Morphometry and anatomical variations of the inferior oblique muscle as relevant to the strabismus surgeries.

Effective outcome of inferior oblique (IO) corrective surgeries demands a detailed knowledge of morphometry and variations of IO. Our aim was to study and morphometrically define the surgical anatomy of the IO muscle and its variations. Also to provide easily identifiable surgical coordinates to locate, the IO origin and the oculomotor nerve entry point into the IO. Dissection was performed on 16 cadaveric orbits. IO anatomy, variations, morphometry and relevant surgical distances were measured using digital caliper. IO with multiple bellies was found in five specimens. The IO mean length was 33.1 ± 3.3 mm, width at origin was 3.1 ± 0.6 mm, and width at insertion was 8.8 ± 1.5 mm. For easy localization of origin, its distance from the palpable landmarks, Zygomatico-maxillary suture and fronto-maxillary suture was measured. The mean distance between IO and the optic nerve was 10 mm. Distance of the nerve to inferior oblique entry point to the origin and insertion of the inferior oblique was measured. The nerve to IO was 28 mm long. The mean distance of the nerve entry point to IO origin was 15.5 ± 2.3 mm and distance to IO insertion was 15.2 ± 2.8 mm. A muscular bridge between the Inferior rectus (IR) & IO was found in one case, affecting ~» of the IO length; the distal end of the bridge was 5 mm from the IO insertion. Origin of the IO can be localized on the orbital surface of maxilla, 1-2 cm from the point where zygomatico-maxillary suture cuts the inferior orbital margin and 1-2 cm from the fronto-maxillary suture. In 19% of the orbits, the IO length was less than 30 mm, which may cause traction injury in muscle transposition procedures. The width at insertion is useful as most corrective surgeries are performed at the insertion site. The nerve to IO consistently entered at the center of medial border. The nerve entry point is important surgically as myectomy is performed between it and the insertion point. The safe distance available from the optic nerve was 7 mm. Detailed morphometry of IO may aid surgeons in better surgical planning and execution.

The trajectory of the medial longitudinal fasciculus in the human brain: A diffusion imaging-based tractography study.

The aim of this study is to investigate the trajectory of medial longitudinal fasciculus (MLF) and explore its anatomical relationship with the oculomotor nerve using tractography technique. The MLF and oculomotor nerve were reconstructed at the same time with preset three region of interests (ROIs): one set at the area of rostral midbrain, one placed on the MLF area at the upper pons, and one placed at the cisternal part of the oculomotor nerve. This mapping protocol was tested in an HCP-1065 template, 35 health subjects from Massachusetts General Hospital (MGH), 20 healthy adults and 6 brainstem cavernous malformation (BCM) patients with generalized q-sampling imaging (GQI)-based tractography. Finally, the 200 µm brainstem template from Center for In Vivo Microscopy, Duke University (Duke CIVM), was used to validate the trajectory of reconstructed MLF. The MLF and oculomotor nerve were reconstructed in the HCP-1065 template, 35 MGH health subjects, 20 healthy adults and 6 BCM patients. The MLF was in conjunction with the ipsilateral mesencephalic part of the oculomotor nerve. The displacement of MLF was identified in all BCM patients. Decreased QA, RDI and FA were found in the MLF of lesion side, indicating axonal loss and/or edema of displaced MLF. The reconstructed MLF in Duke CIVM brainstem 200 µm template corresponded well with histological anatomy. The MLF and oculomotor nerve were visualized accurately with our protocol using GQI-based fiber tracking. This GQI-based tractography is an important tool in the reconstruction and evaluation of MLF.

Overall distribution pattern of the intramuscular nerves of the extraocular muscles and its clinical implications / Patrón de distribución general de los nervios intramusculares de los músculos extraoculares y sus implicaciones clínicas

SUMMARY: The purpose of this study was to reveal the overall distribution pattern of the intramuscular nerves of each extraocular muscle and provide morphological guidance for the selection of the neuromuscular compartment during extraocular muscle transplantation and target localization of the botulinum toxin A injection to correct strabismus. We studied 12 Chinese head specimens that were fixed with formalin. The extraocular muscles from both sides of each head were removed, and a modified Sihler's staining technique was used to reveal the overall distribution pattern of the intramuscular nerves. We observed an intramuscular nerve-dense region formed by the intramuscular arborized branches in the semitransparent superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique, and levator palpebrae superioris muscles with Sihler's staining technique. The seven extraocular muscles can each be divided into two neuromuscular compartments. The intramuscular nerve-dense regions of the superior, inferior, medial, and lateral rectus and the superior oblique, inferior oblique, and levator palpebrae superioris muscles were positioned at 33.50 % -72.72 %, 40.21 % - 66.79%, 37.92 % - 64.51 %, 31.69 % - 56.01 %, 26.35 % - 64.98 %, 40.46 % - 73.20 %, and 27.72 % - 66.07 % of the lengths of the muscle bellies, respectively, and the centers of intramuscular nerve dense regions were located at 59.50 %, 54.18 %, 51.68 %, 50.08 %, 48.38 %, 56.49 %, and 50.77 % of the length of each muscle belly, respectively. The aforementioned values are the means of the actual values. These results suggest that when the strabismus is corrected with muscle transplantation, the extraocular muscle should be transplanted based on the neuromuscular compartment, which would benefit the function of both donor and recipient muscles. The localization of these nerve dense regions is recommended as an optimal target for the injection of botulinum toxin A to treat strabismus.

RESUMEN: El objetivo de este estudio fue revelar el patrón de distribución de los nervios intramusculares de cada músculo extraocular y, proporcionar una guía morfológica para la selección del compartimento neuromuscular durante el trasplante de músculo extraocular, y la localización de la inyección de toxina botulínica A para corregir el estrabismo. Estudiamos 12 muestras de cabezas de individuos chinos fijadas en formalina. Se extrajeron los músculos extraoculares de ambos lados de cada cabeza y, se utilizó una técnica de tinción de Sihler modificada para revelar el patrón de distribución general de los nervios intramusculares. Observamos una región densa en nervios intramusculares formada por los ramos intramusculares en los músculos recto superior semitransparente, recto inferior, recto medial, recto lateral, oblicuo superior, oblicuo inferior y elevador del párpado superior con técnica de tinción de Sihler. Los siete músculos extraoculares se pueden dividir cada uno en dos compartimentos neuromusculares. Las regiones intramusculares densamente nerviosas de los músculos recto superior, inferior, medial y lateral y los músculos oblicuo superior, oblicuo inferior y elevador del párpado superior se colocaron en 33,50 % -72,72 %, 40,21 % -66,79 %, 37,92 % -64,51 % , 31,69 % -56,01 %, 26,35 % -64,98 %, 40,46 % -73,20 % y 27,72 % -66,07 % de las longitudes de los vientres musculares, respectivamente, y los centros de las regiones densamente nerviosas intramusculares se ubicaron en 59,50 %, 54,18 % , 51,68 %, 50,08 %, 48,38 %, 56,49 % y 50,77 % de la longitud de cada vientre muscular, respectivamente. Los valores antes mencionados son medios de los valores reales. Estos resultados sugieren que cuando el estrabismo se corrige con trasplante de músculo, el músculo extraocular debe trasplantarse en función del compartimento neuromuscular, lo que beneficiaría la función tanto de los músculos donantes como receptores. Se recomienda la localización de estas regiones densas en nervios, como un objetivo óptimo para la inyección de toxina botulínica A para tratar el estrabismo.

Surgical anatomy and nuances of the expanded endonasal transdorsum sellae and posterior clinoidectomy approach to the interpeduncular and prepontine cisterns: a stepwise cadaveric dissection of various pituitary gland transpositions.

BACKGROUND: Excelsior knowledge of endoscopic anatomy and techniques to remove the natural barriers preventing full endonasal access to the interpeduncular and prepontine cisterns determines the ease of transposing the pituitary gland (hypophysiopexy) preserving the glandular function without manipulating the optic apparatus and the oculomotor nerves. METHODS: Throughout stepwise cadaveric dissections, we describe the expanded endonasal approach (EEA) to the interpeduncular and prepontine cisterns with special references to the intricate anatomy of the region and techniques for hypophysiopexy and posterior clinoidectomies. CONCLUSION: This article illustrates sellar-diaphragmatic dural incisions and various "pituitary gland transpositions" techniques performed via extradural (lifting the gland still covered by both dural layers), interdural (transcavernous), and intradural (between the medial wall of the cavernous sinus and the pituitary tunica) to access the prepontine and interpeduncular cisterns.

Intramuscular Nerves of the Inferior Rectus Muscle: Distribution and Characteristics.

PURPOSE: Knowledge of the distribution of intramuscular nerves of the extraocular muscles is crucial for understanding their function. The purpose of this study was to elucidate the intramuscular distribution of the oculomotor nerve within the inferior rectus muscle (IRM) using Sihler's staining. METHOD: Ninety-three IRM from 50 formalin-embalmed cadavers were investigated. The IRM including its branches of the oculomotor nerve was finely dissected from its origin to the point where it inserted into the sclera. The intramuscular nerve course was investigated after performing Sihler's whole-mount nerve staining technique that stains the nerves while rendering other soft tissues either translucent or transparent. RESULTS: The oculomotor nerve enters the IRM around the distal one-fourth of the muscle and then divides into multiple smaller branches. The intramuscular nerve course finishes around the distal three-fifth of the IRM in gross observations. The types of branching patterns of the IRM could be divided into two subcategories based on whether or not topographic segregation was present: (1) no significant compartmental segregation (55.9% of cases) and (2) a several-zone pattern with possible segregation (44.1% of cases). Possible compartmentalization was less clear for the IRM, which contained overlapping mixed branches between different trunks. CONCLUSION: Sihler's staining is a useful technique for visualizing the gross nerve distribution of the IRM. The new information about the nerve distribution and morphological features provided by this study will improve the understanding of the biomechanics of the IRM, and could be useful for strabismus surgery.

Comparison of the Superior and Inferior Rectus Muscles in Humans: An Anatomical Study with Notes on Morphology, Anatomical Variations, and Intramuscular Innervation Patterns.

A comparison of the superior and inferior rectus muscles was performed to determine whether they have similar structures and innervation attributable to their participation in the same type of, although antagonistic, eye movements. The study was conducted on 70 cadaveric hemiheads, and the anatomical variations in the superior and inferior rectus muscles were assessed. Sihler's whole mount nerve staining technique was used on 20 isolated superior and 20 isolated inferior rectus muscle specimens to visualize the intramuscular distribution of the oculomotor nerve subbranches. In two cases (~2.8%), variant muscular slips were found that connected the superior and inferior rectus muscles. In 80% of cases, muscular branches arising directly from the inferior branch of the oculomotor nerve innervated the inferior rectus muscle, while in 20% of cases, the nerve to the inferior oblique muscle pierced the inferior rectus muscle and provided its innervation. In 15 of 70 specimens (21.4%), a branch to the levator palpebrae superioris muscle pierced the superior rectus muscle. The distance between the specific rectus muscle's insertion and the anterior-most terminations of the nerves' subbranches with reference to the muscle's total length ranged from 26.9% to 47.2% for the inferior rectus and from 34.8% to 46.6% for the superior rectus, respectively. The superior rectus muscle is slightly longer and its insertion is farther from the limbus of the cornea than is the inferior rectus muscle. Both muscles share a common general pattern of intramuscular nerve subbranches' arborization, with characteristic Y-shaped ramifications that form the terminal nerve plexus located near half of the muscles' length. Unexpected anatomical variations of the extraocular muscles may be relevant during orbital imaging or surgical procedures.

Comparison of lateral and medial rectus muscle in human: an anatomical study with particular emphasis on morphology, intramuscular innervation pattern variations and discussion on clinical significance.

This paper aims to present various aspects of the anatomy of horizontal (i.e., lateral and medial) rectus muscles. It mainly compares morphology and detailed patterns of intramuscular innervation of those muscles. It is also one of the first reports that uses the Sihler's stain to examine human extraocular muscles. The study was conducted on 80 isolated cadaveric hemi-heads. Sihler technique of nerves staining served to expose the course of intramuscular branches of the oculomotor and abducens nerves. The lateral rectus was longer (48 mm versus 46.5 mm) and more distant from the limbus (6.8 mm versus 5.7 mm) than the medial rectus muscle. Three variants of the abducens nerve primary division were observed in the lateral rectus muscle. In the medial rectus muscle, the motor branch from the oculomotor nerve was more evenly divided into sub-branches. In both examined horizontal rectus muscles, primary muscular branches split into secondary sub-branches, which undergo numerous further divisions. The most numerous terminal sub-branches formed the terminal plexus. The distance between the insertion and the anterior-most end of the terminal plexus referenced to the total length of the muscle ranged from 35.4 to 48.5% for the lateral rectus muscle and from 36.3 to 50.5% for medial rectus muscle. Both horizontal rectus muscles share similar general pattern of distribution of intramuscular nerves, with characteristic root-like arborizations of sub-branches. The terminal nerve plexus was observed near half of both muscles' length. Knowledge of variations and innervation pattern of the extraocular muscles may be relevant during ophthalmology surgeries.

Intramuscular Nerve Distribution of the Inferior Oblique Muscle.

Purpose: The intramuscular nerve distribution in the extraocular muscles is important for understanding their function. This study aimed to determine the intramuscular nerve distribution of the oculomotor nerve within the inferior oblique muscle (IO) using Sihler's staining.Method: Seventy-two IOs from 50 formalin-embalmed cadavers were investigated. The IO including its branch of the oculomotor nerve was finely dissected from its origin to its insertion point into the sclera. The total length of the muscle and its width were measured. The intramuscular nerve course was investigated after performing Sihler's staining, which is a whole-mount nerve-staining technique that stains the nerves while rendering other soft tissues either translucent or transparent.Results: The total length of the muscle and muscle width were 30.0 ± 2.8 mm (mean±standard deviation), 8.8 ± 1.2 mm, respectively. The oculomotor nerve enters the IO around the middle of the muscle and then divides into multiple smaller branches without distinct subdivisions. The intramuscular nerve distribution within the IO has a root-like arborization and supplies the entire width of the muscle. The Sihler's stained intramuscular nerve course (covering a length of 7.6 ± 1.2 mm) finishes around the distal one-third of the IO in gross observations.Conclusion: Sihler's staining is a useful technique for visualizing the gross nerve distribution of the IO. This new information about the nerve distribution and morphological features will improve the understanding of the biomechanics of the IO.

Transnasal prelacrimal approach to the inferior intraconal space: a feasibility study.

BACKGROUND: Endonasal access to the inferomedial and inferolateral intraconal space via the orbital floor has not been reported. The primary purpose of this study was to assess the feasibility of accessing the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. Secondarily, it aims to highlight anatomical relationships of neurovascular structures in this space, as a requirement to prevent complications. METHODS: Six cadaveric heads (12 sides) were dissected using a transnasal prelacrimal approach. The orbital floor, medial to the infraorbital canal, was removed and the periorbita opened to expose the inferior rectus muscle. The inferomedial and inferolateral intraconal space was accessed alongside the medial and lateral border of inferior rectus muscle, respectively. Various anatomical relationships of adjacent neurovascular structures were recorded, and the distances among the recti muscles and optic nerve were also measured. RESULTS: The infraorbital nerve is located at the inferolateral aspect of inferior rectus muscle. In the inferomedial intraconal space, we identified the inferomedial muscular trunk of the ophthalmic artery, optic nerve, and branches of the oculomotor nerve; whereas the inferolateral intraconal space contained the inferolateral muscular trunk of ophthalmic artery, branches of the oculomotor and nasociliary nerve, and abducens nerve. Distances from the medial, inferior, and lateral recti muscles to the optic nerve were (mean ± standard deviation) 4.70 ± 1.18 mm, 5.60 ± 0.93 mm, and 7.98 ± 1.99 mm, respectively. Distances from the inferior rectus muscle to the inferior borders of medial and lateral recti muscles were 4.45 ± 1.23 mm and 8.77 ± 1.80 mm. CONCLUSION: It is feasible to access the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. The access may be subdivided into inferomedial and inferolateral corridors according to the entry point at the medial or lateral border of the inferior rectus muscle. Neurovascular structures in the inferior intraconal space are visualized directly, which should enhance their preservation.

Mouse Extraocular Muscles and the Musculotopic Organization of Their Innervation.

The organization of extraocular muscles (EOMs) and their motor nuclei was investigated in the mouse due to the increased importance of this model for oculomotor research. Mice showed a standard EOM organization pattern, although their eyes are set at the side of the head. They do have more prominent oblique muscles, whose insertion points differ from those of frontal-eyed species. Retrograde tracers revealed that the motoneuron layout aligns with the general vertebrate plan with respect to nuclei and laterality. The mouse departed in some significant respects from previously studied species. First, more overlap between the distributions of muscle-specific motoneuronal pools was present in the oculomotor nucleus (III). Furthermore, motoneuron dendrites for each pool filled the entire III and extended beyond the edge of the abducens nucleus (VI). This suggests mouse extraocular motoneuron afferents must target specific pools based on features other than dendritic distribution and nuclear borders. Second, abducens internuclear neurons are located outside the VI. We concluded this because no unlabeled abducens internuclear neurons were observed following lateral rectus muscle injections and because retrograde tracer injections into the III labeled cells immediately ventral and ventrolateral to the VI, not within it. This may provide an anatomical substrate for differential input to motoneurons and internuclear neurons that allows rodents to move their eyes more independently. Finally, while soma size measurements suggested motoneuron subpopulations supplying multiply and singly innervated muscle fibers are present, markers for neurofilaments and perineuronal nets indicated overlap in the size distributions of the two populations. Anat Rec, 302:1865-1885, 2019. © 2019 American Association for Anatomy.

Intramuscular Nerve Distribution in the Medial Rectus Muscle and Its Clinical Implications.

PURPOSE: The intramuscular nerve distribution in the extraocular muscles may be crucial for understanding their physiological and pathological responses. This study aimed to determine the oculomotor nerve distribution in the medial rectus muscle (MR) using Sihler's staining. METHOD: Thirty-seven MRs from 23 cadavers were investigated. The MR including the oculomotor nerve was finely dissected from its origin to its insertion point into the sclera. The total length of the muscle-belly, tendon length and maximum width of the muscle were measured. We evaluated the pattern of distribution and the length of the intramuscular nerve distribution by gross observation after performing Sihler's staining, which is a method for visualizing the distribution of nerve fibers without alteration of the nerve. RESULTS: The total length of the muscle-belly, tendon length, and muscle width were 37.6 ± 4.6 mm, 4.4 ± 1.9 mm, and 10 ± 1.8 mm, respectively. The oculomotor nerve enters the MR at a mean of two-fifths along the muscle (24 ± 2.0 mm posterior to the insertion point) and then typically divides into a few branches (mean of 2.1). The intramuscular nerve distribution showed a Y-shaped ramification, forming the terminal nerve plexus, and its course typically finished at around 17 ± 1.5 mm posterior to the muscle insertion point by gross observation. The nerve plexus in the upper part generally coursed more distally than the lower part. CONCLUSION: This new information regarding the nerve distribution pattern of MR will be helpful for understanding MR function and the diverse pathophysiology of strabismus.

Normal Anatomy and Anomalies of the Rectus Extraocular Muscles in Human: A Review of the Recent Data and Findings.

Development of modern surgical techniques is associated with the need for a thorough knowledge of surgical anatomy and, in the case of ophthalmologic surgery, also functional aspects of extraocular muscles. Thus, the leading idea of this review was to summarize the most recent findings regarding the normal anatomy and anomalies of the extraocular rectus muscles (ERMs). Particular attention was paid to the presentation of detailed and structured data on the gross anatomy of the ERMs, including their attachments, anatomical relationships, vascularization, and innervation. This issue of ERMs innervation was presented in detail, considering the research that has recently been carried out on human material using advanced anatomical techniques such as Sihler's technique of the nerves staining. The text was supplemented with a carefully selected graphic material (including anatomical specimens prepared specially for the purpose of this review) and discussion of the clinical cases and practical significance of the presented issues.

[Neuroanatomy of the Oculomotor System]. / Neuroanatomie des okulomotorischen Systems.

After just a clinical examination, the experienced neurologist can assign specific symptoms quite precisely to distinct lesions within the brain and other parts of the nervous system, on the basis of his neuroanatomical knowledge. This also holds true for lesions affecting the oculomotor system. The aim of this article is to give a comprehensive overview of the neuroanatomical basis of the oculomotor system, in order to facilitate the precise spatial assignment of potential lesions affecting the control of eye movements. After a brief introduction, the components of the system are discussed, including the extraocular muscles and their innervating nerves. The following section will then cover the control of eye movements and will specifically address distinct patterns of eye movements and areas within the central nervous system controlling these. This article also gives a brief overview of the intraocular muscles and their control.

Microsurgical Anatomy of the Oculomotor Nerve.

The oculomotor nerve supplies the extraocular muscles. It also supplies the ciliary and sphincter pupillae muscles through the ciliary ganglion. The nerve fibers leave the midbrain through the most medial part of the cerebral peduncle and enter the interpeduncular cistern. After the oculomotor nerve emerges from the interpeduncular fossa, it enters the cavernous sinus slightly lateral and anterior to the dorsum sellae. It enters the orbit through the superior orbital fissure, after exiting the cavernous sinus, to innervate the extraocular muscles. Therefore, knowledge of the detailed anatomy and pathway of the oculomotor nerve is critical for the management of lesions located in the middle cranial fossa and the clival, cavernous, and orbital regions. This review describes the microsurgical anatomy of the oculomotor nerve and presents pictures illustrating this nerve and its surrounding connective and neurovascular structures. Clin. Anat. 30:21-31, 2017. © 2016 Wiley Periodicals, Inc.

Distance between intramuscular nerve and artery in the extraocular muscles: a preliminary immunohistochemical study using elderly human cadavers.

PURPOSE: Extraocular muscles are quite different from skeletal muscles in muscle fiber type and nerve supply; the small motor unit may be the most well known. As the first step to understanding the nerve-artery relationship, in this study we measured the distance from the arteriole (25-50 µm in thickness) to the nerve terminal twigs in extraocular muscles. MATERIALS AND METHODS: With the aid of immunohistochemistry for nerves and arteries, we examined the arteriole-nerve distance at 10-15 sites in each of 68 extraocular muscles obtained from ten elderly cadavers. The oblique sections were nearly tangential to the muscle plate and included both global and orbital aspects of the muscle. RESULTS: In all muscles, the nerve twigs usually took a course parallel to muscle fibers, in contrast to most arterioles that crossed muscles. Possibly due to polyinnervation, an intramuscular nerve plexus was evident in four rectus and two oblique muscles. The arteriole-nerve distance usually ranged from 300 to 400 µm. However, individual differences were more than two times greater in each of seven muscles. Moreover, in each muscle the difference between sites sometimes reached 1 mm or more. The distance was generally shorter in the rectus and oblique muscles than in the levator palpebrae muscle, which reached statistical significance (p < 0.05). CONCLUSIONS: The differences in arteriole-nerve distances between sites within each muscle, between muscles, and between individuals might lead to an individual biological rhythm of fatigue in oculomotor performance.

The cisternal segments of the oculomotor nerve: a magnetic resonance imaging study.

PURPOSE: The cisternal segments of the oculomotor nerve (OMN), which courses through the interpeduncular and oculomotor cisterns (OMC) have not been well delineated on neuroimages. The present study aimed to explore the cisternal segments of the OMN using magnetic resonance (MR) imaging. METHODS: A total of 92 patients were enrolled in this study. A constructive interference in steady-state sequence was performed in coronal and axial sections. RESULTS: On coronal images, cisternal portions of the OMN were entirely delineated in 97 % on the right and in 98.5 % on the left. Most of the OMCs were of a round shape, with a centrally located OMN, while 9 % were ectatic with the OMN located eccentrically. In 5.3 % of cases, fetal-type posterior communicating arteries (PCoAs), which coursed adjacent to the superior surfaces of the OMNs at the oculomotor triangle (OMT), were observed. On axial images, cisternal portions of the OMN were identified in all cases. The OMN segment passing through the OMT showed medial, central, and lateral courses. The PCoAs and P2 segments of the posterior cerebral artery (PCA) were adjacent to the OMNs in 17 and 19 % of cases, respectively. CONCLUSIONS: The OMN most frequently courses in the medial part of the OMT and enters into the OMC. These findings indicate that OMN paresis can be caused by vascular compression at any site of the interpeduncular cistern and OMT.

Development of a Generic Tubular Tree Structure for the Modeling of Orbital Cranial Nerves.

We developed a generic approach for modeling tubular tree structures as triangle meshes for the extension of our biomechanical eye model SEE-KID with a visualization of the orbital cranial nerves. Since three of the orbital nerves innervate extraocular eye muscles and move together with them, the structure must also support the partial translation and rotation of the nerves. For the SEE-KID model, this extension allows a better parameterization as well as an easier simulation of innervational disorders. Moreover, it makes the model even more useful for education and training purposes in contrast to other anatomical models. Due to its generic nature, the developed data structure and the associated algorithms can be used for any tubular tree structures, even in non-medical application areas.

Morphological Characteristics of the Sphenoid Sinus and Endoscopic Localization of the Cavernous Sinus.

The aim of this study was to investigate the relationship between the morphological characteristics of the sphenoid sinus and endoscopic localization of the cavernous sinus (CS) using an extended endoscopic endonasal transsphenoidal approach. Thirty sides of CS in 15 adult cadaver heads were dissected to simulate the extended endoscopic endonasal transsphenoidal approach, and the morphology of the sphenoid sinus and anatomic structures of CS were observed. The opticocarotid recess (OCR), ophthalmomaxillary recess (V1V2R), and maxillomandibular recess (V2V3R) in the lateral wall of the sphenoid sinus were presented in 16 sides (53.3%), 6 sides (20%), and 4 sides (13.3%) of the 30 sides, respectively. OCR is a constant anatomic landmark in endoscopy and coincides with the anterior portion of the clinoidal triangle. The C-shaped internal carotid artery (ICA) in the lateral wall of the sphenoid sinus was presented in 11 sides (36.7%), the upper one-third of which corresponds to the middle portion of the clinoidal triangle, and the lower two-thirds of which correlates to the supratrochlear triangle, infratrochlear triangle, and ophthalmic nerve in CS, around which the medial, lateral, and anteroinferior interspaces are distributed. From a front-to-behind perspective, the C-shaped ICA consists of inferior horizontal segment, anterior vertical segment, clinoidal segment as well as partial subarachnoid segment of the ICA. OCR and C-shaped ICA in the lateral wall of the sphenoid sinus are the 2 reliable anatomic landmarks in the intraoperative location of the parasellar region of CS.

ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY.

For accurate interpretation of magnetic resonance (MR) images of the equine brain, knowledge of the normal cross-sectional anatomy of the brain and associated structures (such as the cranial nerves) is essential. The purpose of this prospective cadaver study was to describe and compare MRI and computed tomography (CT) anatomy of cranial nerves' origins and associated skull foramina in a sample of five horses. All horses were presented for euthanasia for reasons unrelated to the head. Heads were collected posteuthanasia and T2-weighted MR images were obtained in the transverse, sagittal, and dorsal planes. Thin-slice MR sequences were also acquired using transverse 3D-CISS sequences that allowed mutliplanar reformatting. Transverse thin-slice CT images were acquired and multiplanar reformatting was used to create comparative images. Magnetic resonance imaging consistently allowed visualization of cranial nerves II, V, VII, VIII, and XII in all horses. The cranial nerves III, IV, and VI were identifiable as a group despite difficulties in identification of individual nerves. The group of cranial nerves IX, X, and XI were identified in 4/5 horses although the region where they exited the skull was identified in all cases. The course of nerves II and V could be followed on several slices and the main divisions of cranial nerve V could be distinguished in all cases. In conclusion, CT allowed clear visualization of the skull foramina and occasionally the nerves themselves, facilitating identification of the nerves for comparison with MRI images.

[T2-SPACE MRI for the ocular motor nerves in the brainstem of normal controls].

OBJECTIVE: To study the detail functional anatomy of ocular motor nerves in the brainstem by high-resolution magnetic resonance imaging (MRI). METHODS: Sixty eight normal subjects with high resolution MRI were recruited in our study. The ocular motor nerves at the brainstem were performed using 3-dimensional, T(2)-weighted Turbo-Spin-Echo sequence with high sampling efficiency sequence (3D T(2)-SPACE), Parameters: TR = 1000 ms, TE = 134 ms, averages = 2, thickness = 0.8 mm, FOV = 225 mm×225 mm, matrix = 384×384, total scanning time is 4 min 2 s. Nerves in the brainstem were observed in oblique axial, oblique sagittal and coronal planes acquired with multi-planar reformation (MPR). The diameters of oculomotor nerves (CN3) and abducens (CN6) in the brainstem were measured in 68 normal subjects on MR images by 2 neuro-radiologists. RESULTS: All of 136 CN3 and CN6 of the cisternal segment were well demonstrable in 68 normal subjects (100%). Trochlear nerves (CN4) were depicted 87%. The diameters of CN3 and CN6 in the cistern were 2.2 mm, 1.3 mm, had no linear correlation with age. There were no significant difference between the results of the 2 radiologist (F = 2.557, 1.329, P = 0.085, 0.271). CONCLUSIONS: T(2)-SPACE sequence combined with MPR could precisely show the ocular motor nerves, as well as the relationship with adjacent structures in the cistern. The exact data measurement can provide more accurate anatomical basis for some special forms of neuropathic strabismus.