IJHNS Frontal10.5005/jp-journals-10001-1257 Sinus Surgery: The State of the Art REVIEW ARTICLE Frontal Sinus Surgery: The State of the Art 1Michael J Marino, 2Edward D McCoul ABSTRACT classification, and instrumentation have been essential in pacing that evolution.1 There has been increased interest Aim: Review and describe the essential components of modern frontal sinus surgery. in rigorous outcomes assessments that are necessary for Background: Frontal sinus surgery has evolved considerably an evidence-based approach to frontal sinus surgery. State- over the last century, and advances in imaging, optics, and of-the-art frontal sinus surgery is the product of techno- instrumentation have contributed to contemporary treatment logical advancements and growing outcomes evidence. paradigms. Outcomes assessment has had an important role in This review addresses the elemental components of identifying indications for surgery and future areas of research. modern frontal sinus surgery. Included are a discussion of Review results: Numerous advancements are part of modern frontal sinus surgery and the treatment of frontal sinusitis. Ana­ the relevant anatomical considerations and contemporary tomic studies have revealed variations that are associated with indications for frontal sinus surgery. Open approaches disease and pose challenges for surgery. Open approaches to the frontal sinus are addressed and remain relevant remain relevant in situations of difficult disease or as part of in the endoscopic era. Nevertheless, advancements in combined approaches. Endoscopic surgery, however, is central to contemporary surgical management of frontal sinus disease. optics have propelled endoscopic approaches to the Evolving instrumentation and the development of new implan­ forefront, and are described in detail. Instrumentation table devices are increasingly relevant in the endoscopic era. and implantable devices serve as important adjuncts, Outcomes research has refined indications for surgery and identifies areas for ongoing research. and their application in modern frontal sinus surgery is considered. Outcome studies form the framework for Conclusion: State­of­the­art frontal sinus surgery is the pro­ duct of significant evolution and advancement. Modern surgery evidence-based treatment of frontal sinus disease and is reflective of improved optics and new instrumentation, and the identify areas for future research. central role of endoscopic approaches in treating frontal sinus disease. Outcomes research has been essential for developing FRONTAL SINUS ANATOMY an evidenced­based approach to frontal sinus surgery. Clinical significance: A review of the essential components The frontal sinus represents a complex anatomical region of state­of­the­art frontal sinus surgery for the practicing oto­ with wide variation between patients and sides.2 This has laryngologist. important consequences for frontal sinus disease, techni- Keywords: Chronic sinusitis, Draf procedure, Endoscopic sinus cal considerations during surgical dissection and potential surgery, Frontal sinus, Minimally-invasive surgery. complications. Preoperative evaluation of the radiographic How to cite this article: Marino MJ, McCoul ED. Frontal Sinus anatomy by computed tomography (CT) is an essential Surgery: The State of the Art. Int J Head Neck Surg 2016;7(1): 5-12. part of performing frontal sinus surgery. The location of the nasofrontal duct, also called the frontal recess or fron- Source of support: Nil tal outflow tract, can often be determined preoperatively Conflict of interest: None from the CT scan. Familiarity with common anatomic variations enhances interpretation of preoperative images INTRODUCTION and is helpful during frontal sinus dissection. Frontal sinus surgery has evolved considerably over The frontal sinus is thought to be the last paranasal the last century. Advances in imaging, optics, anatomic sinus to develop,3 and may represent superior and late- ral pneumatization of an anterior ethmoid cell.4 This may account for the significant variation in frontal sinus 1 2 Clinical Instructor, Associate Professor anatomy between patients and even between sides in the 1 Department of Otolaryngology-Head and Neck Surgery, Tulane same patient. Variation of the ethmoid sinuses also impact University School of Medicine, New Orleans, Louisiana, USA drainage and ventilation of the frontal sinus due to the 2Department of Otorhinolaryngology, Ochsner Clinic Foundation University of Queensland School of Medicine, Ochsner Clinical proximity of the ethmoid sinuses to the nasofrontal duct. School, New Orleans, Louisiana, USA These include variations, such as the agger nasi cell (pre- Corresponding Author: Edward D McCoul, Department of infundibular ethmoid cell) pneumatization, prominent Otolaryngology 1514 Jefferson Highway, CT-4, New Orleans ethmoid bullae and supraorbital cells. Louisiana, USA, Phone: (504)-842-4080, e-mail: emccoul@ Ethmoid air cells may be contained wholly within gmail.com the frontal recess or frontal sinus, and are termed frontal International Journal of Head and Neck Surgery, January-March 2016;7(1):5-12 5 Michael J Marino, Edward D McCoul cells (Fig. 1). Bent and Kuhn proposed a classification particularly as endoscopic approaches have become the scheme with 4 types of frontal cells.4 In a type I frontal standard for the treatment of frontal sinusitis. cell, a single air cell is located superior to the agger nasi cell, while in a type II frontal cell a tier of cells is located INDICATIONS FOR SURGERY within the frontal recess superior to the agger nasi cell. The indications for frontal sinus surgery are not, in prin- Both type I and II frontal cells are cephalad to the agger ciple, different from those for endoscopic sinus surgery. nasi cell, but remain inferior to the frontal sinus floor. A Surgery may be indicated for the treatment of chronic type III frontal cell represents a single large cell that has rhinosinusitis (CRS), cerebrospinal fluid leak, and benign pneumatized superiorly into the frontal sinus, and may and malignant tumors of the frontal sinuses. Defining be anterior or posterior to the frontal sinus outflow tract. indications for the surgical treatment of CRS can be Finally, a type IV cell is a single, isolated air cell contained complex. Surgery typically follows maximal medical entirely within the frontal sinus. Type IV frontal cells therapy, but a consensus as to what this entails has not may be difficult to appreciate on CT due to thin walls been established. Nevertheless, maximal medical therapy and surrounding inflammatory mucosa. is often considered to include intranasal steroids, nasal Frontal cells occur as an anatomic variant in a substan- saline irrigations, and oral antibiotics, with oral steroids tial minority of patients. An analysis of 768 coronal CT used in cases of polypoid disease. Failure of medical scans indicated the overall prevalence of frontal cells was therapy warrants CT imaging and surgical evaluation. 20.4%.5 Type I frontal cells were present more frequently Maximal medical therapy also prepares the operative (14.9%) than type II (3.1%), type III (1.7%), or type IV cells field for surgery, which is especially important in the (2.1%). Frontal sinus hyperpneumatization, in general, frontal sinus where the anatomy can be challenging.2 was associated with the presence of frontal cells, while Of particular importance when considering indica- hypopneumatization was negatively associated with tions for frontal sinus surgery is selecting the appropriate these variations (Fig. 2). In the original classification of procedure. The majority of primary procedures for CRS frontal cells, these variations were described as treatable can be addressed by a limited endoscopic sinusotomy causes of frontal sinus obstruction with associated case (Draf 1 or 2A). More challenging is identifying indications reports.4 The study by Meyer et al, found a statistically for extended approaches (Draf 2B and 3). These procedures significant increase in maxillary, ethmoid, and frontal will be detailed in a subsequent section. Failed prior sinus mucosal thickening in the presence of type III and IV frontal sinus surgery is the most common indication for frontal cells.5 an extended endoscopic approach. Neo-osteogenesis and Frontal sinus anatomy is highly variable. This includes lateralized middle turbinate are also potential indications variation of the pneumatization within the frontal sinus for extended approaches, and are often seen with failed itself and of the surrounding anterior ethmoid cells. prior frontal sinus surgery. Pre sence of a mucocele may These variations have been described as causes of frontal also necessitate an extended endoscopic approach. Anom- sinus obstruction and resultant frontal sinus disease. Fur- alous frontal sinus anatomy, including type III and IV thermore these variations can pose surgical challenges, frontal cells, can also be an indication for extended Fig. 1: Sagittal CT showing a large anterior ethmoid cell Fig. 2: Coronal CT showing a hyperpneumatized frontal sinus with pneumatizing into the frontal sinus lumen multiple frontal cells (types 3 and 4) within the lumen. The sinuses are completely opacified due to polyposis 6 IJHNS Frontal Sinus Surgery: The State of the Art approaches. Conversely, narrow anterior-posterior dimen- During cranialization a pericranial flap can be raised sion at the nasofrontal beak may be a relative contraindica- and sutured in continuity with the dura.8 Direct external