Anatomical aspects in the transsphenoidal-transethmoidal approach to the optic canal: an anatomic-cadaveric study

Anatomical Study and Clinical Application of Optic Canal Decompression Via Transethmoid-sphenoid Approach Under Endoscope

This study aimed to evaluate the safety and accuracy of the endoscopic transethmoid-sphenoid approach for optic canal decompression. Twelve sides of 6 adult cadaveric heads fixed in formalin were selected to simulate optic canal decompression using the endoscopic transethmoid-sphenoid approach. Furthermore, this approach was used for optic canal decompression in 10 patients (11 eyes) with optic nerve canal injury. Related anatomical structures were observed using a 0-degree endoscope, and the anatomical characteristics as well as the surgical data were collected. The maximum effective widths of the cranial opening, orbital opening, and middle segment of the canal that could be drilled open endoscopically were 7.82±2.63, 8.05±2.77, and 6.92±2.01 mm, respectively. The angle between the line linking the center point of the tubercular recess with the midpoint of the cranial opening of the optic canal and the horizontal coordinate was 17.23±1.34 degrees. At the orbital opening of the optic canal, the ophthalmic artery was located directly inferior to the optic nerve in 2 cases (16.7%) and laterally inferior to the optic nerve in 10 cases (83.3%). Six of the operational eyes were effective while the remaining 5 were ineffective. No postoperative complications such as bleeding, infection, or cerebrospinal fluid leakage were observed during the follow-up period (6-12 mo). In conclusion, optic canal decompression positively impacts the prognosis of partial traumatic optic neuropathy. Furthermore, the endoscopic transethmoid-sphenoid approach for optic canal decompression is a minimally invasive procedure that provides direct access and adequate decompression. This technique is easy to master and suitable for clinical applications.

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.

Change in the Location of the Optic Strut Relative to the Anterior Clinoid Process Pneumatization

OBJECTIVE

This study aimed to peruse the alteration of the position of the optic strut (OS) according to the anterior clinoid process (ACP) pneumatization.

METHODS

This retrospective study conducted on cone-beam computed tomography images of 400 patients with a mean age of 36.49±15.91 years.

RESULTS

Anterior clinoid process length, width, and angle were measured as 10.56±2.42 mm, 5.46±1.31 mm, and 42.56±14.68 degrees, respectively. The tip of ACP was measured as 6.60±1.50 mm away from the posterior rim of OS. In the 631 sides (78.87%) did not have ACP pneumatization. In the cases with ACP pneumatization, three different configurations were identified as follows: Type 1 in 71 sides (8.87%), Type 2 in 56 sides (7%), and Type 3 in 42 sides (5.23%). Relative to ACP, the location of OS was determined as follows: Type A in 29 sides (3.64%), Type B in 105 sides (13.12%), Type C in 344 sides (43%), Type D in 289 sides (36.12%), and Type E in 33 sides (4.12%). The spread of data related to the attachment site of OS according to the presence or absence of ACP pneumatization showed that the location of OS was affected by ACP pneumatization (P<0.001). In ACPs with pneumatization, the frequency of OS position relative to ACP was found as follows: Type A in none of sides (0%), Type B in 8 sides (7.6%), Type C in 53 sides (15.4%), Type D in 88 sides (30.4%), and Type E in 20 sides (60.6%).

CONCLUSIONS

The main finding of this study was that the location of OS relative to ACP was affected by ACP pneumatization. In ACPs with pneumatization, OS was located more posteriorly compared with ACPs without pneumatization.

Evaluation of the Cranial Aperture of the Optic Canal on Cone-Beam Computed Tomography Images and its Clinical Implications for the Transcranial Approaches

OBJECTIVE

This study aimed to investigate morphometric properties of the cranial aperture (CA) of the optic canal.

METHODS

Cone-beam computed tomography images of 400 individuals (200 males and 200 females) aged 37.32 ± 15.87 years were retrospectively examined to assess the morphometry and morphology of the CA.

RESULTS

The height and width of CA were found as 4.22 ± 0.74 mm and 7.27 ± 1.15 mm, respectively. The distances between the CA and the midsagittal line, the anterior and lateral boundaries of the anterior skull base were measured as 5.77 ± 1.32 mm, 64.97 ± 6.36 mm, and 41.00 ± 4.05, respectively. The angle of the optic canal in the sagittal plane was measured as 7.57° ± 3.95°, whereas in the horizontal plane as 38.96° ± 4.36°. The aperture shape was defined as the tear-drop (413 foramina, 51.62%), triangular (180 foramina, 22.50%), oval (158 foramina, 19.75%), round (30 foramina, 3.75%), and polygonal (19 foramina, 2.38%).

CONCLUSIONS

The authors observed that the diameters, and angulations of the CA may change relative to gender and the shape. The anatomic features of CA are important for the positioning of the patient's head, the choice of the appropriate surgical approach or equipment, and the detection of anatomical landmarks during interventions. In this context, our dataset may be beneficial for surgeons helpful as a reference for radiological evaluations.

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.

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.

Anatomic Nuances of the Ophthalmic Artery Origin from a Ventral Viewpoint: Considerations and Implications for Endoscopic Endonasal Surgery

BACKGROUND

The origin of the ophthalmic artery is within the surgical field of endoscopic endonasal approaches (EEAs) to the suprasellar and parasellar regions. However, its anatomy from the endoscopic point-of-view has not been adequately elucidated.

OBJECTIVE

To highlight the anatomy of the ophthalmic artery origin from an endoscopic endonasal perspective.

METHODS

The origin of the ophthalmic artery was studied bilaterally under endoscopic visualization, after performing transplanum/transtubercular EEAs in 17 cadaveric specimens (34 arteries). Anatomic relationships relevant to surgery were evaluated. To complement the cadaveric findings, the ophthalmic artery origin was reviewed in 200 "normal" angiographic studies.

RESULTS

On the right side, 70.6% of ophthalmic arteries emerged from the superior aspect, while 17.6% and 11.8% emerged from the superomedial and superolateral aspects of the intradural internal carotid artery, respectively. On the left, 76.5%, 17.6%, and 5.9% of ophthalmic arteries emerged from the superior, superomedial, and superolateral aspects of the internal carotid, respectively. Similar findings were observed on angiography. All ophthalmic arteries emerged at the level of the medial opticocarotid recess. Overall, 47%, 26.5%, and 26.5% of ophthalmic arteries (right and left) were inferolateral, inferior, and inferomedial to the intracranial optic nerve segment, respectively. On both sides, the intracranial length of the ophthalmic artery ranged from 1.5 to 4.5 mm (mean: 2.90 ± standard deviation of 0.74 mm).

CONCLUSION

Awareness of the endoscopic nuances of the ophthalmic artery origin is paramount to minimize the risk of sight-threatening neurovascular injury during EEAs to the suprasellar and parasellar regions.

Refining Operative Strategies for Optic Nerve Decompression: A Morphometric Analysis of Transcranial and Endoscopic Endonasal Techniques Using Clinical Parameters

BACKGROUND

Various approaches can be considered for decompression of the intracanalicular optic nerve. Although clinical experience has been reported, no quantitative study has yet compared the extent of decompression achieved by an endoscopic endonasal versus transcranial approach.

OBJECTIVE

Toward this aim, our morphometric analysis compared both approaches by quantifying the circumferential degree of optic canal decompression that is possible before any meningeal violation, which would result in cerebrospinal fluid (CSF) leak.

METHODS

From 10 cadaver heads, 20 optic canals were sequentially decompressed using an endoscopic endonasal approach and pterional craniotomy with extradural clinoidectomy. Dissections ended before violation of the sphenoid sinus during the transcranial approach, and before intracranial transgression from the endonasal corridor. Based on our study criteria, decompressions were not maximal for either approach, but were maximal before violating the other compartment. Decompression achieved from each approach was quantified using CT scans for each stage.

RESULTS

Greater circumferential bony optic canal decompression was obtained from transcranial (245.2°) than endonasal (114.8°) routes (P < .001). By endonasal perspective, the anatomical point where the optic nerve traverses intracranially was approximated by the medial border of the anterior ascending cavernous internal carotid artery.

CONCLUSION

Our morphometric analysis comparing optic canal decompression for endonasal and transcranial corridors provides important guidance for this location. Ample visualization and wide exposure can be achieved via a transcranial approach with limited risk of CSF leak. A landmark, where the intracanalicular segment ends and optic nerve traverses intracranially, can mark the extent of decompression safely obtained before risking CSF leak.

An Anatomically-Based Endoscopic Endonasal Model to Navigate the Anterior Ventral Skull Base

BACKGROUND

Endoscopic endonasal approaches to access the sellar and parasellar regions are challenging in the face of anatomical variations or pathologic conditions. We propose an anatomically-based model including the orbitosellar line (OSL), critical oblique foramen line (COFL), and paramedial anterior line (PAL) facilitating safe, superficial-to-deep dissection triangulating upon the medial opticocarotid recess.

METHODS

Five cadaveric heads were dissected to systematically expose the OSL, COFL, and PAL, illustrated with image guidance. Application of the coordinate system and a 6-step dissection sequence is described.

RESULTS

The coordinate system consists of 1) the OSL, connecting a) the anterior orbital point, junction of the anterior buttress of the middle turbinate with the agger nasi region, located 34.3 ± 0.9 mm above the intersection of the vertical plane of the lacrimal crest, and the orthogonal plane of the maxillo-ethmoidal suture; b) the posterior orbital point, junction of the optic canal with the lamina papyracea, located 4 ± 0.7 mm below the posterior ethmoidal artery; and c) the medial opticocarotid recess; 2) COFL (15 ± 2.8 mm), connecting the palatovaginal canal, vidian canal, and foramen rotundum; and 3) PAL (39 ± 0.06 mm), connecting the vidian canal with the posterior ethmoidal artery.

CONCLUSIONS

OSL, COFL, and PAL form an anatomically-based model for the systematic exposure when accessing the parasellar and sellar regions. Preliminary anatomical data suggest that this model may be of value when normal anatomy is distorted by pathology or anatomic variations.

Measurements and Clinical Application of Anatomical Space for Transfrontal Pituitary Surgery Through Magnetic Resonance Imaging Reconstruction

OBJECTIVE

This study aims to clarify the relative position of the normal important structures and anatomical spaces formed by the structures passed through during the transfrontal pituitary surgery, and discuss how to avoid some eloquent structures.

METHODS

A total of 120 cases of magnetic resonance imaging images from normal adult brains were selected as the object of study and divided into male and female groups. The important adjacent structures of the pituitary passed through during the transfrontal pituitary surgery were marked on the reconstructed images. In all planes of the spaces passing through successively during the pituitary surgery, the morphological parameters such as the size, boundary, structure, and spatial extent of the spaces were measured.

RESULTS

The size, boundary, structure, and spatial extent of the space between the 2 optic nerves, the space between the optic nerves and the pituitary stalk, and the space between the tuber cinereum and the interal carotid artery in the plane of the pituitary stalk were measured, the anterior part and the posterior part in male were shorter than those in female (P = 0.021; P = 0.029); no statistically significant difference was found in the measurements of the lengths and angles of these spaces.

CONCLUSIONS

The authors' findings provide the surgeons with the detailed anatomical data and help to provide a morphological basis for intraoperative protection of the pituitary and vital adjacent structures and surgical approach.

Anatomical assessment of the endoscopic endonasal approach for the treatment of paraclinoid aneurysms

OBJECTIVE

Endoscopic endonasal approaches (EEAs) are increasingly being incorporated into the neurosurgeon's armamentarium for treatment of various pathologies, including paraclinoid aneurysms. However, few anatomical assessments have been performed on the use of EEA for this purpose. The aim of the present study was to provide a comprehensive anatomical assessment of the EEA for the treatment of paraclinoid aneurysms.

METHODS

Five cadaveric heads underwent an endonasal transplanum-transtuberculum approach to expose the paraclinoid area. The feasibility of obtaining proximal and distal internal carotid artery (ICA) control as well as the topographic location of the origin of the ophthalmic artery (OphA) relative to dural landmarks were assessed. Limitations of the EEA in exposing the supraclinoid ICA were also recorded to identify favorable paraclinoid ICA aneurysm projections for EEA.

RESULTS

The extracavernous paraclival and clinoidal ICAs were favorable segments for establishing proximal control. Clipping the extracavernous ICA risked injury to the trigeminal and abducens nerves, whereas clipping the clinoidal segment put the oculomotor nerve at risk. The OphA origin was found within 4 mm of the medial opticocarotid point on a line connecting the midtubercular recess point to the medial vertex of the lateral opticocarotid recess. An average 7.2-mm length of the supraclinoid ICA could be safely clipped for distal control. Assessments showed that small superiorly or medially projecting aneurysms were favorable candidates for clipping via EEA.

CONCLUSIONS

When used for paraclinoid aneurysms, the EEA carries certain risks to adjacent neurovascular structures during proximal control, dural opening, and distal control. While some authors have promoted this approach as feasible, this work demonstrates that it has significant limitations and may only be appropriate in highly selected cases that are not amenable to coiling or clipping. Further clinical experience with this approach helps to delineate its risks and benefits.

Endoscopic Transnasal Resection of Solitary Fibrous Tumor in the Optic Canal

BACKGROUND

Tumors extending into the optic canal can cause progressive visual impairment because of optic nerve compression. Prompt surgical resection is often necessary. When the tumor is located medially in the optic canal, endoscopic transnasal surgery provides a safer, less invasive alternative to a transcranial approach.

CASE DESCRIPTION

We recently encountered a case of small solitary fibrous tumor in the optic canal causing rapid visual deterioration. The radiographic findings of preoperative imaging studies were compatible with those of meningioma; however, unlike meningioma, bleeding from the tumor was profuse during the operation. The endoscopic transnasal approach was effective for handling the highly vascularized tumor in this delicate region, and gross total removal was achieved with postoperative gradual improvement in his visual function. Nevertheless, the tumor recurred after 6 months, and re-resection was performed using the same surgical corridor, followed by adjuvant radiotherapy.

CONCLUSIONS

Endoscopic transnasal surgery is a valuable option for aggressive lesions in the optic canal. Although the efficacy of radiotherapy for solitary fibrous tumor remains controversial, it should be considered when the tumor shows progressive features.

Optic Canal Decompression: Comparison of 2 Surgical Techniques

BACKGROUND

The optic canal is a bony channel that connects the anterior cranial fossa and orbit and contains the optic nerve and ophthalmic artery. It can be affected by several pathologies, leading to compression of the nerve nearby or inside the canal, leading to visual impairment. The usual technique to decompress the canal is through a craniotomy, but recently endoscopic endonasal approaches (EEAs) have surfaced as an interesting alternative due to direct access to the canal without the need for manipulation of neurovascular structures.

METHODS

Six specimens were dissected. The right optic canal was drilled on the right side via the EEA, and the left optic canal was drilled via frontotemporal craniotomy. The amount of decompression was measured using a 3-dimensional reconstruction on computed tomography scans and compared.

RESULTS

The EEA generated an average of 267.8 (221-294) degrees of decompression in the anterior portion of the canal versus 258.3 (219-300) degrees of decompression in the posterior portion of the canal, whereas the craniotomy generated an average of 229.3 (101-289) degrees of decompression in the anterior portion of the canal versus 250.3 (76-300) degrees of decompression in the posterior portion of the canal. There was no significant difference statistically.

CONCLUSION

The decision for an approach for optic canal decompression should be based on the site of the pathology and localization of canal involvement. Both techniques are equivalent in terms of proportion of nerve decompression.

Evaluation of Optic Canal and Surrounding Structures Using Cone Beam Computed Tomography: Considerations for Maxillofacial Surgery

The optic canal connects the anterior cranial fossa and the orbit and maintains the optic nerve and the ophthalmic artery. Within the extent of the surgical approach of the region, risk of iatrogenic injury of the neural and vascular structures increases. The aim of this retrospective morphometric study is to investigate the radiological anatomy of orbita, optic canal, and its surrounding using cone beam computed tomography (CBCT) scans in a group of Turkish population.Cone beam computed tomography images of a total of 182 patients were evaluated by 2 observers. Anatomical parameters regarding optic canal and orbita were measured for all patients from axial, sagittal, and three-dimensional reconstructed images. To assess intraobserver reliability, the Wilcoxon matched-pairs test was used. Pearson χ test and Student t test were performed for statistical analysis of differences, sex, localization, and measurements (P < 0.05).Repeated CBCT evaluation and measurements indicated no significant inter and intra-observer difference were found (P > 0.05). The orbita width and height were larger for the males than females (P < 0.05). No significant difference was observed for optic canal shape, dimensions of infraorbital foramen (IOF) and supraorbital foramen (SOF), SOF-midline distance, and SOF-IOF distance according to sex and location (P > 0.05). Examination CBCT scans revealed that the shape of the optic canal was 70% funnel and 28% Hourglass shape, 2% amorph type round.These results provide detailed knowledge of the anatomical characteristics in the orbital area which may be of assistance for surgeons preoperatively. Cone beam computed tomography scans can be an alternative modality for multislice computed tomography with submillimeter resolution and lower dose in preoperative imaging of the orbit.

Anatomical Study and Locating Nasolacrimal Duct on Computed Topographic Image

PURPOSE

We performed a novel anatomical and radiological investigation to understand the structure of nasolacrimal duct (NLD) and to provide data to help surgeons locate the openings of NLD efficiently based on landmarks.

MATERIALS AND METHODS

We examined the NLD region using computed tomography images of 133 individuals and 6 dry skull specimens. Multiplanar reconstruction of the computed tomography images was performed, and the anatomical features of the NLD were studied in the coronal, sagittal, and axial planes. The long and short diameters of NLD were measured along its cross-section. The position of NLD was localized using the nostril, concha nasalis media, and medial orbital corner as landmarks. The free and open source software, 3D Slicer, was used for the segmentation of the NLD and 3D visualization of the superior and inferior openings of the NLD.

RESULTS

The length, angle, and diameter of NLD were significantly influenced by the age in females compared to those in males. The inferior opening of the NLD could be located efficiently using the nostril and the midsagittal line while the superior opening of NLD could be located using the medial orbital corner. Third, 3D Slicer enabled us to measure the distance between the skin and the bony structure in the image.

CONCLUSION

Our study indicates that the sex and age of the patient should be considered while selecting the optimal NLD stent for a patient, and that the precise location of NLD in reference to landmarks can simplify the surgical difficulties and reduce the risk of injury during the transnasal operation.

Location of Pterygopalatine Fossa and its Relationships to the Structures in Sellar Region

PURPOSE

The aim of this study is to locate pterygopalatine fossa (PPF) and the opening of its communicating canals by accessing the relationship between PFF and the endoscopic landmarks such as the tubercular recess (TR) and middle lowest point of sellar floor (SF) as well as analyze the relation between PPF and important structures such as internal carotid artery (ICA) and optic canal (OC).

MATERIALS AND METHODS

Computer topographic angiography (CTA) images of 118 PPF regions were reviewed. The measurement was on coronal, sagittal, and axial planes after multiplanar reconstruction (MPR). The location of PPF and its relationship to the sphenoid sinus, ICA, and OC were studied. The communicating canals of PPF, which were related to the transsphenoid approach, were three-dimensionally measured by the stationary structures, such as the middle lowest point of SF, the sagittal midline, and the top and bottom wall of sphenoid sinus.

RESULT

The posterior part of PPF was located by the middle lowest point of SF. The anterior opening of sphenopalatine foramen (SPF), pterygoid canal (PC), palatovaginal canal (PVC), and foramina rotundum (FR) have relative stationary position, which can be located by the landmarks of sellar region during the endoscopic surgery.

CONCLUSIONS

Pterygopalatine fossa is related to numerous neurovascular structures. Accurate understanding of the radiologic anatomy of PPF is beneficial for the PPF disease diagnosis, the selection of treatment plan and the prognosis evaluation.

A new method of locating foramen rotundum and its anatomic study

PURPOSE

The purpose of this study is to provide a new method to locate the foramen rotundum (FR) based on the structures in the wall of sphenoid.

MATERIALS AND METHODS

Computed tomographic angiography images of 172 FR in adults and 10 bony specimens were reviewed. The measurement was on coronal, sagittal, and axial planes after multiplanar reconstruction. The diameter, length, and direction of FR were measured. The middle lowest point of sellar region, the sagittal midline, and the bottom of sphenoid sinus were selected as the landmarks to locate the FR.

RESULT

The FR can be found and identified easily on computed tomographic angiography image. The bony diameter measured in CT image is in accordance with that in specimen. The anterior opening and posterior opening can be located by the stationary structures in the sphenoid sinus.

CONCLUSIONS

The FR is a stationary bony structure; its length, diameter, and angle are relatively constant; and it can be easily located by the data measured in this study. The FR should be protected in the process of transsphenoid approach as well as be precisely located by the procedure about it.

Safe Corridor to Access Clivus for Endoscopic Trans-Sphenoidal Surgery: A Radiological and Anatomical Study

PURPOSE

Penetration of the clivus is required for surgical access of the brain stem. The endoscopic transclivus approach is a difficult procedure with high risk of injury to important neurovascular structures. We undertook a novel anatomical and radiological investigation to understand the structure of the clivus and neurovascular structures relevant to the extended trans-nasal trans-sphenoid procedure and determine a safe corridor for the penetration of the clivus.

METHOD

We examined the clivus region in the computed tomographic angiography (CTA) images of 220 adults, magnetic resonance (MR) images of 50 adults, and dry skull specimens of 10 adults. Multiplanar reconstruction (MPR) of the CT images was performed, and the anatomical features of the clivus were studied in the coronal, sagittal, and axial planes. The data from the images were used to determine the anatomical parameters of the clivus and neurovascular structures, such as the internal carotid artery and inferior petrosal sinus.

RESULTS

The examination of the CTA and MR images of the enrolled subjects revealed that the thickness of the clivus helped determine the depth of the penetration, while the distance from the sagittal midline to the important neurovascular structures determined the width of the penetration. Further, data from the CTA and MR images were consistent with those retrieved from the examination of the cadaveric specimens.

CONCLUSION

Our findings provided certain pointers that may be useful in guiding the surgery such that inadvertent injury to vital structures is avoided and also provided supportive information for the choice of the appropriate endoscopic equipment.

A new method of locating the optic canal based on structures in sella region: computed tomography study

BACKGROUND

The location of optic canal and the intracranial segment of optic nerve is difficult because of the high possibility of the deficiency of optic protuberance as well as its complex relationship to sphenoid and ethmoidal sinus. A new method of locating the optic canal and a comprehensive analysis of it and the structures around is of great importance.

PURPOSE

Our study aimed to provide a new method to locate the optic canal and analyze the relationship between optic canal and other structures in the sella region, which can be a guidance for endoscopic sinus surgery such as the optic nerve decompression and transsphenoidal approach to the pituitary adenoma and reduced complications caused by the injury of optic nerve.

METHODS

Computed tomography images of 120 sphenoid sinuses in adults were reviewed, and multiplanar reconstruction was used to make it possible to make the measurement in coronal, sagittal, and axial plane at the same time. The positional relationship between optic canal and the stationary structures in sella region was analyzed.

RESULTS

The horizontal distance between the lowest point of sella bottom (SB) and sulcus prechiasmaticus in the sagittal plane was 8.08 (SD, 0.79) mm. The distance between the medial wall of optic canal and the midline of SB were 7.01 (SD, 1.43) mm in plane 1, 7.78 (SD, 0.86) mm in plane 2, 11.08 (SD, 0.82) mm in plane 3, and 13.81 (SD, 0.66) mm in plane 4; the angles between line BO and line BC were 87.99 (SD, 5.04) degrees in plane 1, 87.71 (SD, 4.98) degrees in plane 2, 82.54 (SD, 5.78) degrees in plane 3, and 82.57 (SD, 6.99) degrees in plane 4. As for the relationship between optic canal and the sphenoid sinus, there were 2.08% of sphenoid sinus of type A, 19.17% of type B, 45.00% of type C, 17.50% of type D, and 16.25% of type E.

CONCLUSIONS

Optic canal can be located by the structures or markers in sella region such as the midline of SB, the lowest point of SB, the midpoint in the top edge of sphenoid sinus, and tubercular recess. The analysis of the relationship between optic canal and the sphenoid sinus as well as the data measured in our study is helpful to make an accurate location of the optic canal when the bony landmarks of optic canal are not available.

The recesses of the sellar wall of the sphenoid sinus and their intracranial relationships

BACKGROUND

The sellar wall of the sphenoid sinus and its recesses have been previously studied, but their intracranial relationships to the diaphragma sellae, tuberculum, clinoid segment of the internal carotid artery, chiasmatic sulcus, and middle clinoid process need further definition.

OBJECTIVE

To describe these intra- and extracranial relationships of the recesses in the anterior sellar wall.

METHODS

The middle clinoid was studied in 132 parasellar areas of dry crania. Thirty-eight parasellar areas of formalin-fixed/silicone-colored specimens were dissected. After transsphenoidal endoscopic exposure, the optic, carotid, and sellar prominences; lateral opticocarotid and tuberculum recesses; and caroticosellar and medial opticocarotid points were identified. High-speed drills opened 1-mm perforations at these points to allow study of intracranial relationships.

RESULTS

Two recesses and 2 junction points can be recognized in the sphenoid sinus: lateral opticocarotid and tuberculum recesses and medial opticocarotid and caroticosellar points. The lateral opticocarotid recess corresponds to the optic strut base, and the clinoid segment of the internal carotid artery is located medially. The diaphragma sellae attachment is at the level of the tuberculum recess, which in 50% of cases corresponds to the tuberculum. A middle clinoid in base or height greater than 1.5 mm is present in 21.1% and a caroticoclinoid ring in 3%. The middle clinoid is 1 mm inferior and lateral to the caroticosellar point and 4.7 mm inferior to the medial opticocarotid point.

CONCLUSION

An understanding of the intra- and extracranial relationships of the recesses of the sphenoid sinus will aid in accurately directing transsphenoidal approaches.

Minimal invasive biopsy of intraconal expansion by PET/CT/MRI image-guided navigation: a new method

Intraorbital tumours are often undetected for a long period and may lead to compression of the optic nerve and loss of vision. Although CT, MRI's and ultrasound can help in determining the probable diagnosis, most orbital tumours are only diagnosed by surgical biopsy. In intraconal lesions this may prove especially difficult as the expansions are situated next to sensitive anatomical structures (eye bulb, optic nerve). In search of a minimally invasive access to the intraconal region, we describe a method of a three-dimensional, image-guided biopsy of orbital tumours using a combined technique of hardware fusion between (18)F-FDG Positron Emission Tomography ((18)F-FDG PET), magnetic resonance imaging (MRI) and Computed Tomography (CT).

METHOD AND MATERIAL

We present 6 patients with a total of 7 intraorbital lesions, all of them suffering from diplopia and/or exophthalmos. There were 3 female and 3 male patients. The patients age ranged from 20 to 75 years. One of the patients showed beginning loss of vision. Another of the patients had lesions in both orbits. The decision to obtain image-guided needle biopsies for treatment planning was discussed and decided at an interdisciplinary board comprising other sub-specialities (ophthalmology, neurosurgery, maxillofacial surgery, ENT, plastic surgery). All patients underwent 3D imaging preoperatively ((18)F-FDG PET/CT or (18)F-FDG PET/CT plus MRI). Data was transferred to 3D navigation system. Access to the lesions was planned preoperatively on a workstation monitor. Biopsy-needles were then calibrated intraoperatively and all patients underwent three-dimensional image-guided needle biopsies under general anaesthesia.

RESULTS

7 biopsies were performed. The histologic subtype was idiopathic orbital inflammation in 2 lesions, lymphoma in 2, Merkel cell carcinoma in 1, hamartoma in 1 and 1 malignant melanoma. The different pathologies were subsequently treated in consideration of the actual state of the art. In cases where surgical removal of the lesion was performed the histological diagnosis was confirmed in all cases.

CONCLUSION

There is a wide range of possible treatment modalities for orbital tumours depending on the nature of the lesion. Histological diagnosis is mandatory to select the proper management and operation. The presented method allows minimal-invasive biopsy even in deep intraconal lesions, enabling the surgeon to spare critical anatomical structures. Vascular lesions such as cavernous haemangioma, tumour of the lacrimal gland or dermoid cysts present a contraindication and have to be excluded.

Optic canal (OC) and internal carotid artery (ICA) in sellar region

PURPOSE

OC and ICA are important structures in sellar region, the injury of ICA and optic nerve can be the severe complications in the operations related to sellar region such as the transsphenoidal surgery and extended transsphenoidal surgery. So knowing their position and their relationship to stable structures in sellar region is of great importance. The aim of our study is to provide specific and comprehensive data about the location of OC and ICA in sellar region in order to guide the surgeons through difficulties in surgeries related to sellar region.

METHODS

Computer topographic angiography (CTA) images of 200 individuals were reviewed, the measurement was performed on coronal, sagittal and axis planes after multiplanar reformation (MPR). We located OC by the tubercular recess (TR) and the top edge of sphenoid sinus, we located ICA by the midpoint of sellar floor (SF) and the top edge of sphenoid sinus.

RESULT

OC can be located by TR and the distance between OC and sagittal midline; ICA can be located by midpoint of SF and distance between ICA and sagittal midline; ICA has stationary relationship to ACP.

CONCLUSION

Knowing the anatomical position of OC and ICA and the positional relationship between them and the sellar region is of great importance in the surgeries related to the sellar region such as the trans-sphenoidal approach to pituitary and extended transsphenoidal surgery to non-pituitary adenoma lesions.