The Frontal Sinus: Surgical Approaches and Controversies

The Frontal Sinus: Surgical Approaches and Controversies
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Tittle Page
Copyright
Dedication
Foreword
Foreword
Preface
Acknowledgments
Contributors
Contents
Videos
Section I Anatomy of the Frontal Sinus and Frontal
	1 Developmental Bases of the Anatomy of the Frontal Sinus
		1.1 Introduction
		1.2 Frontal Sinuses and Ethmoid Lateral Masses have Different Evolutionary and Developmental Origins
			1.2.1 The Ethmoid Develops from the Olfactory Cartilaginous Capsule
			1.2.2 The Frontal Sinuses Pneumatize after Erythropoietic Bone Marrow Conversion into Fatty Marrow
		1.3 The Nitric Oxide “Story” of the Paranasal Sinuses Makes them Playa Role in Blood Oxygenation on Demand
		1.4 Pneumosinus Dilatans and Arrested Pneumatization Could Bear Witness to Sinus Development
			1.4.1 Pneumosinus Dilatans
			1.4.2 Arrested Pneumatization
		1.5 Conclusion
	2 Radiological Anatomy
		2.1 Introduction
		2.2 Lamina Papyracea
		2.3 Uncinate Process
		2.4 Floor of Olfactory Recess
		2.5 Agger Nasi Air Cell
		2.6 Accessory Air Cells
		2.7 Anterior Ethmoidal Artery
		2.8 Bulla Ethmoidalis
		2.9 Middle Turbinate
		2.10 Conclusion
	3 Applied Surgical Anatomy
		3.1 General Considerations
		3.2 Applied Anatomy for Endonasal Approaches
		3.3 Applied Anatomy for External Approaches
			3.3.1 Coronal Approach
			3.3.2 Transpalpebral Approach
		3.4 Blood Supply
		3.5 Innervation
		3.6 Anatomical Variations and Surgical Considerations
		3.7 Conclusions
Section II Endoscopic Surgical Approaches to Frontal Sinus Disease
	4 Draf Frontal Sinusotomy I and IIa
		4.1 Indications
		4.2 Surgical Steps
		4.3 Tips and Tricks
		4.4 Case Examples
		4.5 Complications Management
		4.6 Conclusion
	5 Draf Frontal Sinusotomy IIb
		5.1 Indications
		5.2 Anatomy
		5.3 Surgical Steps
			5.3.1 Lateral Approach
			5.3.2 Median Approach
		5.4 Tips and Tricks
		5.5 Complications
	6 Extended Draf IIb and Other Modifications of the Lothrop Procedure
		6.1 Introduction
		6.2 Indications
		6.3 Surgical Steps
			6.3.1 Overview of Standard Draf IIb
		6.4 Modifications of the Standard Draf IIb Procedure
			6.4.1 Modified Hemi-Lothrop Procedure (Eloy IIC)
			6.4.2 Modified Mini-Lothrop Procedure (Eloy IID)
			6.4.3 Modified Subtotal-Lothrop Procedure (Eloy IIE)
			6.4.4 Modified Central-Lothrop Procedure (Eloy IIF)
		6.5 Tips and Tricks
		6.6 Case Examples
			6.6.1 Example 1
			6.6.2 Example 2
			6.6.3 Example 3
		6.7 Complications
			6.7.1 Recurrence and Chronic Scarring
			6.7.2 Cerebrospinal Fluid Leak
			6.7.3 Orbital Injury
			6.7.4 Anterior Ethmoid Artery Injury
	7 The Frontal Sinus Rescue Procedure
		7.1 Indications
		7.2 Surgical Steps
			7.2.1 Step 1
			7.2.2 Step 2
			7.2.3 Step 3
			7.2.4 Step 4
		7.3 Reverse Frontal Rescue Procedure
		7.4 Complications
		7.5 Tips and Tricks
		7.6 Conclusion
	8 Draf III (Endoscopic Modified Lothrop)— Inside-Out and Outside-In Approaches
		8.1 Indications
			8.1.1 Relative Contraindications
		8.2 Surgical Steps
		8.3 Lateral-to-Medial/Inside-Out Technique
		8.4 Outside-In/Medial-to-Lateral Technique
		8.5 Tips and Tricks
		8.6 Case Examples
			8.6.1 A Case of Allergic Fungal Rhinosinusitis with Fronto-orbital Mucocele
			8.6.2 A Case of Chronic Frontal Sinusitis with a High Posterior Frontal (Type 3) Cell
			8.6.3 A Case of Chronic Frontal Sinusitis—Riedel’s Procedure Reversal
		8.7 Postoperative Management
		8.8 Complications and their Management
			8.8.1 Skull Base Injury and Cerebrospinal Fluid Leak
			8.8.2 Hemorrhage
			8.8.3 Orbital Injury
			8.8.4 Skin Injury
			8.8.5 Stenosis of the Frontal Sinus Neo-ostium
	9 Transseptal Approach
		9.1 Background and CT Review
		9.2 Indications and Contraindications
		9.3 Advantages
		9.4 Disadvantages
		9.5 Surgical Steps
		9.6 Tips and Tricks
			9.6.1 Case Example
		9.7 Complications
	10 Endoscopic Endonasal Orbital Transposition for Lateral Frontal Sinus Lesions
		10.1 Indications
		10.2 Surgical Steps
		10.3 Tips and Tricks
		10.4 Case Example
		10.5 Complications
	11 The Role of Frontal Sinus in Anterior Skull Base Surgery and the Transcribriform Approach
		11.1 Indications
		11.2 Surgical Steps
		11.3 Tips and Tricks
		11.4 Complications
	12 Extended Endonasal Anterior Skull Base Approaches
		12.1 Indications
		12.2 Surgical Steps
			12.2.1 Principles
			12.2.2 Operative Setup
			12.2.3 Surgical Technique
			12.2.4 Reconstruction
			12.2.5 Postoperative Considerations
		12.3 Tips and Tricks
		12.4 Case Examples
			12.4.1 Esthesioneuroblastoma (Transcribriform Approach)
			12.4.2 Tuberculum Sellae Meningioma: Endoscopic Transtuberculum/Transplanum Approach
		12.5 Complications and Management
			12.5.1 Vascular Complications
			12.5.2 Cranial Nerve Injury
			12.5.3 Cerebrospinal Fluid Fistulas
			12.5.4 Postoperative Infection
			12.5.5 Other Complications
	13 Revision Endoscopic Frontal Sinus Surgery
		13.1 Introduction
		13.2 Indications
			13.2.1 Ongoing Mucosal Disease
			13.2.2 Incomplete Dissection
			13.2.3 Lateralization of the Middle Turbinate
			13.2.4 Scarring and Synechiae
			13.2.5 Neo-Osteogenesis
		13.3 Patient Selection
		13.4 Preoperative Planning
			13.4.1 Analyzing the Computed Tomography Imaging
			13.4.2 Computer-Assisted Navigation during Surgery
			13.4.3 Endoscopes and Equipment
		13.5 Choice of Procedure
		13.6 Surgical Steps
			13.6.1 The Axillary Flap Technique
			13.6.2 Frontal Sinus Mini-Trephine
		13.7 Specific Scenarios
			13.7.1 Retained Cells in the Frontal Recess or Extending into the Frontal Sinus (Draf I or International Classification of Extent of Endoscopic Frontal Sinus Surgery Grades 1–3)
			13.7.2 A Narrow Frontal Ostium and/or Extensive Supra Agger/Bulla Frontal Cells, or Ongoing Significant Burden of Disease (CRSwNP, Aspirin-Sensitive Asthma, Allergic Fungal Disease [Draf III/EFSS 6])
		13.8 Tips and Tricks
		13.9 Case Example
		13.10 Complications: Management
			13.10.1 Scarring and Restenosis
			13.10.2 Anterior Ethmoid Artery
			13.10.3 Orbital Injury
			13.10.4 Cerebrospinal Fluid Leak
	14 Complications of Frontal Sinus Surgery
		14.1 Introduction
		14.2 Epidemiology and Etiology
		14.3 Specific Complications of Endoscopic Approaches to the Frontal Sinus
			14.3.1 Failure to Accomplish the Specific Aim of the Procedure
			14.3.2 Pain
			14.3.3 Bleeding
			14.3.4 Infection
			14.3.5 Scar/Stenosis
			14.3.6 Mucocele Formation
			14.3.7 Anterior Skull Base Injury/Cerebrospinal Fluid Leak
			14.3.8 Orbital Injury
		14.4 Prevention of Complications
			14.4.1 Preoperative Planning
			14.4.2 Perioperative Technique
			14.4.3 Postoperative Care
	15 Delivery of Topical Therapy to the Frontal Sinus
		15.1 Introduction
		15.2 Basic Science Research on Topical Distribution to the Sinuses
		15.3 Clinical Research on Topical Distribution to the Sinuses
			15.3.1 Tips and Tricks
		15.4 Conclusion
	16 Postoperative Management: Dressings and Toilet
		16.1 Natural History of Sinus Ostia after Surgery
		16.2 Intranasal Packing
			16.2.1 Nonabsorbable Packs
			16.2.2 Absorbable Packings
		16.3 To Pack or Not to Pack
		16.4 Inert Stents
		16.5 Drug-Eluting Stents
		16.6 Postoperative Care
			16.6.1 Saline Irrigations
			16.6.2 Endoscopic Debridement
			16.6.3 Topical Treatments
		16.7 Conclusion
	17 Office-Based Frontal Sinus Procedures
		17.1 Indications
			17.1.1 Anatomic Considerations
			17.1.2 Patient Selection
			17.1.3 Frontal Sinusitis
			17.1.4 Frontal Mucoceles
			17.1.5 Nasal Polyps
		17.2 Surgical Steps/Anesthesia
		17.3 Postoperative Management and Procedures
			17.3.1 Nasal Irrigations and Topical Therapies
		17.4 Tips and Tricks
			17.4.1 Case Examples
		17.5 Controversies
			17.5.1 Balloon Catheter Dilation
		17.6 Emerging Technologies
		17.7 Conclusion
Section III Open Surgical Approaches to Frontal Sinus Disease
	18 Mini- and Maxi-Trephines
		18.1 Indications
		18.2 Surgical Steps
		18.3 Tips and Tricks
		18.4 Case Example
		18.5 Complications
	19 Osteoplastic Flap Approach with and without Obliteration
		19.1 Indications
		19.2 Surgical Steps
			19.2.1 Osteoplastic Flap without Obliteration
			19.2.2 Osteoplastic Flap with Obliteration
		19.3 Tips and Tricks
		19.4 Complications: Management
		19.5 Conclusion
	20 Riedel’s Procedure and Cranialization of the Frontal Sinus
		20.1 Riedel’s Procedure
			20.1.1 Historic Perspective
			20.1.2 Indications
			20.1.3 Technique
		20.2 Cranialization of the FrontalSinus
			20.2.1 Historic Perspective
			20.2.2 Indications
			20.2.3 Technique
Section IV Management of Specific Frontal Sinus Conditions
	21 Frontal Sinus Barosinusitis
		21.1 Epidemiology and Etiology
		21.2 Clinical Presentation and Investigations
		21.3 Management
		21.4 Case Example (Courtesy of Christos Georgalas)
	22 Frontal Sinus in Patients with Cystic Fibrosis
		22.1 Epidemiology and Etiology
		22.2 Clinical Presentation and Investigations
			22.2.1 Radiographic Abnormalities in Cystic Fibrosis and the Frontal Sinus
		22.3 Management
			22.3.1 Medical Therapy
			22.3.2 Nasal Saline Irrigations
			22.3.3 Corticosteroids
			22.3.4 Topical Antibiotics
			22.3.5 Oral Antibiotics
			22.3.6 Dornase Alfa
			22.3.7 Cystic Fibrosis Transmembrane Conductance Regulator modulators
			22.3.8 Surgical Therapy
			22.3.9 Endoscopic Approaches
		22.4 Complications: Management
	23 Pneumosinus Dilatans
		23.1 Introduction
		23.2 Epidemiology and Etiology
		23.3 Clinical Presentation and Investigations
		23.4 Diagnosis
		23.5 Management
		23.6 Complications
		23.7 Conclusion
	24 Frontal Sinusitis in Chronic Rhinosinusitis without Nasal Polyposis
		24.1 Introduction
		24.2 Epidemiology
		24.3 Pathophysiology
			24.3.1 Anatomic Factors
			24.3.2 Physiological Factors
		24.4 Management
			24.4.1 Medical Management
			24.4.2 Surgical Management
		24.5 Conclusion
	25 Frontal Sinus Surgery in CRSwNP, AFRS, and ASA Triad
		25.1 Epidemiology and Etiology
			25.1.1 Chronic Rhinosinusitis with Nasal Polyps
			25.1.2 Aspirin-Exacerbated Respiratory Disease
			25.1.3 Allergic Fungal Sinusitis
		25.2 Clinical Presentation and Investigations
			25.2.1 Chronic Rhinosinusitis with Nasal Polyps
			25.2.2 Aspirin-Exacerbated Respiratory Disease
			25.2.3 Allergic Fungal Sinusitis
		25.3 Management Overview
			25.3.1 Chronic Rhinosinusitis with Nasal Polyps
			25.3.2 Aspirin-Exacerbated Respiratory Disease
			25.3.3 Allergic Fungal Sinusitis
		25.4 Extent of Surgery and Outcomes
			25.4.1 Goals of Surgery
			25.4.2 Effect of Extent of Surgery on Outcomes for Maxillary and Ethmoid Sinuses
			25.4.3 Effect of Extent of Surgery on Outcomes for the Frontal Sinus
		25.5 Case Examples
			25.5.1 Samter’s Triad Successfully Managed with Draf IIa
			25.5.2 Samter’s Triad Only Controlled after Draf III
			25.5.3 Nasal Polyp Recurrence in Frontal Ostium Managed in the Office
			25.5.4 Allergic Fungal Sinusitis Presenting with Proptosis
		25.6 Complications
	26 Frontal Sinus Mucoceles
		26.1 Terminology
		26.2 Epidemiology
		26.3 Pathology
		26.4 Clinical Presentation
		26.5 Investigations
		26.6 Classification
		26.7 Management
		26.8 Outcomes
		26.9 Conclusion
	27 Frontoethmoidal Osteomas
		27.1 Epidemiology and Etiology
		27.2 Histology
		27.3 Clinical Presentation and Investigations
		27.4 Management
		27.5 Approaches for Frontoethmoidal Osteomas
			27.5.1 External Approaches
			27.5.2 Endoscopic Approaches
		27.6 Summary
		27.7 Case Examples
			27.7.1 Case 1
			27.7.2 Case 2
			27.7.3 Case 3
			27.7.4 Case 4
	28 Frontal Inverted Papilloma
		28.1 Epidemiology and Etiology
		28.2 Clinical Presentation and Investigations
		28.3 Management
		28.4 Case Examples
			28.4.1 Case 1
			28.4.2 Case 2
			28.4.3 Case 3
		28.5 Complications: Management
	29 The Frontal Sinus: Fibro-Osseous Lesions
		29.1 Fibrous Dysplasia
			29.1.1 Epidemiology and Etiology
			29.1.2 Clinical Presentation and Investigations
			29.1.3 Management
		29.2 Ossifying Fibroma
			29.2.1 Epidemiology and Etiology
			29.2.2 Clinical Presentation and Investigations
			29.2.3 Management
			29.2.4 Surgical Steps
			29.2.5 Consent
		29.3 Summary
	30 Malignant Disease Involving the Frontal Sinus
		30.1 Epidemiology and Etiology
		30.2 Clinical Presentation and Investigation
		30.3 Staging
		30.4 Management
		30.5 Case Example
		30.6 Complications: Management
		30.7 Tips and Tricks
	31 Acute Frontal Osteomyelitis: Intracranial and Orbital Complications
		31.1 Epidemiology and Etiology
			31.1.1 Epidemiology
			31.1.2 Etiology
		31.2 Clinical Presentation and Investigations
			31.2.1 Orbital Complications
			31.2.2 Intracranial Complications
			31.2.3 Osseous Complications
			31.2.4 Investigations
		31.3 Management
			31.3.1 Frontal Sinus Drainage Techniques
			31.3.2 Management of Orbital Complications
			31.3.3 Management of Intracranial Complications
			31.3.4 Management of Osseous Complications
		31.4 Case Examples
			31.4.1 Case 1: Subperiosteal Abscess (Contrast-Enhanced CT)
			31.4.2 Case 2: Orbital Abscess (Magnetic Resonance Imaging)
			31.4.3 Case 3: Cerebral Abscess (Magnetic Resonance Imaging)
			31.4.4 Case 4: Epidural Abscess (Contrast-Enhanced CT)
			31.4.5 Case 5: Subdural Abscess (Contrast-Enhanced CT)
			31.4.6 Case 6: Pott’s Puffy Tumor
	32 Fungal Frontal Sinusitis: Allergic and Nonallergic
		32.1 Introduction
		32.2 Epidemiology and Etiology
			32.2.1 Invasive
			32.2.2 Noninvasive
		32.3 Clinical Presentation and Investigations
			32.3.1 Invasive
			32.3.2 Noninvasive
			32.3.3 Special Considerations in Frontal Sinus Fungal Disease
		32.4 Management
			32.4.1 Medical Management
			32.4.2 Surgical and Postoperative Management in the Frontal Sinus
			32.4.3 Complications: Management
		32.5 Conclusion
	33 Frontal Sinus Trauma and Its Management
		33.1 Epidemiology and Etiology
			33.1.1 Anatomy
			33.1.2 Trauma Mechanism
		33.2 Clinical Presentation and Investigations
			33.2.1 Initial Examination of the Patient
			33.2.2 Imaging and Paraclinical Investigations
		33.3 Management
			33.3.1 Surgical Techniques
			33.3.2 Surgical Decision-Making
		33.4 Case Example
		33.5 Complications: Management
	34 Cerebrospinal Fluid Leak in the Frontal Sinus: Endoscopic Management
		34.1 Epidemiology and Etiology
			34.1.1 Etiologies
		34.2 Clinical Presentation and Investigations
		34.3 Management
			34.3.1 Surgical Management
			34.3.2 Endoscopic versus Open Repair
			34.3.3 Postprocedural Care
			34.3.4 Postprocedural Adjuvants
			34.3.5 Outcomes
		34.4 Case Examples
		34.5 Complications: Management
		34.6 Conclusion
Section V Controversial Topics in Current Practice
	35 The Use of Flaps in Frontal Sinus Surgery
		35.1 Published Evidence
			35.1.1 Background
			35.1.2 Rationale for Flaps
			35.1.3 Literature Review and Surgical Techniques
		35.2 Controversies and Opinions
			35.2.1 Promising Outcome for Flaps
			35.2.2 Recommendation for Future Studies
			35.2.3 Flaps Feasibility
			35.2.4 Illustrative Cases
		35.3 Surgical Tips
		35.4 Unanswered Questions
	36 Osteitis and the Frontal Sinus
		36.1 Introduction
		36.2 Epidemiology and Etiology
			36.2.1 Definitions
			36.2.2 Histology: Pathophysiology
			36.2.3 Allergy
			36.2.4 Bacteriology
			36.2.5 Biofilms
			36.2.6 Incidence
		36.3 Clinical Presentation and Investigations
			36.3.1 Radiological Features
			36.3.2 Clinical Implications
			36.3.3 Prognostic Factor
		36.4 Management
		36.5 Case Example
		36.6 Summary
		36.7 Key Points
	37 Extreme Lateral Lesions: What Is the Limit of Endoscopic Surgery?
		37.1 Published Evidence
			37.1.1 Traditional External Approaches for Far Lateral Lesions
			37.1.2 Endonasal Endoscopic Surgery and Evolution of Lateral Disease Management
			37.1.3 Evolution of Far Lateral Frontal Sinus Surgery: Exploring Limits of ESS
		37.2 Controversies and Opinions
		37.3 Unanswered Questions
	38 Use of Image Guidance Technology: Mandatory or Not
		38.1 Introduction
			38.1.1 Indications
			38.1.2 Applications
		38.2 Published Evidence
			38.2.1 Complications
			38.2.2 Revision Rate
			38.2.3 Clinical and Quality-of-Life Outcomes
			38.2.4 Medicolegal Concerns
			38.2.5 Cost
		38.3 Controversies and Opinions
			38.3.1 Indications
			38.3.2 Surgical Training
			38.3.3 Future Use
		38.4 Unanswered Questions
	39 Balloon Technology in the Frontal Sinus: Useful or Gimmick
		39.1 Published Evidence
			39.1.1 Level 1 Evidence
			39.1.2 Nonrandomized Studies
		39.2 Controversies and Opinions
			39.2.1 Diffuse versus Localized CRS
			39.2.2 Polyp Disease
			39.2.3 Miscellaneous Uses
			39.2.4 Contraindications
			39.2.5 Preoperative Preparation
			39.2.6 Training Requirements
			39.2.7 Complications
		39.3 Unanswered Questions
			39.3.1 Cost-Effectiveness
			39.3.2 Extrapolation to Wider Patient Cohort
	40 Minimum versus Maximal Surgical Sinusotomy
		40.1 Published Evidence
			40.1.1 Balloon Dilation
			40.1.2 Draf I
			40.1.3 Draf IIa
			40.1.4 Draf IIb
			40.1.5 Draf III
		40.2 Controversies and Opinions
		40.3 Case Studies
			40.3.1 Case 1
			40.3.2 Case 2
			40.3.3 Case 3
		40.4 Unanswered Questions
	41 Patient-Reported Outcome Measures and Outcomes in Frontal Sinus Surgery: Do They Make a Difference?
		41.1 Published Evidence
			41.1.1 Patient-Reported Outcome Measures in Rhinology
			41.1.2 Patient-Reported Outcome Measures in Frontal Sinus Treatment
		41.2 Controversies and Opinions
		41.3 Unanswered Questions
	42 Symptoms of Frontal Sinus Disease: Where Is the Evidence?
		42.1 Published Evidence
		42.2 Controversies and Opinions
		42.3 Case Examples
			42.3.1 Case 1
			42.3.2 Case 2
			42.3.3 Case 3
			42.3.4 Case 4
			42.3.5 Case 5
		42.4 Unanswered Questions
	43 Anatomy and Classification of Frontoethmoidal Cells
		43.1 Introduction
		43.2 Published Evidence
		43.3 Controversies and Opinions
	44 To Drill or Not to Drill
		44.1 Published Evidence
		44.2 Indications for Drilling Approaches of the Frontal Sinus
		44.3 Results of Drilling Approaches of the Frontal Sinus
		44.4 Complications
		44.5 Controversies and Opinions
		44.6 Unanswered Questions
	45 Indications for Operating the Frontal Sinus: Primary Surgery or Always Second Line?
		45.1 Introduction
		45.2 Controversies and Opinions
			45.2.1 Does OMC/Frontal Recess Obstruction Cause Frontal CRS?
			45.2.2 Is Anterior Ethmoidectomy (Draf I) Optimal as First-Line Surgery for Frontal CRS?
			45.2.3 What Are the Clinical Characteristics of Patients Who Fail Draf I?
			45.2.4 Why Is Draf I not Successful in Some Patients with Frontal CRS?
			45.2.5 Is Primary Draf IIa Effective as an Initial Surgical Intervention for Frontal CRS?
		45.3 Case Studies
			45.3.1 Case 1: Mild Diffuse CRSwNP Involving the Frontal Sinus
			45.3.2 Case 2: Failed Draf I Procedure Requiring at least Draf IIa—Ciliary Dysfunction?
			45.3.3 Case 3: Severe CRSwNP Requiring EMLP as Initial Surgical Intervention
			45.3.4 Case 4: Odontogenic Frontal CRS
		45.4 Unanswered Questions
	46 Economic and Quality-of-Life Evaluation of Surgery and Medical Treatment for Chronic Rhinosinusitis
		46.1 Published Evidence
			46.1.1 What is Known about the Economic Burden of Chronic Rhinosinusitis
			46.1.2 What Are the Wider Costs of CRS?
			46.1.3 What Is the Impact of CRS on QOL?
			46.1.4 Cost and Cost-Effectiveness of Treatment for CRS
		46.2 Controversies Surrounding the Cost-Effectiveness of Treatment for CRS
		46.3 Unanswered Questions and Future Research
	47 Training Models and Techniques in Frontal Sinus Surgery
		47.1 Introduction
		47.2 Published Evidence
		47.3 Controversies and Opinions
		47.4 Unanswered Questions
	48 Augmented Reality in Frontal Sinus Surgery
		48.1 Role of Augmented Reality in Preoperative Planning
		48.2 Role of Augmented Reality during Surgery
	49 Robotic Surgery: Beyond DaVinci
		49.1 Published Evidence
			49.1.1 Shortcomings of DaVinci
		49.2 Steering at Greater Simplicity
		49.3 Steering at Reduced Dimensions
		49.4 Controversies and Opinions
			49.4.1 Maneuvering beyond DaVinci
		49.5 Maneuvering Like a Snake
		49.6 Future Steps toward Clinical Practice
		49.7 Unanswered Questions
	50 Pathophysiology of the Failed Frontal Sinus and Its Implications for Medical Management
		50.1 Introduction
		50.2 Failure due to Errors in Patient Selection
		50.3 Local Causes of Recalcitrant Frontal Sinus Disease
		50.4 Systemic Causes of Recalcitrant Frontal Sinus Disease
		50.5 Conclusion
Index
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