Twig-like middle cerebral artery: Clinical and radiological features — a study of three patients from a single center

Article information

J Cerebrovasc Endovasc Neurosurg. 2026;28(2):177-183

Publication date (electronic) : 2026 February 11

doi : https://doi.org/10.7461/jcen.2026.E2025.10.007

, Hadi Ebrahimi , Hamed Ahmadian , Amir-Hosein Zohrevand , Mostafa Esmaeilnia Shirvani , Shahriyar Nikouhemat , Morteza Sharifzadeh

Department of Neurosurgery, Babol University of Medical Sciences, Babol, Iran

Correspondence to Iman Kazemi Department of Neurosurgery, Babol University of Medical Sciences, Babol, Mazandaran Province, Iran Tel +98 91 1127 0839 Fax +981132252071 E-mail Imaankaazemi@gmail.com

Received 2025 October 19; Revised 2025 December 29; Accepted 2025 December 29.

Abstract

Twig-like middle cerebral artery (T-MCA) is a vascular anomaly in which the M1 segment of the MCA is replaced by a plexiform network of small vessels. It may present with hemorrhagic or ischemic stroke or be detected incidentally. In this paper, we report three rare cases of T-MCA and describe their clinical and radiological characteristics as well as their clinical courses. A secondary objective was to provide a rough estimate of the occurrence of T-MCA among patients who underwent cerebral angiography in our center.

From 2019 to 2023, 810 patients underwent brain digital subtraction angiography (DSA) at our center, of which three (0.37%) had T-MCA. Two patients presented with subarachnoid hemorrhage, and one was incidentally diagnosed. None were candidates for bypass surgery due to comorbidities, overall clinical condition, or patient preference, and all received conservative management. Two patients were discharged alert and without deficits, while one had a poor outcome, remaining in a vegetative state after complications of hemorrhage, hydrocephalus, and meningitis.

T-MCA is a rare congenital anomaly with an estimated occurrence of approximately 0.37% among patients undergoing cerebral angiography in our center. This study adds three new patients to the limited literature and highlights their clinical presentations, radiological features, management decisions, and short-term outcomes. Further studies are needed to clarify its epidemiology, natural history, and optimal management strategies.

Keywords: Twig-like MCA; Middle cerebral artery anomaly; Subarachnoid hemorrhage; Cerebral angiography; CNS vascular malformation

INTRODUCTION

Twig-like middle cerebral artery (T-MCA), also called rete MCA, aplastic MCA, or unfused MCA, is a rare vascular anomaly [13]. In T-MCA, the M1 segment of the MCA is absent and replaced by a plexiform network of small vessels [16].

Due to its rarity, the true incidence is unknown and has been estimated at approximately 0.088%–1.17% [1-3,5,6,11,17,22].

T-MCA may present with hemorrhagic or ischemic stroke, or it may be detected incidentally [12,24].

The aim of this paper is to present three rare cases diagnosed with T-MCA. Furthermore, as a secondary objective, we aim to estimate its occurrence among patients undergoing cerebral angiography.

CASE DESCRIPTION

Between 2019 and 2023, brain digital subtraction angiography (DSA) was performed in 810 patients at Rouhani Center, Babol, Iran. All documented angiography reports were reviewed, and three patients with T-MCA anomaly were identified. One case was diagnosed incidentally, while two patients presented with subarachnoid hemorrhage (SAH). These cases are described below and summarized in Table 1.

Table 1.

Summary of three cases with T-MCA

Case 1

A 21-year-old woman was admitted to our center with the sudden onset of severe headache, blurred vision, and dizziness. She had no history of recent head trauma; her past medical history was significant only for depression. Physical examination on admission revealed no neurological deficits, and laboratory findings were within normal limits. Brain computed tomography (CT) and magnetic resonance imaging (MRI) were unremarkable. Magnetic resonance angiography (MRA) demonstrated a suspicious lesion in the M1 segment of the right MCA (Fig. 1A). Subsequent cerebral digital subtraction angiography (DSA) revealed an abnormal plexiform vascular network with a “twig-like” appearance in the right M1 segment (Fig. 1B). The patient was treated conservatively and discharged with a Glasgow Coma Scale (GCS) score of 15 with recommendations for follow-up.

Fig. 1.

(A) Axial view of brain MRA in Case 1 showing absence of flow in the first segment (M1) of the right middle cerebral artery (MCA), replaced by a plexiform vascular network. (B) Cerebral DSA in Case 1 (right internal carotid artery injection) demonstrating replacement of the M1 segment of the right MCA by a plexiform arterial network (arrow). MRA, magnetic resonance angiography; DSA, digital subtraction angiography

Case 2

A 57-year-old female was admitted to our center with loss of consciousness (LOC). On admission, she presented with frontal headache and LOC, with a Glasgow Coma Scale (GCS) score of 5. She had no history of recent head trauma but had a past medical history of subarachnoid hemorrhage (SAH) two years earlier and a history of coronary artery bypass graft (CABG). Brain CT scan demonstrated subarachnoid hemorrhage in the perimesencephalic cisterns, predominantly involving the right ambient cistern, and hydrocephalus (Fig. 2A). Cerebral DSA revealed an abnormal plexiform vascular network replacing the M1 segment of the right MCA, consistent with twig-like MCA (T-MCA) (Fig. 2B). The patient was managed conservatively; however, she was eventually discharged in a vegetative state due to complications from meningitis and hydrocephalus.

Fig. 2.

(A) Axial view of brain CT scan in Case 2 showing subarachnoid hemorrhage in the perimesencephalic cisterns, predominantly involving the right ambient cistern, and hydrocephalus. (B) Brain DSA (right internal carotid artery injection) demonstrating a twig-like vascular network (arrow). CT, computed tomography; DSA, digital subtraction angiography

Case 3

A 45-year-old male was admitted to our center with a sudden onset of severe headache that did not improve with outpatient treatment. His past medical history was unremarkable, apart from occasional headaches. Brain computed tomography (CT) scan revealed subarachnoid hemorrhage in the left sylvian fissure (Fig. 3A). Cerebral DSA demonstrated an abnormal plexiform vascular network with a “twig-like” appearance replacing the M1 segment of the left MCA, consistent with twig-like MCA (T-MCA) (Fig. 3B). The patient was managed conservatively due to mild disturbance of consciousness, headache, and patient preference. His symptoms gradually improved, and he was discharged in good condition. Clinical and radiological follow-up was recommended.

Fig. 3.

(A) Brain CT scan in Case 3 showing subarachnoid hemorrhage in the left sylvian fissure. (B) Brain DSA demonstrating a left twig-like MCA (arrow). CT, computed tomography; DSA, digital subtraction angiography; MCA, middle cerebral artery

DISCUSSION

Twig-like MCA is a rare congenital anomaly in which the MCA trunk (M1) fails to develop and is replaced by a plexiform vascular network [9,23].

Its main differential diagnosis is unilateral moyamoya disease. In unilateral moyamoya, there is stenosis or occlusion of the ICA terminus, attenuation of the MCA and ACA, and prominent “puff-of-smoke” collaterals. In contrast, in twig-like MCA, the ICA terminus appears normal, and the M1 segment is absent, being replaced by a plexus of small vessels [6,15]. It is worth mentioning that two cases of twig-like MCA have been reported in the literature, both demonstrating genetic polymorphisms related to moyamoya, suggesting a potential similarity in the genetic origins of these anomalies [4,7,16].

Due to its rarity, the exact prevalence of T-MCA is unknown and may vary among countries. It has been reported more frequently in East Asian populations. T-MCA is estimated to occur in approximately 0.088%–1.17% of patients undergoing cerebral angiography [1,2,6,11,17-19,21,23].

In the study by Viso et al. in Argentina and Chile, of a total of 10,234 patients who underwent cerebral angiography, nine cases (0.088%) of T-MCA were identified [21]. Liu et al. reported two cases (0.11%) among 1,814 patients who underwent consecutive cerebral angiograms in Taiwan [11]. In the study by Akkan et al. in Turkey, six cases (0.14%) out of 4,372 patients who underwent cerebral angiography had T-MCA [1]. Onoue et al. studied 657 patients in the United States who underwent four-vessel diagnostic cerebral angiography and reported three cases (0.45%) of T-MCA [14]. In the study by Cho et al. in Korea, among 1,937 patients who underwent cerebral angiography, 13 cases (0.67%) had T-MCA [2]. Seo et al. reported 15 cases (1.17%) among 1,282 patients who underwent cerebral angiography in Korea; this was the second-largest case series reporting T-MCA [17].

To our knowledge, the largest case series was reported by Goto et al. in a multicenter study in Japan, which included 29 cases of T-MCA (bilateral: 0; unilateral: 29) and 57 cases with moyamoya angiopathy (bilateral: 41 cases; unilateral: 16 cases). They did not estimate the incidence of T-MCA or moyamoya angiopathy. Interestingly, 20 patients (69%) with T-MCA were initially diagnosed with unilateral moyamoya angiopathy, leading the authors to suggest that the prevalence of T-MCA may be underestimated, with many cases potentially hidden among the population diagnosed with moyamoya angiopathy [6]. As mentioned above, the main diagnostic challenge in differentiating T-MCA is moyamoya disease. Goto et al. [6] compared 29 cases of T-MCA with 57 cases of moyamoya disease. In moyamoya disease, steno-occlusive changes are typically observed at the ICA terminus as well as in the MCA and ACA, whereas in T-MCA, steno-occlusive change of the M1 segment of the MCA with replacement by a twiglike vascular network is observed. Importantly, involvement of the ICA terminus—considered a key differentiating feature—was present in all moyamoya cases (57/57) but in none of the T-MCA cases (0/29). Additional differences were also noted: none of the T-MCA cases were bilateral, whereas 72% (41/57) of moyamoya cases showed bilateral involvement. Furthermore, PCA involvement and transdural anastomoses were significantly more frequent in moyamoya disease, while coexisting arterial anomalies, such as intracranial aneurysms, were more commonly observed in T-MCA cases [6].

In our study in Iran, among 810 cerebral DSA procedures performed between 2019 and 2023, three cases (0.37%) of T-MCA were identified, representing the estimated occurrence of T-MCA in cerebral angiographic investigations at our center.

In previous literature, the mean age of patients with T-MCA was about 50 years [6,14,24]. In our cases, the patients were 21, 57, and 45 years old, which is consistent with the previous reports.

T-MCA can present with hemorrhagic events, ischemic stroke, or remain asymptomatic [24]. According to previous studies, about 65% of patients experienced hemorrhagic stroke, 20% experienced ischemic stroke, and 15% were asymptomatic [9].

In our series, two cases presented with subarachnoid hemorrhage, while workup of one case did not reveal any ischemic or hemorrhagic events. A reason hemorrhage is common in twig-like MCA is that the abnormal plexiform vessels are fragile and prone to rupture.

In our series, all cases were treated conservatively. Case 1 did not show any hemorrhagic or ischemic events, and follow-up was recommended. Case 2 had medical comorbidities, including a history of CABG, and presented with poor neurological status. Hydrocephalus was managed in this case; however, due to comorbidities and the assumption of poor outcome, nonoperative therapy was also recommended. Case 3 presented with a subarachnoid hemorrhage and was fully alert. After explaining the possible risks and benefits of treatment options, the patient opted for conservative therapy.

The exact management of twig-like MCA remains unclear. Management should focus on addressing concurrent anomalies, such as aneurysms, and treating complications, such as hydrocephalus. Superficial temporal artery to middle cerebral artery (STA–MCA) bypass surgery has shown acceptable results in some cases. However, data on the management of T-MCA are limited, and further studies are required [10,18,19,20,24].

This study had some limitations. The number of cases was small, and therefore our estimation of the prevalence of T-MCA was not precise, a limitation also noted in previous reports, in which only 2–15 cases were described [1,2,6,11,17-19,21,23]. Furthermore, long-term follow-up was not performed for our cases.

CONCLUSIONS

We report three cases of twig-like MCA, adding to the existing literature on this rare anomaly. Two of our cases presented with SAH, and one was identified without ischemic or hemorrhagic signs. Based on our rough estimate, the occurrence of T-MCA was approximately 0.37% in our series. Further studies are required to improve the understanding of the diagnosis and management of this anomaly.

Notes

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

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