Racial, Ethnic, and Gender Variations in Sinonasal Anatomy.

BACKGROUND: Complications during endoscopic sinus surgery often result from unfavorable anatomy. The prevalence rates of such anatomic findings vary tremendously in the literature, in part due to the small, homogenous populations previously studied. OBJECTIVE: To characterize the prevalence of sinonasal anatomic variants among ethnic groups and genders seen at an academic medical center. METHODS: This is a retrospective cross-sectional study of adult subjects who underwent CT imaging of the sinuses from January 2019 to November 2020 at a tertiary academic setting. CT scans were analyzed systematically by 3 trained study personnel for the presence of critical sinus anatomic variants that endoscopic sinus surgeons typically evaluate for preoperatively. Chi-squared tests and analyses of variance were conducted to detect differences in the prevalence of structural findings between genders and races/ethnicities. RESULTS: A total of 489 subjects (57% female) were included: 44 Asian, 14 Black/African American, 101 Hispanic/Latino, 203 White, 127 Other. The prevalence of the following anatomical variants differed by race/ethnicity: Haller cells, Type 3 optic nerve, Onodi cells, maxillary septations, sphenoid lateral recess, anterior clinoid process pneumatization, and carotid artery dehiscence. Asian subjects had higher rates of Haller cells (48% vs 16%, P < .001) and Type 3 optic nerve (18% vs 4%, P = .022) compared to Hispanic subjects, as well as a higher prevalence of Onodi cells (39% vs 17%, P = .003) compared to White subjects. Males had a higher prevalence of mesenteric anterior ethmoid arteries (62% vs 45%, P < .001) and dehiscent carotid arteries (30% vs 21%, P = .024). CONCLUSION: Certain sinonasal anatomic variants, which have direct implications for complications during endoscopic sinus surgery, were found to be significantly more prevalent in some demographic groups. Surgeons should be aware of these differences in their review of preoperative imaging for safe surgical planning.

Endoscopic endonasal surgical anatomy of the optic canal: key anatomical relationships between the optic nerve and ophthalmic artery.

PURPOSE: A detailed understanding of the neurovascular relationships between the optic nerve (ON) and the ophthalmic artery (OA) in the optic canal (OC) is paramount for safe surgery. We focused on the neurovascular anatomy of this area from both an endoscopic endonasal and transcranial trajectories to compare the surgical exposures and perspectives offered by these different views and provide recommendations to increase the intraoperative safety. METHODS: Twenty sides of ten formalin-fixed, latex-injected head specimens were utilized. The surgical anatomy and anatomical relationships of the OA in relationship to the ON along their intracranial and intracanalicular segments was studied from endoscopic endonasal and transcranial perspectives. RESULTS: Three types of OA-ON relationships at the origin of the OA were identified: inferomedial (type 1, 35%), inferior (type 2, 55%), and inferolateral (type 3, 10%). The endoscopic endonasal trajectory offers an inferomedial perspective of the ON-OA neurovascular complex, in which the OA, especially when located inferomedially, is first encountered. When comparing with the transcranial view, all OA were covered by the nerve, type 1 was located below the medial third, type 2 below the middle third, and type 3 below the lateral third of the OC. The mean extension of the intracanalicular portion of both OA and ON was 8.9 mm, while the intracranial portion of the OA and ON were 9.3 mm and 12.4 mm, respectively. The OA, endoscopically, is located within the inferior half of the OC, and occupies 39%, 43%, and 42% of the OC height at its origin, mid, and end points, respectively. The mean distance between the superior margin of the OC at its origin and superior margin of the OA is 1.4 mm. CONCLUSIONS: Detailed anatomical understanding of the OC, and the ON and OA at their intracranial and intracanalicular segments is paramount to safe surgery. When opening the OC dura endoscopically, our results suggest that a medial incision along the superior third of the OC with a proximal to distal direction is recommended to avoid injury of the OA.

Visualization of human optic nerve by diffusion tensor mapping and degree of neuropathy.

Diffusion-weighted magnetic resonance imaging of the human optic nerve and tract is technically difficult because of its small size, the inherent strong signal generated by the surrounding fat and the cerebrospinal fluid, and due to eddy current-induced distortions and subject movement artifacts. The effects of the bone canal through which the optic nerve passes, and the proximity of blood vessels, muscles and tendons are generally unknown. Also, the limited technical capabilities of the scanners and the minimization of acquisition times result in poor quality diffusion-weighted images. It is challenging for current tractography methods to accurately track optic pathway fibers that correspond to known anatomy. Despite these technical limitations and low image resolution, here we show how to visualize the optic nerve and tract and quantify nerve atrophy. Our visualization method based on the analysis of the diffusion tensor shows marked differences between a healthy male subject and a male subject with progressive optic nerve neuropathy. These differences coincide with diffusion scalar metrics and are not visible on standard morphological images. A quantification of the degree of optic nerve atrophy in a systematic way is provided and it is tested on 9 subjects from the Human Connectome Project.

Subarachnoid space of the optic nerve sheath and intracranial hypertension: a macroscopic, light and electron microscopic study.

PURPOSE: The optic nerve (ON) is an extension of the central nervous system via the optic canal to the orbital cavity. It is accompanied by meninges whose arachnoid layer is in continuity with that of the chiasmatic cistern. This arachnoid layer is extended along the ON, delimiting a subarachnoid space (SAS) around the ON. Not all forms of chronic intracranial hypertension (ICH) present papilledema. The latter is sometimes asymmetric, unilateral, or absent. The radiological signs of optic nerve sheath (ONS) dilation, in magnetic resonance imaging, are inconsistent or difficult to interpret. The objective of this study was to analyze the anatomy, the constitution, and the variability of the SAS around the ON in its intraorbital segment to improve the understanding of the pathophysiologic mechanism of asymmetric or unilateral or absent papilledema in certain ICH. METHODS: The study was carried out on nine cadaveric specimens. In four embalmed specimens, macroscopic analysis of the SAS of the ONS were performed, with description about density of the arachnoid trabecular meshwork in three distinct areas (bulbar segment, mid-orbital segment and the precanal segment). In three other embalmed specimens, after staining of SAS by methylene blue (MB), we performed macroscopic analysis of MB progression in the SAS of the ONS. Then, in two non-embalmed specimens, light and electron microscopy (EM) analysis were also done. RESULTS: On the macroscopic level, after staining of SAS, we found in all cases that MB progressed on 16 mm average throughout the SAS of the ONS without reaching the papilla. In four embalmed specimens, in the SAS of the ONS, the density of the arachnoid trabecular meshwork showed inter-individual variability (100%) and intra-individual variability with bilateral variability (50%) and/or variability within the same ONS (88%). On the microscopic level, the arachnoid trabeculae of the ONS are composed of dense connective tissue. The EM perfectly depicted its composition which is mainly of collagen fibers of parallel orientation. CONCLUSION: The variability of the SAS around the ONS probably impacts the symmetrical or asymmetrical nature of papilledema in ICH.

Lost or fragmented bony septum of the optic canal facing the sphenoid sinus: a histological study using elderly donated cadavers.

PURPOSE: To histologically describe a direct contact (the so-called dehiscence) of the optic nerve (ON) and/or internal carotid artery (ICA) to the mucosa of posterior paranasal sinuses represented by the sphenoid sinus (SS). METHODS: Observations of histological sections of unilateral or bilateral skull bases (parasellar area and orbital apex) from 22 elderly cadavers were made. RESULTS: A bony septum was less than 300 µm between the SS and ICA and 200 µm between the SS and optic nerve. Parts of the septa were sometimes absent due to fragmentation and holes of the bony lamella (2/22 facing the ICA; 4 facing the ICA in combination with an absent bony septum facing the nerve). In these dehiscence sites, the SS submucosal tissue attached to a thick sheath (50-100 µm in thickness) enclosing the optic nerve and ophthalmic artery and/or the ICA adventitia (50-200 µm in thickness). The ICA sometimes contained a sclerotic plaque that attached to or even protruded into the SS. With or without dehiscence, the SS mucosa was always thin (50-100 µm in thickness) and accompanied no mononuclear cellular infiltration or tumor. CONCLUSIONS: A thin bony septum of the optic nerve or ICA had been notable as a danger point during surgery, but even a 0.05-mm-thick bone lamella might be an effective barrier against cellular infiltration or bacterial invasion from the SS. Fragmentation and holes of the bony lamella in 4 cadavers might allow cellular invasion to the optic nerve. Accordingly, unknown immunological cross talks might occur to cause demyelination.

Microanatomic Study of the Optic Canal.

BACKGROUND: The continuous development of microsurgical techniques to treat lesions in and around the optic canal (OC) emphasizes the need for an accurate understanding of the microanatomy of the region. METHODS: Forty anatomic specimens were studied, with emphasis on the OC. The sphenoid bone and related structures were decalcified, added to animal gelatin, cut into 1-mm thick slices, and observed through a surgical microscope. The OC was considered the course that contained exclusively the optic nerve (ON) and ophthalmic artery. RESULTS: The mean distance between the medial walls of the OC was 12.2 mm, and the OC had an average length of 12.06 mm. The OC has a horizontal oval shape in the proximal (internal) segment; a round shape in the middle segment; and a vertical oval shape in the distal (external) segment at the orbital cavity. In the middle segment of the OC, the thickest wall of the OC was the lateral (average: 0.68 mm), while the medial, inferior, and superior wall measures had averages of 0.75, 0.40, and 0.39 mm, respectively. The lateral wall of the sphenoid sinus is located under the OC, and the inferior wall of the OC separates both structures. The ophthalmic artery inside the OC was always located under the ON, between the dural sheaths, and had an average diameter of 1.03 mm. CONCLUSIONS: The neurovascular structures within the OC vary in size and shape. The anatomic knowledge of the OC and its variations allows better surgical results and minimizes the surgical morbidity.

Orbital lymphatic vessels: immunohistochemical detection in the lacrimal gland, optic nerve, fat tissue, and extrinsic oculomotor muscles / Vasos linfáticos orbitários: identificação imunohistoquímica na glândula lacrimal, no nervo óptico, no tecido adiposo e nos músculos extrínsecos oculomotores

ABSTRACT Purpose: To identify the lymphatic vessels in orbital specimens from human cadavers using light microscopy and immunohistochemical analysis. Methods: A postmortem study included 10 orbital specimens from 10 human cadavers. The orbital specimens were obtained no later than 12 hours after death. The orbital specimens were dissected into lacrimal gland, optic nerve, fat tissue, and oculomotor muscles. The histologic criteria to qualify as a lymphatic vessel were thin-walled channels of endothelium without a well-developed basal membrane and with an erythrocyte-free, irregular lumen. The immunohistochemical criteria were irregularly shaped, thin-walled vessels with an erythrocyte-free, irregular lumen and immunopositivity for podoplanin D2-40. Results: The lacrimal gland, optic nerve, fat tissue, and extraocular muscle sections were positively stained with podoplanin D2-40. Conclusions: This study demonstrated lymphatic vessels in the human orbit, more precisely, in the lacrimal gland, dura mater of the optic nerve, adipose tissue, and extrinsic oculomotor muscles via light microscopy and immunohistochemistry.(AU)

RESUMO Objetivos: Identificar vasos linfáticos em espécimes orbitários de cadáveres humanos através de microscopia óptica e análise imunohistoquímica. Métodos: Um estudo postmortem incluiu dez espécimes orbitários provenientes de dez cadáveres humanos. Todos os espécimes orbitários foram obtidos até 12 horas após a morte com uma técnica cirúrgica de exenteração orbitária e dissecados em glândula lacrimal, nervo óptico, gordura órbitária e músculos extraoculares. Para classificar como um vaso linfático, os critérios histológicos incluíram vasos endoteliais de parede única sem membrana basal bem desenvolvida, irregulares e lúmen sem hemácias, e os critérios imunohistoquímicos incluíram vasos endoteliais de parede única, com formato irregular e lúmen sem hemácias e reagentes a podoplanina D2-40. Resultados: As lâminas histológicas de glândula lacrimal, nervo óptico, tecido adiposo e músculos extraoculares reagiram positivamente a podoplanina D2-40. Conclusão: Este estudo demonstrou vasos linfáticos na órbita humana, mais exatamente, na glândula lacrimal, no nervo óptico, na gordura orbitária e nos músculos extrínsecos extraoculares via microscopia óptica e imunohistoquímica.(AU)

Effects of sevoflurane and propofol on the optic nerve sheath diameter in patients undergoing laparoscopic gynecological surgery: a randomized controlled clinical studies.

BACKGROUND: The results of studies on changes in intracranial pressure in patients undergoing laparoscopic surgery are inconsistent. Meanwhile, previous neurosurgery studies have suggested that propofol and sevoflurane have inconsistent effects on cerebral blood flow and cerebrovascular self-regulation. The purpose of this study is to compare changes in the optic nerve sheath diameter in patients undergoing laparoscopic gynecological surgery under anesthetic maintenance with propofol versus sevoflurane. METHODS: This study included 110 patients undergoing laparoscopic gynecological surgery with an estimated operative time of more than 2 h under general anesthesia. The study was a randomized controlled study. The optic nerve sheath diameter (ONSD) at various time points was measured by ultrasound, including when the patients entered the operating room (Tawake), after successful anesthesia induction and endotracheal intubation (Tinduction), when the body position was adjusted to the Trendelenburg position and the CO2 pneumoperitoneum pressure reached 14 mmHg, which was recorded as T0. Then, measurements were conducted every 15 min for the first 1 h and then once every hour until the end of the surgery (T15, T30, T45, T1h, T2h …), after the end of surgery and the tracheal tube was removed (Tend), and before the patients were transferred to the ward (Tpacu). RESULTS: A significant difference in optic nerve sheath diameter was found between two groups at T15, T30, T45 (4.64 ± 0.48 mm and 4.50 ± 0.29 mm, respectively, p = 0.031;4.77 ± 0.45 mm and 4.62 ± 0.28 mm, respectively, p = 0.036;4.84 ± 0.46 mm and 4.65 ± 0.30 mm, respectively, p = 0.012), while there was no significant difference at Tawake and other time points. CONCLUSION: During laparoscopic gynecological surgery lasting more than 2 h, the optic nerve sheath diameter was slightly larger in the propofol group than that in the sevoflurane group in the first 45 min. No significant difference was observed between the two groups 1 h after surgery. TRIAL REGISTRATION: clinicaltrials.gov, NCT03498235 . Retrospectively registered 1 March 2018. The manuscript adheres to CONSORT guidelines.

Hyperintense areas in the intraorbital optic nerve evaluated by T2-weighted magnetic resonance imaging: a glymphatic pathway?

PURPOSE: The present study aimed to explore the glymphatic pathway in the intraorbital optic nerve (ON) using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, a total of 89 outpatients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections. Moreover, three injected cadaver heads were dissected. RESULTS: In the cadaver specimens, differences in appearance between the central and peripheral parts of the ON were not observed. On the axial T2-weighted MRI performed in the initial examination, the central part of the intraorbital ONs was delineated as a well-demarcated, linear hyperintense area in 19% of patients. On the thin-sliced serial coronal images, the hyperintense areas were identified on both sides in 91% of patients. They were delineated as continuous hyperintense areas in the ONs with an inconsistent appearance even in the same nerve. In 12.4% of patients, the areas were divided into the upper and lower parts by a horizontal septum, while others showed variable morphologies, lacking a septum. On thin-sliced sagittal images, hyperintense areas were identified in 46% of patients. CONCLUSION: Hyperintense areas in the intraorbital ON detected on T2-weighted sequences may involve a glymphatic pathway with perivascular spaces of the ON and central retinal artery. These may be collapsed and difficult to identify on surgical and cadaver specimens.

Variation in the Anatomy of the Normal Human Optic Chiasm: An MRI Study.

BACKGROUND: Compression of the optic chiasm typically leads to bitemporal hemianopia. This implies that decussating nasal fibers are selectively affected, but the precise mechanism is unclear. Stress on nasal fibers has been investigated using finite element modeling but requires accurate anatomical data to generate a meaningful output. The precise shape of the chiasm is unclear: A recent photomicrographic study suggested that nasal fibers decussate paracentrally and run parallel to each other in the central arm of an "H." This study aimed to determine the population variation in chiasmal shape to inform future models. METHODS: Sequential MRI scans of 68 healthy individuals were selected. 2D images of each chiasm were created and analyzed to determine the angle of elevation of the chiasm, the width of the chiasm, and the offset between the points of intersection of lines drawn down the centers of the optic nerves and contralateral optic tracts. RESULTS: The mean width of the chiasm was 12.0 ± 1.5 mm (SD), and the mean offset was 4.7 ± 1.4 mm generating a mean offset:width ratio of 0.38 ± 0.09. No chiasm had an offset of zero. The mean incident angle of optic nerves was 56 ± 7°, and for optic tracts, it was 51 ± 7°. CONCLUSIONS: The human optic chiasm is "H" shaped, not "X" shaped. The findings are consistent with nasal fibers decussating an average of 2.4 mm lateral to the midline before travelling in parallel across the midline. This information will inform future models of chiasmal compression.

ISNT rule satisfaction in Korean non-glaucomatous subjects.

PURPOSE: To evaluate the efficacy of the ISNT rule in normal eyes of Koreans. METHODS: We retrospectively reviewed medical records of 890 subjects with fundus photographs and evaluated the presence of the cup and ISNT rule satisfaction. If the ISNT rule was violated, the quadrants in which the neuroretinal rim was thinnest and thickest, respectively, were evaluated. RESULTS: Among 890 eyes, 84.7% showed the cup. The subjects without the cup were significantly younger and more hyperopic. Among 754 eyes with the cup, 53.5% showed ISNT rule satisfaction. In 351 eyes violating the ISNT rule, the most common quadrant showing the thickest neuroretinal rim was the inferior (65.5%), and the thinnest, the temporal (98.3%). CONCLUSION: The cup was absent in 15% of the assessed eyes. Only about half of eyes with the cup showed ISNT rule satisfaction. Even in eyes violating ISNT rule, the inferior was the most common quadrant with the thickest neuroretinal rim and the temporal, the thinnest.

Anatomic features of the cranial aperture of the optic canal in children: a radiologic study.

OBJECTIVE: This study aimed to peruse anatomic features of the cranial aperture of the optic canal (CAOC) for obtaining an extended morphometric dataset in children. METHODS: Computed tomography images of 200 children were included in this retrospective work to analyze the shape, location and diameters of the CAOC. RESULTS: The CAOC area, width and height were observed as 17.53 ± 2.80 mm2, 6.12 ± 0.84 mm, and 4.35 ± 0.64 mm, respectively. The angle of the optic canal in axial plane was found as 39.28 ± 5.13°, while in sagittal plane as 16.01 ± 6.76°. The distance between the CAOC and the midsagittal line was 7.17 ± 1.48 mm. The CAOC was measured as 54.04 ± 5.23 mm and 42.55 ± 3.28 mm away from the anterior and lateral boundary of the anterior skull base, respectively. The CAOC shape was described as the tear-drop (186 foramina, 46.5%), triangular (156 foramina, 39%), oval (47 foramina, 11.8%), and round (11 foramina, 2.8%). CONCLUSION: The depth, angle and diameter measurements belonging to the CAOC were changing according to its shape or demographic data (e.g., sex and age). Therefore, preoperative radiologic evaluation containing the shape, location and size of the CAOC should be considered by multidisciplinary operating teams in terms of surgical interventions such as implant positioning.

Radioanatomic Characteristics of the Posteromedial Intraconal Space: Implications for Endoscopic Resection of Orbital Lesions.

BACKGROUND AND PURPOSE: Imaging is essential in the diagnostic work-up of patients with orbital lesions. The position of an orbital lesion relative to the inferomedial muscular trunk of the ophthalmic artery determines endoscopic resectability, anticipated technical difficulty, and patient morbidity. Although the inferomedial muscular trunk is not readily identifiable on preoperative imaging, we hypothesize that it is spatially approximate to the location where the ophthalmic artery crosses the optic nerve. Our aim was to determine whether the ophthalmic artery-optic nerve crosspoint anatomically approximates the inferomedial muscular trunk in a cadaver study and can be appreciated on imaging of known posteromedial orbital lesions. MATERIALS AND METHODS: Dissection was performed on 17 fresh-frozen cadaver orbits to assess the relationship between the inferomedial muscular trunk and ophthalmic artery-optic nerve crosspoint. Retrospective review of imaging in 9 patients with posteromedial orbital lesions assessed posteromedial orbital compartment characteristics and the ability to locate the ophthalmic artery-optic nerve crosspoint. RESULTS: In our cadaver study, the mean distance between the ophthalmic artery-optic nerve crosspoint and the inferomedial muscular trunk was 1.21 ± 0.64 mm. Retrospectively, the ophthalmic artery-optic nerve crosspoint was identifiable in 9/9 patients, whereas the inferomedial muscular trunk was not identifiable in any patient. Total or partial effacement of the posteromedial intraconal fat triangle was observed in 9/9 patients. CONCLUSIONS: This study of neurovascular relationships within the posteromedial orbit demonstrates that the ophthalmic artery-optic nerve crosspoint closely approximates the inferomedial muscular trunk and can be seen in patients with posteromedial orbital lesions. Posteromedial intraconal fat effacement may help to localize these lesions. These findings may facilitate multidisciplinary communication and help predict lesion resectability and patient outcomes.

Normal Age- and Sex-Related Values of the Optic Nerve Sheath Diameter and Its Dependency on Position and Positive End-Expiratory Pressure.

Optic nerve sheath diameter (ONSD) sonography is a reliable method for evaluation of intracranial pressure, yet there is a lack of reliable normal values. In the study described here, we established normal ONSD values in three different age groups and both sexes. One hundred eighty-seven volunteers without central nervous system disease were enrolled in this prospective study. ONSD measurements were taken in volunteers in the supine and upright positions and after application of positive end-expiratory pressure (PEEP). Normal ONSD values were 4.9-5.3 mm (patient age range: 20-85), with significant differences between men and women (p < 0.001). ONSD values increased with age (∆ = 0.34 mm, p < 0.001). There were no differences compared with the upright position but application of PEEP led to significantly increased ONSD values (∆ = 0.21 mm, p = 0.008). ONSD values increased with age, correlated well with the width of the third ventricle, were significantly lower in the female cohort and quickly responded to PEEP, especially in women.

The effect of laryngoscope types on hemodynamic response and optic nerve sheath diameter. McCoy, Macintosh, and C-MAC video-laryngoscope.

OBJECTIVES: This study aims to investigate the effect of McCoy, Macintosh laryngoscope, and C-MAC video-laryngoscopes on optic nerve sheath diameter (ONSD) and hemodynamic responses to laryngoscopy and intubation. METHODS: This prospective randomized study was conducted in Zonguldak Bülent Ecevit University Hospital, Zonguldak, Turkey, between July 2019 and January 2020. Informed written consent was obtained from all patients. Patients with previous intracranial/ocular surgery or glaucoma were excluded from the study. The patients were randomized to use McCoy, Macintosh, and C-MAC (30 per group). Intubations were performed by the same person. Mean arterial pressure, heart rate (HR), and ONSD were recorded before the induction and repeated in 1, 3, 5, and 10 minutes after the intubation. RESULTS: The effects of laryngoscopy and intubation on hemodynamic responses and ONSD were similar between groups (p greater than 0.05). While the comparison within groups showed ONSD increase in McCoy group and HR and ONSD increase in the Macintosh group compared to baseline 1 min after the intubation, no change was observed in hemodynamic responses and ONSD measurements in the C-MAC® group (p greater than 0.05). CONCLUSIONS: In this study, there was no significant difference between the groups in terms of ONSD and hemodynamic responses to laryngoscopy and intubation. It was observed that there were no significant changes in ONSD values just in C-MAC® video-laryngoscope group. Therefore, intubations with C-MAC® video-laryngoscope are thought to be more appropriate for patients with an increase in intracranial pressure.

The falciform ligament: Anatomical study with microsurgical implications.

OBJECTIVES: The current study aims to increase awareness of the falciform ligament and its anatomical and surgical relationships, for the benefit of the neurosurgeon. PATINENTS AND METHODS: Twenty-four sides from twelve Caucasian cadaveric heads (all fresh-frozen) were used in this study. The length and thickness of the falciform ligament were recorded. The relationship of the falciform ligament to the optic nerve was also observed and documented. Finally, the force needed to avulse the falciform ligament was recorded. RESULTS: In all specimens, the ligament was identified as a continuation of the outer dural layer, forming a roof at the entrance of the optic canal. The mean medial-to-lateral length, anteroposterior length, and thickness of the falciform ligament were 7.97 mm, 2.12 mm, and 0.26 mm, respectively. The mean distance from the medial attachment of the ligament to the midline was 5.54 mm. For the undersurface of the falciform ligament, the optic nerve occupied the middle third in 50.0 %, the lateral third in 44.4 %, and the medial third in 5.6 % of sides. The mean optic nerve diameter at the entrance of the optic canal was 4.20 mm. The mean failure force was 2.47 N. CONCLUSION: The anatomical measurements and relationships provided in this description of the falciform ligament serve as a tool for surgery selection and planning, as well as an aid to improving microsurgical techniques, with the final goal being better patient outcomes.

The anatomic variations and surgical windows among optic chiasm/nerves and carotid arteries in the sellar region play a role in choosing the best surgical approaches: A Cadaveric study / Las variaciones anatómicas y las vías de acceso quirúrgico en el quiasma, los nervios ópticos y las arterias carótidas de la región selar influyen en la elección de los mejores abordajes quirúrgicos: un estudio en cadáveres

OBJECTIVE: Understanding the relationship between the carotid artery, optic nerve and the anterior clinoid process is the basis of surgical approaches performed in the subchiasmal region. The location of the optic chiasm, the length of the optic nerves, and the distance and angle between the optic nerves determine the route of surgical approaches. We have determined the types of optic chiasm to study the relationship between vascular and neural structures in this region. MATERIALS AND METHODS: Thirty autopsy specimens were investigated at the Bursa Forensic Medicine Institute for optic chiasm types and the relationship between the neural and vascular anatomical structures of the sellar-parasellar and subchiasmal region was examined between June 2016 and November 2016. RESULTS: In this study, 4 prefix types (13%), 6 postfix types (20%), and 20 central types (67%) of chiasm were defined. Furthermore, we measured this angle between two optic nerves, which indirectly shows the location of chiasm according to the diaphragma sellae, and then detected the mean value of this angle as 87.1 ± 11.6°. The "limit" value to designate a chiasm as prefix was measured in the current study as ≥ 101.1°. The angle between optic nerves ranged from a mean value of 69.9 ± 3.7° in 6 cases with postfix chiasm, to a mean value of 104.0±2.1° in 4 cases with prefix chiasm and a mean value of 88.8 ± 6.7° in 20 cases with central chiasm. CONCLUSIÓN: In this study, we showed that the relationship among optic chiasma types, optic nerves and bony and vascular structures around the sellar area was effective at determining the surgical approach to this región

OBJETIVO: Comprender la relación entre la arteria carótida, el nervio óptico y la apófisis clinoides anterior es la base de los tratamientos quirúrgicos realizados en la región subquiasmática. La ubicación del quiasma óptico, la longitud de los nervios ópticos, y la distancia y el ángulo entre dichos nervios determinan la vía de acceso quirúrgico. Hemos determinado los tipos de quiasma óptico para estudiar la relación entre las estructuras vasculares y neurales en esta región. MATERIALES Y MÉTODOS: Entre junio y noviembre de 2016, se analizaron 30 muestras de autopsia en el Instituto de Medicina Legal de Bursa (Turquía) para determinar los tipos de quiasma óptico, y examinar la relación entre las estructuras anatómicas neurales y vasculares de las regiones selar-paraselar y subquiasmática. RESULTADOS: En este estudio, se definieron 4 casos de quiasma prefijado (13%), 6 de quiasma posfijado (20%) y 20 de quiasma central (67%). Además, medimos el ángulo entre 2 nervios ópticos que muestra indirectamente la ubicación del quiasma según el diafragma selar, y luego detectamos el valor medio de este ángulo (87,1 ± 11,6°). El valor «límite» para designar un quiasma como «prefijado» se midió en el estudio actual como ≥ 101,1°. El valor medio del ángulo entre los nervios ópticos osciló entre 69,9 ± 3,7° en los 6 casos de quiasma posfijado, 104,0 ± 2,1° en los 4 casos de quiasma prefijado y 88,8 ± 6,7° en los 20 casos de quiasma central. CONCLUSIÓN: En este estudio, pusimos de manifiesto que la relación entre los tipos de quiasma óptico, los nervios ópticos y las estructuras óseas y vasculares alrededor del área selar fue eficaz para determinar el acceso quirúrgico en esta región

Ultrasonic Assessment of Optic Nerve Sheath Diameter in Patients at Risk of Sepsis-Associated Brain Dysfunction: A Preliminary Report.

Sepsis-associated brain dysfunction (SABD) with increased intracranial pressure (ICP) is a complex pathology that can lead to unfavorable outcome. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) is used for non-invasive assessment of ICP. We aimed to assess the role of ONSD as a SABD screening tool. This prospective preliminary study covered 10 septic shock patients (5 men; aged 65, IQR 50-78 years). ONSD was measured bilaterally from day 1 to 10 (n = 1), until discharge (n = 3) or death (n = 6). The upper limit for ONSD was set at 5.7 mm. Sequential organ failure assessment score was calculated on a daily basis as a surrogate formulti-organ failure due to sepsis in the study population. On day 1, the medians of right and left ONSD were 5.56 (IQR 5.35-6.30) mm and 5.68 (IQR 5.50-6.10) mm, respectively, and four subjects had bilaterally elevated ONSD. Forty-nine out of 80 total measurements performed (61%) exceeded 5.7 mm during the study period. We found no correlations between ONSD and sequential organ failure assessment (SOFA) during the study period (right: R = -0.13-0.63; left R = -0.24-0.63). ONSD measurement should be applied for screening of SABD cautiously. Further research is needed to investigate the exact role of this non-invasive method in the assessment of brain dysfunction in these patients.

Finite element analysis of trans-lamina cribrosa pressure difference on optic nerve head biomechanics: the Beijing Intracranial and Intraocular Pressure Study.

The present study aims to assess the potential difference of biomechanical response of the optic nerve head to the same level of trans-lamina cribrosa pressure difference (TLCPD) induced by a reduced cerebrospinal fluid pressure (CSFP) or an elevated intraocular pressure (IOP). A finite element model of optic nerve head tissue (pre- and post-laminar neural tissue, lamina cribrosa, sclera, and pia mater) was constructed. Computed stresses, deformations, and strains were compared at each TLCPD step caused by reduced CSFP or elevated IOP. The results showed that elevating TLCPD increased the strain in optic nerve head, with the largest strains occurring in the neural tissue around the sclera ring. Relative to a baseline TLCPD of 10 mmHg, at a same TLCPD of 18 mmHg, the pre-laminar neural tissue experienced 11.10% first principal strain by reduced CSFP and 13.66% by elevated IOP, respectively. The corresponding values for lamina cribrosa were 6.09% and 6.91%. In conclusion, TLCPD has a significant biomechanical impact on optic nerve head tissue and, more prominently, within the pre-laminar neural tissue and lamina cribrosa. Comparatively, reducing CSFP showed smaller strain than elevating IOP even at a same level of TLCPD on ONH tissue, indicating a different potential role of low CSFP in the pathogenesis of glaucoma.