The superior orbital fissure and its contents

Fetal Development of the Orbit

Human prenatal development is divided into an embryonic period and a fetal period. Intense organogenetic activity occurs in the embryonic period of prenatal life, while the fetal period is marked by less intense changes. Knowledge of the embryology of the orbit not only allows insights into how normal variations in the orbital structure arise but also provides an understanding of how congenital deformities occur when normal orbital development goes awry. In order to explore our understanding of the developmental anatomy of the orbit during the fetal period of prenatal life, the authors have summarized the major milestones in orbital morphogenesis, a temporally precise and morphogenetically intricate process. This process can be considered as an anatomic series of complex, well-orchestrated changes in morphology as well as a series of complex biochemical and molecular events that coordinate and control the anatomic development. Identifying and linking signaling pathways and regulatory genes linked with normal orbital morphogenesis is a crucial step to offer patients with chronic or incurable orbital diseases effective treatment options in the future.

Bimodal Approach: A Key to Manage a Case of Traumatic Superior Orbital Fissure Syndrome

An unusual complication associated with maxillofacial trauma is the superior orbital fissure syndrome (SOFS). Trauma-related SOFS often presents within 48 h of injury, but presentation can be delayed by several days. This article sums up the particulars of the syndrome and treatments done in the literature and discusses our experience of managing this complex case.

A systematic review of the surgical anatomy of the orbital apex

Purpose

The orbital apex is the narrowest part of the orbit, housing the link between the intracranial cavity and orbit. Knowledge of orbital apex anatomy is crucial to selecting a surgical approach and reducing the risk of complications. Our purpose is to summarize current knowledge on surgical anatomy and attempt to reach a consensus on definition of the orbital apex.

Methods

The online databases of Embase, the Cochrane library, Web of Science and PubMed (MEDLINE) were queried in a comprehensive bibliographic search on the (surgical) anatomy of the orbital apex and consisted of a combination of two subjects, using indexed terms and free text: “Orbital Apex” and “Orbital Anatomy.”

Results

A total of 114 relevant papers were included in this review. Numerous anatomical variations are described in the literature. Variations of the optic canal include duplication (0.64%) and keyhole anomaly (2.65%). Variations in pneumatization of the anterior clinoid process were unilateral in almost 10%, bilateral in 9%, and normal in 72%. A rare variant of the superior orbital fissure (SOF) is Warwick’s foramen, which appears as if the lowest portion of the SOF was separated from the main fissure by a transverse bony bridge.

Conclusion

The definition of the orbital apex varies in the literature, and further research would most likely identify additional variations. A universal definition reporting these variations and pathology and imaging findings is essential for determining the optimal surgical approach to the orbital apex.

Electronic supplementary material

The online version of this article (10.1007/s00276-020-02573-w) contains supplementary material, which is available to authorized users.

Traumatic Orbital Apex Syndrome: An Uncommon Sequela of Facial Trauma

Orbital apex syndrome (OAS) is a rare ocular complication following craniomaxillofacial trauma. This traumatic syndrome is a combination of features seen in both superior orbital fissure syndrome and traumatic orbital neuropathy due to nerve impingement. Due in part to the rarity of this disorder, the optimal treatment of traumatic OAS has yet to be determined. We present a case in which traumatic OAS was caused by direct compression due to a displaced fracture segment from the superior orbit. The patient was successfully treated with a combination of emergent decompression and urgent reconstruction suggesting that this may be an effective strategy in OAS resulting from direct nerve compression as a result of craniomaxillofacial fracture.

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.

Detailed anatomy of the abducens nerve in the lateral rectus muscle

The aims of this study were to elucidate the detailed anatomy of the abducens nerve in the lateral rectus muscle (LRM) and the intramuscular innervation pattern using Sihler staining. In this cohort study, 32 eyes of 16 cadavers were assessed. Dissection was performed from the LRM origin to its insertion. The following distances were measured: from LRM insertion to the bifurcation point of the abducens nerve, from LRM insertion to the entry site of the superior branch or inferior branch, from the upper border of the LRM to the entry site of the superior branch, from the lower border of LRM to the entry site of inferior branch, and the widths of the main trunk and superior and inferior branches. The single trunk of the abducens nerve divided into two branches 37 mm from insertion of the LRM, and 22 of 32 (68.8%) orbits showed only two superior and inferior branches with no subdivision. The superior branch entered the LRM more anteriorly (P = 0.037) and the superior branch was thinner than the inferior branch (P = 0.040). The most distally located intramuscular nerve ending was observed at 52.9 ± 3.5% of the length of each muscle. Non-overlap between the superior and inferior intramuscular arborization of the nerve was detected in 27 of 32 cases (84.4%). Five cases (15.6%) showed definite overlap of the superior and inferior zones. This study revealed the detailed anatomy of the abducens nerve in the LRM and provides helpful information to understand abducens nerve palsy. Clin. Anat. 30:873-877, 2017. © 2017 Wiley Periodicals, Inc.

The revised anatomy of the canals connecting the orbit with the cranial cavity

Orbits are connected with the middle cranial fossa via the optic canal, the superior orbital fissure, the M-type orbitomeningeal foramen, the metoptic canal, an accessory anterior opening of the foramen rotundum, and Warwick's canal. They are also in communication with the anterior cranial fossa via the ethmoidal canals and the A-type orbitomeningeal foramen. The anatomy of these conduits has been recently enriched with several details that are summarized and reviewed in this article.

Superior Orbital Fissure Syndrome in Lateral Orbital Wall Fracture: Management and Classification Update

The superior orbital fissure syndrome (SOFS) is an uncommon complication rarely occurring in association with craniofacial trauma. Work-up of a patient injured by a traumatic right orbitozygomatic complex fracture and SOFS is presented. Accurate computed tomography scan and three-dimensional reconstruction showed a medial displacement of the lateral orbital wall, compressing the right superior orbital fissure (SOF), without intraorbital bone fragment displacement or hemorrhage. Imaging also revealed a frontosphenotemporal fracture, according to Pellerin et al, that is, frequently associated with visual impairment. Our primary choice of therapy was a corticosteroid treatment in association with an early surgical approach. It consisted in en bloc reduction and osteosynthesis of the fracture through a bicoronal approach, recovering SOF size. A prompt and almost complete recovery of the abducens movement, without diplopia, was achieved in 1 week. The authors discuss indications and management of SOFS. The presence of fractures should urgently lead to surgery. We deny waiting for a medical treatment result, while preferring the prompt reduction of the fractures and extrication of the soft tissues. The main focus of this study is on patient's anatomical feature and fracture patterns.

Metoptic canal, duplication of the optic canal and Warwick’s foramen in human orbits

The region of the optic strut is sometimes traversed by some minor canals whose incidence and general characteristics have never been studied. As such canals could be the route for vessels that could interfere in the surgery of the orbital apex, we undertook a detailed anatomical study on a vast collection of dry skulls. The examination of 943 dry adult skulls and 360 foetal skulls was carried out to precise the anatomy of canals in the optic strut area, their development and relationships with the optic canal. A canal traversing the optic strut was present in 8.54 % of the orbits. Based on diameter, position within the optic strut, and thickness of the bony plate separating it from the optic canal or from the superior orbital fissure, the canals piercing the optic strut were classified into four types, which include the well-known duplication of the optic canal, different aspects of the metoptic canal and a type of canal that to our knowledge has never been reported. Warwick’s foramen was found in 0.74 % of orbits. The area of the optic strut is the frequent site of canals joining the orbit with the middle cranial fossa. Some of them can host the ophthalmic artery; others could be run by minor vessels which, however, could be the source of annoying bleedings in surgical procedures.

Differential lateral rectus compartmental contraction during ocular counter-rolling

PURPOSE

The lateral rectus (LR) and medial rectus (MR) extraocular muscles (EOMs) have largely nonoverlapping superior and inferior innervation territories, suggesting functional compartmental specialization. We used magnetic resonance imaging (MRI) in humans to investigate differential compartmental activity in the rectus EOMs during head tilt, which evokes ocular counter-rolling, a torsional vestibulo-ocular reflex (VOR).

METHODS

MRI in quasi-coronal planes was analyzed during target-controlled central gaze in 90° right and left head tilts in 12 normal adults. Cross sections and posterior partial volumes of the transverse portions of the four rectus EOMs were compared in contiguous image planes 2 mm thick spanning the orbit from origins to globe equator, and used as indicators of contractility.

RESULTS

Horizontal rectus EOMs had significantly greater posterior volumes and maximum cross sections in their inferior compartments (P < 10(-8)). In orbit tilt up (extorted) compared with orbit tilt down (intorted) head tilts, contractile changes in LR maximum cross section (P < 0.0001) and posterior partial volume (P < 0.05) were significantly greater in the inferior but not in the superior compartment. These changes were not explainable by horizontal or vertical eye position changes. A weaker compartmental effect was suggested for MR. The vertical rectus EOMs did not exhibit significant compartmental contractile changes during head tilt. Mechanical modeling suggests that differential LR contraction may contribute to physiological cyclovertical effects.

CONCLUSIONS

Selective activation of the two LR, and possibly MR, compartments correlates with newly recognized segregation of intramuscular innervation into distinct compartments, and probably contributes to noncommutative torsion during the VOR.

Traumatic superior orbital fissure syndrome: current management

Traumatic superior orbital fissure syndrome is an uncommon complication of craniomaxillofacial trauma with an incidence of less than 1%. The syndrome is characterized by ophthalmoplegia, ptosis, proptosis of eye, dilation and fixation of the pupil, and anesthesia of the upper eyelid and forehead. This article describes a detailed anatomy of the superior orbital fissure as it related to pathophysiology and clinical findings. Etiology and diagnosis are established after detailed physical and radiographic examination. On the basis of our clinical experience in the management of superior orbital fissure syndrome and from the data reported previously in the literature, an algorithm for treatment of traumatic superior orbital fissure syndrome including use of steroid, surgical decompression of superior orbital fissure, and reduction of concomitant facial fracture is presented and its rationale discussed.

Expanding repertoire in the oculomotor periphery: selective compartmental function in rectus extraocular muscles

Since connective tissue pulleys implement Listing's law by systematically changing rectus extraocular muscle (EOM) pulling directions, non-Listing's law gaze dependence of the vestibulo-ocular reflex is currently inexplicable. Differential activation of compartments within rectus EOMs may endow the ocular motor system with more behavioral diversity than previously supposed. Innervation to horizontal, but not vertical, rectus EOMs of mammals is segregated into superior and inferior compartments. Magnetic resonance imaging in normal subjects demonstrates contractile changes in the lateral rectus (LR) inferior, but not superior, compartment during ocular counter-rolling (OCR) induced by head tilt. In human orbits ipsilesional to unilateral superior oblique palsy, neither LR compartment exhibits contractile change during head tilt, although the inferior compartment contracts normally in contralesional orbits. This suggests that differential compartmental LR contraction assists normal OCR. Computational simulation suggests that differential compartmental action in horizontal rectus EOMs could achieve more force than required by vertical fusional vergence.

Neuronavigation-guided endoscopic decompression of superior orbital fissure fracture: case report and literature review

OBJECTIVE

We present a rare case of an isolated superior orbital fissure fracture resulting from blunt injury to the face and presenting with selective cranial nerve deficits surgically treated with a neuroendoscopic approach. The anatomy of the superior orbital fissure is detailed, and the peculiarities of the surgical approach described.

METHOD

A review of the existing literature reveals this is the first reported case of a neuronavigation-assisted endoscopic approach used in the extraction of a superior orbital fracture fragment with good outcome. Current guidelines for an endoscopic approach in orbital trauma are reviewed, and pertinent literature is discussed.

CONCLUSION

Neuronavigation-assisted decompression should be considered as an effective means of removing superior orbital fissure fractures.

Intramuscular innervation of primate extraocular muscles: unique compartmentalization in horizontal recti

PURPOSE

It has been proposed that the lateral rectus (LR), like many skeletal and craniofacial muscles, comprises multiple neuromuscular compartments subserving different physiological functions. To explore the anatomic potential of compartmentalization in all four rectus extraocular muscles (EOMs), evidence was sought of possible regional selectivity in intramuscular innervation of all rectus EOMs.

METHODS

Whole orbits of two humans and one macaque monkey were serially sectioned at 10 μm thickness and stained with Masson's trichrome. Three-dimensional reconstruction was performed of the intramuscular courses of motor nerves from the deep orbit to the anterior extents of their arborizations within all four rectus EOMs in each orbit.

RESULTS

Findings concorded in monkey and human orbits. Externally to the global surface of the lateral (LR) and medial rectus (MR) EOMs, motor nerve trunks bifurcated into approximately equal-sized branches before entering the global layer and observing a segregation of subsequent arborization into superior zones that exhibited minimal overlap along the length of the LR and only modest overlap for MR. In contrast, intramuscular branches of the superior and the nasal portion of the inferior rectus were highly mixed.

CONCLUSIONS

Consistent segregation of intramuscular motor nerve arborization suggests functionally distinct superior and inferior zones within the horizontal rectus EOMs in both humans and monkeys. Reduced or absent compartmentalization in vertical rectus EOMs supports a potential functional role for differential innervation in horizontal rectus zones that could mediate previously unrecognized vertical oculorotary actions.

Compartmentalized innervation of primate lateral rectus muscle

PURPOSE

Skeletal and craniofacial muscles are frequently composed of multiple neuromuscular compartments that serve different physiological functions. Evidence of possible regional selectivity in LR intramuscular innervation was sought in a study of the anatomic potential of lateral rectus (LR) muscle compartmentalization.

METHODS

Whole orbits of two humans and five macaque monkeys were serially sectioned at 10-microm thickness and stained with Masson trichrome. The abducens nerve (CN6) was traced anteriorly from the deep orbit as it branched to enter the LR and arborized among extraocular muscle (EOM) fibers. Three-dimensional reconstruction was performed in human and monkey orbits.

RESULTS

Findings were in concordance in the monkey and human orbits. External to the LR global surface, CN6 bifurcated into approximately equal-sized trunks before entering the global layer. Subsequent arborization showed a systematic topography, entering a well-defined inferior zone 0.4 to 2.5 mm more posteriorly than branches entering the largely nonoverlapping superior zone. Zonal innervation remained segregated anteriorly and laterally within the LR.

CONCLUSIONS

Consistent segregation of intramuscular CN6 arborization in humans and monkeys suggests functionally distinct superior and inferior zones for the LR. Since the LR is shaped as a broad vertical strap, segregated control of the two zones could activate them separately, potentially mediating previously unappreciated but substantial torsional and vertical oculorotary LR actions.

Superior orbital fissure syndrome after repair of maxillary and naso-orbito-ethmoid fractures: a case study

OBJECTIVE

The superior orbital fissure syndrome results from damage to the nerves passing through the superior orbital fissure. In the present case, the superior orbital fissure syndrome developed after repair of facial bone fractures, although the symptoms were not observed before surgery and no obvious cause was found. To investigate the aetiology of this syndrome, we examined the superior orbital fissure anatomically.

METHODS

We measured the width of superior orbital fissure on the horizontal plane including the optic canal using the computed tomography (CT) scans of other patients and cadavers.

RESULTS

The results indicated that the width was 3.73+/-1.64 mm in the CT scans of patients and 3.21+/-1.09 mm in the cadavers. There was no significant difference between the width in the CT scans and cadavers. The width in the present patient on the affected side was 1.6mm, that is relatively narrow.

CONCLUSION

After operation, narrow superior orbital fissure may reduce the tolerance to compression of the nerves by oedema. We consider the narrow superior orbital fissure as a risk factor for superior orbital fissure syndrome. When the superior orbital fissure is congenitally narrow, the surgeons should try to avoid excessive pulling of the bone fragment and compression of the orbital tissue during repair of the facial bone fractures.

Innervation features of the extraocular muscles

Several transcranial surgical approaches such as frontoorbital, lateral, medial, central, inferolateral, and transmaxillary orbitotomy have been used for exposure of lesions within the orbit. During surgical approaches, detailed anatomic knowledge regarding neural, muscular, and neighboring structures for preservation of the neurovascular structures is important in avoiding traumatic retraction of the nerves of the extraocular muscles. For this study, a total of 22 formalin-fixed cadavers were dissected. Vascular structures were perfused with colored latex to facilitate their definition. In this study, the orbit was investigated in two divisions, superior and inferior. In the superior division, innervation features of the levator palpebrae superioris, the superior rectus, and superior oblique muscles were examined. In the inferior division, innervation features of the medial rectus, the lateral rectus, the inferior rectus, inferior oblique muscles, and ciliary ganglion were investigated. The diameter of the oculomotor nerve (CN3) within the superior orbital fissure was measured as 2.10 mm on the right and 2.09 mm on the left. The diameter of the superior division of the CN3 was on average 1.54 +/- 0.30 mm on the right and 1.65 +/- 0.30 on the left. The mean diameter of the inferior division was measured as 1.85 +/- 0.22 mm on the right and 1.94 +/- 0.20 on the left. In the lower wall of the orbit, different branching types of inferior division of CN3 were observed. The diameter of the trochlear nerve in the superior orbital fissure was on average 1.15 +/- 0.19 mm on the right and 1.21 +/- 0.21 mm on the left. The diameter of the abducens nerve in the superior orbital fissure was on average 1.54 +/- 0.24 mm on the right and 1.54 +/- 0.22 on the left. The number of small branches entering the muscle was on average three branches. Areas nervosa of the nerves were located in the middle one third of the muscles. In this study, detailed knowledge regarding the innervation features of extraocular muscles was attained. An understanding of the innervation features of extraocular muscles is important for the preservation of neural structures during intraorbital procedures.

Anatomical study of the superior orbital fissure as seen during a pterional approach

Object

The superior orbital fissure (SOF) is an important landmark in the neurosurgical pterional approach, but the anatomical features of the SOF and the procedures necessary to fully expose it and its contents have not been detailed. Although the pterional approach is commonly used during skull base or vascular surgery by neurosurgeons who may already be familiar with its nuances and anatomical relationships to the SOF, this knowledge may also be useful to the wider neurosurgical community. The authors describe the spatial relationships of the contents of the SOF and suggest a specific sequence of steps for exposing the SOF region in a pterional approach.

Methods

Using standard microsurgical equipment and instruments, the authors performed 20 pterional approaches in 10 embalmed cadaver heads in which the vascular systems had been injected with colored material.

Five sequential steps were delineated for approaching and dissecting the SOF and its contents: 1) drilling the sphenoidal ridge, anterior clinoidal process, and part of the greater and lesser wings of the sphenoid; 2) resecting the dural bridge; 3) detaching the hemispheric dura mater, thereby exposing the anterior portion of the cavernous sinus and the neural component entering the SOF; 4) identifying and dissecting the extraanular structures; and 5) opening the anulus of Zinn and identifying its neural constituents.

Conclusions

Knowing the 3D relationships of the contents of the SOF encountered in the pterional approach enables safe neurosurgical access to the area. The proposed sequence of steps allows a controlled exposure of the SOF and surrounding areas. Untethering the frontotemporal lobe by transecting the dural bridge connecting the dura to the perior-bita allows good exposure of the basal frontotemporal lobes, both intra- and extradurally, and reduces brain retraction.