Rete middle cerebral artery anomalies: a unifying name, case series, and literature review

Current state and confusion of twig-like middle cerebral artery

A twig-like middle cerebral artery (MCA) is an uncommon lesion in which a plexiform network of small vessels replaces the M1 segment of the MCA. Currently, we have insufficient information for twig-like MCAs. Therefore, a review of the literature using PubMed was conducted. In this review of twig-like MCAs, the following were discussed: the definition, pathogenesis, hemodynamics, associated aneurysm, clinical manifestations, imaging examinations, therapeutic strategies, therapeutic complications and prognosis. In addition, we proposed a reasonable grading system for twig-like MCAs, which is significant. For a twig-like MCA, the pathogenesis is unclear, and congenital and acquired factors can be involved. A twig-like MCA disturbed cerebral hemodynamics. An associated aneurysm can occur in patients with twig-like MCAs. Twig-like MCAs can present subclinically and without clinical symptoms, hemorrhage, or ischemic strokes. Of all the available imaging examinations, digital subtracted angiography is the gold standard. When treating a twig-like MCA, it is feasible to target the associated aneurysm, and extracranial-intracranial bypass can be effective in reducing the risk of strokes, but more evidence is needed. Now, the decision to perform surgery for twig-like MCAs should be made on a case-by-case basis.

Coiling an aneurysm in the twig-like MCA via a Marathon microcatheter: A case report

INTRODUCTION AND IMPORTANCE

The twig-like middle cerebral artery (MCA) is rare and has a plexiform network of small vessels that replaces the MCA trunk, with a prevalence ranging from 0.11 %-1.17 %. It can be associated with an aneurysm. A Marathon microcatheter may be an alternative for coiling procedures. However, this technique has rarely been reported.

PRESENTATION OF CASE

A 63-year-old man suffered from headaches. The neurological examination results were unremarkable. Angiography revealed a twig-like MCA with an unruptured aneurysm. Due to stenosis of the aneurysm neck, a Marathon microcatheter was used to successfully reach the aneurysm, and coiling was completed with Chinese Visee coils. Postoperatively, the patient recovered uneventfully. Due to the lack of ischemic changes in the right hemisphere, the patient was kept under follow-up observation. At the 8-month follow-up by telephone, the patient was healthy.

CLINICAL DISCUSSION

Aneurysms in the twig-like MCA may have stenosis of the aneurysm neck, and routine microcatheters used to deliver coils are often too thick to catheterize the aneurysm neck. The Marathon microcatheter has a distal inner diameter (ID) of 0.013, and as an alternative for coiling procedures, it may be soft enough to thin enough to go into the aneurysm. However, it can be used in the delivery of certain coils.

CONCLUSION

Aneurysms in the twig-like MCA are difficult to catheterize with the routine microcatheters used to deliver coils. A Marathon microcatheter may be used to perform the coiling procedure. However, only certain coils that match the Marathon microcatheter can be chosen.

Rete middle cerebral artery presenting with a ruptured aneurysm

ABSTRACT

The developmental anomaly of the middle cerebral artery (MCA) is a rare occurrence. Rete MCA, also known as "unfused," "twig-like," and aplastic MCA, is an even rarer anomaly. These immature rete vessels are prone to flow-related aneurysms which rupture themselves presenting with intraparenchymal hematoma. We here with present a case of rete MCA with a ruptured aneurysm and discuss its pathophysiology and management.

Revised concept of rete-like collateral formation: Rete mirabile does not exist in humans

The carotid rete is a physiological network between the external and internal carotid arteries (ICA) in lower vertebrates. However, true carotid rete does not exist in humans. This review aimed to contrast the physiological function of human "rete-like collaterals" with that of lower vertebrate "rete mirabile". An explanation for the development of rete-like collaterals in human intracranial arteries was also discussed. The rete mirabile (carotid, vertebral, spinal, and thoracic) in lower vertebrates has a specific physiological role and does not form vasculature for the same purpose in humans. Therefore, the term "rete mirabile" should not be used for cases reported in humans. Instead, "rete-like collaterals" is preferred. In the literature, rete-like or arterial anastomosis was observed in the ICA cavernous portion and the intradural arteries. Based on the hypothesis of the segmental concept, it applies to the ICA and intracranial arteries. Whether in the ICA, middle cerebral artery, posterior cerebral artery, or posterior inferior cerebellar artery, the segmental concept is the same and should be considered to have formed secondary collaterals after segmental regress or dysgenesis of affected arteries. Summarily, the significance of this review lies in its reevaluation of vascular structures previously described as "carotid rete" in humans to a true and preferred term, "rete-like collaterals". It also provides insights into the historical context and potential genetic factors associated with the formation of arteries in humans, contributing to a better understanding of human vascular anatomy.

Rete Middle Cerebral Artery Aneurysm: A Case Report and Systematic Review

Background  Middle cerebral artery (MCA) anomalies are a rare finding and may be associated with vascular changes, such as intracranial aneurysms. Among them, the rete MCA aneurysm is very rare, with only 22 cases reported to date. Case Description  A 50-year-old woman presented with subarachnoid, intraventricular, and intracerebral hemorrhage secondary to a ruptured aneurysm of rete MCA from an anomalous collateral artery of the anterior cerebral artery, treated successfully by microsurgical clipping. She presented a good recovery after a 2-year follow-up. Conclusion  A systematic review of rete MCA aneurysms is presented, comparing aneurysms originating from twig-like MCA, with 16 reports, and twig-like networks of an anomalous collateral artery, with 6 reports including ours. Several factors influence the treatment decision-making, though microsurgical clipping is the main procedure. A wider use of coiling is requested for a better comparison of the treatment approaches.

De novo formation of twig-like middle cerebral artery: An illustrative case

Background

Twig-like middle cerebral artery (T-MCA) is a rare vascular abnormality characterized by the replacement of the M1 segment of the middle cerebral artery (MCA) with a plexiform arterial network of small vessels. T-MCA is generally regarded as an embryological persistence. Conversely, T-MCA may also be a secondary sequela but no reports of cases of de novo formation exist. Here, we report the first case describing possible de novo T-MCA formation.

Case Description

A 41-year-old woman was referred to our hospital from a nearby clinic because of transient left hemiparesis. Magnetic resonance (MR) imaging revealed mild stenosis of the bilateral MCAs. The patient then underwent MR imaging follow-ups once a year. MR imaging at the age of 53 showed a right M1 occlusion. Cerebral angiography revealed a right M1 occlusion and formation of a plexiform network consistent with the occlusion site, leading to the diagnosis of de novo T-MCA.

Conclusion

This is the first case report describing possible de novo T-MCA formation. Although a detailed laboratory examination did not confirm the etiology, autoimmune disease was suspected to have precipitated this vascular lesion.

Anterior cerebral artery dissection for a patient with ipsilateral aplastic or twig-like middle cerebral artery: An illustrative case report

Background

An aplastic or twig-like middle cerebral artery (Ap/T-MCA) is a rare anomaly, which sometimes causes ischemic infarction. Collateral flow from the ipsilateral anterior cerebral artery (ACA) is important for patients with Ap/T-MCA. If ipsilateral ACA stenosis or occlusion occurs, a large infarction with a wider field than the ACA territory could happen. First, mechanical thrombectomy was performed for the right ACA near occlusion caused by arterial dissection with ipsilateral Ap/T-MCA in this case. Second, Wingspan stenting was performed for the right ACA restenosis.

Case Description

A 77-year-old female presented to the hospital with the left hemiparesis. We diagnosed a right ACA infarction caused by right ACA occlusion. Digital subtraction angiography showed right Ap/T-MCA and ipsilateral ACA near occlusion. Thrombectomy was performed, and recanalization was achieved with mild ACA stenosis. The lesion was the dissection due to angiographical finding. Two months after treatment, transient left hemiparesis occurred and right ACA stenosis progressed. Computed tomography perfusion showed hypoperfusion of the right hemisphere. Wingspan stenting was performed from the left internal carotid artery through the anterior communicating artery with an intermediate catheter. The patient was discharged without any neurological deficit.

Conclusion

We reported the first case of a patient who underwent Wingspan stenting for the right ACA dissection with Ap/T-MCA. Short-term follow-up and aggressive intervention should be considered for collateral pathway dissection with Ap/T-MCA because the symptoms can become serious. The patients with Ap/T-MCA should be cautious about the collateral pathway arterial changes in particular ipsilateral ACA due to the increasing hemodynamic stress.

A Ruptured Aneurysm in Aplastic or Twig-like Middle Cerebral Artery: A Case Report with Histological Investigation

Aplastic or twig-like middle cerebral artery (Ap/T-MCA) is a rare vascular anomaly that can cause a hemorrhagic or ischemic event. We report a 38-year-old man who presented with intracerebral hemorrhage from a ruptured aneurysm associated with an Ap/T-MCA. After aneurysm trapping and resection, histopathological examination revealed an internal elastic lamina (IEL) disruption and a thin aneurysmal wall. The patient recovered well after surgery and rehabilitation. No hemorrhagic or ischemic events have occurred during 2 years of follow-up. Ap/T-MCA-associated aneurysms exhibit a disrupted IEL and thin wall, which demonstrates the fragility of the “twig-like” vessels.

Radiological and clinical features of twig-like middle cerebral artery in comparison with moyamoya angiopathy: a multicenter retrospective study

OBJECTIVE

Twig-like middle cerebral artery (T-MCA) is a rare congenital anomaly that is difficult to distinguish from moyamoya angiopathy (MMA), given the similarity of the angioarchitectures. The aim of this study was to gain insights into the radiological and clinical features of T-MCA and to distinguish this condition from MMA.

METHODS

A multicenter retrospective study was conducted in 29 patients with T-MCA and 57 patients with MMA. Demographic, radiological, and clinical data were compared between the patients with T-MCA and those with MMA.

RESULTS

The T-MCA group tended to be older than the MMA group (mean age 47 ± 18 vs 39 ± 22 years). Twenty patients with T-MCA (69%) were initially diagnosed with MMA. All T-MCA cases had twig-like networks and steno-occlusive changes involving the MCA. The T-MCA group had a higher incidence of intracranial aneurysms (35% vs 11%) and coexisting arterial anomalies (48% vs 12%). T-MCA and MMA cases had significant differences in involvement of the internal carotid artery terminus (0% vs 100%) and posterior cerebral artery (0% vs 23%), and in transdural anastomosis (0% vs 51%). T-MCA cases were less likely to present with stroke (59% vs 86%) and more likely to be asymptomatic (28% vs 12%). Of the patients with stroke, those with T-MCA had more hemorrhagic strokes (41% vs 29%) and fewer ischemic strokes (59% vs 71%) compared to those with MMA.

CONCLUSIONS

This study suggests that T-MCA is a different disease entity from MMA based on significant differences in the radiological and clinical features. Neurosurgeons should recognize this anomaly and understand the key features that differentiate T-MCA from MMA.

Ruptured aneurysm associated with a twig-like middle cerebral artery: An illustrative case report

Background:

Anomalies of the middle cerebral artery (MCA) are rare; among the different types of anomalies, the aplastic or twig-like (Ap/T) MCA is extremely rare and has been reported under various names, including aplastic, unfused, or rete type anomaly. The occurrence of a brain aneurysm associated with this anatomic variant is an even rare event, and probably their development and rupture are related to hemodynamic stress of the tinny wall of vessels forming the network.

Case Description:

We present a 43-year-old male patient with an explosive and persistent right orbitofrontal headache. A computed tomography showed a right frontobasal hematoma with intraventricular disruption. Magnetic resonance angiography showed a right MCA aneurysm and what seems to be a MCA trunk stenosis. Cerebral digital subtraction angiography demonstrated a plexiform arterial network and one aneurysm arising from the network. The patient was successfully treated by surgical clipping to evacuate the hematoma and to prevent further intracranial hemorrhages.

Conclusion:

The Ap/T-MCA may be associated with hemodynamic stress with a significant effect through the tinny wall of the vessels causing hemorrhage or leading to the formation and rupture of cerebral aneurysms. Based on a correct diagnosis of the anomaly, treatment can be completed successfully through different standard methods.

Three-Dimensional Angioarchitecture of Rete Middle Cerebral Artery Anomalies and the Clinical Significance

PURPOSE

Rete middle cerebral artery (MCA) anomaly is characterized by a web-like network of arteries involving the first MCA segment (M1) and a normal downstream MCA. The detailed composition of this anomaly and the hemodynamic impacts on cerebral perfusion are rarely addressed. The purpose of this study was to elucidate the anatomical and hemodynamic perspectives of the rete MCA anomaly.

METHODS

From August 2020 to December 2021, 4 rete MCA anomalies were identified at Shuang Ho hospital. Clinical information, perfusion magnetic resonance (MR) imaging, and angiographic images were collected. Detailed angioarchitecture, including types of arterial feeders and extent of rete involvement, were analyzed based on three-dimensional volume-rendering reconstruction images obtained from the catheter-based angiographies.

RESULTS

Despite their variable clinical presentations (two hemorrhage, one ischemia, and one asymptomatic), all cases shared common angiographic findings as follows: (1) the internal carotid artery did not connect directly to the rete, (2) the anterior choroidal artery (AChA) was the artery constantly supplying the rete and (3) there was a watershed zone shift toward MCA territory. The perfusion MR cerebral blood flow map was symmetric in all studied cases.

CONCLUSION

The AChA is an artery constantly supplying the rete, which suggests that the angioarchitectural features associated with this anomaly may be the result of both congenital and acquired compensatory processes. Cerebral perfusion remains preserved at the lesion side, despite angiographic evidence of watershed zone shift. These findings will be important for making better clinical judgments about this condition.

Aplastic or twiglike middle cerebral artery with contralateral middle cerebral artery stenosis showing transient ischemic attack: illustrative case

BACKGROUND

Aplastic or twiglike middle cerebral artery (Ap/T-MCA) is a rare anomaly characterized by a unilateral MCA occlusion with plexiform vessels that causes hemorrhagic and (less commonly) ischemic strokes. The reasons for this are rarely discussed, and thus optimal treatment for ischemic Ap/T-MCA remains controversial. Here, the authors report a case of Ap/T-MCA with transient ischemic attacks treated by bypass surgery and discuss the mechanism of ischemic development and treatment methods.

OBSERVATIONS

A 62-year-old hypertensive man with transient, recurrent left hemiparesis visited the authors’ hospital. Magnetic resonance angiography showed proximal occlusion of the right MCA and stenosis in the left MCA. Digital subtraction angiography revealed occlusion of the right MCA and abnormal vascular networks, leading to a diagnosis of Ap/T-MCA with contralateral MCA stenosis. Antiplatelet therapy with aspirin was insufficient, and a superficial temporal artery–MCA bypass was performed. There were no ischemic or hemorrhagic events postoperatively.

LESSONS

Atherosclerosis seems to have a significant impact on the development of ischemic stroke in patients with Ap/T-MCA, and the presence of coexisting atherosclerotic stenotic vascular lesions outside the Ap/T-MCA site is substantial in its development. Bypass surgery is a promising treatment option for ischemic Ap/T-MCA.

Lethal subarachnoid haemorrhage in a patient with rete mirabile network of the posterior circulation with associated aneurysm

Rete mirabile (RM), an arterial network normally existing in some vertebrate animals interconnecting the extracranial and intracranial arterial circulation, can rarely be found in humans whether asymptomatic or presenting with cerebral ischaemia or haemorrhage. Encompassing diverse angiographic characteristics and similarities with other arterial malformations, proper diagnosis and differential diagnosis is challenging. We hereby describe an unusual RM case variant, presenting to us with lethal subarachnoid haemorrhage owing to a ruptured small aneurysm associated with the RM network. Angiography disclosed an absent P1 segment of the posterior cerebral artery (PCA) and an RM network anastomosing the basilar apex with the normal distal PCA. Brain death was confirmed on the fifth day after admission and attributed to the severity of subarachnoid haemorrhage (SAH). This is an exceedingly rare case representing an intradural-to-intradural RM anastomosis in a patient presenting with lethal SAH. RM epidemiology, pathophysiology, presentation, angiographic findings and prognosis are reviewed.

Rete Middle Cerebral Artery Anomaly Presenting with a Large Intracerebral Hemorrhage: A Case Report

Rete MCA anomaly is extremely rare and has been seldomly discussed in literature. Embryologically MCA develops by fusion of multiple twigs which form a single channel. If there is failure to fuse a plexiform network of vessels persists known as rete MCA. This web like network of vessels is at high risk of haemorrhagic stroke and therefore for patients presenting incidentally correct diagnosis is paramount. Here we report a case of rete MCA anomaly in a 35-year-old gentle man who presented with a large haemorrhagic stroke in emergency. DSA showed unilateral involvement of proximal MCA, and otherwise normal intra-cranial vasculature. With this report we aim to correctly diagnose this rare condition and avoid misdiagnosis leading to unnecessary treatments.

A Case of Aneurysmal Subarachnoid Hemorrhage with Middle Cerebral Artery Aplasia at 30 Weeks of Pregnancy

Objective

We report a case of subarachnoid hemorrhage (SAH) that occurred at 30 weeks of pregnancy and was treated by coil embolization in a woman with middle cerebral artery (MCA) aplasia.

Case Presentation

A 40-year-old woman who was 30 weeks pregnant presented to the emergency department with a half-day history of headache and nausea. She had sudden onset headache and her symptom did not improve. There was no neurological deficit. Head CT at the referring hospital revealed SAH. The fetal state was stable. There was no sign of threatened premature delivery. Head MRA revealed aplasia of the left MCA and aneurysm with a daughter sac at the A1 segment of the anterior cerebral artery (ACA). Head DSA revealed that the A1 aneurysm with a daughter sac arose from the anomalous collateral artery leading to a plexiform network. The diagnosis was SAH due to rupture of an A1 aneurysm. Performance of less invasive coil embolization seemed to be possible and was carried out under general anesthesia. The operation was completed after placing one coil and confirming that most of the aneurysmal dome was embolized, including the daughter sac. There was no cerebral vasospasm and no obvious neurological deficit. Antiplatelet drugs were only required for 10 days after the operation. Pregnancy was stable and the patient delivered a baby by cesarean section at 38 weeks of pregnancy.

Conclusion

A rare case of aneurysmal SAH in a pregnant woman with MCA aplasia was successfully treated by endovascular surgery.

Mechanical Thrombectomy for ICA Top Occlusion with Twig-Like MCA: A Case Report

Objective

We report a case of hemorrhagic complication after mechanical thrombectomy (MT) for internal carotid artery (ICA) occlusion with twig-like middle cerebral artery (MCA).

Case Presentation

A 75-year-old man was admitted to our hospital with ICA occlusion. Recanalization was achieved by a direct aspiration first pass technique (ADAPT). The peripheral MCA was twig-like, but operators thought that a thrombus remained in the MCA first segment. The procedure was continued and suspended with perforation of the microguidewire.

Conclusion

When performing MT for large vessel occlusion (LVO) with twig-like MCA, it is difficult to proceed a device to the periphery and there is a risk of hemorrhage.

Successful thrombolysis in essential thrombocythemia-related acute ischaemic stroke

Essential thrombocythemia (ET)-related acute ischaemic stroke (AIS) may account for approximately 0.25%-0.5% of all ischaemic strokes. If left undiagnosed and untreated, patients with ET carry an increased risk of recurrent thrombosis involving major organs including the brain. We report an interesting case of a 67-year-old man, who was successfully thrombolysed for AIS resulting from ET. He presented with sudden onset of left-sided hemiparesis with a left-ventricular clot. His subsequent investigations including positive JAK2 V617F mutation confirmed the diagnosis of ET. He made a significant recovery with thrombolysis, anticoagulation, antiplatelet and hydroxyurea. A fear of post-thrombolytic haemorrhagic complications appears the major reason for the lack of reports of thrombolysis in ET-related AIS. Although the diagnosis of ET was confirmed on subsequent investigations, successful thrombolysis in our case provides preliminary evidence that ET-related AIS cases can undergo successful thrombolysis using tenecteplase. To date, ours is only the second case of ET-related AIS being thrombolysed.

Rete middle cerebral artery: a rare association with anterior cerebral artery aneurysm rupture

Haemodynamic flow-related stress at the vessel curvatures is an important risk factor for intracranial aneurysmal growth and rupture. The rete middle cerebral artery (MCA) is a rare entity causing hyperdynamic blood flow into the ipsilateral anterior cerebral artery (ACA), especially when the contralateral A1-segment is non-dominant. Ruling out the clinicoradiological mimics like vasculitis, moyamoya and chronic occlusive disease with vessel wall imaging and detailed investigations helps manage the clinical entity effectively. We present a successfully managed case of ruptured ACA aneurysm at the acute curvature of the A1-A2 junction associated with ipsilateral rete MCA. Pre-emptive diagnosis of the rete MCA can aid preventive strategies to manage rupture and regrowth of the aneurysm at the points of flow-related stress.