Frontal sinus outflow anatomy

Anatomy of the Frontal Sinus Drainage Pathway Evaluated in 247 Cadavers to Prevent Cerebrospinal Fluid Leakage After Frontobasal Craniotomy

BACKGROUND AND OBJECTIVES

The frontal sinus (FS) drainage pathway (FSDP) may be a conduit for cerebrospinal fluid leakage after frontobasal craniotomy. In this cadaveric study, we aimed to evaluate the anatomy of the FSDP.

METHODS

The FSs and FSDPs of 247 cadavers were investigated. We counted the number of FSs and FSDPs in each half-head, verified the presence of a narrowing section in each FSDP, and evaluated the depth, shape, and size of each narrowing FSDP section.

RESULTS

We investigated 494 sides and 472 FSDPs of 247 cadavers. FSs were unilaterally undeveloped in 13 of 247 cadavers (5.3%) and bilaterally in 8 (3.2%). FSs were unilaterally duplicated in 7 of 247 cadavers (2.8%), and no FSs were bilaterally duplicated or triplicated. No FSs had 2 or more FSDPs, and all 472 investigated FSDPs were invariably narrowed at various depths. The narrowing FSDP sections were elliptical (78.6%), circular (18.1%), triangular (1.8%), or crescent-shaped (1.4%) and of varying thickness and orientation. Although FSDPs were asymmetric in 92.2% of cadavers and narrowing FSDP sections were located deep (8.9 ± 4.4 mm from the anterior skull base), the narrowing FSDP sections were typically small (area: 5.9 ± 3.3 mm 2 ) or thin (short diameter: 2.1 ± 0.7 mm).

CONCLUSION

Each FS had only one FSDP, all FSDPs were invariably narrowed at various depths, and the narrowing FSDP sections were sufficiently small or thin to allow local closure, facilitating prevention of cerebrospinal fluid leakage after frontobasal craniotomy.

Multidetector CT of the Nasal Cavity and Paranasal Sinuses Variations in 73 Patients

Detailed knowledge of the anatomy of the nasal cavity and paranasal sinuses is very important in the diagnosis of pathological processes, planning of endoscopic surgery, and radiologic guiding techniques during certain operations. Observational study. Clinic of Neurosurgery, Institute and Department of Anatomy and Pathology, Clinic and Department for Otorhinolaryngology and Maxillofacial Surgery, Faculty of Medicine. Two heads with brains were serially cut in the axial and coronal planes. 73 individuals, who were enrolled among 1848 patients, underwent examination by multidetector computerized tomography. A nasal septal deviation was seen in 65.8%, and septal pneumatization in 11%. Superior concha pneumatization was observed in 1.4% of patients, middle concha bullosa in 30.2%, and its hypoplasia in 1.4%. The lamina papyracea dehiscence was also present in 1.4%. The uncinate process was absent in 1.4%, and it was pneumatized in 4.2%. Agger nasi cells were noticed in 34.3%, and Haller and Onodi cells in 20.7% each. The olfactory fossa was shallow in 9.7%, deep in 31.6%, and very deep in 58.9%. Absence of the frontal sinus was seen in 9.7%. The presellar type of the sphenoidal sinus was present in 11%, the sellar in 35.7%, and the postsellar in 53.5%. Hypoplasia of the maxillary sinus was revealed in 1.4%, and hyperpneumatization in 4.2%. The sinus floor was usually below the level (60.3%), at the same level (20.7%), or above the level of the nasal floor (19.2%). The bony septum within the sinus was seen in 52.1%. The presented data are of a great significance in order to avoid a misdiagnosis of the anatomic variations, to make a proper diagnosis of certain diseases, and for safe endonasal operations.

The Frontal Sinus and Frontal Recess: Anatomical, Radiological and Surgical Concepts

Introduction  The frontal sinus (FS) is the most complex of the paranasal sinuses due to its location, anatomical variations and multiple clinical presentations. The surgical management of the FS and of the frontal recess (FR) is technically challenging, and a complete understanding of its anatomy, radiology, main diseases and surgical techniques is crucial to achieve therapeutic success. Objectives  To review the FS and FR anatomy, radiology, and surgical techniques. Data Synthesis  The FS features a variety of anatomical, volumetric and dimensional characteristics. From the endoscopic point of view, the FR is the point of greatest narrowing and, to have access to this region, one must know the anatomical limits and the ethmoid cells that are located around the FR and very often block the sinus drainage. Benign diseases such as chronic rhinosinusitis (CRS), mucocele and osteomas are the main pathologies found in the FS; however, there is a wide variety of malignant tumors that can also affect this region and represent a major technical challenge to the surgeon. With the advances in the endoscopic technique, the vast majority of diseases that affect the FS can be treated according to Wolfgang Draf, who systemized the approaches into four types (I, IIa, IIb, III). Conclusion  Both benign and malignant diseases that affect the FS and FR can be successfully managed if one has a thorough understanding of the FS and FR anatomy, an individualized approach of the best surgical technique in each case, and the appropriate tools to operate in this region.

Use of 3D-Printed and 2D-Illustrated International Frontal Sinus Anatomy Classification Anatomic Models for Resident Education

OBJECTIVE

To examine the impact of 2-dimensional (2D) illustrations and 3-dimensonal (3D)-printed anatomic models of the frontal sinuses according to the International Frontal Sinus Anatomy Classification in the education of otolaryngology and radiology residents.

STUDY DESIGN

A crossover study design with half of the study participants randomized to the 2D illustration intervention first and the other half randomized to the 3D-printed model first.

SETTING

Regularly scheduled resident didactic lectures at a tertiary care center.

SUBJECTS AND METHODS

Forty-one otolaryngology and radiology residents were assessed with pre- and postintervention questionnaires that included subjective and objective methods of assessment.

RESULTS

Overall, there was a statistically significant improvement in total number of answers correct and in confidence score between the pre- and postintervention assessments (P < .0001). The primary outcome of order of intervention (ie, 2D → 3D vs 3D → 2D) did not result in statistically significant differences in postevaluation scores. In regard to the secondary outcome of learner preference for educational modality, radiology residents favored the 2D illustrations to understand anatomic relationships, while otolaryngology residents preferred the 3D model to be more helpful in surgical planning (P = .0075).

CONCLUSION

There is no difference between 2D-illustrated and 3D-printed International Frontal Sinus Anatomy Classification anatomic models in overall educational outcome, despite the preference of learners. Together, these models can be used as helpful tools in frontal sinus education for otolaryngology and radiology trainees.

Teaching Residents Frontal Sinus Anatomy Using a Novel 3-Dimensional Conceptualization Planning Software-Based Module

BACKGROUND

The Frontal Sinus Masterclass (FSMC) is an effective method for teaching frontal sinus anatomy. A third party developed new software using the same 3-dimensional building block concept. The authors sought to determine whether the use of the software for the educational module yielded similar results to the original FSMC, which used wooden blocks.

METHODS

The study was performed at a sinus course for residents. A precourse test assessed the ability to decipher frontal sinus anatomy prior to the course. Computed tomography (CT) scans of the sinuses were evaluated in triplanar view, and participants attempted to reconstruct the anatomy using the new software. Subsequently, the course instructor explained the anatomy and showed a short corresponding surgical video of the frontal sinusotomy. Cases progressed in anatomical difficulty and inflammatory load. A postcourse test determined knowledge after the course.

RESULTS

In sum, 50 residents completed the pre- and postcourse tests. Overall scores increased from 60.5% to 65.2% ( P = .004). Subanalysis also demonstrated improved ability to locate the frontal drainage pathway from 32.5% to 46% ( P = .011) and label the frontal recess cell structures from 64% to 67.6% ( P = .045).

CONCLUSION

There is minimal literature on proven methods for teaching frontal sinus anatomy. Objectively, participants of the modified FSMC simulation training using new software improved their ability to recognize cells of the frontal recess on CT scans. They especially exhibited better localization of the frontal sinus drainage pathway. Subjectively, participants reported benefit from the course and felt they would be better surgeons.

Virtual Functional Endoscopic Sinus Surgery Simulation with 3D-Printed Models for Mixed-Reality Nasal Endoscopy

The surgeon's knowledge of a patient's individual anatomy is critical in skull base surgery. Trainees and experienced surgeons can benefit from surgical simulation; however, current models are expensive and impractical for widespread use. In this study, we report a next-generation mixed-reality surgical simulator. We segmented critical anatomic structures for 3-dimensional (3D) models to develop a modular teaching tool. We then developed a navigation tracking system utilizing a 3D-printed endoscope as a trackable virtual-reality (VR) controller and validated the accuracy on VR and 3D-printed skull models within 1 cm. We combined VR and augmented-reality visual cues with our 3D physical model to simulate sinus endoscopy and highlight segmented structures in real time. This report provides evidence that a mixed-reality simulator combining VR and 3D-printed models is feasible and may prove useful as an educational tool that is low cost and customizable.

Teaching frontal sinus anatomy using the frontal sinus masterclass 3- D conceptualization model

OBJECTIVE

Frontal sinus anatomy is complex and often is a difficult subject to both teach and learn. The traditional surgical dogma of "see one, do one, teach one" is impractical and dangerous in the frontal sinus. Based on the building block three-dimensional conceptualization module, the Frontal Sinus Masterclass (FSMC) was created to teach this anatomy.

METHODS

Study was performed at two academic centers among second- to fifth-year otolaryngology residents. A pretest assessed knowledge prior to the course. Computed tomography scans of the sinuses were evaluated in triplanar view, and participants attempted to reconstruct the anatomy. Subsequently, the course instructor explained the anatomy using the building block method and showed a short video of the surgical dissection, pointing out relevant anatomy. Cases progressed in anatomical difficulty and inflammatory load. A posttest determined knowledge after the course.

RESULTS

Thirty of 50 participating residents completed the pre- and posttests (14 junior, 16 senior residents). Correct identification of the frontal sinus drainage pathway increased from 42% to 63% correct (P = 0.054). Anatomical assessment increased from 61% to 68% correct (P = 0.047), and overall assessment increased from 52% to 66% correct (P = 0.016).

CONCLUSION

Objectively, participants of the FSMC expanded on their ability to recognize cells of the frontal recess on CT scans. Before the class, residents could answer less than half of the answers correctly, and by the end of the class they were answering over two-thirds of these complex questions correctly. Subjectively, participants reported benefit from the course and felt they would be better surgeons.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:1294-1298, 2018.

Analysis of the Agger nasi cell and frontal sinus ostium sizes using computed tomography of the paranasal sinuses

The Agger nasi cell (ANC) and the frontal sinus ostium (FO) are important structures that can influence the anatomy and physiology of the frontal recess. The aim of this study was to evaluate the presence and size of ANC and the FO and correlate them according to gender, race and among themselves.

Method

A prospective study with 40 patients who underwent CT of the paranasal sinuses with sagittal reconstruction. Measurements: ANC (APAN) anteroposterior diameter, ANC (CCAN) craniocaudal diameter, ANC (LLAN) side-to-side diameter, anteroposterior diameter of the FO (APFO) and side-to-side diameter of the FO (LLFO).

Results

Twenty-two patients were male and 18 females, mean age 33.7 years. Most patients were white (45%), followed by browns (32.5%), blacks (20%) and asians (2.5%). The ANC was present in 98.7% of patients. There was statistical difference for APAN on females and LLAN on females and on the total sample. There were no differences for all measurements regarding gender, as well as the race. ANC and FO measurements showed positive correlation, but poor or very poor.

Conclusion

The prevalence of ANC in our sample was high and did not show a statistically significant difference for most measurements. The correlation between measurements of ANC and the FO was poor or very poor.

Twenty-six-year experience treating frontal sinus fractures: a novel algorithm based on anatomical fracture pattern and failure of conventional techniques

BACKGROUND

Frontal sinus fracture treatment strategies lack statistical power. The authors propose statistically valid treatment protocols for frontal sinus fracture based on injury pattern, nasofrontal outflow tract injury, and complication(s).

METHODS

An institutional review board-approved retrospective review was conducted on frontal sinus fracture patients from 1979 to 2005. Fractures were categorized by location, displacement, comminution, and nasofrontal outflow tract injury. Demographic data, treatment, and complications were compiled.

RESULTS

One thousand ninety-seven frontal sinus fracture patients were identified; 87 died and 153 were excluded because of insufficient data, leaving a cohort of 857 patients. The most common injury was simultaneous displaced anteroposterior walls (38.4 percent). Nasofrontal outflow tract injury constituted the majority (70.7 percent), with 67 percent having a diagnosis of obstruction. Of the 857 patients, 504 (58.8 percent) underwent surgery, with a 10.4 percent complication rate; and 353 were observed, with a 3.1 percent complication rate. All complications except one involved nasofrontal outflow tract injury (98.5 percent). Nasofrontal outflow tract injuries with obstruction were best managed by obliteration or cranialization (complication rates: 9 and 10 percent, respectively). Fat obliteration and osteoneogenesis had the highest complication rates (22 and 42.9 percent, respectively). The authors' treatment algorithm provides a receiver operating characteristic area under the curve of 0.8621.

CONCLUSIONS

A frontal sinus fracture treatment algorithm is proposed and statistically validated. Nasofrontal outflow tract involvement with obstruction is best managed by obliteration or cranialization. Osteoneogenesis and fat obliteration are associated with unacceptable complication rates. Observation is safe when the nasofrontal outflow tract is intact.

Frontal recess anatomy study by endoscopic dissection in cadavers

INTRODUCTION AND AIMS

The frontal sinus ostium is frequently difficult to recognize because of anatomical structures that hide it. The objective of the present study was to identify and describe the frontal recess anatomy that impairs the endoscopic recognition of the frontal sinus ostium.

STUDY DESIGN AND METHODS

A prospective study was conducted by consecutive endoscopic dissections of 32 cadavers (59 sides), 10 (31.25%) females and 22 (68.75%) males. After resection of the lower portion of the uncinate process, with preservation of its upper insertion, we evaluated which anatomical structures needed to be removed for complete visualization of the frontal sinus ostium.

RESULTS AND CONCLUSIONS

Visualization of the frontal sinus ostium after resection of the lower portion of the uncinate process was possible in only 11 (18.64%) nasal cavities. The uncinate process (terminal recess) was the main anatomical structure that impaired the recognition of the frontal sinus ostium, present in 45 (76.27%) nasal cavities, followed by the ethmoid bulla (16.95%) and agger nasi cells (6.78%).

A computed tomographic guide to endoscopic sinus surgery: axial and coronal views

SUMMARY

The purpose of this article is to correlate endoscopic surgical procedures in the sinuses with computer tomographic (CT) scans. Twelve commonly performed procedures were color-coded on a set of normal coronal and axial CT scans. The illustrated procedures are uncinectomy/antrostomy, anterior ethmoidectomy, posterior ethmoidectomy, sphenoidotomy, partial inferior turbinectomy, partial middle turbinectomy, septoplasty, frontal recess approach, dacrocystorhinostomy, orbital decompression, optic nerve decompression, and medial maxillectomy. Drainage of a medial orbital abscess is discussed but not illustrated. A brief description of the indications, surgical approach, and complications of each procedure is also provided.

Clinically relevant frontal sinus anatomy and physiology

Management of frontal sinus disease has evolved considerably with the advent of endoscopic paranasal sinus instrumentation. With this evolution has come the increased demand for anatomic competence among otolaryngologists. Armed with a better understanding of the complex frontal sinus and anterior ethmoid complex anatomy, the otolaryngologist can target the anatomic abnormalities that predispose an individual to frontal sinus disease and limit the effectiveness of medical and surgical management.

History of surgical approaches to the frontal sinus

Despite the enormous number of external and endonasal surgical techniques described for the treatment of frontal sinus disease, a single time-proven technique has yet to be obtained. The purpose of this article is to critically evaluate the lessons of more than a century of endonasal and external procedures. The past has taught us a cautionary lesson for the surgical management of chronic frontal sinus disease, respect for the severity of iatrogenic disease caused by surgical trauma, and the need for long-term follow-up before embracing any new technique to treat this notoriously difficult clinical problem.

Transnasal endoscopic management of frontal mucoceles

Traditional teaching has emphasized the need for complete removal of sinus mucocele to achieve a cure. With the introduction of endoscopic sinus surgical instruments and techniques, however, there has been a trend toward transnasal endoscopic management of frontal mucoceles with recurrence rates at or close to 0%. This article presents a useful classification of frontal mucoceles and the transnasal endoscopic surgical technique.