used for the diagnosis of IAD [30]. It is known that DSA provides a reference standard for diagnosing IAD. However, in the DSA examination, the direct signs of artery dissection such as double lumen and intimal flap can be seen in less than 10% of IAD cases [12]. The application of black blood sequence can suppress the blood flow signal, so that the tube wall is well displayed on HR-MRI. In the T1 black blood sequence, the intimal flap located in the vascular cavity, was observed to manifest as a petal-like structure with equal or high signal. The three-dimensional black blood sequence better displays the intimal flap through multi-planar reorganization. In a previous study [31], 84.3% of IAD patients showed the presence of an intimal flap on T1WI sequence of HR-MRI. Consistent with that research, here it was found that 82.8% and 84.3% of IAD patients showed double lumen and intimal flap, respectively, on HR-MRI. There findings confirmed that HR-MRI has great potential for been used to IAD.

Lumen imaging can indicate the location of a lesion. As for luminal changes, beaded or segmental stenosis were the most common signs of IAD on DSA [32]. When the lesion is small, common lumen imaging may not be sufficiently specific and currently HR-MRI has an absolute diagnostic advantage. In IAD patients, intramural hematoma usually manifests as crescent thickening of the arterial wall with increased diameter, stenosis or occlusion of the true lumen, while the signal of intramural hematoma depends on the time of hematoma formation. The hematoma manifests high signal in the T1WI sequence after 48–72 hours of IAD, which is the same as atherosclerotic plaque hemorrhage in T1WI sequences [33]. However, the detection of intramural hematomas of IAD can be improved by use of HR-MRI and black blood technology [34]. In the current study 92.9% and 38.6% of IAD patients were respectively found to show altered lumen shape and visible hematoma on HR-MRI. Additionally, 28.6% and 88.6% of IAD patients showed enhanced thrombosis and endometrial flap enhancement, respectively. So HR-MRI may make easy visualization possible for abnormal morphologies of artery dissection lesions in IAD patients.

An ischemic event was one of the common symptoms of IAD and in this study more than 90% of IAD patients had clinical symptoms. Since an ischemic event caused by a culprit dissection might seriously affect the prognosis of an IAD patient, finding predictive factors is of great significance. It was suggested in a previous study that hypertension was a key factor for vertebral artery dissection [35]. In accordance with previous studies, a remarkable difference was found here in the percentage of patients with hypertension, together with double lumen and intimal flap between culprit and non-culprit. The results of ROC analysis showed that the AUCs of hypertension, double lumen and intimal flap were 0.604, 0.671 and 0.658, respectively. Additionally, all AUCs of combinations of two or three factors were above 0.7, suggesting they provided high value for predicting ischemic events caused by the culprit dissection.

Nevertheless, there were limitations in this study. First of all, the simple size of patients recruited was relatively small. More patients are needed to verify the reported conclusions. Secondly, the HR-MRI technique had more requirements for both operators and patients. As the HR-MRI scan time was longer, slight movements of the patient seriously affected image quality. Further, some patients have severe motion artifacts and cannot be diagnosed. Finally, it is easy to misjudge flow artifacts as intimal flap in the area of large aneurysm or severe lumen stenosis.

In summary, HR-MRI allowed easy visualization of the blood vessel wall, which enabled visual observation of direct and indirect signs of IAD. HR-MRI not only improves the diagnostic rate of IAD, but also provides useful information for a better understanding of its pathophysiological mechanisms. Additionally, hypertension, double lumen and intimal flap were identified as the risk factors for predicting the occurrence of an ischemic event caused by the culprit dissection.

QW—Conceptualization, Writing-Original Draft, Writing-Review & Editing. YL—Methodology, Formal analysis. BD—Data Curation, Visualization. XY—Conceptualization, Data Curation. ZZ—Data Curation, Resources. FO-Y—Formal analysis, Data Curation. MY—Data Curation, Visualization. YC—Formal analysis, Data Curation. XZ—Supervision, Methodology, Writing-Review & Editing.

This study was approved by the medical research ethics committee of the First Affiliated Hospital of Nanchang University (No. 2022-3-008). All individuals understood the purpose and latent risks, and signed informed consent.

Not applicable.

This research was funded Science and Technology Research Project of Jiangxi Provincial Department of Education, grant number 150246; This research was funded by Natural Science Foundation of Jiangxi Province, grant number 20192ACBL20040.

The authors declare no conflict of interest.