Letter to the editor - embryology of the ophthalmic artery: a revived concept

Superior hypophyseal arteries: angiographic re-discovery, comprehensive assessment, and embryologic implications

The superior hypophyseal arteries (SHAs) are well known in anatomical and surgical literature, with a well-established role in supply of the anterior hypophysis and superjacent optic apparatus. However, due to small size and overlap with other vessels, in vivo imaging by any modality has been essentially non-existent. Advances in high resolution cone beam CT angiography (CBCTA) now enables this deficiency to be addressed. This paper presents, to the best of our knowledge, the first comprehensive in vivo imaging evaluation of the SHAs.

METHODS

Twenty-five CBCTA studies of common or internal carotid arteries were obtained for a variety of clinical reasons. Dedicated secondary reconstructions of the siphon were performed, recording the presence, number, and supply territory of SHAs. A spectrum approach, emphasizing balance with adjacent territories (inferior hypophyseal, ophthalmic, posterior and communicating region arteries) was investigated.

RESULTS

The SHAs were present in all cases. Supply of the anterior pituitary was nearly universal (96%) and almost half (44%) originated from the 'cave' region, in excellent agreement with surgical literature. Optic apparatus supply was more difficult to adjudicate, but appeared present in most cases. The relationship with superior hypophyseal aneurysms was consistent. Patency following flow diverter placement was typical, despite a presumably rich collateral network. Embryologic implications with respect to the ophthalmic artery and infraoptic course of the anterior cerebral artery are intriguing.

CONCLUSIONS

SHAs are consistently seen with CBCTA, allowing for correlation with existing anatomical and surgical literature, laying the groundwork for future in vivo investigation.

Embryological consideration of the inferolateral trunk

Inferolateral trunk (ILT), also called inferior or lateral cavernous branch, of the internal carotid artery is an important artery during neuro-intervention and neurosurgery. However, its embryological background is not well elucidated. Review of the developmental biology of this small artery indicated that the alleged nomenclatures of the remnant of the primitive maxillary artery of Sabin (1917) and primitive dorsal ophthalmic artery of Lasjaunias (1977) are misnomers because the primordium of the ILT does not nourish the maxilla or retina essentially, but it supplies the premandibular region where the premandibular (prechordal) mesoderm and its surrounding premandibular trigeminal neural crests are distributed. Thus, this embryological artery might be called the primitive premandibular artery more appropriately, and its remnant, i.e., the ILT, might be recognized as the remnant of the primitive premandibular artery.

Unruptured Paraclinoid Carotid Aneurysms Occur More Frequently in Younger Ages

Purpose

We investigated the age distribution of cerebral saccular aneurysms in various locations to clarify the differences by location and discuss the mechanism of formation.

Materials and Methods

We retrospectively assessed clinical material obtained from 1,252 unruptured aneurysms treated with endovascular embolization between 2004 and 2019. Age, sex, laterality, and size were investigated by the location of aneurysms, classified as cavernous internal carotid artery (ICA), paraclinoid ICA, supraclinoid ICA, anterior communicating artery, anterior cerebral artery, middle cerebral artery, basilar artery complex, and posterior inferior cerebellar artery. Paraclinoid aneurysms were subclassified into 3 patterns according to their projecting direction: S-type, with superior protrusion; M-type, with medial protrusion; and P-type, with posteroinferior protrusion.

Results

There was no significant difference by location for sex, laterality, and size. The mean age of patients with paraclinoid aneurysms (56.5 years old) was significantly lower than that of other aneurysm patients (64.3 years old). Notably, 40% of the patients with M-type aneurysms were <50 years old. This percentage was significantly higher than that of aneurysms at other locations (P<0.05).

Conclusion

We found a young female predominance for patients with paraclinoid carotid aneurysms. This study may suggest that congenital factors contribute to paraclinoid aneurysm formation as well acquired factors, such as hemodynamic stress, atherosclerotic wall damage, and local inflammation.

Basilar artery origin of an orbital artery – A rare variant and review of the embryology of the orbital arterial supply

We present a patient with separation of the arterial supply to the globe and the extra-ocular muscles. The ophthalmic artery originates from the typical adult location and supplies only the globe. Arising from the basilar artery was a branch that supplies the extra-ocular muscles. There was no apparent connection between these vessels around the optic nerve and no evidence of supply from the external carotid artery. We discuss the embryology of the ophthalmic artery from the point of view of Padget and Lasjaunias and offer our opinion on the on-going controversy. We believe this is the first case to highlight the trigeminal-primitive maxillary-stapedial anastamotic pathway.

Anomalous origin of the middle meningeal artery from the inferolateral trunk with an arterial circle around a hypoplastic internal carotid artery in an infant with a dural arteriovenous fistula

Deviations from normal embryologic development can manifest in different anatomical variants of the ophthalmic artery. We present a case of an infant treated for a high-flow dural arteriovenous fistula of the superior sagittal sinus, in whom an arterial circle involving the ophthalmic artery, the middle meningeal artery, the inferolateral trunk and a hypoplastic segment of the internal carotid artery was found. The embryologic development is briefly reviewed with emphasis on the possible genesis of this interesting constellation.

Bilateral anomalous origin of ophthalmic artery from middle meningeal artery and coincidence of bilateral carotid artery aneurysm: Case report and literature review

Ophthalmic artery (OA) is known for anomalous origin and aberrant course probably attributable to its complex embryology. Anomalous origin of OA can be associated with intracranial aneurysm. Anomalous origins have been reported from middle meningeal artery (MMA), cavernous carotid, posterior communicating, anterior cerebral and basilar artery. Even though bilateral anomalous origin of OA from MMA is a rare finding, to the author's best knowledge, association of above condition with bilateral internal carotid artery aneurysms has not been described in the literature. We present a case of such anomalous bilateral OA originating from MMA and associated with bilateral internal carotid artery aneurysms. We have also reviewed the pertinent literature regarding anomalous OA origin.

Embryology and anatomical variations of the ophthalmic artery

PURPOSE

The ophthalmic artery (OA) has one of the most complex anatomy and the most fascinating embryological development.

METHODS

The complexity of the embryologic development of the OA resides in the implication of three different embryological systems: the carotid system, the stapedial system, and the ventral pharyngeal system.

RESULTS

This explains very well the numerous variations in origin of the OA and the importance of vascular anastomoses developed with branches of the external carotid artery and with the middle meningeal artery.

CONCLUSION

In this review, authors propose a comprehensive description of different hypotheses on the embryologic development of the OA and, in a second part, explain all anatomical variations and clinical implications of this artery.

Unusual ophthalmic artery origin: Implications for intraarterial chemotherapy of retinoblastoma

We report two pediatric retinoblastoma patients with unusual ophthalmic artery (OA) origins who were referred to our interventional neuroradiology department for intraarterial chemotherapy. The first patient had double OAs arising from the ipsilateral internal carotid artery and a central retinal artery (CRA) arising from the more cranially located artery, whereas the second patient had an OA originating from the A1 segment of the ipsilateral anterior cerebral artery. In both cases the CRA arose from the artery entering the orbit through the optic foramen. Both patients tolerated the procedures well. To the best of our knowledge, our retinoblastoma patients with unusual OA origins are the first in the literature in which detailed knowledge of the orbital vasculature and especially CRA origin carried immediate clinical implications, altering access strategies. These variations were proved both by flat-panel detector computed tomography findings and superselective injections of OAs with unusual origins. Our results show that in patients with retinoblastoma, a detailed angiographic work-up may be necessary to evaluate the orbital vasculature and possible abnormal origin of the OA. Recognition of possible variations of OA origin and its branching patterns is of the utmost importance for successful treatment and avoidance of adverse events among retinoblastoma patients.

The ophthalmic artery: a new variant involving two branches from the supracavernous internal carotid artery

PURPOSE

We report an extremely rare, double ophthalmic artery configuration.

METHODS

We present 2D- and 3D-angiographic features of an anomalous origin of the ophthalmic artery.

RESULTS

The double ophthalmic artery was the result of the persistence of the primitive dorsal ophthalmic artery combined with the presence of a second orbital artery originating from the supracavernous internal carotid artery, passing through the superior orbital fissure and into the orbit to furnish the muscular, lacrimal and ethmoidal arteries and the medial long posterior ciliary artery.

CONCLUSIONS

A heretofore undocumented instance of ophthalmic artery duplication is presented. Knowledge of such variations is important for the planning of endovascular treatments and the comprehension of unusual angiographic images. Such fine arterial variants may very well be frequent, but difficult to demonstrate on simple 2D angiographies. Multiplanar reconstructions of 3D angiography data make it possible to diagnose rare, but embryologically predictable arterial variants.

Embryologic and Fetal Development of the Human Orbit

PURPOSE

To review the recent data about orbital development and sort out the controversies from the very early stages during embryonic life till final maturation of the orbit late in fetal life, and to appreciate the morphogenesis of all the definitive structures in the orbit in a methodical and timely fashion.

METHODS

The authors extensively review major studies detailing every aspect of human embryologic and fetal orbital morphogenesis including the development of extraocular muscles, orbital fat, vessels, nerves, and the supportive connective tissue framework as well as bone. These interdisciplinary studies span almost a century and a half, and include some significant controversial opposing points of view which the authors hopefully sort out. The authors also highlight a few of the most noteworthy molecular biologic studies regarding the multiple and interacting signaling pathways involved in regulating normal orbital morphogenesis.

RESULTS

Orbital morphogenesis involves a successive series of subtle yet tightly regulated morphogenetic events that could only be explained through the chronological narrative used by the authors. The processes that trigger and contribute to the formation of the orbits are complex and seem to be intricately regulated by multifaceted interactions and bidirectional cross-talk between a multitude of cellular building raw materials including the developing optic vesicles, neuroectoderm, cranial neural crest cells and mesoderm.

CONCLUSIONS

Development of the orbit is a collective enterprise necessitating interactions between, as well as contributions from different cell populations both within and beyond the realm of the orbit. A basic understanding of the processes underlying orbital ontogenesis is a crucial first step toward establishing a genetic basis or an embryologic link with orbital disease.

Anatomy of the Ophthalmic Artery: Embryological Consideration

There are considerable variations in the anatomy of the human ophthalmic artery (OphA), such as anomalous origins of the OphA and anastomoses between the OphA and the adjacent arteries. These anatomical variations seem to attribute to complex embryology of the OphA. In human embryos and fetuses, primitive dorsal and ventral ophthalmic arteries (PDOphA and PVOphA) form the ocular branches, and the supraorbital division of the stapedial artery forms the orbital branches of the OphA, and then numerous anastomoses between the internal carotid artery (ICA) and the external carotid artery (ECA) systems emerge in connection with the OphA. These developmental processes can produce anatomical variations of the OphA, and we should notice these variations for neurosurgical and neurointerventional procedures.

Double ophthalmic arteries arising from the internal carotid artery: a case report of a hidden second ophthalmic artery

A case of double ophthalmic arteries arising from the internal carotid artery with unique features is reported. This case was discovered following in the course of time the progress of a thrombosis of the anterior cavernous sinus associated with a low-flow direct arteriovenous fistula of the superior ophthalmic vein. At different time points, the same patient underwent four angiographic studies and one computerized tomography with contrast medium. Angiographies showed that the double internal carotid artery origin of the ophthalmic artery was detectable only within a short range of time. To the best of our knowledge, this case is unique as it demonstrates that a second ophthalmic artery may lie hidden, showing itself only under particular hemodynamic requirements.

Different ophthalmic artery origins: Embryology and clinical significance

This retrospective study gives a summary of ophthalmic artery (OA) variations to serve as guidelines for surgical interventionists and trainees. Pubmed and Medline searches were conducted. The OA usually arises intradurally (superomedial, anteromedial, or rarely superolateral) from the internal carotid artery (ICA). Rare extradural origin (primitive dorsal OA) (PDOA) remnant and extremely rare interdural origin (primitive ventral OA) (PVOA) remnant are of significance when sectioning the dural ring. Rarely, a persistent PDOA with ICA origin, or a PDOA remnant with inferolateral trunk origin, enters the orbit via the superior orbital fissure (SOF) for sole or partial orbital supply. Extremely rare, the PDOA and PVOA persist and form double OAs that arise from the ICA and run via the SOF and optic foramen. Occasionally, the OA arises from the middle meningeal artery (MMA), when both the PDOA and VDOA regress and enter the orbit via the SOF. Sole orbital supply via the external carotid artery (ECA), i.e. meningo-ophthalmic artery and/or MMA branches, or dual OAs (ECA and ICA origins) may occur. Other rare OA origins include anterior or posterior communicating artery; anterior or middle cerebral artery; basilar artery; posterior inferior cerebellar artery; and the carotid bifurcation. Primitive arteries (persistent or remnant), and/or abnormal anastomoses play pivotal roles in manifestations of OA variations. Of clinical importance are orbital collateral routes and dangerous extracranial-intracranial anastomoses. Awareness of OA origins and collateral routes is imperative for transarterial embolizations or infusion chemotherapy in the ECA territory to prevent visual complications.