Stapedial Artery: From Embryology to Different Possible Adult Configurations.

The stapedial artery is an embryonic artery that represents the precursor of some orbital, dural, and maxillary branches. Although its embryologic development and transformations are very complex, it is mandatory to understand the numerous anatomic variations of the middle meningeal artery. Thus, in the first part of this review, we describe in detail the hyostapedial system development with its variants, referring also to some critical points of ICA, ophthalmic artery, trigeminal artery, and inferolateral trunk embryology. This basis will allow the understanding of the anatomic variants of the middle meningeal artery, which we address in the second part of the review.

Middle Meningeal Artery: Anatomy and Variations.

The middle meningeal artery is the major human dural artery. Its origin and course can vary a great deal in relation, not only with the embryologic development of the hyostapedial system, but also because of the relationship of this system with the ICA, ophthalmic artery, trigeminal artery, and inferolateral trunk. After summarizing these systems in the first part our review, our purpose is to describe, in this second part, the anatomy, the possible origins, and courses of the middle meningeal artery. This review is enriched by the correlation of each variant to the related embryologic explanation as well as by some clinical cases shown in the figures. We discuss, in conclusion, some clinical conditions that require detailed knowledge of possible variants of the middle meningeal artery.

Bilateral persistent stapedial arteries associated with unilateral moyamoya disease: a particular anatomic variant.

PURPOSE: The persistence of the stapedial artery is a rare vascular variant that could explain the origin of the middle meningeal artery from the petrous segment of the internal carotid artery. The anatomic variations are illustrated and a summary of the possible hypothesis of the origin of the middle meningeal artery from the internal carotid artery is discussed, analysing the embryological works of the Carnegie Institute and the vascular development of the middle meningeal. METHODS AND RESULTS: The authors present a young patient showing a particular vascular variant on diagnostic imaging. These showed a bilateral internal carotid artery that gives origin of the middle meningeal artery in a patient affected by moyamoya disease. A literature review was performed to analyze the particular variant of the radiologic anatomy. CONCLUSION: The internal carotid artery origin of the middle meningeal artery is a wonderful anatomic variant that permits to understand the complex embryological development and then involution of the stapedial artery.

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.

Persistent stapedial arteries in human: from phylogeny to surgical consequences.

The stapedial artery is an embryonic artery which disappears during the tenth week in utero, in human species. During its short life, this artery shapes the stapes and transforms the middle meningeal artery from the internal carotid artery to a branch of the external carotid system. Nevertheless, a persistent stapedial artery is seen in 0.2-4.8 per thousand of human adults. This persistence is usually asymptomatic but can sometimes cause pulsatile tinnitus or conductive hearing loss. Despite the risk of facial palsy, hearing loss and even hemiplegia argued by several authors, some surgeons have succeeded in coagulation without side effects. Reviewing the literature, we seek to enlighten the actual knowledge about the persistent stapedial artery to evaluate the risk to coagulate it. Embryologic studies explain the four types of persistent stapedial arteries: the hyoido-stapedial artery, the pharyngo-stapedial artery, the pharyngo-hyo-stapedial artery and aberrant internal carotid with persistent stapedial artery. Phylogenetic studies show that the stapedial artery persists in adulthood in many vertebrates. Its disappearance is therefore either a random effect or an adaptative convergence. This adaptation could be partially linked to the negative allometry of the stapes. Practically, the risk to coagulate a stapedial artery seems limited thanks to anastomoses, for example with the stylomastoid artery. The risk of hemiplegia reported is in fact an extrapolation of variation in rats' embryos. A persistent stapedial artery can therefore reasonably be coagulated, with special attention to the facial nerve, because the facial canal is always dehiscent where the artery penetrates.

Origins of the middle meningeal artery and its probableembryological mechanism: a review

The middle meningeal artery is traditionally described by the human anatomy books as having its origin inthe first portion of the maxillary artery. However, more detailed studies have shown that there are numerousvariations on this arterial segment with considerable clinical importance. Therefore, the aim of this study wasto perform a wide review about this aspect analyzing scientific articles and textbooks. Thus, this review shallbe useful for clinicians, surgeons and academics that manipulate and keep interest for this particular anatomicalsite.

Middle meningeal artery arising from the basilar artery: report of a case and its probable embryological mechanism.

An extremely rare variation of the (left) middle meningeal artery (MMA) originating from the basilar artery, detected incidentally during cerebral angiography, is reported. The right MMA was normal and an accessory meningeal artery arising from the maxillary artery was present on both the sides. The foramen spinosum on the variant side was absent. This abnormal origin of the MMA can be explained by the presence of a perineural arterial network in the region of the Gasserian ganglion, formed by branches of the developing basilar and stapedial arterial systems; the middle meningeal-basilar arterial channel opening up in the absence of a normally developing MMA.

Landmark-based analysis of the morphological relationship between endocranial shape and traces of the middle meningeal vessels.

The morphogenesis and evolution of the cranium are the result of structural interactions among its components, leading to covariance between traits. Soft and hard tissues exert a reciprocal physical and physiological influence, leading to the final phenotype in terms of both ontogeny and evolution. The middle meningeal vessels, interfacing the brain and the braincase, provide an opportunity to study this network, even in extinct human species. Between and within-species variations of the vascular patterns may be mechanically influenced by the cranial morphology (structural hypothesis) or else by actual physiological responses and adaptations, mostly related to oxygen supply and/or thermoregulation (functional hypothesis). In this analysis, we tested the relationship between neurocranial shape and the general morphology of the traces of the middle meningeal vessels in a modern human population, by using landmark-based geometrical models. Although there are some neurocranial differences between groups with different vascular patterns, they are very small or not statistically significant. Only the depth of the imprints may be more influenced by the endocranial morphology. Even if the neurocranial differences among extinct hominids are definitely larger than those within the modern species, the present analysis suggests that it is unlikely that the differences in vascular patterns among the human species are related only to the effects of different neurocranial geometry. This is rather relevant when the marked development of the meningeal network in Homo sapiens is taken into account, compared with the patterns described for nonmodern human species.

Homologies of the meningeal-orbital arteries of humans: a reappraisal.

Two arteries connect the anterior branch of the middle meningeal artery to the lacrimal artery. One vessel, the sphenoidal artery, passes through the superior orbital fissure. The other vessel, the meningolacrimal artery, passes through the cranio-orbital foramen. An analysis of data derived from embryology, comparative anatomy, and patterns of adult variation indicates that the meningolacrimal artery is homologous with the ramus superior of the stapedial artery, an embryologically and phylogenetically primitive vessel. The sphenoidal artery probably forms late in human ontogeny and represents an evolutionary novelty. Its distribution is probably restricted to hominoids and may be exclusive to humans and orangutans (Pongo pygmaeus). The sphenoidal artery is associated with three other derived features: the sphenoparietal sinus and sulcus and a laterally expanded superior orbital fissure. The high frequency of the sphenoidal artery in Homo and Pongo probably represents a case of parallelism. The earliest paleontological evidence of an enlarged sphenoidal artery in the Hominidae occurs in Indonesian Homo erectus (Sangiran VI).

Variations of the ophthalmic and middle meningeal arteries: relation to the embryonic stapedial artery.

Recognition of the anatomic variations of the ophthalmic and middle meningeal arteries may be pertinent in tailoring the angiographic study to resolve a given clinical problem. An understanding of these anomalies is based on knowledge of the normal embryology. Unfortunately some early aspects of vascular development remain obscure. Fragmentary observations gleaned from the embryologic literature were correlated with selective and/or subselective angiography performed in 42 patients with such anomalies. This analysis has provided the basis for a tenable scheme for development of the ophthalmic and middle meningeal arteries as they relate to the embryonic stapedial artery. A classification for anomalies of these arteries is proposed based on deviation from this normal embryologic mechanism.

The development of the anterior falcate and lacrimal arteries in the human.

Certain arteries of the head were studied in injected human fetuses from 143 to 290 mm C.-R., as well as in the orang-utan and gorilla, and in microscopical sections from 29 to 162 mm C.-R., as well as in an adult. It was found that, during human ontogenesis, an anterior falcate artery supplies the dura mater of the medial part of the frontal bone. It appears at 40 mm and reaches its full development by 115 mm. Normally it becomes reduced and is transformed into the anterior meningeal artery postnatally. It communicates with the meningeal branches of the lacrimal artery. Under pathological conditions that affect the dura mater, the falcate artery may appear postnatally in angiograms.

Persistent basilar/middle meningeal artery anastomosis.

Three cases of a basilar/middle meningeal artery anastomosis are demonstrated angiographically. No reference to previous angiographic demonstration of this vascular anomaly has been found in the literature, and only one similar case with an anatomical description has been located. An embryological explanation of this rare anastomosis is presented.