Frontal sinus cells: identification, prevalence, and association with frontal sinus mucosal thickening

Does Frontal Recess Cell Variation Associate with the Development of Frontal Sinusitis? A Narrative Review

Chronic rhinosinusitis (CRS) can have a significant impact on quality of life. With persistent symptoms and the failure of initial medical treatments, surgical management is indicated. Despite the excellent results of endoscopic sinus surgery for persistent CRS, it is quite a challenging procedure for frontal sinusitis given the complex anatomy and location of the frontal sinus. Frontal recess cells significantly contribute to the complexity of the frontal sinus, and numerous studies have sought to establish their association with sinusitis. This review offers a comprehensive understanding of frontal recess cells, their different classifications, their prevalence among different populations, and their relationship to sinusitis. After an extensive review of the current literature, the International Frontal Sinus Anatomy Classification (IFAC) is the most recent classification method and a preferred practical preoperative assessment tool. Although the agger nasi cell is the most prevalent cell among all reported populations, ethnic variations are still influencing the other cells' distribution. Studies are inconsistent in reporting a relationship between frontal recess cells and sinusitis, and that is mainly because of the differences in the classification methods used. More research using a standardized classification method is needed to understand the association between frontal recess cells and sinusitis.

Normal and Variant Sinonasal Anatomy

The anatomy of the paranasal sinuses is complex with multiple anatomic variants that can predispose patients to disease. Knowledge of this complex anatomy is important not only for successful treatment but to also avoid complications at the time of surgery. This article will review the anatomy with emphasis on a variety of clinically important anatomic variants.

Is There Any Racial Difference in Term of Anatomical Variations of Nasal and Paranasal Sinus Structures

The aim of our study was to determine the anatomical variations detected on computed tomography radiological imaging of the paranasal sinus between citizens and refugees patient groups and to reveal the differences between the two patient groups. In this study, the data from the files of 38 Turkish Citizens (Group 1), 41 Syrian Refugees (Group 2), a total of 79 patients who were admitted to the ENT Clinic of Adana City Training and Research Hospital due to rhinological complaints between 01.01.2019 and 01.01.2020 and had paranasal sinus tomography, were analyzed retrospectively. Due to the Syrian Civil War that started in 2011, more than 10 million Syrian have left their countries and immigrated to neighboring countries as refugees. The paranasal sinus area has a wide variety of variations. Congenital anomalies and normal anatomical variations in this area are important, although rarely, as they may have pathological consequences or may be a source of difficulty during surgery. In the study, 38 of 79 patients were in Group 1 (48.1%) and 41 were in Group 2 (51.9%). Of the patients, 30 were female (38%) and 49 were male (62%). The ages of the patients ranged from 9 to 78 years, with a mean age of 32.52 years. In our study, we could not find a statistically significant difference between Turkish Citizens and Syrian refugees in terms of anatomical variations detected on paranasal radiological imaging. We consider the number of patients in our study as a limitation of our study and we think that it is important to conduct studies with larger populations.

Anatomical Variations of the Sinonasal Area and their Clinical Impact on Sinus Pathology: A Systematic Review

Introduction  Anatomical variations of the nasal cavity and of the paranasal sinuses are frequently encountered and play an important role in dysfunctional drainage of sinuses. However, it is not clear in the literature whether they predispose to sinus pathology.

Objectives  The aim of the present review is to summarize the understanding of the association between anatomical variations of the sinonasal area and sinus pathology.

Data Synthesis  The present review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We performed a thorough research on PubMed from October 2004 until May 2020 by using the search terms paranasal sinus anatomical variations and sinus disease , sinusitis , and mucosal disease .

Thirty studies were eligible and were included in the analysis. Overall, the studies encompassed a total of 6,999 patients included in the present review. In many studies, it has been statistically established that certain anatomical variations increase the risk of sinus disease. On the other hand, the rest of the collected studies failed to show any statistically significant correlation between anatomical variants and sinus pathology.

Conclusion  The present study highlights the possible correlation between some anatomical variations of the sinonasal area and pathologies of the paranasal sinuses. Careful assessment and computed tomography (CT) in patients with chronic rhinosinusitis is needed, especially in those undergoing endoscopic surgery, to identify and treat anatomical variations in the paranasal sinuses that may be correlated with rhinosinusitis. Due to contradictory results in the literature, further research is needed to elucidate the effects of anatomical variants of the sinonasal area.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Anatomical Variations of the Nasal Cavities and Paranasal Sinuses: A Systematic Review

The anatomy of the nasal cavities and paranasal sinuses is one of the most varied in the human body. The aim of this study is to review the prevalence of anatomical variations in the sinonasal area. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We performed on PubMed a literature search from October 2004 until May 2020. The search strategy included the following keywords: ('paranasal sinus' OR 'frontal sinus' OR 'maxillary sinus' AND ('anatomical variants' OR 'anomalies')). Fifty studies were eligible and included in the analysis. Overall, the studies encompassed a total of 18,118 patients included in this review. Most common anatomical variations include agger nasi cells, nasal septum deviation and concha bullosa. Other variations seen in this region are uncinate process variations, paradoxical middle turbinate, Haller, Onodi and supraorbital ethmoid cells, accessory ostia of maxillary sinus. Less common variations include any sinus aplasia, crista galli pneumatization and dehiscence of the optic or maxillary nerve, internal carotid artery and lamina papyracea. Anatomical variations of this region also differ among ethnic groups. This study highlights the amount, variability and significance of most anatomical variants reported in the literature in the last years. It is essential for the sinus surgeon to have a broad spectrum of knowledge not only of "the typical" anatomy but also all the possible anatomical variations. With modern imaging modalities, anatomical variations can be detected, and uneventful pitfalls might be prevented.

Computed tomographic analysis of the prevalence of International Frontal Sinus Anatomy Classification cells and their association with frontal sinusitis

OBJECTIVES

To determine the radiological prevalence of frontal cells according to the International Frontal Sinus Anatomy Classification in patients undergoing computed tomography of the paranasal sinuses for clinical symptoms of chronic rhinosinusitis, and to examine the association between cell classification and frontal sinusitis development.

METHODS

A total of 180 (left and right) sides of 90 patients were analysed. The prevalence of each International Frontal Sinus Anatomy Classification cell was assessed. Logistic regression analysis was used to compare the distribution of various cells in patients with and without frontal sinusitis.

RESULTS

The agger nasi cell was the most commonly occurring cell, seen in 95.5 per cent of patients. The prevalence rates for supra agger cells, supra agger frontal cells, supra bullar frontal cells, supra bullar cells, supra-orbital ethmoid cells and frontal septal cells were 33.3 per cent, 22.2 per cent, 21.1 per cent, 36.1 per cent, 39.4 per cent and 21.1 per cent, respectively. There was no significant difference in the occurrence of any of the cell types in patients with frontal sinusitis compared to those without (p > 0.05).

CONCLUSION

The presence of any of the International Frontal Sinus Anatomy Classification cells was not significantly associated with frontal sinusitis.

Three-dimensional computed tomography analysis of frontoethmoidal cells: A critical evaluation of the International Frontal Sinus Anatomy Classification (IFAC)

OBJECTIVES

Two major classifications of frontoethmoidal cells, Lee and Kuhn and the IFAC (International Frontal Sinus Anatomy Classification), distinguish anterior, posterior and medial cells. The European anatomical position paper includes also lateral cells. According to the IFAC, anterior cells push the frontal sinus drainage pathway (FSDP) medially, posteriorly or posteromedially. Posterior cells push the FSDP anteriorly. The only medial cell, pushing the FSDP laterally is the frontal septal cell, which is attached to or located in the interfrontal sinus septum. The aim of this study was to verify the IFAC and characterise cells, which are inconsistent with this classification.

DESIGN

A radioanatomic analysis.

SETTING

Tertiary university hospital.

PARTICIPANTS

One hundred and three Caucasian adult patients with no inflammatory changes in paranasal sinuses CT.

MAIN OUTCOMES MEASURE

Results of assessment of multiplanar reconstruction of thin slice CT.

RESULTS

Two types of cells that cannot be classified using the IFAC were found: (a) Lateral cells extending between the skull base and the anterior buttress, pushing the FSDP anteromedially or medially, present in 34 (16.5%) of the sides, (b) Paramedian cells: medially based, not adjacent to the interfrontal septum, pushing the FSDP laterally and posteriorly, present in 33 (16%) of sides. Suprabulla cells and suprabulla frontal cells were found to push the FSDP in directions other than anterior 28% and 31% of the time respectively.

CONCLUSIONS

Neglecting lateral and paramedian cells may lead to inconsistent results between radioanatomical studies and impede communication between surgeons. They should be included in existing classifications of frontoethmoidal cells.

A Radiological Study Assessing the Prevalence of Frontal Recess Cells and the Most Common Frontal Sinus Drainage Pathways

BACKGROUND

To date, there are numerous studies documenting the prevalence of frontal recess cells, but only 1 study using the newly developed International Frontal Sinus Anatomical Classification (IFAC) system. The identification of the frontal cells and their influence on the frontal drainage pathway plays an important role in endoscopic frontal sinus surgery.

OBJECTIVE

The aim of this study is to document the radiological prevalence of various types of frontal cells, as classified by IFAC and the most common frontal sinus drainage pathways based on its anatomic relationships with these cells.

METHODS

Using a novel preoperative virtual planning software (Scopis Building Blocks), consecutive computerized tomography scans of the sinuses of patients were analyzed for the prevalence of frontal cells, as classified by the by IFAC, and the frontal sinus drainage pathways at the Ear Nose Throat Hospital of Ho Chi Minh City, Vietnam.

RESULTS

In this study, 208 computed tomography scans of consecutively selected frontal sinuses of 114 patients were included for analysis. The agger nasi cell was present in 95.7% of reviewed scans. The frontal cells prevalence was as follows: supra agger cell (SAC): 16.3%, supra agger frontal cell (SAFC): 13%, supra bulla cell (SBC): 46.2%, supra bulla frontal cell (SBFC): 4.3%, supra orbital ethmoid cell: 17.3%, and frontal septal cell: 10.6%. The most common frontal sinus pathway type in relation to frontal cells was medial to SAC (70.6%), medial to SAFC (81.5%), anterior to SBC (88.5%), and anterior to SBFC (100%). In cases that had 2 frontal cells group, the drainage pathway was medial to SAC/SAFC and anterior to SBC/SBFC in most cases.

CONCLUSION

This study documents the prevalence of frontal cells (classified by IFAC) using a novel preoperative virtual planning software in the Vietnamese population. It demonstrates predominantly medial anteromedial frontal drainage pathways as related to these frontal cells.

International assessment of inter- and intrarater reliability of the International Frontal Sinus Anatomy Classification system

BACKGROUND

Inconsistencies in the nomenclature of structures of the frontal sinus have impeded the development of a validated "reference standard" classification system that surgeons can reliably agree upon. The International Frontal Sinus Anatomy Classification (IFAC) system was developed as a consensus document, based on expert opinion, attempting to address this issue. The purposes of this study are to: establish the reliability of the IFAC as a tool for classifying cells in the frontal recess among an international group of rhinologists; and improve communication and teaching of frontal endoscopic sinus surgery (ESS).

METHODS

Forty-two computed tomography (CT) scans, each with a marked frontal cell, were reviewed by 15 international fellowship-trained rhinologists. Each marked cell was classified into 1 of 7 categories described in the IFAC, on 2 occasions separated by 2 weeks. Inter- and intrarater reliability were evaluated using Light's kappa (κ), the interclass correlation coefficient (ICC), and simple proportion of agreement.

RESULTS

Interrater reliability showed pairwise κ values ranging from 0.7248 to 1.0, with a mean of 0.9162 (SD, 0.0537). The ICC was 0.98. Intrarater reliability showed κ values ranging from 0.8613 to 1.0, with a mean of 0.9407 (SD, 0.0376). The within-rater ICC was 0.98.

CONCLUSION

Among a diverse sample of rhinologists (raters), there was substantial to almost perfect agreement between raters, and among individual raters at different timepoints. The IFAC is a reliable tool for classification of cells in the frontal sinus. Further outcome studies are still needed to determine the validity of the IFAC.

Fronto-septal rostrum: prevalence, classification and clinical implications

OBJECTIVE

To describe a newly observed frontal sinus anatomical variant, the fronto-septal rostrum.

METHODS

Consecutive sinus computed tomography scans performed during 2013 were reviewed. The fronto-septal rostrum was defined as a mucosa-lined air space formed in the attachment of the most upper bony nasal septum and the central floor of the frontal sinuses.

RESULTS

The study included 400 computed tomography scans from 189 women (47.3 per cent) and 211 men (52.8 per cent), with a mean age of 46.8 years. A fronto-septal rostrum was observed in 122 patients (30.5 per cent), with a mean length of 10.63 mm, width of 4.52 mm, height of 2.18 mm and volume of 63.52 mm3. There was no statistically significant difference related to gender (p = 0.343), and no association between the side of the fronto-septal rostrum and age (p = 0.811) or volume (p = 0.203).

CONCLUSION

The newly described fronto-septal rostrum has possible clinical and surgical implications. It is suggested that this aerated space is used in specific surgical indications and its presence evaluated in cases of septal infection.

Computed tomography analysis of frontal cell prevalence according to the International Frontal Sinus Anatomy Classification

BACKGROUND

The International Frontal Sinus Anatomy Classification (IFAC) is an international consensus document published in 2016 to standardize the nomenclature of cells in the region of the frontal recess and frontal sinus. The IFAC was designed to be surgically relevant and anatomically precise. The current study was undertaken to assess the prevalence of the frontal cell variants as defined by the IFAC, as well as to determine the interrater reliability of the IFAC.

METHODS

Three independent reviewers examined triplanar nondiseased maxillofacial computed tomography (CT) scans to assess the anatomy of the frontal recess according to the IFAC system. The prevalence of each cell type was assessed and interrater reliability was measured using an intraclass correlation coefficient (ICC).

RESULTS

One hundred CT scans (200 sides) were examined. Of the 200 sides, 96.5% contained an agger nasi cell (ICC, 0.82; 95% confidence interval [CI], 0.77-0.86), 30.0% contained a supra agger cell (ICC, 0.89; 95% CI, 0.86-0.92), 20.0% contained a supra agger frontal cell (ICC 0.80; 95% CI 0.74-0.84), 72.0% contained a supra bulla cell (ICC, 0.81; 95% CI, 0.76-0.85), 5.5% contained a supra bulla frontal cell (ICC, 0.71; 95% CI, 0.63-0.77), 28.5% contained a supraorbital ethmoid cell (ICC, 0.78; 95% CI, 0.72-0.83), and 30.0% contained a frontal septal cell (ICC, 0.80; 95% CI, 0.74-0.84). The ICC was good to excellent for identification of all frontal cell types.

CONCLUSIONS

This study describes the normative distribution of frontal recess cells in a nondiseased population according to IFAC and demonstrates favorable interrater reliability of the classification system.

Computed Tomographic Analysis: The Effects of Frontal Recess Morphology and the Presence of Anatomical Variations on Frontal Sinus Pneumatization

The aim of this study is to describe the morphology of frontal recess area with its anatomical variations and to reveal if frontal recess morphology and the anatomical variations related to that region have effects on the pneumatization of the frontal sinuses. The frontal sinus and recess morphometry of 136 sides of 68 dry skulls were evaluated on multislice high-resolution computed tomography. The relationships between frontal sinus and frontal recess measurements were analyzed by correlation and linear regression analysis. The variables between the groups of anatomical variations were analyzed by Mann-Whitney U test and χ test or Fisher exact test. A positive relationship between the sagittal length of spina nasalis interna and morphometric measurements of frontal sinus was revealed (P <0.05). Agger nasi cells were present in 64.2% of sides, supraorbital ethmoid cells (SOECs) in 19.6%, type 3 frontal cells (FCs) in 18.9%, suprabullar cells in 24.3%, and frontal bulla was noted in 5.4%. Intersinus septal cells were observed in 16.2% of the skulls. There were statistically different increases in the measurements of frontal sinus morphometry in the presences of SOECs and type 3 FCs (P <0.05). The diameter of frontal sinus ostium was decreased in the presences of AN, SOEC, type 3 FC, and supraorbital ethmoid cell statistically (P = 0.049, P = 0.029, P = 0.043, P <0.001 respectively). In conclusion, frontal sinus pneumatization was affected by the spina nasalis interna and the presence of anatomical variations related to frontal recess or ostium region instead of the morphology of that area.

Computed tomographic analysis of frontal recess cells in pediatric patients

OBJECTIVE

To describe the prevalence of frontoethmoid cells and superior uncinate process attachment in pediatric patients with sinonasal symptoms.

METHOD

Fifty high-resolution computed tomographies of the paranasal sinuses for pediatric patients were evaluated for the presence of frontoethmoid cells and uncinate process insertion. The computed tomographies were randomly collected for patients with sinonasal symptoms (age range, 4-15 years) at our clinic. The prevalence of these cells was compared against age group and type of uncinate process.

RESULTS

The prevalence of each structure was agger nasi cell (97%), type 1 frontal cell (39%), type 2 frontal cell (27%), type 3 frontal cell (11%), type 4 frontal cell (1%), supraorbital ethmoid cell (38%), suprabullar cell (57%), frontal bullar cell (9%), and interfrontal septal cell (16%). When excluding the agger nasi cell, 48 patients (96%) had at least one type of frontoethmoid cell and 43 (86%) had at least one frontal cell. The frequency of these cells did not significantly differ based on sex or uncinate process insertion, but it did with age. Lamina papyracea was the most common site of superior uncinate process attachment.

CONCLUSION

Our results indicated a high frequency of frontoethmoid cells in the pediatric age group. The prevalence of these variations changes during childhood development. As in adults, lamina papyracea is the most common site of superior uncinate process attachment. Recognition of these variations in the frontal recess can provide useful information for safe and efficient endoscopic dissection in the frontal recess region.

Anatomic Considerations in Frontal Sinus Surgery

Comprehension of the complex anatomic variants comprising the frontal sinus outflow tract is essential for successful surgical intervention. Deviation from sound technique increases the potential for a variety of deleterious sequelae, including recurrent disease as well as catastrophic intracranial and orbital injury. Furthermore, incomplete removal of elements occluding the frontal recess can result in severe stenosis that can increase the difficulty of further interventions. This review covers anatomic considerations that should be kept in mind when performing frontal sinus surgery.

Anatomic variants of the paranasal sinuses in patients with recurrent acute rhinosinusitis

BACKGROUND

The incidence and potential disease impact of paranasal sinus anatomic variants in patients with recurrent acute rhinosinusitis (RARS) has important implications for management, including surgery, but is incompletely defined.

METHODS

A retrospective review of 26 patients with RARS who had undergone computed tomography (CT) was performed. Patient demographics, RARS severity and comorbidities were reviewed. CT scans were reviewed for the incidence of anatomic variants in all patients. The pattern of inflammatory changes was explored in the subset of patients with acute rhinosinusitis at the time of CT. Potential correlation between the presence of anatomic variants and disease severity were investigated.

RESULTS

In the patient cohort who met inclusion criteria, the most common variants included agger nasi cell (88.5%), concha bullosa (53.8%), infraorbital cell (50%), and deviated nasal septum with middle meatus obstruction (42%). In exploring correlations with RARS severity, type 2 frontal cells correlated with a greater number of years with RARS (0.0363). In the 23 patients who underwent CT at the time of an acute infection, no statistically significant correlation was found between severity or location of inflammatory changes and the presence of anatomic variants.

CONCLUSION

This study describes the incidence of anatomic variants in a cohort of patients with RARS. A correlation between the presence of anatomic variants and the pattern of inflammatory changes was not identified.

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.

Evaluation of sinus computed tomography scans: a collaborative approach between radiology and otolaryngology

PURPOSE OF REVIEW

Sinus computed tomography (CT) interpretation is subject to individual variation. We propose a template-driven approach as a method to ensure CT interpretation that is complete and efficient.

RECENT FINDINGS

Recent years have seen the description of newly noted anatomic abnormalities in the paranasal sinuses that should be noted during sinus CT interpretation.

SUMMARY

There exists significant variation in the methodology by which sinus CT scans are interpreted and the findings are reported. We believe that it will benefit radiologists and otolaryngologists alike to use a simple, template-driven approach to describe the findings encountered on a sinus CT. In this study, we present one such approach.