Ethmoidectomy and Sphenoidotomy

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Ethmoidectomy and Sphenoidotomy

Surgical Procedure
Rhinosinusitis
Rhinology
Author Credentials 

Zara M. Patel, MD
Assistant Professor
Director of Endoscopic Skull Base Surgery
Department of Otolaryngology – Head and Neck Surgery
Division of Rhinology and Endoscopic Skull Base Surgery
Stanford University
801 Welch Rd
2nd floor M/C 5739
Stanford, CA 94305-5739
zmpatel@stanford.edu

Garret W. Choby, MD
Clinical Instructor
Department of Otolaryngology – Head and Neck Surgery
Division of Rhinology and Endoscopic Skull Base Surgery
Stanford University
801 Welch Rd
2nd floor M/C 5739
Stanford, CA 94305-5739
chobygw@stanford.edu

Module Summary

Ethmoid and sphenoid sinus surgery can be simple and straightforward at times, but also complex and challenging, due to the close proximity to brain, orbit and important neurovascular structures. Both inflammatory and neoplastic conditions are commonly found in this region. In order to perform these surgeries safely, a thorough anatomic understanding is imperative to understand this complex region.

Module Learning Objectives 
  1. Explain the complexity of ethmoid and sphenoid sinus anatomy.
  2. Cite the rationale underlying surgical approaches to the ethmoid and sphenoid sinuses.
  3. Analyze the advantages and disadvantages of specific techniques for ethmoid and sphenoid sinus surgery.
  4. Recognize common errors in surgical technique.
  5. Describe complications of ethmoid and sphenoid sinus surgery.

Embryology

Learning Objectives 

Be familiar with the embryologic development of the ethmoid and sphenoid sinuses.

  1. Sequential development of the paranasal sinuses
    1. Maxillary
    2. Ethmoid
    3. Sphenoid
    4. Frontal
  2. Ethmoid and sphenoid sinus development are variable and may impact surgical approaches.
  3. Ethmoid sinus development tends to be complete in early adolescence, but sphenoid sinus development is usually not complete until late adolescence.
References 
  1. Patel ZM, Lin FY eds. ENT Board Prep High Yield Review for the Otolaryngology Inservice and Board Exams. Springer, New York, NY. 2013.
  2. Halewyck S, Louryan S, Van Der Veken P, Gordts F. Craniofacial embryology and postnatal development of relevant parts of the upper respiratory system. B-ENT. 2012. Suppl 19: 5-11.

Anatomy

Learning Objectives 

Understand the anatomic complexities of the ethmoid and sphenoid sinuses:

  1. Be familiar with the pneumatization pattern of the ethmoid air cells and structures which affect frontal, maxillary and sphenoid sinus drainage
    1. Agger nasi
    2. Ethmoid bulla
    3. Suprabullar cells
    4. Supra-agger cells
    5. Haller cells (infraorbital ethmoid cells)
    6. Onodi cells (cells pneumatizing superior and posterior to the sphenoid sinus)
    7. Uncinate process
  2. The pneumatization of the sphenoid sinus is frequently asymmetric
    1. Degree of pneumatization
    2. Understand the importance of the attachment point at the skull base of the septation dividing the sphenoid sinuses and its relation to carotid artery and optic nerve
  3. Understand the relationship of the ethmoid sinuses to the cribriform plate, the orbit and the anterior ethmoid artery
  4. Understand the relationship of the sphenoid and ethmoid sinuses to the posterior ethmoid artery
  5. Know the important anatomic structures running within the skull base that surround the sphenoid sinus
    1. Carotid artery
    2. Cavernous sinus and the cranial nerves within it (III, IV, V1, V2, VI)
    3. Optic nerve (CN II)
    4. V2 at foramen rotundum
    5. Vidian nerve and artery within vidian canal
  6. Anatomical classification and description of pneumatization patterns of the ethmoid cells with regard to the frontal sinus outflow path
    1. International frontal sinus anatomy and classification (IFAC)
References 
  1. Dalgorf DM, Harvey RJ. Chapter 1: Sinonasal anatomy and function. Am J Rhinol Allergy. 2013 May-Jun;27(Suppl 1):S3-6.
  2. Wormald PJ, Hosoeman W, Callejas C, et al. The international frontal sinus anatomy classification (IFAC) and classification of the extent of endoscopic frontal sinus surgery (EFSS). Int Forum Allergy Rhinol. 2016;6(7):677-96.

Pathogenesis

Learning Objectives 

Know the pathogenesis of chronic sphenoid and ethmoid sinusitis, as well as alternative indications for sphenoid and ethmoid sinus surgery:

  1. Acute sinusitis
    1. Prevention of secondary complications
  2. Chronic rhinosinusitis (CRS)
    1. Criteria for diagnosis
    2. Role of medical therapy
    3. Predisposing conditions
      1. Anatomic variables
        • Pneumatization pattern
        • Onodi cells
        • Mucocele
      2. Systemic disease
        • Immunodeficiency
        • Cystic fibrosis
    4. CRS without nasal polyposis (CRSsNP) vs CRS with nasal polyposis (CRSwNP)
  3. Alternative indications for sphenoid or ethmoid sinus surgery
    1. Neoplasm
      1. Benign
        • Inverted papilloma
        • Osteoma
        • Juvenile Nasopharyngeal Angiofibroma (JNA)
      2. Malignant
        • See full differential below under Pathology
    2. CSF leak
    3. Encephalocele
    4. Trauma
    5. Epistaxis
References 
  1. Orlandi RR, Kingdom TT, Hwang PH, et al. International consensus statement on allergy and rhinology: rhinosinusitis. Int Forum Allergy Rhinol. 2016;Suppl 1:S22-209.
  2. Scangas GA, Gudis DA, Kennedy DW. The natural history and clinical characteristics of paranasal sinus Mucocele: a clinical review. Int Forum Allergy Rhinol. 2013;3(9):712-7.
  3. Lund VJ, Howard DJ, Wei MI, et al. Craniofacial resection for tumours of the nasal cavity and paranasal sinuses a 17 year experience. Head Neck. 1998 Mar;20(2):97-105.

Basic Science

Learning Objectives 

Understand the basic physiologic principles underlying the pathogenesis of CRS:

  1. Microbiology and the microbiome
  2. Immune mechanisms
  3. Local development of chronic inflammation
  4. Mucosal epithelial barrier
  5. Mucociliary clearance
  6. Unified airway theory
  7. Genetic variability
References 
  1. Hulse KE. Immune mechanisms of chronic rhinosinusitis. Curr Allergy Asthma Rep. 2016;16(1):1.
  2. Orlandi RR, Kingdom TT, Hwang PH, et al. International consensus statement on allergy and rhinology: Rhinosinusitis. Int Forum Allergy Rhinol. 2016;Suppl 1:S22-209.
  3. Demirdag YY, Ramadan HH. Direct measurement of upper airway inflammation in children with chronic rhinosinusitis: implications for asthma. Curr Opin Allergy Clin Immunol. 2016;16(1):16-23.
  4. Cohen NA. The genetics of the bitter taste receptor T2R38 in upper airway innate immunity and implications for chronic rhinosinusitis. Laryngoscope. 2017 Jan;127(1):44-51.

Incidence

Learning Objectives 

Understand the frequency and healthcare impact of CRS

  1. True incidence of CRS remains unknown
  2. CRS has numerous direct and indirect costs to healthcare
    1. Diminished productivity
    2. Work days missed
    3. Reduced cognition and sleep quality
    4. Chronic fatigue
References 
  1. DeConde AS, Soler ZM. Chronic rhinosinusitis: epidemiology and burden of disease. Am J Rhinol Allergy. 2016;30(2):134-9.
  2. Rudmik L. Chronic rhinosinusitis: an under-researched epidemic. J Otolaryngol Head Neck Surg. 2015;5(44):11.

Genetics

Learning Objectives 

Understand that the role of genetics and immune dysregulation is becoming increasingly well understood in CRS:

  1. Defects in adaptive and innate immunity may play a role in the development of CRS
  2. Potential genetic links for the predisposition to refractory CRS are increasingly being studied
References 
  1. Halderman A, Lane AP. Genetic and immune dysregulation in chronic rhinosinusitis. Otolaryngol Clin North Am. 2017;50(1):13-28.

Patient Evaluation

Learning Objectives 

For each patient, recognize the symptoms, disease history, medical therapy and previous surgical therapy:

  1. Overall health
    1. Presence of underlying pulmonary disease
      1. Asthma
      2. Cystic fibrosis
      3. Bronchiectasis
    2. Other comorbidities
      1. Allergies
      2. Autoimmune disease
      3. Immunocompromised patients
      4. Diseases affecting ciliary function
      5. Anticoagulation status
  2. Validated symptom scores
    1. SNOT-22, RSDI
  3. Disease history
    1. Duration of symptoms
    2. Type of symptoms
    3. Previous and current medication history
      1. Symptom response to individual medications
  4. Previous surgery
  5. Imaging
  6. Alternative testing
    1. Olfaction evaluation
    2. Allergy testing
References 
  1. McCoul ED, Tabaee A. A practical approach to refractory chronic rhinosinusitis. Otolalryngol Clin North Am. 2017;50(1):183-98.
  2. Desrosiers M, Evans GA, Keith PK, et al. Canadian clinical practice guidelines for acute and chronic rhinosinusitis. J Otolaryngol Head Neck Surg. 2011;Suppl 2:S99-193.
  3. Orlandi RR, Kingdom TT, Hwang PH, et al. International consensus statement on allergy and rhinology: rhinosinusitis. Int Forum Allergy Rhinol. 2016;Suppl 1:S22-209.
  4. Rosenfeld RM, Piccirillo JF, Chandrasekhar SS, et al. Clinical practice guideline (update): Adult sinusitis. Otolaryngol Head Neck Surg. 2015;152:S1-S39.

Imaging

Learning Objectives 

Understand the critical role that imaging plays in understanding the distribution of disease and for surgical planning:

  1. CT scan
    1. Non-contrast CT scan is the only necessary imaging in most cases of sphenoid and ethmoid sinus surgery for CRS
      1. Should include axial, sagittal and coronal images
      2. Fine cuts preferred (2mm or less)
    2. Vitally important to evaluate extent of disease
    3. Helps to identify “danger zones” of surgery
      1. Slope of skull base
      2. Integrity of orbit and skull base
      3. Location of anterior ethmoid artery
      4. Relationship of ethmoid cells to cribriform plate
  2. MRI
    1. Useful in cases where surgery is planned for neoplasm
    2. Helps to differentiate soft tissue vs. intracranial contents vs. inspissated secretions
      1. Encephalocele
      2. CSF leak
References 
  1. Iida E, Anzai Y. Imaging of the Paranasal Sinuses and Anterior Skull Base and Relevant Anatomic Variations. Radiol Clin N Am. 2017 Jan;55(1):31-52.
  2. Sen S, Chandra A, Mukhopadhyay S, Ghosh P. Sinonasal tumors: Computed Tomography and MR Imaging Features. Neuroimag Clin N Am. 2015 Nov; 25:595-618.

Pathology

Learning Objectives 

Recognize the importance of pathology in various disease processes of the sphenoid and ethmoid sinuses:

  1. CRS
    1. CRSsNP vs. CRSwNP
      1. CRSwNP
        • Eosinophil vs. neutrophil predominance
    2. Allergic fungal sinusitis
      1. Charcot-Leyden crystals
      2. Allergic mucin
    3. Autoimmune disease
      1. Granulomatosis with polyangitis
      2. Sarcoidosis
  2. Neoplasm
    1. Benign
      1. Inverted papilloma
      2. Osteoma
      3. Hamartoma
      4. JNA
    2. Malignant
      1. Squamous cell carcinoma
      2. Lymphoma
      3. Mucosal melanoma
      4. Sinonasal undifferentiated carcinoma
      5. Salivary gland origin tumors
        • Adenocarcinoma
        • Adenoid cystic carcinoma
      6. Sarcoma
      7. Hemangiopericytoma
      8. Plasmacytoma
      9. Metastatic disease
        • Prostate
        • Thyroid
        • Breast
        • Lung
        • Renal cell carcinoma
References 
  1. Montone KT. Pathology of fungal rhinosinusitis: a review. Head Neck Pathol. 2016;10(1):40-6.
  2. Patel ZM, Lin FY eds. ENT Board Prep-High Yield Review for the Otolaryngology Inservice and Board Exams. Springer, New York, NY. 2013.

Medical Therapies

Learning Objectives 

Understand the importance of appropriate medical management in CRS:

  1. Antiinflammatory therapy
    1. Topical corticosteroids
    2. Systemic corticosteroids
  2. Saline irrigations
  3. Antihistamine therapy
    1. Topical antihistamines
    2. Systemic antihistamines
  4. Mucolytics
  5. Antimicrobial therapy
    1. Culture directed antibiotics
    2. Topical antibiotics
    3. Macrolide therapy
      1. Antibacterial and anti-inflammatory effects
  6. Other
    1. Aspirin exacerbated respiratory disease
      1. Aspirin desensitization
      2. Anti-leukotriene agents
    2. Cystic fibrosis
      1. Hypertonic saline
References 
  1. Chandra RK. Medical management of chronic rhinosinusitis. In: Thaler ER and Kennedy DW, Editors. Rhinosinusitis: a guide for diagnosis and management. New York, NY: Springer; 2008:75-92.
  2. McCoul ED, Tabaee A. A practical approach to refractory chronic rhinosinusitis. Otolalryngol Clin North Am. 2017;50(1):183-98.

Pharmacology

Learning Objectives 

Understand pharmacologic implications for commonly used medications to treat CRS:

  1. Corticosteroids (topical and systemic)
    1. Dosing
    2. Side effects
    3. Long-term implications
  2. Antimicrobial therapy
    1. Antibiotics
      1. Side effects
      2. Dosing
      3. Medication interactions
      4. Other considerations
        • Macrolide therapy: QT prolongation
    2. Antifungals
      1. Liver function testing
  3. Other therapies
    1. Antihistamines
    2. Leukotriene receptor antagonists
    3. 5-Lipooxygenase inhibitors
References 
  1. Simon RA, Dazy KM, Waldram JD. Aspirin-exacerbated respiratory disease: characteristics and management strategies. Expert Rev Clin Immunol. 2015;11(7): 805-17.
  2. Chandra RK. Medical management of chronic rhinosinusitis. In: Thaler ER and Kennedy DW, Editors. Rhinosinusitis: a guide for diagnosis and management. New York, NY: Springer; 2008:75-92.

Surgical Therapies

Learning Objectives 

Understand the options for approaching the ethmoid and sphenoid sinuses:

  1. Medial approach versus trans-ethmoidal approach to sphenoid sinus
    1. Consider possible stability issues of the middle turbinate
    2. Consider what other procedures would be included in a given surgery (are other sinuses going to opened anyway or not) and how that may affect your approach
  2. Posterior to anterior approach to clearing the skull base of ethmoid septations versus anterior to posterior approach
    1. Understand where the slope of the skull base is most consistent
      1. Understand where you can identify the anterior ethmoid artery most consistently
      2. Understand how to visualize the ethmoid cells in relation to the frontal sinus outflow path
References 
  1. Patel ZM, Govindaraj S. The prevention and management of complications in ethmoid sinus surgery. Otolaryngol Clin N Am. 2010 Aug;43(4):855-64.
  2. Moeller CW. Welch KC. Prevention and management of complications in sphenoidotomy. Otolaryngol Clin N Am. 2010 Aug;43(4):839-54.
  3. Patel ZM, Thamboo A, Rudmik L, Nayak JV, Smith TL, Hwang PH. Surgical therapy vs continued medical therapy for medically refractory chronic rhinosinusitis: a systematic review and meta-analysis. Int Forum Allergy Rhinol. 2017 Feb;7(2):119-127.
  4. http://www.american-rhinologic.org/videos (Surgical dissection videos on the ARS website, for members. ARS membership is FREE for residents.)

Case Studies

  1. 39yoM with intermittent pressure at the vertex of his head and behind his right eye for the last few years, no other sinonasal symptoms. He has undergone previous appropriate medical therapy. No previous sinus surgery. Endoscopy is normal. CT scan demonstrates opacified right sphenoid sinus with heterogeneity.
    1. What are your treatment options?
    2. If you recommend surgery, what surgical approach to the sphenoid sinus would be most appropriate?
  2. 66yoF with history of inverted papilloma within the left ethmoid cavity, who has undergone two previous surgeries for resection and resection of recurrence. She now again demonstrates recurrence on endoscopy, this time at the skull base. CT and MRI demonstrate tumor involving skull base, but it does not appear to invade dura.
    1. What are your options for management?
    2. What are the pro’s and con’s of your proposed procedures?

Complications

Learning Objectives 

Understand the various complications that can occur with these surgical techniques and principles of management of these complications:

  1. Bleeding
    1. Anterior ethmoid artery injury
    2. Posterior ethmoid artery injury
    3. Carotid artery injury
    4. Cavernous sinus bleeding
  2. Orbital complications
  3. CSF leak
  4. Unfavorable healing/scarring
    1. Mucocele formation
    2. Need for revision surgery
References 
  1. Patel ZM, Govindaraj S. The prevention and management of complications in ethmoid sinus surgery. Otolaryngol Clin N Am. 2010 Aug;43(4):855-64.
  2. Moeller CW. Welch KC. Prevention and management of complications in sphenoidotomy. Otolaryngol Clin N Am. 2010 Aug;43(4):839-54.
  3. Patel AB, Hoxworth JM, Lal D. Orbital Complications Associated with the Treatment of Chronic Rhinosinusitis. Otolaryngol. Clin. North Am. Oct 2015;48 (5);749-68.
  4. Gardner PA, Snyderman CH, Fernandez-Miranda JC, Jankowitz BT. Management of Major Vascular Injury During Endoscopic Endonasal Skull Base Surgery. Otolaryngol Clin North Am. 2016 Jun;49(3):819-28.

Review

Review Questions 
  1. What are the important anatomical structures surrounding the ethmoid and sphenoid sinuses?
  2. Describe the different approaches to the sphenoid sinus or ethmoid skull base and give examples of when they would be most useful.
  3. What are the most common pathologies affecting the ethmoid and sphenoid sinuses on a list of differential diagnosis along with CRS?
  4. What is the role of imaging in various pathologies affecting the sphenoid and ethmoid sinuses?
  5. What are the potential complications associated with ethmoid and sphenoid sinus surgery?
Resources 

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