1 INTRODUCTION

The superior cerebellar artery (SCA), which is a crucial branch of the vertebrobasilar artery system, plays an essential role in the vascular network of the infratentorial cerebellar artery. The SCA has a consistent origin and vascularization, which makes it an invaluable anatomical landmark in neuroimaging and neurosurgical procedures of the cerebellum and brainstem. In particular, the SCA is an ideal marker for delineating the path and position of the trochlear nerve [1].

In the 1990s, Barker et al. first highlighted the clinical significance of the SCA, particularly in the context of trigeminal neuralgia. In that study of 1185 cases of microvascular decompression of trigeminal nerve roots, 75% of trigeminal neuralgia cases were associated with the SCA [2]. Additionally, ischemic cerebellar strokes involving the SCA region account for approximately 36% of cerebellar infarctions [3]. As such, detailed imaging of the anatomy of the SCA is critical in diagnosing and treating cerebellar infarction, trigeminal neuralgia, hemifacial spasm, and tumors at the cerebellopontine angle.

Conventionally, assessment of the SCA involves autopsy and digital subtraction angiography (DSA), although the invasive nature and associated risks (e.g., X-ray radiation and contrast agent allergies) of DSA limit its suitability, especially for patients with mild symptoms. As such, there is increasing need for noninvasive imaging modalities for the SCA [4].

Magnetic resonance angiography (MRA), and more specifically three-dimensional time-of-flight MRA (3D-TOF-MRA), has become a prevalent noninvasive technique for examining the intracranial arteries [5, 6]. 3D-TOF-MRA has a high spatial resolution, signal-to-noise ratio, and soft tissue clarity, which provide detailed visualization of the cerebral vascular structures [7, 8]. Advances in 5.0T ultra-high field magnetic resonance (MR) scanning have significantly improved image quality [9, 10], especially for distal intracranial and small branch arteries. The high spatial resolution of 3D-TOF-MRA at 5.0T, which is based on inflow enhancement for bright blood imaging, ensures minimal phase flow loss, reduced turbulence effects, and enhanced image quality post-processing [10]. The improved contrast-to-noise ratio with this method is essential for visualizing small branch arteries [10-13]. The aim of the present study was to examine the feasibility of 3D-TOF-MRA at 5.0T for detailed analysis and visualization of the SCA.

2 MATERIALS AND METHODS

3 RESULTS

The 5.0T 3D-TOF-MRA effectively displayed the origin and shape of the SCA (Figures 1 and 2). Approximately 87% of patients showed an SCA that was longer than the P3 segment of the PCA. A total of 123 superior cerebellar arteries were identified in 55 patients (61 on the right and 62 on the left side of the basilar artery, BA). There was no significant difference in the diameters of the left and right vessels (t = 1.345, p = 0.184; Table 1).

Based on the origin of the SCA and its relationship with the PCA, the 55 patients were categorized into nine SCA-origin types (Figure 3). Type A was the most common (approximately 49% of cases), followed by type b (approximately 24%). The proportions of the other types are detailed in Table 2.

4 DISCUSSION

In the present study, we performed a retrospective analysis of the SCA using 3D-TOF-MRA at 5.0T. Because of its superior spatial resolution, we found that this technique was an excellent noninvasive tool for detailed evaluation of the SCA, which included clear delineation of its origin, caliber, and course.

The SCA is recognized for its consistent vascularization in the infratentorial cerebellar artery. It typically originates from the BA near the superior margin on the pons, and then courses around the cerebral peduncle to supply blood to key cerebellar regions [15]. The SCA is divided into distinct segments based on its distribution, and its accurate identification and clear display are crucial, especially when evaluating cerebellar infarction, trigeminal neuralgia, hemifacial spasm, and cerebellopontine angle tumors.

Previous morphological studies of the SCA were largely based on autopsy findings [11, 16, 17], although there is now increasing use of computed tomography angiography (CTA) [4, 18]. However, to our knowledge only one other study has used MRA to observe SCA morphology [19], in which 145 images were examined using a 1.5T MRI and 3D-TOF. Previous autopsy studies also reported the transverse diameter of the starting part of the SCA [1, 18]. Importantly, the SCA diameter measured by 5.0T MRA in the present study was consistent with those CTA and anatomical studies. Note that the variation in SCA diameter depending on its origin suggests a link to ischemic events, particularly post-surgical manipulations [4], which indicates the importance of cautious imaging.

Our study categorized the SCA origins into nine types, which provides valuable insight into their anatomical and clinical significance. Type a was the most common type (49.09% of patients), in which the SCA originated directly from the BA [16, 18]. Type b, which was the second most common type (23.64%), had origins from the PCA, which highlights that variations may influence the vascular supply during PCA-related pathologies or surgeries [16]. The less common types (e.g., Type c: 9.09%, Types d, e, f, g, h, and i: 1.82%–5.45%) highlight the diversity in SCA anatomy, which is critical for anticipating anatomical variations during diagnostic and therapeutic interventions [15, 16, 18].

In surgical procedures involving the cerebellum and the cerebellopontine angle, as well as in trigeminal microvascular decompression, SCA treatment was traditionally guided by clinical experience, which poses a risk for injury. Therefore, noninvasive imaging of the origin and shape of the SCA is important for early diagnosis and choosing appropriate treatment methods for SCA-related diseases. The diversity in the origin and morphology of the SCA, and its potential involvement in trigeminal neuralgia, is increasingly recognized. A number of studies have confirmed that the SCA plays a role in trigeminal nerve compression previously [20-22]. The classification of the origins of the SCA into nine types [4] (with Type A being the most common) was somewhat reflected in the present study, although we saw differing proportions, which was likely because of our smaller sample size.

Venti reported that cerebellar infarction caused by SCA lesions accounts for approximately 36% of all ischemic cerebellar strokes [3], with common symptoms including gait or saccade disorders [23]. Note that in that study, 5.0T MRA was also effective for evaluating the SCA in patients with isolated gait instability or acute attacks. The high-resolution imaging capacity of 5.0T MRA allows for detailed visualization of the SCA, which aids in the early diagnosis and management of these conditions. Compared with CTA, which is also a viable option for SCA evaluation [4, 18], 5.0T MRA avoids the risks associated with radiation and contrast agent allergies, and thus provides a safer and noninvasive alternative for these patients.

The development of 5.0T ultra-high field whole-body MR imaging has facilitated extensive clinical research, particularly in cerebrovascular applications [9, 10]. Our research demonstrates that 5.0T MR 3D-TOF-MRA imaging can effectively visualize the origin and shape of the SCA, with high consistency through anatomical findings. Our findings also suggest that 5.0T MRA is an effective strategy for diagnosing and differentiating diseases related to the SCA. The high spatial resolution and enhanced image quality of 5.0T MRA enables precise visualization of the SCA anatomy, which is crucial for identifying variations and abnormalities. These capabilities can improve the diagnosis and differentiation of conditions such as cerebellar infarction, trigeminal neuralgia, hemifacial spasm, and tumors at the cerebellopontine angle, which allows more accurate and effective clinical decision-making.

There are a number of limitations in our study. First, the limited number of patients may have restricted the statistical significance and generalizability of our results. Nevertheless, our detailed imaging and consistent methodology provide valuable insight into the anatomy and pathology of the SCA, which contributes to the existing body of knowledge in neurovascular imaging. Second, we did not perform a quantitative analysis of SCA signal strength. Nonetheless, our qualitative assessments provide substantial clinical value by improving our understanding of the anatomical variations of the SCA, as well as their potential implications in various cerebrovascular diseases. Third, the absence of further investigation into SCA-related diseases in this study limits the scope of clinical applicability. Exploring the direct correlation between SCA abnormalities and specific cerebrovascular diseases could provide more comprehensive insight. Finally, we did not validate our findings with CTA/DSA or compare with 3.0T systems. However, our study highlights the capacity of advanced 5.0T technology for high-resolution imaging and provides a basis for future comparative studies.

5 CONCLUSION

In summary, 5.0T ultra-high field 3D-TOF-MRA provides clear visualization of the origin, diameter, and course of the SCA. Thus, 5.0T 3D-TOF-MRA represents a new strategy for diagnosing and differentiating SCA-related diseases, which is a significant step forward in neurovascular imaging.

AUTHOR CONTRIBUTIONS

Ning Tian: Writing—original draft (lead). Xiangsen Jiang: Data curation (supporting). Lei Yu: Investigation (equal). Zudong Yin: Methodology (equal). Dan Yu: Writing—review & editing (supporting). Jie Gan: Supervision (lead).

CONFLICT OF INTEREST STATEMENT

The authors declare that they have no conflict of interest.

ETHICS STATEMENT

Not applicable.

INFORMED CONSENT

Not applicable.