Twig-like middle cerebral artery mimicking moyamoya syndrome : a case report and literature review.

Abstract

Background

Twig-like middle cerebral artery (T-MCA) is a rare vascular anomaly characterized by the replacement of the M1 segment of the middle cerebral artery (MCA) by a plexiform network of small vessels (1,2). This anomaly is often misdiagnosed due to its resemblance to Moyamoya disease (MMD), a progressive occlusive condition affecting the internal carotid artery (ICA) and associated with abnormal collateral vessel formation (1). While MMD typically involves bilateral ICA occlusion, T-MCA is unilateral and arises from an embryonic abnormality in MCA development (1). Awareness of T-MCA is crucial to avoid unnecessary or inappropriate treatments (1,3).

Aims The purpose of this case report is to highlight the clinical and radiological characteristics of twig-like middle cerebral artery (T-MCA) and its distinction from moyamoya disease (MMD). Given the rarity of T-MCA, which is often mistaken for MMD due to similar imaging patterns, this report aims to raise awareness of T-MCA as a separate congenital anomaly that can mimic progressive occlusive diseases like MMD. Accurate diagnosis is essential to avoid unnecessary treatments and to guide proper management for patients presenting with T-MCA.

Case Presentation

We present the case of a 57-year-old male who arrived at our institution with symptoms of sudden-onset headache, nausea, and vomiting. Initial CT imaging revealed a right MCA occlusion, raising suspicion for Moyamoya disease due to the plexiform arterial network. However, the MRI confirmed the diagnosis of T-MCA. The patient was managed conservatively due to the stable neurological status and absence of hemorrhagic stroke.

Discussion

T-MCA is a rare anomaly, identified in 0.11?1.17% of individuals undergoing angiography (4). Approximately 70% of affected individuals experience hemorrhagic stroke, 20% suffer ischemic events, and a minority remain asymptomatic (4,5). The most critical differential diagnosis is Moyamoya disease, which, unlike T-MCA, involves progressive bilateral ICA occlusion and basal ganglia moyamoya vessels (1). The differentiation between T-MCA and Moyamoya disease is essential due to the differing clinical implications and management approaches for these two conditions (3). T-MCA, although often mistaken for MMD, is a non-progressive vascular anomaly that is congenital in nature (1). MMD, on the other hand, is characterized by progressive stenosis or occlusion of the internal carotid artery (ICA) and its branches, which leads to the formation of compensatory basal ganglia collateral vessels (5). These compensatory vessels resemble a puff of smoke, or "moyamoya" in Japanese, as visualized on angiographic imaging (5). Misidentifying T-MCA as MMD can lead to overly aggressive treatments, including unnecessary surgical revascularization procedures intended for MMD (5). In our case, the patient presented with symptoms commonly associated with cerebrovascular events, including a sudden-onset headache, nausea, and vomiting. Initial imaging suggested a right MCA occlusion, raising suspicion for Moyamoya disease due to the appearance of a plexiform network. However, further MRI studies confirmed a stable, non-progressive T-MCA anomaly, allowing us to avoid more invasive interventions and opt for conservative management. In this case, the unilateral nature of the occlusion and lack of progressive stenosis of the ICA terminals differentiated T-MCA from MMD (1). The underlying pathology of T-MCA is rooted in a developmental anomaly, wherein the MCA fails to complete its formation, resulting in a plexiform arterial network instead of a single, well-formed M1 segment (1). This congenital defect is thought to occur early in embryonic development, distinguishing T-MCA?s etiology from the progressive occlusive nature of MMD (1). Due to its rarity, T-MCA is frequently undiagnosed or misdiagnosed, especially in cases where imaging reveals extensive collateral vessels mimicking Moyamoya disease (1). Given the high risk of hemorrhagic stroke in T-MCA patients, awareness of this anomaly is critical (6). Clinicians and radiologists should maintain a high index of suspicion when unilateral MCA abnormalities are detected without accompanying ICA stenosis (5). This distinction can be critical in tailoring treatment plans, particularly when the patient's neurological symptoms are stable and the risk of invasive intervention outweighs potential benefits (5). Further research into T-MCA is needed to better understand its clinical trajectory and to establish guidelines for optimal management (6). Data on the natural history, prevalence, and potential risk factors for ischemic or hemorrhagic events in T-MCA patients are limited, necessitating larger studies and registry-based data collection (6). Such insights would assist clinicians in balancing the benefits and risks of various treatment strategies and, importantly, in avoiding the overtreatment often associated with misdiagnosis (6).

Conclusion

The distinction between T-MCA and Moyamoya disease is essential for appropriate management and treatment planning. T-MCA should be considered in cases where unilateral MCA occlusion and plexiform networks are observed. Recognition of this rare anomaly will help avoid misdiagnosis and unnecessary interventions, particularly in patients with stable neurological symptoms. Further research and data collection are needed to fully understand the clinical implications and optimal management strategies for T-MCA.