Evolving materials and techniques for endoscopic sinus surgery

Safety and Pharmacokinetics of a Ciprofloxacin and Azithromycin Stent for Chronic Rhinosinusitis

OBJECTIVES

Previously, we developed a novel double-coated sinus stent containing ciprofloxacin (inner layer) and azithromycin (outer layer) (CASS), but released drug concentrations were found to be insufficient for clinical usage. Our objectives are to improve drug release of CASS and assess safety and pharmacokinetics in rabbits.

METHODS

Dip coating was used to create the CASS with 2 mg ciprofloxacin and 5 mg azithromycin. A uniformed double coating was assessed with scanning electron microscopy (SEM), and the release patterns of both drugs and lactate dehydrogenase (LDH) assay were evaluated over 14 days in vitro. Safety, tolerability, and pharmacokinetics of the CASS were tested in rabbits through insertion into the maxillary sinus and evaluated with nasal endoscopy, CT scans, histology, blood counts and chemistries, and in vivo drug release.

RESULTS

SEM confirmed the uniformity of the dual coating of ciprofloxacin and azithromycin, and thickness (μm) was found to be 14.7 ± 2.4 and 28.1 ± 4.6, respectively. The inner coated ciprofloxacin showed a sustained release over 14 days (release %) when soaked in saline solution (day 7, 86.2 ± 3.4 vs. day 14,99.2 ± 5.1). In vivo analysis showed that after 12 days, 78.92 ± 7.67% of CP and 84.12 ± 0.45% of AZ were released into the sinus. There were no significant differences in body weight, white blood cell counts, and radiographic changes before and after CASS placement. No significant histological changes were observed compared to the contralateral control side.

CONCLUSION

Findings suggest that the CASS is an effective method for delivering therapeutic levels of antibiotics. Further studies are needed to validate efficacy in a preclinical sinusitis model.

LEVEL OF EVIDENCE

N/A Laryngoscope, 2024.

Advances in Sinus Surgery for Nasal Polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is comprised of a diverse group of endotypes that cause significant morbidity for afflicted patients. While endoscopic sinus surgery helps ameliorate the disease, polyps frequently recur. Newer strategies are intended to provide access for topical steroid irrigations in attempts to improve the disease process and quality of life, and decrease overall recurrence of polyps.

OBJECTIVE

To review the current literature examining the latest surgical approaches for CRSwNP.

METHODS

Review article.

RESULTS

In dealing with the recalcitrant nature of CRSwNP, surgical techniques have simultaneously become more nuanced and aggressive. Bony resection in anatomically unfavorable areas such as the frontal, maxillary, and sphenoid outflow regions, replacing diseased or denuded mucosa with healthy grafts or flaps at the neo-ostia, and introducing drug-eluting biomaterials to newly opened sinus outflow tracts are highlights in the recent advancements in sinus surgery for CRSwNP. The Draf 3 or modified endoscopic Lothrop procedure has become a standard technique and demonstrated to improve quality of life and decrease polyp recurrence. A number of mucosal grafting or mucosal flap techniques have been described that cover exposed bone of the neo-ostium and evidence shows that this improves healing and diameter of the Draf 3. Partial middle turbinectomy, while controversial, appears to help decrease polyp recurrence in long-term follow-up studies. Modified endoscopic medial maxillectomy improves access to the maxillary sinus mucosa, facilitates debridement and, particularly, in the cystic fibrosis nasal polyp patient, improves overall management of the disease. Sphenoid drill-out procedure provides wider access for topical steroid irrigations and also may improve management of CRSwNP.

CONCLUSION

Surgical intervention remains a mainstay of therapy for CRSwNP. Newer techniques revolve around improving access for topical steroid therapy.

Image guided dilation of sinus ostium in revision sinus surgery

PURPOSE

Assess if a rigid, image-guided balloon could be used effectively and safely in revision sinus surgery.

MATERIALS AND METHODS

A prospective, non-randomized, single-arm, multicenter study to assess the safety and device performance of the NuVent™ EM Balloon Sinus Dilation System. Adults with CRS in need of revision sinus surgery were enrolled for balloon sinus dilation of a frontal, sphenoid, or maxillary sinus. The primary device performance endpoint was the ability of the device to (1) navigate to; and (2) dilate tissue in subjects with scarred, granulated, or previously surgically-altered tissue (revision). Safety outcomes included the assessment of any operative adverse events (AEs) directly attributable to the device or for which direct cause could not be determined. A follow-up endoscopy was conducted at 14 days post-treatment for assessment of any AEs. Performance outcomes included the surgeon's ability to reach the target sinus (es) and dilate the ostia. Endoscopic photos were captured for each treated sinus pre- and post-dilation.

RESULTS

At 6 US clinical sites, 51 subjects were enrolled; 1 subject withdrew before treatment due to a cardiac complication from anesthesia. 121 sinuses were treated in 50 subjects. The device performed as expected in 100 % of the 121 treated sinuses, with investigators able to navigate to the treatment area and dilate the sinus ostium without difficulty. Ten AEs were seen in 9 subjects, with 0 related to the device.

CONCLUSION

The targeted frontal, maxillary or sphenoid sinus ostium were safely dilated in every revision subject treated, with no AEs directly attributed to the device.

Perspective review on applications of optics in skull base surgery

The use of optic technology in skull base surgeries has the potential to revolutionize the field of medicine, particularly neurosurgery and neurology. Here, we briefly present the past, present, and future of skull-base surgery, with an emphasis on the applications of optical topography techniques. We discuss optical topography techniques such as functional near-infrared spectroscopy, optical diffusion tomography, and optical topographical imaging. Optical topography techniques are particularly advantageous when combined with other imaging methods. For instance, optical topography can be combined with techniques such as functional magnetic resonance imaging (fMRI) to combine the temporal resolution of optical topography with the spatial resolution of fMRI. Multimodal approaches will be critical to advance brain-related research as well as medicine. Structured light imaging techniques are also writing the future of 3-dimensional imaging. In short, optical topography can allow for non-invasive, high-resolution imaging that will provide real-time visualizations of the brain that are ideal for neurosurgery. From the limitations of traditional skull base surgeries to the newest developments in optical neuroimaging, here we will discuss the potential applications of optics in skull base procedures.

Above and Beyond: Periorbital Suspension for Endoscopic Access to Difficult Frontal Sinus Pathology

OBJECTIVES/HYPOTHESIS

The periorbital suspension (PS) is an advanced adjunctive technique performed during endoscopic approaches to frontal sinus pathology that would be too far lateral or superior to address using traditional endoscopic transnasal approaches. The objectives of this study are to characterize the utility of this technique for frontal sinus pathology, determine anatomic limitations, and assess clinical outcomes following surgical treatment.

STUDY DESIGN

Prospective case series.

METHODS

Patient data including demographics, etiology, technique, complications, and clinical follow-up were collected. Preoperative computed tomography scans were reviewed for maximum lateral and superior extent of pathology, supraorbital recess height, anterio-posterior (AP) diameter of the frontal sinus, interorbital distance, and orbital-first olfactory neuron distance.

RESULTS

The PS approach was used in 30 surgeries (29 patients) for cerebrospinal fluid leaks (n = 5), benign tumors (n = 17), malignant tumors (n = 5), allergic fungal sinusitis (n = 2), and mucocele (n = 1) between 2018 and 2020. Approaches included 15 Draf IIB and 15 Draf III frontal sinusotomies. All pathology was surgically accessible using the PS approach and there were no intraoperative or postoperative complications. Postoperative follow-up was 11.7 ± 7.6 months. Mean recorded measurements (in mm) were as follows: maximum lateral extent -15.0 ± 7.7, superior extent 21.2 ± 7.7 in surgical plane and 20.9 ± 9.8 in the vertical plane, supraorbital recess height -2.6 ± 1.9, AP frontal sinus diameter -13.2 ± 4.7, interorbital distance -29.8 ± 5.4, and orbital-olfactory neuron distance -14.8 ± 2.9.

CONCLUSIONS

The PS technique can be safely and successfully utilized to provide endoscopic endonasal access to lateral and superior frontal sinus pathology.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Plasma Ablation-Assisted Endoscopic Endonasal Transpterygoid Approach to Sphenoid Lateral Recess Cerebrospinal Fluid Leaks: Technique and Outcome

BACKGROUND

Management of sphenoid lateral recess (SLR) cerebrospinal fluid (CSF) leaks present a challenge because of the location and requiring complete visualization of the defect for a successful repair. The endoscopic endonasal transpterygoid approach (EETPA) is considered the gold standard in addressing these defects. We lay out our experience in implementing this approach with plasma ablation.

METHODS

This is a case series of 11 diagnosed patients of SLR CSF leaks who underwent plasma ablation-assisted EETPA repair by a single surgeon between 2011 and 2020 at our institution. Outcomes in terms of surgical field grade on the Wormald 11-point grading scale, postoperative complications, healing on nasal endoscopy and imaging, and surgical success rate were assessed.

RESULTS

The etiology was spontaneous leak in 10 (90.9%) patients and secondary to temporal lobe abscess and/or meningitis in one (9.09%). Three (27%) patients were previously operated elsewhere by the transsphenoidal route, which we reoperated by this technique. As per Wormald grading, grade 1 field in 3 (27.27%), grade 2 in 6 (54.5%), and grade 3 in 2 cases (18.18%) were noted. Complications occurred in 3 patients (27%) in the form of dry eye (9%), meningitis (9%), and transient CSF rhinorrhea in the immediate postoperative period (9%). Repair sites were well healed on follow-up nasal endoscopy and imaging. The surgical success rate was 100%.

CONCLUSIONS

Plasma ablation-assisted EETPA allows for a uninostril approach to the SLR, easy accessibility, and better visualization with a bloodless field, which allows appropriate repair, thus minimizing complications and preventing recurrence.

Surgery around the Orbit: How to Select an Approach

Orbital region pathologies may be safely and effectively treated through a various number of approaches. As the concept of "outcome" and minimally invasive surgery keeps gaining popularity in neurosurgery, these approaches-each with specific indications and limitations-together provide the best surgical options.

Hemostatic Materials and Devices

Numerous absorbable substances have been introduced to aid hemostasis in sinus and skull base surgery. Within the confines of the sinus and nasal cavities, ideal hemostatic agents must have several qualities. They must provide hemostasis, conform to an irregular wound bed, and enable healing of the traumatized mucosa without additional detriment to the epithelium. Traditional nasal packing has been substituted largely by absorbable materials designed to improve patient comfort and outcomes. Although many promising agents exist, none have become standard therapy.

Inaccurate Assessments of Anterior Cranial Base Malignancy Following Nasoseptal Flap Reconstruction

Objective The nasoseptal flap (NSF) provides vascularized tissue for repair of skull base defects of various etiologies. However, the NSF repair after skull base resection for anterior cranial base malignancies may demonstrate radiologic findings confusing for recurrent or residual disease on postoperative surveillance imaging. The objective of the current study was to review neuroradiologic misinterpretations of NSF reconstruction following anterior cranial base malignancies. Methods A multicenter review of patients reconstructed with the NSF after endoscopic resection of anterior cranial base malignancies from 2008 to 2013 was performed. Data were collected regarding etiology, surgical technique, locoregional control, and postoperative radiologic assessments. Only patients with at least one postoperative surveillance scan with inaccurate assessment of residual or recurrent malignancy were included in the study. Results Over 5 years, 13 patients were identified who had erroneous reporting of malignancy due to NSF reconstruction. On average, two neuroradiologists interpreted the NSF as persistent or recurrent malignancy over this time period (range: 1-7). The key findings suspicious for recurrence were enhancement and soft tissue thickening of the NSF. These findings were present in at least one postoperative scan in all patients. Conclusion Neuroradiologists and rhinologists performing surveillance on patients with a history of skull base malignancy with NSF reconstruction should maintain collaborative efforts to accurately interpret radiologic findings of the NSF during postoperative imaging.

The use of image-guidance during transsphenoidal pituitary surgery in the United States

BACKGROUND

Intraoperative image guidance is a useful modality for transsphenoidal pituitary surgery. However, the outcomes associated with this technology have not been systematically evaluated.

OBJECTIVE

The purpose of the study was to quantify complication rates with and without the use of image guidance during transsphenoidal pituitary surgery using a nationwide database with broadly applicable results.

METHODS

A retrospective analysis of the Nationwide Inpatient Sample was performed from 2007 to 2011. Transsphenoidal pituitary resections for adenomas were identified by International Classification of Diseases-9th Revision, Clinical Modification code. The effect of image guidance on cerebrospinal fluid (CSF) leak complications and cost-benefit was analyzed.

RESULTS

A total of 48,848 transsphenoidal pituitary resections were identified, of which 77.5% were partial resections and 22.5% were complete. Pathologic indications included benign (89.3%), malignant primary (0.6%), and malignant secondary (0.4%). Complications included same-stay death (0.4%), CSF leak (8.8%), postoperative CSF rhinorrhea (1.9%), diabetes insipidus (12.4%), and meningitis (0.4%). Image guidance was employed in 7% (n = 3401) of all cases. When analyzed by modality, computed tomography (CT)-assisted procedures had lower CSF rhinorrhea rates (1.1%) compared with cases with no image guidance (1.9%), whereas magnetic resonance (MR)-assisted procedures had the highest rates (2.7%, χ2 p < 0.001). Rates of CSF leak demonstrated a similar pattern (CT 6.4%, no image guidance 8.9%, MR 9.2%, χ2 p < 0.001). CT-assisted surgery had significantly shorter length of stay (2.9 days) versus no image guidance (3.7 days, p < 0.001), lower total charges ($47,589 versus $62,629, p < 0.001), and lower total cost ($16,748 versus $20,530, p < 0.001).

CONCLUSIONS

CT-assisted surgery is associated with a lower rate of CSF leak, shorter length of stay, and lower cost compared with patients without image guidance. Further studies that control for severity and extent of disease are warranted to confirm this finding.

Regional variation and factors associated with image guidance utilization during endoscopic sinus surgery in the ambulatory setting

OBJECTIVE

Determine regional variation and factors associated with the use of image guidance (IG) during endoscopic sinus surgery (ESS) in the ambulatory surgery center setting.

METHODS

All cases of ESS in 2010 were extracted from the state ambulatory surgery databases for New York, North Carolina, Florida, Iowa, and California. Current Procedural Terminology codes for individual sinusotomies and IG and International Classification of Diseases codes along with insurance and regional data were analyzed to determine factors that were associated with the use of IG during ESS.

RESULTS

Among 36 646 ambulatory ESS procedures (mean age 46.0 years; 49.0% female), 6676 cases utilized IG (18.2%). Polyps were present in 27.9% of cases. North Carolina had the highest utilization rate for IG (26.0%), whereas Iowa had the lowest (12.8%). On multivariate analysis, use of IG was associated with state, insurance status, community setting, total ethmoidectomy, frontal sinusotomy, sphenoidotomy, and polyps (all P < .001), but not maxillary antrostomy (P = .197). The highest procedural odds ratio for IG use was noted for total ethmoidectomy (2.07), followed by frontal sinusotomy (1.97) and sphenoidotomy (1.26).

CONCLUSION

Although IG is utilized in a relative minority of ESS cases, there is considerable regional variation in use. Factors other than complexity of surgery influence IG utilization as well.

Increased Intracranial Pressure in Spontaneous CSF Leak Patients Is Not Associated with Papilledema

Objective

Spontaneous cerebrospinal fluid (CSF) leaks typically present in patients with undiagnosed idiopathic intracranial hypertension (IIH) secondary to pressure erosion of the skull base. Despite elevated intracranial pressure (ICP) on lumbar puncture or ventriculostomy, patients with spontaneous CSF leaks rarely complain of visual disturbances. The objective of this study is to correlate the presence of preoperative papilledema with opening ICP in patients undergoing endoscopic repair of spontaneous CSF leaks.

Study Design

Prospective study.

Setting

Tertiary hospital.

Methods

Prospective evaluation of patients with spontaneous CSF leaks was performed over a 1-year period (December 2012 to December 2013). Fundoscopic examination for papilledema was completed preoperatively and CSF pressure measured by lumbar puncture or ventriculostomy intraoperatively. Data regarding demographics, nature of presentation, and body mass index (BMI) were also recorded and compared to a control cohort of IIH patients with papilledema.

Results

Sixteen patients (average age 52) were evaluated. Obesity was present in 94% of individuals (average BMI = 43, range, 27-65). Papilledema was absent preoperatively in all subjects. Opening pressures via lumbar puncture/ventriculostomy were 27.4 ± 7.7 cmH20. Following 6 hours of clamping, measurements significantly increased to 36 ± 9.6 cmH20 ( P < .001). IIH controls (average age 33, average BMI = 36, range, 21-52) exhibited average ICP (36.2 ± 11.7) identical to postclamp measurements in the spontaneous CSF leak cohort.

Conclusions

Subjects with spontaneous CSF leaks had postclamping average ICP identical to controls with IIH and papilledema. Such evidence suggests that a CSF leak in this patient population provides sufficient pressure diversion to avoid the development of papilledema.

Topical triamcinolone acetonide/carboxymethylcellulose foam for acute exacerbations of chronic rhinosinusitis/nasal polyposis

BACKGROUND

Chronic rhinosinusitis with nasal polyposis (CRS/NP) is a medical disease that is managed more effectively after endoscopic sinus surgery (ESS). Despite topical treatment with intranasal steroids, acute inflammatory exacerbations (AEs) are common and are typically treated with oral prednisone, which has significant and well-documented side effects. The objective of the current study was to critically evaluate the topical application of triamcinolone acetonide (80) in carboxymethylcellulose (TA/CMC) foam for AEs in CRS/NP patients after ESS.

METHODS

CRS/NP patients managed with ESS by a single rhinologist over a 5-year period were included in the study. Data were reviewed regarding demographics, number of AEs, revision surgery, 22-item Sino-Nasal Outcomes Test (SNOT-22) scores, frequency of oral prednisone and/or TA/CMC, and notable side effects.

RESULTS

A total of 371 CRS/NP patients were treated with ESS over a 5-year period. Mean follow-up was 49.3 weeks (range, 2-249 weeks). During this time period, 130 patients (46 years; range, 28-48 years) developed a cumulative 267 AEs. Before initiating use of TA/CMC in 2010, 66 AEs were treated with prednisone. Subsequently, 116 of 201 AEs were managed with TA/CMC with a sequential decrease in prednisone use over the last 3 years (77, 39, and 32%). SNOT-22 scores (n = 33) decreased significantly after TA/CMC instillation (preinstillation, 1.69 ± 0.86, versus postinstillation, 1.23 ± 0.8; p < 0.01).

CONCLUSION

Management of AEs with TA/CMC decreased overall prednisone use in a large population of CRS/NP patients in this retrospective evaluation. TA/CMC appears well tolerated and is a useful treatment option for AEs in postoperative CRS/NP patients.

Management of Lateral Frontal Sinus Pathology in the Endoscopic Era

OBJECTIVES

Considerable advances in endoscopic technique and experience have allowed an increasing number of patients with complex frontal sinus disease to be treated with endoscopic surgery. The objective of the current study was to evaluate management strategies and outcomes regarding treatment of lateral frontal sinus disease.

STUDY DESIGN

Prospective case series.

SETTING

Academic tertiary medical center.

SUBJECTS AND METHODS

Prospectively collected data concerning frontal sinus pathology located lateral to the plane of the lamina papyracea (lateral disease) were reviewed. Data were collected regarding demographics, etiology, surgical technique, revision rate, anatomic considerations, and clinical follow-up. Only patients with at least 24 weeks of clinical follow-up and pathology who required removal and dissection in this region were included in the study.

RESULTS

Over 5 years, 156 patients (mean age, 47.9 years; range, 14-84 years) with 183 lateral frontal sinus pathologies and an average clinical follow up of 76 weeks (range, 24-237 weeks) were evaluated. Endoscopic or open surgery was attempted in 84 patients (54%) prior to intervention at our institution. Primary pathologies included inflammatory/obstructive diseases (n = 119), skull base defects (n = 33), and tumors (n = 31). Initial interventions included endoscopic (Draf IIA, n = 76; Draf IIB, n = 52; Draf III, n = 23), extended (IIA + trephine, n = 1; III + trephine, n = 2; III + osteoplastic flap, n = 2), and open (osteoplastic flap, n = 3; Reidel, n = 1; cranialization, n = 1) procedures. Seven patients (4%) required a subsequent revision procedure.

CONCLUSION

The vast majority of lateral frontal sinus pathology was managed using endoscopic techniques with excellent outcomes and a low revision rate in the current study.

Juvenile nasopharyngeal angiofibroma

Juvenile nasopharyngeal angiofibromas (JNAs) are rare, benign, highly vascular, locally aggressive tumors that primarily affect male adolescents. Historical treatment of these neoplasms has been primarily surgical. In the past decade, endoscopic resection of JNAs has become a viable and promising surgical treatment option. Endoscopic resection has many advantages over traditional open techniques, including better cosmesis, decreased blood loss, shortened hospital stays, and equivalent or improved recurrence rates. Emerging endoscopic technology continues to push the boundaries of resection of skull base tumors and will no doubt become the surgical treatment of choice for most JNAs in the near future.

Early experience of radio frequency coblation in the management of intranasal and sinus tumors

The purpose of this study was to evaluate the safety and efficacy of the use of radiofrequency coblation for endoscopic resection of intranasal and sinus tumors. A review was conducted of 15 adult patients with intranasal and or sinus tumors endoscopically treated with radio frequency coblation between November 2008 and November 2010 at St. John's Hospital at Livingston, a tertiary referral center that covers otolaryngology services for the southeast of Scotland. Fifteen patients with intranasal and sinus tumors were treated with transnasal endoscopic resection using radiofrequency coblation. The tumors included inverted papilloma (seven), paraganglioma (one), glomangiopericytoma (one), capillary hemangioma (one), hemangiopericytoma (one), juvenile angiofibroma (one), juvenile ossifying fibroma (one), oncocytic adenoma (one), and transitional cell carcinoma (one). We found that radiofrequency coblation is a useful and safe tool associated with minimal blood loss (<200 mL to 600 mL) in the resection of these tumors, and the average operating time was 1.67 hours. Radio frequency is a rapidly evolving technique and in the future will have an increasing role to play in the endoscopic resection of intranasal and sinus tumors.

The Draf III Mucosal Grafting Technique

Objective. The Draf III procedure is an advanced surgical option for frontal sinus disease refractory to endoscopic frontal sinusotomy and is used to expose the anterior limit of resection of the skull base during endoscopic management of anterior skull base tumors. Our objective was to evaluate outcomes of a strategy using mucosal grafts to decrease postoperative closure.

Study Design. Prospective cohort.

Setting. Tertiary care facility.

Subjects and Methods. Patients requiring a Draf III procedure were prospectively enrolled in the study. Demographics, reason for the procedure, percentage graft viability, and complications were recorded. The primary outcome measure was anterior-posterior (AP) diameter at 3 months.

Results. Mucosal grafting was performed during 29 Draf III procedures from 2008 to 2011. Twenty-seven patients (average age, 58 years) were available for measurement at 3 months (average postoperative follow-up, 15.4 months; range, 3–30 months). Reasons for the procedure included tumor (n = 14), chronic rhinosinusitis (CRS) with frontal ostium stenosis (n = 12), and trauma (n = 1). Average intraoperative AP diameter was 11.7 mm. All patients met the definition of success (<50% reduction in diameter), maintaining a patent combined frontal sinus ostium for the duration of follow-up (average diameter 10.8 mm at 3 months). Nine patients with CRS and frontal ostium stenosis had openings similar to the entire cohort (>1-year follow-up; average, 19.3 months) with significant symptom reduction (SNOT-22 preop 62.3 ± 20.8 vs 3 months 27.8 ± 14.8 and 1 year 21.4 ± 13.6; P < .0001).

Conclusion. Cicatricial stenosis and osteoneogenesis are common following the Draf III procedure. This study indicates that the use of mucosal grafts may assist with postoperative stenosis and should be considered a routine strategy for preventing closure.

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

BACKGROUND

Determining anatomic landmarks during a transsphenoidal-transethmoidal approach to the optic canal region is of critical importance.

METHODS

Sella-parasella sphenoid bone blocks were extracted from adult cadavers. Anatomic dissections were performed in the optic canal region using a surgical microscope in 30 samples. Quantitative measurements were done using photographic techniques. For histological evaluation, coronal and longitudinal cross-sections were taken from the bilateral optic canal in seven decalcified samples.

RESULTS

Optic protuberance (OP), carotid protuberance (CP), medial opticocarotid recess (MOCR) and lateral opticocarotid recess (LOCR) were defined as lateral landmarks determining the width of the opening in the extended transsphenoidal-transethmoidal approach. Among all anatomic markers, LOCR was the most determinant lateral marker with tubercular recess the most prominent central marker. OPs showing the optic canal direction and inter-recessal sulci had similar distinguishing rates in the sphenoid sinus base. Inter-recessal sulci formed by OPs and CPs were observed between MOCR and LOCR in most samples. In histologic sections, the dural sheath was thicker inferolaterally to the optic nerve compared to superiorly and medially; collagen arrangement was dense and irregular.

CONCLUSION

Although LOCRs and tubercular recesses are safe and prominent markers in extended transsphenoidal-transethmoidal approaches, other anatomic markers should also be taken into consideration to perform an efficient optic canal approach and optic canal decompression. Other factors for safe dissection are the length of the optic canal, bone thickness, adherence of dural structures and the course of the intradural ophthalmic artery.