Morphometric and morphological evaluation of the optic canal in three different parts in MDCT images

PURPOSE

This study aimed to classify the morphometry and variations of optic canal by examining its changes according to gender and body side, and developments according to age.

METHODS

We retrospectively evaluated the orbit and paranasal sinus computerized tomography images of 200 individuals (age range 3 months-90 years;106 female, 94 male). In this study, three different parts of optic canal in evaluated morphometric and morphological.

RESULTS

The intracranial aperture was found to be statistically significantly wide in males than females on both sides (p ˂ 0.05). When optic canal types were evaluated, the most common type among healthy individuals was conical type (right: 68%, left:67.5%), and the least common type was irregular type (right and left:1.5%). According to the type of optic waist, the most common was triangle type.

CONCLUSION

Considering the possible effect of optic canal size on pathologies, it is important to establish a basis for the parameters of this structure in healthy individuals. In this study, both the morphology and morphometry of the canal as well as variations were examined and it was determined that the structure was affected by gender, body side and age group. Knowledge of anatomic morphometry, variations and complexities arising from these are important for clinical diagnosis and management.

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.

Modified extradural selective anterior clinoidectomy leaving the optic canal unopened for internal carotid aneurysms: A technical note

Background

Anterior clinoidectomy is an established procedure used to decompress the optic nerve, mobilize the internal carotid artery (ICA), or enlarge the retrocarotid space. However, its use carries the risk of optic nerve injury. In certain surgeries, such as those for internal carotid aneurysms, propose modification to the anterior clinoidectomy for enlarging the retrocarotid space, especially in operations for ICA aneurysms.

Methods

After the anterior clinoid process (ACP) is sufficiently exposed, the internal cancellous bone or pneumatization can be removed through a small window created at its lateral edge to reveal the compact bone of the optic canal. Since the compact bone of the inferior surface facing the ICA is absent or very thin, the ACP can be removed by drilling through the anchoring compact bone with the optic canal in direct sight.

Results

In 10 consecutive internal carotid aneurysm cases, the ACP was successfully removed without opening of the optic canal to enlarge the retrocarotid space.

Conclusions

Anterior clinoidectomy can be performed to enlarge the retrocarotid space without opening the optic canal from outside the dura.

Monocular visual loss in a disseminated colorectal malignancy-A case report of a rare skull base metastasis

Neoplasms of the orbit may be primary, secondary (infiltration from the adjacent structures), or metastatic (from distant structures). It can be divided into 3 histologic categories: benign, benign but locally aggressive, and malignant. Primary and secondary orbital tumors, including intra-orbital and optic nerve tumors are uncommon observations in daily medical practice. Orbital tumors represent approximately 0.1% of all tumors and approximately 18% of all orbital diseases. We report a case of a 42 year old male patient with colorectal malignancy with basal skull metastasis involving the orbital apex and involving the optic nerve causing visual loss.

Pneumosinus dilatans of the sphenoid and visual loss: when should the optic nerve be decompressed?

Pneumosinus dilatans of the sphenoid sinus is a rare disorder which can be responsible for visual impairment and blindness. We present the case of an adolescent female who experienced progressive decrease in right-eye vision over 2 years. CT scan of the head showed an extensive pneumatization of the sphenoid bone extending to the lesser wing of the sphenoid and to the anterior clinoid process on the right side. MRI revealed right nerve atrophy in the optic canal and in the posterior part of the orbit. A surgical decompression of the right optic canal was performed via an intradural fronto-pterional approach. Postoperatively, her vision worsened, and at 3 years the patient was able to count fingers at 2.5 m. Our case and literature review of symptomatic sphenoidal pneumosinus dilatans confirmed that visual prognosis in such cases depended on the preoperative visual status. Early surgical decompression should be proposed whenever possible, before signs of severe visual disorders and optic atrophy.

Optic canal characteristics in pediatric syndromic craniosynostosis

The aim of this study was to compare optic canal parameters of syndromic craniosynostosis patients with those of normal patients to visit the possibility of optic nerve impingement as a cause of visual impairment. Computed tomography scan images were processed using the Materialise Interactive Medical Image Control System (MIMICS) Research 21.0 software (Materialise NV, Leuven, Belgium). Eleven optic canal parameters were measured: 1) height of optic canal on the cranial side, 2) height of optic canal on the orbital side 3) length of the medial wall of the optic canal, 4) length of the lateral canal wall of the optic canal, 5) diameter of the optic canal at five points (Q1-Q4 and mid canal), and 6) area and perimeter of optic canal. These measurements were obtained for both the right and left optic canals. The study sample comprised four Crouzon syndrome, five Apert syndrome, and three Pfeiffer syndrome patients. The age of these syndromic craniosynostosis patients ranged from 2 to 63 months. The height of the optic canal on the orbital side (p = 0.041), diameter of the mid canal (p = 0.040), and diameter between the mid-canal and the cranial opening (Q3) (p = 0.079) for syndromic craniosynostosis patients were statistically narrower compared with those of normal patients when a significance level of 0.1 was considered. Scatter plots for the ages of patients versus the above parameters gave three separated clusters that suggested the arresting of optic canal development with age. The findings from this study demonstrated a narrowing of the optic canal in syndromic craniosynostosis patients, and indicate that optic canal anatomical characteristics may have an association with visual impairment among pediatric syndromic craniosynostosis patients.

Optic Canal Decompression: Concepts and Techniques: 2-Dimensional Operative Video

The optic canal (OC) is a bony channel that transmits the optic nerve (ON) and ophthalmic artery (OphA) as they course through the lesser wing of the sphenoid bone to the orbital apex. The OC is involved in a variety of intracranial and extracranial pathologies,1 and opening of the canal may be necessary in order to achieve adequate exposure, better disease control, and vision preservation.2 Depending on the location of the pathology and its relationship with the optic nerve, the OC may be decompressed through an open transcranial approach or an endoscopic endonasal approach.1,3 OC drilling can be tailored based on the location of the pathology and its extension. Anterior clinoid process and optic strut drilling can be added based on these factors as well.4,5 In this video, we demonstrate the steps of OC drilling in both transcranial microscopic and endoscopic endonasal approaches through a combination of animated illustrations and operative videos. We present 4 cases, including 2 transcranial microscopic and 2 endoscopic endonasal approaches,6 demonstrating OC decompression and its technical nuances. Each case was selected to represent the range of pathologies relevant to OC drilling to allow for a complete understanding of the techniques and concepts required for optimal treatment. An informed written consent has been obtained from each of the patients in this publication. Video © Mayo Foundation for Medical Education and Research. All rights reserved. Copyright information: Bendok BR, Abi-Aad KR, Sattur MG, Welz ME, Hoxworth JM, Lal D. Endoscopic resection of a paraclinoid meningioma extending into the optic canal: 2-dimensional operative video. Operative Neurosurgery. 2018 September 1;15(3):356 by permission of Oxford University Press. Cadaveric images provided by courtesy of: The Rhoton Collection. http://rhoton.ineurodb.org/.

Hyperostosing sphenoid wing meningiomas

Some sphenoid wing meningiomas are associated with a significant hyperostotic reaction of the adjacent sphenoid ridge that may even exceed the size of the intradural mass. The decision-making process and surgical planning based on neuroanatomic knowledge are the mainstays of management of this group of lesions. Given their natural history and biologic behavior, many hyperostosing meningiomas at this location require long-term management analogous to a chronic disease. This is particularly true when making initial decisions regarding treatment and planning surgical intervention, when it is important to take into consideration the possibility of further future interventions during the patient's life span.

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.

Assessing the abilities of senior otolaryngology residents and graduated otolaryngologists in recognizing skull base elements in axial CT scan: proposing a new method for differentiating superior orbital fissure and optic canal

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate the ability of recognizing some important elements of the skull base in axial CT-scan cuts, including the optic canal (OC), superior orbital fissure (SOF), vidian canal (VC), foramen rotundum (FR), jugular foramen (JF) and hypoglossal canal (HC).

METHODS

In this study, 25 otolaryngology residents and 25 recently graduated otolaryngologists were evaluated in terms of their recognition of skull base elements, using 30 axial CT-scan cuts. Two months later, the exam related to skull base CT scans was taken in groups after a brief anatomy courses for otolaryngology residents.

RESULTS

The percentage of correct answers from otolaryngology residents regarding OC, SOF, VC, FR, JF, and HC in the first exam were 74 ± 26, 47 ± 34, 65 ± 30, 41 ± 38, 58 ± 26, and 68 ± 32, respectively. The correct answer for each element was similar between groups, and the differences were not statistically significant (p > 0.05). p value for the differences observed regarding the percentage of correct answers for the second exam between trained otolaryngology residents and recent otolaryngology graduates regarding OC and JF was no significant (p > 0.05) but significant for the other elements with better result in trained otolaryngology residents and most for SOF (p > 0.0001).

CONCLUSION

This study showed that the ability of recognition for the mentioned elements in axial CT-scan cuts was low among otolaryngology residents and graduated otolaryngologists. The proposed novel method for distinguishing SOF from OC had a powerful and long-lasting effect on trainee.

Reappraising the neurosurgical significance of the pterion location, morphology, and its relationship to optic canal and sphenoid ridge and neurosurgical implications

Frontolateral craniotomy procedures have advanced from conventional craniotomy to mini-craniotomy, and to contemporary keyhole surgery. In this context, it is important for the neurosurgeon to precisely locate the pterion. The distance of the pterion center from midpoint of zygomatic arch and posterolateral margin of frontozygomatic suture was studied bilaterally in 50 whole adult skulls in Indian ethnic group. The depth of optic canal and sphenoid ridge from the pterion was recorded bilaterally in fifty cut adult skulls and fifteen three-dimensional computed tomography scans. The suture length, thickness, and morphology were studied. The data were analyzed using SPSS software, two-tailed Student's t test, binary logistic regression and receiver operating characteristic curve for sexual dimorphism. The pterion center was located at a mean distance of 37.02 mm above the midpoint of zygomatic arch, 28.20 mm behind the posterolateral margin of frontozygomatic suture, 42.73 mm lateral to the optic canal and 10.59 mm from the sphenoid ridge. The location did not exhibit sexual dimorphism. In 20% cases the pterion center was 40 mm or more above the midpoint of the zygomatic arch and in 5% cases 35 mm or more posterior to the posterolateral margin of frontozygomatic suture. The mean suture length was 10±3 mm. The mean thickness at the center of the pterion was 3.52±1.45 mm. The commonest variety was sphenoparietal followed by frontotemporal, epipteric, and stellate types. A thorough knowledge of these dimensions has innumerable neurosurgical implications in resection of sellar, parasellar, and paraclinoid tumors and circulatory aneurysms.

Pediatric nodular fasciitis at the roof of the optic canal causing decreased vision: case report and review of the literature

We present a 3-year-old girl with decreased visual acuity of the left eye. Radiological studies revealed a mass lesion at the roof of the left optic canal with bony erosion, which compressed the left optic nerve. Gross total resection of the mass and decompression of the optic canal were performed. Histopathological study was consistent with nodular fasciitis. This is the first report of nodular fasciitis at the roof of the optic canal in a young child. Nodular fasciitis compressing the optic nerve should be included in differential diagnoses of optic neuropathy in young children.

Technical Description of Minimally Invasive Extradural Anterior Clinoidectomy and Optic Nerve Decompression. Study of Feasibility and Proof of Concept

BACKGROUND

Several diseases that involve the optic canal or its contained structures may cause visual impairment. Several techniques have been developed to decompress the optic nerve.

OBJECTIVE

To describe minimally invasive extradural anterior clinoidectomy (MiniEx) for optic nerve decompression, detail its surgical anatomy, present clinical cases, and established a proof of concept.

METHODS

Anatomic dissections were performed in cadaver heads to show the surgical anatomy and to show stepwise the MiniEx approach. In addition, these surgical concepts were applied to decompress the optic nerve in 6 clinical cases.

RESULTS

The MiniEx approach allowed the extradural anterior clinoidectomy and a nearly 270° optic nerve decompression using the no-drill technique. In the MiniEx approach, the skin incision, dissection of the temporal muscle, and craniotomy were smaller and provided the same extent of exposure of the optic nerve, anterior clinoid process, and superior orbital fissure as that usually provided by standard techniques. All patients who underwent operation with this technique had improved visual status.

CONCLUSIONS

The MiniEx approach is an excellent alternative to traditional approaches for extradural anterior clinoidectomy and optic nerve decompression. It may be used as a part of more complex surgery or as a single surgical procedure.

Optic canal size in idiopathic intracranial hypertension and asymmetric papilledema

OBJECTIVE

Asymmetric papilledema (AP) is a rare condition in idiopathic intracranial hypertension (IIH). As the pathophysiology of papilledema developement in IIH remains unclear, the study of AP could clarify some etiologic aspects. We aimed to evaluate bony optic canal size in IIH patients with AP.

PATIENTS AND METHODS

All IIH patients based on modified Dandy criteria in our referral tertiary eye hospital underwent neuro-opthalmologic exams and grading of papilledema according to modified Frisén scale. Very asymmetric papilledema (VAP) defined as a ≥2 grade difference between the two eyes. Clinical features, cerebrospinal fluid opening pressure (CSF OP), best corrected visual acuity, Humphery visual field, and brain magnetic resonance imaging (MRI) and MR venography was performed for all patients. Spiral orbital computed tomography (CT) scan which is the choice method for details of bony structures with axial, coronal and sagittal planes was done in patients with VAP.

RESULT

59 patients with IIH were diagnosed that 18.6% of them (n = 11) had VAP. There was no IIH patient with strictly unilateral Papilledema. Presenting symptoms and CSF OP was not significantly different between patients with symmetric and asymmetric papilledema. In patients with VAP, bony optic canal size was not statistically significant different in axial, coronal and sagittal plane when comparing the eye with higher grade edema to the fellow eye.

CONCLUSION

Our study showed that bony optic canal size evaluated by orbital CT scan was not different in VAP in IIH patients. Finding the exact pathophysiology of AP need further studies.

Is there a relationship between Onodi cell and optic canal?

OBJECTIVES

We investigated the relationship between Onodi cells and optic canal by paranasal sinus computed tomography (PNSCT).

METHODS

In this retrospective study, 508 PNSCT (265 males and 243 females) was examined. Onodi cell presence, pneumatization types, optic canal types; and also sphenoid sinusitis and anterior clinoid process pneumatization were evaluated.

RESULTS

The prevalence of Onodi cells was 21.2% of the patients. Onodi cells were observed 40.7% on the right side and 25.9% on the left side. In 33.4% of the patients, bilateral Onodi cells were present. Male/Female ratio was 24.5%/17.6%. Onodi cell types were detected as Type I > Type II > Type III bilaterally. There was a positive correlation between the right and left Onodi cell types (p < 0.05). Optic canal types were detected as Type IV > Type I > Type II > Type III. bilaterally. There was a positive correlation between right and left optic canal types. Onodi cell presence and ACP pneumatization were found as statistically significant (p < 0.05). In 65.5% of the patients, Onodi cells and ACP pneumatization were absent. ACP pneumatization was present in 35.4% of the cases. In nine cases, bilateral Onodi cells and ACP pneumatization were detected. Sphenoid sinusitis was detected in 11.4% of Type I and 13.8% of the Type II Onodi cells on the right side. On the left side, it was detected in 12.9% of the Type I and 19.0% of Type II Onodi cells.

CONCLUSION

Identification of Onodi cell is very important clinically because of its proximity to optic nerve canal. We concluded that type IV Onodi-optic canal relationship was the most common finding in our study. Onodi cell presence and their patterns of pneumatization must be evaluated on PNSCT preoperatively to avoid optic canal damage.

Carotid canal and optic canal at sphenoid sinus

In the present study, we investigated the relationship between sphenoid sinus, carotid canal, and optic canal on paranasal sinus computed tomography (PNSCT). This study was performed retrospectively. PNSCT images of 300 adult subjects (159 male, 141 female). Sphenoid sinus (pneumatisation, dominancy, septation, inter-sinus septa deviation), anterior clinoid process pneumatisation, Onodi cell, carotid and optic canals (width, dehiscence, classification) were measured. In males, type 3 pneumatised sphenoid sinus (in both sides) and in females type 2 pneumatised sphenoid sinus (right side) and type 3 pneumatised sphenoid sinus (left side) were detected more. Anterior clinoid pneumatisation was present 47.2% in males and 39.7% in females. In male group, more septation (i.e. 22.6%, ≥ 3 septa) in sphenoid sinus were detected. Onodi cell was present 26.6 and 19.1% in males and females, respectively. Carotid canal protrudation to the sphenoid sinus wall was present 23.9-32.1% in males and 35.5-36.2% in females. Dehiscence in carotid canal was detected more in females (34%) compared to males (22%). Optic canal protrudation was 33.3 and 30.5% in males and females. Type 4 optic canal was detected more in both gender. Optic canal dehiscence was detected 11.3 and 9.9% in males and females. Carotid and optic canal diameters were higher in males. In pneumatised sphenoid sinuses and in females, type 3 carotid canal (Protrudation to SS wall) (bilaterally) and type 1 optic canal type (No indentation) (ipsilateral side) were detected more. In elderly patients, carotid and optic canal width increased. When carotid canal protrudation was detected, there was no indentation in optic canals In pneumatised SS, carotid canal protrudation was observed with a greater risk in surgery. However, type 1 (non indentation) optic canal was present in highly pneumatised SS with lower risk for the surgery. In women, the risk of carotid canal protruding (about 1/3) is greater than that of males, and carotid canal dehiscence rates are also higher in females. Therefore, physicians should be very careful during the preparatory stages of the sphenoid sinus surgery. Otherwise, it may not be possible to prevent lethal carotid artery bleeds.

Extradural resection of the anterior clinoid process: How I do it

BACKGROUND

The anterior clinoid process shares a close relationship with the optic canal, the internal carotid artery, the superior orbital fissure and the cavernous sinus. These structures may be involved in diseases whose surgical exposure requires prior clinoid process resection.

METHOD

Based on operative cases we describe the different steps of this surgical technique and illustrate our surgical procedure with a video. Dividing the orbito-temporal periosteal fold is a key-step in order to optimize the elevation of the periosteal dural layer at the level of the superior orbital fissure to expose the contours of the anterior clinoid process. The clinoid tip is removed after "debulking" the bony content inside the anterior clinoid process in order to leave only a thin shell of bony contour. The bony shell is then detached from the dura, twisted and pulled out. The indications and limitations of the technique are presented.

CONCLUSION

The extradural approach of the anterior clinoid process totally provides a full resection of the anterior clinoid process and safety for the paraclinoid space structures. Meticulous stepwise bony resection and optimized dura opening contribute to reduce the risk inherent to this technique.

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.

Pure Intra-optic Canal Schwannoma: Report of Two Cases

We report two cases of “pure intra-optic-canal schwannoma.” The first patient was a 67-year-old female who presented with a visual field defect and visual impairment in the right eye, and the second patient was a 17-year-old female with progressive visual impairment. Both patients underwent tumor resection through frontotemporal craniotomy combined with extradural anterior clinoidectomy and unroofing of the optic canal. The tumors were not attached to the optic nerve (ON) and were located exclusively inside the optic canal. In both cases, the histological diagnosis was schwannoma. Although the origin of pure intra-optic-canal schwannoma is controversial, intra-operative findings suggested that in these cases, the tumors arose from the sympathetic nerve around the ON.

Internal and external spheno-orbital meningioma varieties: different outcomes and prognoses

BACKGROUND

Internal variation among spheno-orbital meningiomas (SOM) is surgically challenging. Optic canal invasion management is discussed.

METHOD

This retrospective study includes 70 patients with SOM who underwent surgery between 1995 and 2012. Preoperative ophthalmological, neurological and aesthetic clinical signs were collected. All patients benefitted from repeated tomography and magnetic resonance imaging (MRI). The surgical team consisted of a neurosurgeon and a plastic surgeon. In the majority of cases, resection was followed by bone reconstruction using an autologous iliac crest graft. The extent of resection was evaluated on the dural and osseous sides. Early clinical outcomes, long-term follow-up, recurrence and adjuvant therapies were reported.

RESULTS

The mean age was 52 years old, and 91 % of the patients were women. Initial symptoms primarily included proptosis (65 %), decreased visual acuity (39 %) and soft tissue tumefaction (16 %). We classified 40 cases as the internal variety when considering the inner third of the greater wing of the sphenoid, optic canal, anterior clinoid process or cavernous sinus. The remaining cases were described as the external variety. The complete resection rates for the internal and external varieties were 12 % and 61 %, respectively (P < 0.001). In total, 90 % of cases were grade I meningiomas. For grade I, we reported 30 % recurrence, and 50 % of these cases recurred in the first 2 years. Grade II cases without early adjuvant radiotherapy increased at 2 years. We did not observe any difference in recurrence rate among grade I tumours with or without tumour remnants. At the end of follow-up, visual acuity was stabilised or increased in 88 % of patients. In addition, 14 % of patients experienced persistent pain at the location of the iliac harvesting site.

CONCLUSIONS

The internal SOM variety exhibited a reduced total resection rate and a shorter progression-free survival (PFS). Unroofing of the optic canal extended PFS. Among grade I cases, the persistence of a negligible tumour remnant did not alter the probability of recurrence. For superior grades, radiotherapy must be administered in addition to surgery as soon as possible. SOMs require prolonged follow-up. Autologous iliac reconstruction is related to substantial morbidity and could be replaced by prosthetic bone three-dimensional reconstruction.

Endoscopic endonasal anatomy of the ophthalmic artery in the optic canal

BACKGROUND

The endoscopic endonasal opening of the optic canal has been recently proposed for tumors with medial invasion of this canal, such as tuberculum sellae meningiomas. Injury of the ophthalmic artery represents a dramatic risk during this maneuver. Therefore, the aim of this study was to analyze the endoscopic endonasal anatomy of the precanalicular and canalicular portion of this vessel, discussing its clinical implication.

METHODS

The course of the ophthalmic artery was analyzed through five endoscopic endonasal dissections, and 40 nonpathological consecutive MRAs were reviewed.

RESULTS

The ophthalmic artery arises from the intradural portion of the supraclinoid internal carotid artery, in 93 % of cases about 1.9 mm (range: 1-3) posterior to the falciform ligament. At the entrance into the optic canal, the ophthalmic artery is located infero-medially to the optic nerve in 13 % of cases. In 50 % of these cases the artery moves infero-laterally along its course, remaining in a medial position in the others. In cases with an non medial entrance of the ophthalmic artery, it runs infero-lateral to the optic nerve for its entire canalicular portion, with just one exception.

CONCLUSION

The endoscopic endonasal approach gives a direct, extensive and panoramic view of the course of the precanalicular and canalicular portion of the ophthalmic artery. Dedicated high-field neuroimaging studies are of paramount importance in preoperative planning to evaluate the anatomy of the ophthalmic artery, reducing the risk of jeopardizing the vessel, particularly for those uncommon cases with an infero-medial course of the artery.

Simultaneous decompression of the orbital lateral wall and optic canal for fibrous dysplasia in early adolescence

Introduction

Patients with fronto-orbital fibrous dysplasia (FD) occasionally present fronto-orbital protrusion, exophthalmos, and visual acuity disturbance. Simultaneous management of these conditions has not been previously described.

Case description

A-10-year-old female with fronto-orbital FD complained of left visual acuity disturbance. Head computed tomography showed compressed optic canal secondary to thickened bone. Decompression of the optic canal via the left frontotemporal extradural approach, opening of the lateral orbital wall, and dissection of the prominent zygoma were done simultaneously. The patient’s visual acuity disturbance and exophthalmos subsequently improved postoperatively.

Discussion and evaluation

When optic canal decompression is performed by the fronto-temporal approach, opening of the lateral orbital wall can be done simultaneously to decrease the intraorbital pressure and to prevent exophthalmos. In addition, although aesthetic plastic surgery is not generally recommended during the growing phase (due to the possibility of recurrence), this approach can prevent skin loosening and adverse cosmetic outcomes.

Conclusions

Aesthetic plastic surgery for fronto-orbital FD is recommended to prevent skin loosening. Opening of the lateral orbital wall should be performed when optic canal decompression is planned.

Monitoring of Intracranial Pressure by CT-Defined Optic Nerve Sheath Diameter

BACKGROUND AND PURPOSE

Intracranial pressure (ICP) can be monitored by the optic nerve sheath diameter (ONSD) technique. We hypothesized that diameter of the optic canal (OC) can be a limiting factor for this technique.

METHODS

In the prospective cohort study, we analyzed CT scans of 600 OCs of healthy adults and 54 canals of patients with ICP monitoring. The diameters were measured through its length and the narrowest one was chosen for further analysis. ONSD was measured at 3 and 10 mm from the anterior opening of the canal. The correlation analysis was performed between invasive and ONSD methods of ICP monitoring and OC diameters in pathological cases.

RESULTS

The narrowest cross-sectional area of the normal OC was 13.85±2.89 mm² and varied from 25.5 to 6.6 mm². Apparently 9.17% OCs were narrow (˂10.9 mm²). Correlations exist between the optic nerve sheath area at the 3-mm distance from the anterior opening of the canal and the area of the anterior opening itself (P = .012), and the sheath area 10 mm from the anterior opening and the narrowest part of the canal (P = .015). Cases with narrow canals provided false-negative readings via ONSD method if compared with invasive monitoring.

CONCLUSION

In its narrowest part, the average OC is 11 to 16.75 mm² wide. We suggest measuring this area simultaneously with the ONSD during ICP monitoring. If the area of the narrowest lumen of the canal is less than 10 mm², ONSD technique for ICP monitoring should not be used.

Clinical and surgical implications regarding morphometric variations of the medial wall of the orbit in relation to age and gender

The ethmoidal foramens are located on the medial wall of the orbit and are key reference points for intraoperative orientation. Detailed knowledge of the anatomy, bony landmarks and morphometric characteristics of the medial wall of the orbit is essential for various surgical procedures. The aim of this study was to determine the morphometric variations in the medial wall of the orbit and establish significant variations regarding age and gender. A total of 110 orbits were analyzed and subdivided by age (over or under 40 years) and gender. The distances of the medial wall of the orbit between the anterior lacrimal crest, the ethmoidal foramen, the optic canal and the interforamina were determined. Safe surgical areas were sought. Statistical tests were used to determine the differences between groups. In men, there is a safe surgical area proximal to the anterior and posterior ethmoidal foramen. In women, this area is in the posterior third of the medial wall of the orbit between the posterior ethmoidal foramen and the optic canal. Regarding variation according to age, the results of this study suggested that the anteroposterior diameter of the medial wall increases with age. This study showed that the anteroposterior total length of the medial orbit wall is similar between genders of similar age, increases with age, and has significant variations in the distances between the various structures that make up the medial orbit wall with regard to gender and age.

Imaging study on the optic canal using sixty four-slice spiral computed tomography

BACKGROUND

Rapid advances in multislice computed tomography (MSCT) technology facilitate accurate clinical imaging. The newly developed 64-slice CT increases temporal and spatial resolution efficiently.

PURPOSE

The purpose of this study is to evaluate the application of 64 slice spiral computed tomography (CT) on the imaging of the normal optics canal.

METHODS AND MATERIALS

100 healthy adults were investigated using 64 slice spiral CT. The optics canal was scanned, reconstructed and examined.

RESULTS

Among the four walls of the optic canal, the medial wall is the longest one. The upper wall and outer wall are inferior to the medial wall while the inferior wall is the shortest one. All the data accomplished by the 64 slice CT was consistent with the results of previous reports using other methods.

CONCLUSION

The results suggested that the 64 slice spiral CT could be a valuable and accurate method for measuring the length of optics canal walls.

Extension of the frontal sinus into the roof of the optic canal: a cadaveric case report

This case reports a bilateral asymmetrical posterior extension of the frontal sinuses into the orbital roof with an unusual expansion into the roof of the optic canal in a 55-year-old male cadaver. The posterior extensions of the sinus were lined by mucoperiosteum and were separated from the underlying orbital contents and optic nerve by a thin plate of bone. This knowledge of an unusual anatomic variation of the frontal sinus may help understand better the ocular and intracranial complications associated with frontal sinus pathologies.