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. Clin. Anat. 28:576–583, 2015. © 2014 Wiley Periodicals, Inc.     

Persistent dorsal ophthalmic artery and ophthalmic artery arising from the middle meningeal artery diagnosed by MR angiography at 3 T

Introduction

A persistent dorsal ophthalmic artery (OA) is a rare variation that originates from the cavernous segment of the internal carotid artery (ICA) and enters the orbit via the superior orbital fissure (SOF). Occasionally, the OA also arises from the middle meningeal artery (MMA) and enters the orbit via the SOF. These two major variations of the OA have not been well described by magnetic resonance (MR) angiography. We evaluated their prevalence on MR angiography at 3 T.

Methods

We retrospectively reviewed our database of MR angiographic images obtained using a 3 T imager. Of images of 846 patients, we evaluated those of 826 patients (1,652 OAs) with special attention to OA origin and its course into the orbit. We excluded images of the 20 because quality was insufficient to assess.

Results

We found 7 (0.42 %) persistent dorsal OAs among 1,652 OAs (right/left, 6/1; male/female, 3/4). Twenty-four (1.45 %) OAs arose from the MMA (right/left/bilateral, 11/5/4; male/female, 10/10), three of which also demonstrated a small normally branching OA. In one patient, we observed both right persistent dorsal OA and left OA arising from the MMA.

Conclusions

Per OA, the prevalence of persistent dorsal OA was 0.42 % and of OA arising from the MMA, 1.45 %, with a tendency toward right-side predominance. OA arising from the MMA can be seen bilaterally; preprocedural knowledge of this variation is important because of the danger associated with endovascular procedures of the external carotid system when the OA arises from the MMA.     

Persistent trigeminal artery arising from the arterial ring/fenestration of the cavernous segment of the internal carotid artery

A persistent trigeminal artery (PTA) is the most common carotid-vertebrobasilar anastomosis, usually arising from the cavernous or precavernous segment of the internal carotid artery (ICA) and connecting to the distal basilar artery. There are two types of PTA, lateral and medial. We present the first case of a lateral-type PTA arising from the large arterial ring/fenestration of the cavernous segment of the left ICA with findings from both magnetic resonance angiography and selective catheter angiography.     

Visualization of the ophthalmic artery by phase-contrast magnetic resonance angiography: a pilot study

Objective

This study aimed at investigating whether phase-contrast (PC) magnetic resonance (MR) angiography is useful for visualizing the ophthalmic artery (OA).

Methods

This prospective study enrolled 196 consecutive outpatients who underwent three-dimensional PC MR angiography. The basal image parallel to the anteroposterior dimension of the OA was extracted for analysis from the imaging data.

Results

The 99 male and 97 female subjects were aged from 10?years to 80?years (mean 47.9?years). The OAs were supplied only by the external carotid system or in combination with the internal carotid artery (ICA) in 18 subjects (9.2?%). The bilateral OAs were symmetrical in 12?%, asymmetrical in 87?%, and unidentified in 1?%. The contour of the proximal segment of the OAs could be classified into straight, curved, and tortuous types. The ICA–OA angle defined by the angle between the approximate line of the proximal OA and the vertical line was also variable. The first bend of the OA corresponded to the anastomosis site with the external carotid system. The proximal medial bend was the origin of the posterior ethmoidal artery, and the distal medial bend was the origin of the anterior ethmoidal artery.

Conclusions

According to the results the OA not only possesses three characteristic bends, but also shows prominent individual variability and commonly shows bilateral asymmetry. The contour of the OA may be regulated by the anchor effect at the bend sites. PC MR Angiography is useful for visualizing the main trunk of the OA.     

颈内动脉岩段和海绵窦段的显微外科解剖

本文观测了25例(50侧)颈内动脉的岩段和海绵窦段。岩段可分为垂直部与水平部,两部移行处称岩段的膝。岩段垂直部无分支发出,水平部发出翼管动脉和骨膜支。另外指出了凿开颞骨岩部颈动脉管前壁,以暴露颈内动脉的外科途径。海绵窦段可分为后升部、水平部、前升部及后曲、前曲等部。海绵窦段的主要分支是脑膜垂体干和海绵窦下动脉。本文还报道了1例少见的残留性三叉动脉。     

Persistent trigeminal artery and its variants on MR angiography

Introduction  

A persistent trigeminal artery (PTA) is the most common carotid-vertebrobasilar anastomosis. A cerebellar artery that arises from the precavernous segment of the internal carotid artery (ICA) without connecting to the basilar artery is regarded as a PTA variant. Our study aimed to determine the incidence of PTA and its variants and classify them based on magnetic resonance (MR) angiography.     

颈内动脉床突段的解剖特点及毗邻关系

目的　观察颈内动脉床突段的解剖特点,探讨该结构的毗邻关系,为临床工作的开展提供依据。 方法　成人尸头标本7例,分别以红色和蓝色硅胶对动脉、静脉进行灌注;应用显微解剖技术,观察并测量颈内动脉的床突段及与眼动脉、远/近侧硬膜环等重要毗邻结构的位置关系。 结果　(1)与颈内动脉床突段相关的参数：床突段的外径为（5.11±0.81）mm,床突段外侧面远、近侧硬膜环中点间距离为（5.46±1.90）mm,远侧硬膜环形成颈内动脉窝的出现率约为78.6%。(2）床突段与眼动脉的关系：①眼动脉起点与远侧硬膜环的位置关系为近侧约7.1%、恰于远环处约14.3%、远侧78.6%;②眼动脉起点与颈内动脉横截面的位置关系为内1/3约78.6%、中1/3约21.4%（未观察到外1/3的情况）。 结论　(1)术前影像学检查十分必要。(2)对侧翼点入路有利于眼动脉起点处病变的暴露。(3)提出两点术中注意事项：①环切远侧硬膜环时,应注意避免伤及眼动脉或其它视神经管内结构;②磨除前床突时注意其内侧的重要血管、神经组织,应以邻近硬膜瓣加以保护。     

The cavernous sinus: topographic morphometry of its contents

The microsurgical anatomy of the cavernous sinus of 54 Turkish adult cadaveric heads (108 specimens) was examined to provide data for major topographic aspects and morphometry of the region, which is of special clinical importance for neurosurgeons. Significant findings were 1) the abducent nerve in the cavernous sinus was observed as one rootlet in most of the specimens (78%), two rootlets in 14%, three in 5% and four in 3% of the specimens 2) the anterior inferior venous space was dominant in 58%, the posterior superior venous space in 16%, and an intermediate type in 29% of the specimens 3) the artery of the inferior cavernous sinus originated from the internal carotid artery (ICA) in 74% of the cases, and 4) the dorsal meningeal artery originated from the ICA in 6 (5.5%) of the specimens.     

Type 2 proatlantal intersegmental artery associated with persistent trigeminal artery diagnosed by MR angiography

Purpose

The type 2 proatlantal intersegmental artery (PIA) is a rare anastomosis between the external carotid artery (ECA) and vertebral artery (VA) that passes through the foramen magnum. The persistent trigeminal artery (TA) is the most common anastomosis between the internal carotid artery (ICA) and basilar artery. The purpose of this paper is to present the first case of a type 2 PIA associated with an ipsilateral persistent TA diagnosed using magnetic resonance (MR) angiography, and we briefly discuss the embryology of this rare anomaly.

Methods

An 83-year-old man with cerebral infarctions underwent cerebral MR imaging, and head and neck MR angiography using a 1.5?T imager. MR angiography was obtained using the standard non-contrast three-dimensional time-of-flight technique.

Results

MR angiography showed aplasia of the proximal left VA and a large anastomotic artery between the left ECA and distal left VA that passed through the foramen magnum, indicative of a type 2 PIA. This patient also had an anastomosis between the precavernous segment of the left ICA and midbasilar artery via a lateral course, indicative of a lateral-type persistent TA.

Conclusion

We present the first case of type 2 PIA associated with ipsilateral lateral-type persistent TA diagnosed by MR angiography. MR angiography should be performed including the carotid bifurcation to find more frequently extracranial arterial variations, including type 2 PIAs.     

颈内动脉海绵窦段分支及分布的显微解剖

目的 :为海绵窦的直接手术提供显微解剖学基础。方法 :采用 48侧成人新鲜海绵窦标本 ,颈内动脉灌注苯乙烯 (ABS) ,然后在手术显微镜下解剖观察。结果 :脑膜垂体干出现率为 10 0 % ,脑膜垂体干可分为两型 ,典型的脑膜垂体干出现率为 5 8.3 % ,非典型的脑膜垂体干又分为单干型和非单干型 ,前者出现率为 3 1.3 % ,后者为 10 .4%。海绵窦下动脉出现率为 95 .8% ,垂体被囊动脉为 3 1.3 %。另外眼动脉的出现率为 10 .4%。两侧颈内动脉海绵窦段分支之间的吻合 ,提供了重要的侧支循环血液供应。结论 :本文对颈内动脉海绵窦段分支的显微解剖结果 ,对临床显微外科、血管介入、影像学有指导意义。     

Anatomy of the petrosphenoidal and petrolingual ligaments at the petrous apex

The petrous apex is a complex area surrounded by the cavernous sinus, Dorello's canal and Meckel's cave. The petrosphenoidal ligament (PSL) and the petrolingual ligament (PLL) are important structures located in the region. These two ligaments were examined under a surgical microscope in 10 specimens of five adult cadaveric heads fixed in formalin. They were found to span from the petrous apex to the posterior clinoid process, and the lingula of the sphenoid bone, respectively. The dural sleeve of the abducens nerve, the dorsal meningeal artery or its medial branch, and the venous blood space were located below the PSL in all specimens, and the petrous or sphenoidal insertion of the PSL varied in five specimens. The PLL invariably surrounded part of the dorsal and lateral walls of the lacerum segment of the internal carotid artery (ICA), just under the anteroinferior portion of the anteromedial wall of Meckel's cave in all specimens. The PSL and PLL are valuable anatomical landmarks for identifying the ICA and the nerves in this region. A thorough understanding of the relationship of the two ligaments with neurovascular structures is a prerequisite for surgery in and around the petrous apex. Clin. Anat. 22:302–306, 2009. © 2009 Wiley‐Liss, Inc.     

展神经池段的动脉供应及其与邻近血管的关系

目的：研究展神经池段的动脉供应及其与邻近血管的关系。方法：选取18例脑千，观测展神经根池段的滋养动脉来源及其与邻近血管的关系。结果：从展神经根腹面跨过的有小脑下前动脉、脑桥下外侧动脉、小脑下后动脉、迷路动脉、小脑下后和小脑下前动脉总干、椎动脉；从展神经背面跨过的血管有小脑下前动脉、脑桥下外侧动脉等。展神经的滋养动脉主要来自脑桥前外侧穿动脉、小脑下前动脉和脑桥下外侧动脉。接触和压迫展神经根的血管主要是小脑下前动脉和移位的基底动脉或椎动脉，占16．7％，结论：展神经的滋养动脉损伤和血管压迫可导致展神经麻痹，了解展神经的动脉供应及其邻近血管关系对临床诊断和手术治疗具有重要参考作用。     

Rare saccular aneurysm in a medial type persistent trigeminal artery trunk and literature review

Purpose

We report an extremely rare case of saccular aneurysm in the left medial type persistent trigeminal artery (PTA) trunk and discuss its clinical importance.

Materials and methods

A 77-year-old woman who had symptom suggestive of vertebrobasilar insufficiency underwent cerebral magnetic resonance (MR) imaging and non-contrast three dimensional time-of-flight MR angiography (3D TOF MRA) using a 3 T scanner.

Results

3D TOF MRA images revealed a left medial type PTA originated from the left internal carotid artery C5 portion, through cavernous sinus and connected to the basilar artery with a saccular aneurysm in the mid portion of its trunk. The basilar artery (BA) under the union was hypoplastic. The bilateral posterior communicating arteries were absent.

Conclusion

To our knowledge, this is the first report of a medial type PTA associated with a saccular aneurysm in the PTA trunk. Being aware of this is crucial in clinical, because they can influence surgical and interventional procedures.     

The human thyrocervical trunk: Configuration and variability reinvestigated

Summary Reinvestigation of the configuration of the human thyrocervical trunk revealed, that in the presently investigated specimens the dorsal scapular artery is a direct branch of the subclavian artery in approximately 75% of the cases, whereas in the remaining 25% it is derived from the thyrocervical trunk, either directly or via the transverse cervical artery (Nomina anatomica 1977). The internal thoracic artery participates in the thyrocervical trunk in more than 10% of the observed cases. Thus, both dorsal scapular and internal thoracic artery have to be considered as facultative branches of the thyrocervical trunk. According to our results, the subclavian artery must be considered as the most common site of origin of the dorsal scapular artery. This vessel may be replaced by another artery in about one fourth of the cases. A survey of studies on the origin of the dorsal scapular artery clearly demonstrates that it is not warranted to give an overall numerical proportion for the main modes of branching. As yet no satisfactory explanation for the high degree of variability of these subclavian branches has been given. Especially the widely held notion of differences related to race, which is based on Adachi's (1928) work, has turned out to be invalid. Interpretation of variability may rather be based, as a general concept, on the late acquisition of a thyrocervical trunk in phylogeny as well as in ontogeny.     

The gill in the spiny dogfish,Squalus acanthias: Respiratory and nonrespiratory function

Aspects of functional anatomy with respect to water and blood flow through the gills of Squalus acanthias and one specimen of Mustelus mustelus are described. A reconstruction of an entire filament has been made. (1) The cavernous body in the proximal segment of the filament is relatively small, contains a small amount of elastic tissue, and has no connections with the underlying afferent filament artery, except at its junction to the middle segment. In the middle segment of the filament, the wall and columns of the cavernous body are well supplied with elastic tissue. The size of the cavernous body increases gradually distally. The underlying afferent filament artery opens into it with numerous pores and eventually becomes incorporated in the cavernous body. The distal segment of the filament is characterized by the rapid increase in size of the cavernous body. Toward the free edge of the filament it almost reaches the efferent filament artery; toward the diaphragm it forms an anastomosing bridge with the neighboring filaments. Wall and columns in the distal segment of the cavernous body are richly supplied with elastic tissue. The afferent filament artery is no longer discernible. (2) In living specimens the tips of opposite filaments are in close apposition during the whole respiratory cycle. Application of artificial ventral aortic pressure to freshly killed specimens evoked the same reaction in the filament tips. The cavernous bodies provide the hydrostatic skeleton, necessary to keep the gill sieve closed. Lamellae are equipped with finger-like appendages to facilitate adherence to the opposite filament tips. Lamellar appendages also reduce the dead space between lamellae of neighboring filaments. (3) The whole of cavernous bodies may also serve as an elastic blood reservoir with a function similar to that of the bulbus arteriosus in teleost fish. (4) Of all suitable places, only the lamellar streambed was clear and convincing in its response to perfusion with adrenalin or acetylcholine. (5) Structural details of the nonrespiratory circulation within the gills are described.     

Vagal baro‐ and chemoreceptors in middle internal carotid artery and carotid body in rat

The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body. Although neurons in the nodose ganglion were labelled after injecting tracer into the carotid body, the vagal pathway to these baro‐ and chemoreceptors has not been identified. Neither has the glossopharyngeal intracranial afferent/sensory pathway that connects to the brainstem been defined. We investigated both of these issues in male Sprague–Dawley rats (n = 40) by injecting neural tracer wheat germ agglutinin‐horseradish peroxidase into: (i) the peripheral glossopharyngeal or vagal nerve trunk with or without the intracranial glossopharyngeal rootlet being rhizotomized; or (ii) the nucleus of the solitary tract right after dorsal and ventral intracranial glossopharyngeal rootlets were dissected. By examining whole‐mount tissues and brainstem sections, we verified that only the most rostral rootlet connects to the glossopharyngeal nerve and usually four caudal rootlets connect to the vagus nerve. Furthermore, vagal branches may: (i) join the CSN originating from the pharyngeal nerve base, caudal nodose ganglion, and rostral or caudal superior laryngeal nerve; or (ii) connect directly to nerve endings in the middle segment of the ICA or to chemoreceptors in the carotid body. The aortic depressor nerve always presents and bifurcates from either the rostral or the caudal part of the superior laryngeal nerve. The vagus nerve seemingly provides redundant carotid baro‐ and chemoreceptors to work with the glossopharyngeal nerve. These innervations confer more extensive roles on the vagus nerve in regulating body energy that is supplied by the cardiovascular, pulmonary and digestive systems.     

Carotid and vertebrobasilar rete mirabile: a case report

Bilateral symmetrical absence of the cavernous segments of the internal carotid artery (ICA) and absence of proximal basilar artery with a compensating arterial network (rete mirabile) is quite rare. Although it is found in some lower mammals as a physiological network supplying the circle of Willis, it is associated with ICA hypoplasia or nonpersistence in humans. We present a case of both cavernous ICA and proximal part of basilar artery absence associated with rete formation, which was an incidental finding during cerebral angiography in a 32-year-old woman with a complaint of left maxillary sinus mass.     

The anatomic relationship around the horizontal segment of petrous internal carotid artery: a study based on reconstructed computed tomography angiography

Purpose

The anatomic relationship around the horizontal segment of petrous internal carotid artery (ICA) is complicated. Relative researches on human patients using radiographic technique are scarce. It is essential to get adequate anatomic knowledge about this region for performing some bypass procedures.

Methods

Using the independent software Mimics, we prospectively studied the 0.45-mm-thick computed tomography angiography (CTA) images of 29 patients (58 sides). All patients’ middle cranial fossa and related critical anatomic structures were reconstructed in 3D. Some measurements were established on the multiplanar reconstructed images, including the distance from foramen ovale and foramen spinosum to the petrous ICA; the distance from the lumen of cochlea to the edge of trigeminal impression and petrous ICA; and the length of the horizontal segment of petrous ICA.

Results

The horizontal segment of petrous ICA was surrounded by the trigeminal impression, the cochlea and the auditory tube spatially. On the multiplanar reconstructed CTA images, the average distances from foramen ovale and foramen spinosum to the petrous ICA were 4.1?mm and 5.8?mm, respectively; the average distance from the lumen of cochlea to the edge of trigeminal impression and petrous ICA were 8.2?mm and 2.0?mm, respectively; and the mean length of the horizontal segment of petrous ICA was 15.8?mm.

Conclusions

Our results indicate adequate and reliable anatomic information can be obtained using reconstructed CTA on an individualized basis.