Ophthalmic rete mirabile: the first angiographic documentation of embryonic ophthalmic collaterals in a patient with moyamoya disease. A case report

Analysis of macula structural changes in Moyamoya disease using AI-assisted OCT

OBJECTIVE

To investigate macula structure thickness and volume changes in patients with moyamoya disease (MMD).

METHOD

In this cross-sectional study, we used artificial intelligence (AI) -assisted optical coherence tomography (OCT) to analyze the thickness and volume of macula in Moyamoya patients. ETDRS zoning divides the macula into nine different regions. In 15 patients with radial scanning OCT, the average thickness and volume of retina, RNFL, GCL, and choroid in these regions were measured. In 30 patients with radial or horizontal scanning OCT, based on the anatomical structure, the macula is divided into seven segments. Mean Sattler layer-choriocapillaris complex thickness (SLCCT), Haller layer thickness, and total choroidal thickness were measured for each segment using AI-assisted OCT.

RESULTS

We recruited 30 patients (59 eyes) with MMD. In the 15 patients (29 eyes) who underwent radial scanning OCT, no significant change in retina, RNFL, GCL, and choroidal thickness was identified between the two groups (p > 0.05). There was no significant change in retina, RNFL, or choroidal volume between the two groups in different ETDRS macula regions (p > 0.05). The GCL volume in the macula's inner ring nasal portion (IN) was significantly lower. SLCCTs were considerably reduced in six macula regions in moyamoya groups (p < 0.05). There was no statistically significant change in Haller layer thickness. Only the nasal perifovea (PE_N) exhibited a significant variation in choroidal thickness. The Moyamoya group showed reduced choroidal thickness in PE_N segment.

CONCLUSION

In patients with MMD, there is thinning of the Sattler layer-choriocapillaris complex in the choroid.

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.

Role of the ophthalmic artery in the endovascular treatment for intracranial vascular diseases

The ophthalmic artery (OA) is a crucial artery. Centered at the OA, there are numerous extracranial-intracranial anastomoses. The OA and its collaterals can be involved in some intracranial vascular diseases. So, it is very important to understand its specific anatomy, variation, and role in different neurovascular diseases. The OA has various anomalies both in the origin and collateral circulation. When performing endovascular treatment (EVT), the OA may suffer unexpected embolization through the numerous dangerous anastomoses. In case of a dural arteriovenous fistula or brain arteriovenous malformation mainly fed by the OA, the OA can be the passage of EVT, during which the central retinal artery could be injured. During interventional recanalization of steno-occlusive diseases of the internal carotid artery, dissection at the cavernous segment could progress to the OA segment and occlude the origin of OA. Under the circumstance of moyamoya disease, the OA can provide collateral flow to the anterior cerebral artery. When performing EVT for OA aneurysm concurrent with moyamoya disease, the parent OA should be preserved. After placement of a flow-diverting device for ophthalmic ICA aneurysm, the covered OA could experience spontaneous occlusion, leading to visual disturbance. Hence, the OA is an extremely important artery in the EVT for intracranial vascular diseases. In this article, we would extensively review the related literature to increase our understanding of the role of OA in intracranial vascular diseases. In addition, some illustrative cases would also be provided.

Moyamoya Disease Associated With Morning Glory Disc Anomaly and Other Ophthalmic Findings: A Mini-Review

Moyamoya disease (MMD) is a chronic cerebrovascular disease that frequently results in intracranial ischemia or hemorrhage. Its concurrence with varying ophthalmic findings is relatively rare yet may lead to irreversible blindness. We performed a search and review of the literature to characterize the relevance of MMD (excluding moyamoya syndrome) and ophthalmic findings. As a result, a total of 38 articles identified from PubMed and Web of Science were included in this mini-review. Patients with MMD sometimes present with decreased visual acuity or visual field defects before the onset of symptomatic cerebrovascular dysfunction. The most predominant ophthalmic condition in MMD patients is the morning glory disc anomaly (MGDA). Deficiency during neuroectodermal genesis and subsequent mesodermal changes may be responsible for the association between these two diseases. Thus, it may be beneficial for patients with MGDA to receive cerebral vascular examinations as the precaution against life-threatening intracranial angiopathy. Other ophthalmic findings reported in cases of MMD include retinal vascular occlusion, optic disc pallor, cortical blindness, etc. For most of the patients with MMD, retinal examinations would be recommended to prevent potential loss of vision. It is essential for both neurologists and ophthalmologists to be aware of the correlation between cerebrovascular diseases such as MMD and ocular manifestations to achieve a comprehensive diagnosis.

Synchronized tissue-scale vasculogenesis and ubiquitous lateral sprouting underlie the unique architecture of the choriocapillaris

The choriocapillaris is an exceptionally high density, two-dimensional, sheet-like capillary network, characterized by the highest exchange rate of nutrients for waste products per area in the organism. These unique morphological and physiological features are critical for supporting the extreme metabolic requirements of the outer retina needed for vision. The developmental mechanisms and processes responsible for generating this unique vascular network remain, however, poorly understood. Here we take advantage of the zebrafish as a model organism for gaining novel insights into the cellular dynamics and molecular signaling mechanisms involved in the development of the choriocapillaris. We show for the first time that zebrafish have a choriocapillaris highly similar to that in mammals, and that it is initially formed by a novel process of synchronized vasculogenesis occurring simultaneously across the entire outer retina. This initial vascular network expands by un-inhibited sprouting angiogenesis whereby all endothelial cells adopt tip-cell characteristics, a process which is sustained throughout embryonic and early post-natal development, even after the choriocapillaris becomes perfused. Ubiquitous sprouting was maintained by continuous VEGF-VEGFR2 signaling in endothelial cells delaying maturation until immediately before stages where vision becomes important for survival, leading to the unparalleled high density and lobular structure of this vasculature. Sprouting was throughout development limited to two dimensions by Bruch's membrane and the sclera at the anterior and posterior surfaces respectively. These novel cellular and molecular mechanisms underlying choriocapillaris development were recapitulated in mice. In conclusion, our findings reveal novel mechanisms underlying the development of the choriocapillaris during zebrafish and mouse development. These results may explain the uniquely high density and sheet-like organization of this vasculature.

Unilateral cervical and petrosal segment agenesis of the internal carotid artery with rete mirabile

The carotid rete mirabile (RM) is a physiological network between the internal and external carotid arterial systems. In this paper, an extremely rare case is presented, in which internal-external carotid artery anastomoses and a dilated ascending pharyngeal artery, due to unilateral agenesis of the cervical and petrous segments of the internal carotid artery (ICA), is presented.

Anatomic and Angiographic Analyses of Ophthalmic Artery Collaterals in Moyamoya Disease

BACKGROUND AND PURPOSE

Moyamoya disease is a progressive neurovascular pathology defined by steno-occlusive disease of the distal internal carotid artery and associated with the development of compensatory vascular collaterals. The etiology and exact anatomy of vascular collaterals have not been extensively studied. The aim of this study was to describe the anatomy of collaterals developed between the ophthalmic artery and the anterior cerebral artery in a Moyamoya population.

MATERIALS AND METHODS

All patients treated for Moyamoya disease from 2004 to 2016 in 4 neurosurgical centers with available cerebral digital subtraction angiography were included. Sixty-three cases were evaluated, and only 38 met the inclusion criteria. Two patients had a unilateral cervical internal carotid occlusion that limited analysis of ophthalmic artery collaterals to one hemisphere. This study is consequently based on the analysis of 74 cerebral hemispheres.

RESULTS

Thirty-eight patients fulfilled the inclusion criteria. The most frequently encountered anastomosis between the ophthalmic artery and cerebral artery was a branch of the anterior ethmoidal artery (31.1%, 23 hemispheres). In case of proximal stenosis of the anterior cerebral artery, a collateral from the posterior ethmoidal artery could be visualized (16 hemispheres, 21.6%). One case (1.4%) of anastomosis between the lacrimal artery and the middle meningeal artery that permitted the vascularization of a middle cerebral artery territory was also noted.

CONCLUSIONS

Collaterals from the ophthalmic artery are frequent in Moyamoya disease. Their development depends on the perfusion needs of the anterior cerebral artery territories. Three other systems of compensation could be present (callosal circle, leptomeningeal anastomosis, and duro-pial anastomoses).

Unilateral rete mirabile as a result of segmental agenesis of the ascending petrous segment of the internal carotid artery: embryology, differential diagnosis and clinical implications

We describe an extremely rare case of unilateral rete mirabile in a young woman and discuss its significance in embryological development as well as its radiological aspects, differential diagnosis and potential clinical implications.