Functional Endoscopic Sinus Surgery (FESS)

Background and Concept

Indications for Surgery

1. Acute Rhinosinusitis (ARS)

• Complications involving the orbit: sub-periosteal abscess, intra-orbital abscess
• Intracranial complications: epidural or subdural abscesses, meningitis, intracranial sinus thrombosis
• Pott's puffy tumour (frontal bone osteomyelitis)
• Key principle: When a complication is managed medically (e.g. meningitis), the ARS may also be managed medically. When a complication requires surgical management (e.g. orbital or intracranial abscess), simultaneous surgical drainage of the affected sinuses should be considered.

2. Chronic Rhinosinusitis (CRS) - Primary Indication

• CRSwNP - CRS with nasal polyps (requires bilateral nasal polyps for diagnosis)
• CRSsNP - CRS without nasal polyps

1. Primary care: topical steroids + nasal irrigation for at least 4 weeks
2. If diagnosis is clinically confirmed and maximal medical therapy has not improved symptoms, a CT scan is indicated
3. CT findings demonstrate residual disease amenable to surgery AND/OR anatomical risk factors
4. Then surgery is considered - but only after ruling out contraindications

• Patient factors: general cardiorespiratory health, anticoagulation treatment, social factors
• Facility factors: availability of appropriately trained personnel and acceptable equipment
• Economic factors: cost to the individual and healthcare system

• Natural history of the condition
• Risks and sequelae of surgical complications
• Potential for recurrent disease
• The usual need for ongoing medical management post-operatively
• Always the option of continuing non-surgical management

Principles of FESS

General Principles

1. Mandatory pre-operative CT imaging: Recent CT scans must be available to the surgeon throughout the entire operation - either on film (placed on a viewing box adjacent to the surgeon) or in electronic DICOM format on a monitor. Operating without intraoperative imaging access significantly increases the risk of complications due to the multiple anatomical nuances of each individual patient.
2. Image navigation: Intraoperative image navigation is available and used by some surgeons, but standard imaging should always be present as a backup in case of equipment failure or poor registration.
3. Eye preparation: The eyes are lubricated and either left open or taped (providing corneal protection). Corneal abrasions from FESS have resulted in medicolegal cases.

Anaesthesia Principles

• FESS can be performed under local or general anaesthetic; general anaesthetic is standard in Western countries
• Laryngeal mask is preferred over endotracheal intubation (unless risk of laryngeal soiling from reflux, obesity, etc.)
• Total intravenous anaesthesia (TIVA) with short-acting opiates (e.g. Remifentanil) is preferred by many; if used, bispectral index (BIS) monitoring is recommended to avoid awareness under anaesthesia
• Sevoflurane (at low concentration) + remifentanil provides a comparable surgical field without BIS monitoring
• Hypotensive anaesthesia is key to optimising the surgical field: target systolic MAP of ~90 mmHg with HR ~60 bpm
• Volatile agents that reduce systemic vascular resistance (SVR) can paradoxically worsen the surgical field via nasal microvasculature vasodilation

Surgical Position

Surgical Steps (Order of FESS Procedures)

Disease Subtypes and Their Influence on Surgery

• Eosinophilic CRS vs neutrophilic CRS - histological phenotyping now recognized to influence both pre- and post-operative medical management AND surgical approach
• CRSwNP - higher recurrence rates, more aggressive surgical clearance often needed, mandatory post-operative medical therapy
• Exacerbating factors requiring consideration: asthma, aspirin-exacerbated respiratory disease (AERD), cystic fibrosis, immunodeficiency

Post-operative Principles

• Surgery does not cure CRS - ongoing medical management is almost always required after FESS
• Recurrent disease is common, especially in CRSwNP
• Endoscopic surveillance post-operatively is standard to detect recurrence and guide topical therapy

Functional Endoscopic Sinus Surgery (FESS)

Indications and Principles

Conceptual Basis

Indications for Surgery

A. Absolute / Mandatory Indications

Key principle (Scott-Brown's): When a complication is managed medically (e.g. meningitis), the ARS itself may be managed medically. When a complication requires surgery (e.g. orbital abscess, Pott's puffy tumour), simultaneous surgical drainage of the affected sinuses should be considered.

B. Relative Indications

1. Chronic Rhinosinusitis (CRS) - Most Common Indication

• Topical nasal steroids + saline irrigation for at least 4 weeks by primary care
• If symptoms persist: ENT referral → clinical confirmation → maximal medical therapy
• If maximal medical therapy fails → CT scan to assess residual disease
• CT showing persistent inflammation after medical treatment → surgery indicated

• Surgery directed at relieving OMC obstruction, improving drainage and ventilation
• Goal: restore mucociliary function; surgery may be curative in some forms (e.g. odontogenic sinusitis)

• May not be primarily driven by OMC obstruction; often driven by eosinophilic inflammation
• Goal of surgery: remove polyps + associated debris/mucin, create wide passages for:
  • Sinus ventilation and drainage
  • Delivery of topical medical therapy (studies show virtually no penetration of topical agents into unoperated sinus cavities)
  • Office-based debridements
• Long-term maintenance medical therapy remains necessary despite surgery
• A complete ethmoidectomy is most critical
• Associated conditions: asthma, allergic fungal rhinosinusitis (AFRS), aspirin-exacerbated respiratory disease (Samter's triad)

2. Recurrent Acute Rhinosinusitis (RARS)

• Defined as 4 or more clinical episodes per year
• Disease must be confirmed by objective criterion (endoscopy or CT scan) while symptomatic before surgery
• Migraines and headache disorders must be excluded (can mimic RARS)

3. Antrochoanal Polyp

• Arises from maxillary antrum, extends to choana through posterior fontanelle
• Must be differentiated from neoplasm by imaging/biopsy
• Complete removal including the antral component prevents recurrence
• Traditional Caldwell-Luc mucosal stripping is not necessary

4. Mucoceles

• Epithelial-lined mucus-containing sacs that fill a sinus completely
• Expansile, cause bony erosion - must be drained/removed to prevent orbital or intracranial complications

C. Pre-surgical Decision Factors (Scott-Brown's)

1. Patient factors: Cardiorespiratory health, anticoagulation therapy, social/compliance factors
2. Facility factors: Trained personnel, availability of appropriate equipment
3. Economic factors: Cost to individual and healthcare system

• Natural history of the condition
• Risks and sequelae of surgical complications
• Potential for recurrent disease (especially CRSwNP)
• Need for ongoing medical management post-operatively
• Option of continuing non-surgical management

Principles of FESS

1. Mucosal Preservation

2. Restoration of Drainage and Ventilation

3. Mandatory Pre-operative CT Imaging

• Available throughout the entire operation (not just pre-operatively)
• Available in electronic DICOM format on a monitor adjacent to the surgeon, or as film on a viewing box
• Reviewed in all three planes: coronal (OMC), axial (posterior ethmoid + sphenoid), sagittal (frontal recess, skull base slope)
• Operating without intraoperative CT access significantly increases complication risk

Note: Incidental sinus opacification is found on up to 27% of sinus CT scans - CT findings must always be correlated with symptoms before proceeding to surgery. (Cummings)

4. Image Guidance Navigation

• Revision surgery
• Extensive disease near skull base or orbit
• However, standard CT images should always remain available as backup in case of equipment failure or poor registration

5. Anaesthesia Principles (Scott-Brown's)

• General anaesthesia is standard in most Western settings; FESS can be done under local anaesthesia
• Laryngeal mask airway (LMA) preferred over endotracheal intubation (unless risk of laryngeal soiling from reflux, obesity, etc.)
• Total intravenous anaesthesia (TIVA) with Remifentanil preferred by many surgeons; requires bispectral index (BIS) monitoring to prevent awareness
• Hypotensive anaesthesia is key to an optimal surgical field:
  • Target systolic MAP ~90 mmHg
  • Heart rate ~60 bpm
  • Volatile agents that reduce SVR can paradoxically worsen the field through nasal microvasculature vasodilation

6. Surgical Position

7. Eye Preparation

Surgical Steps (Standard FESS Sequence)

Post-operative Principles

• Surgery is adjunctive to medical therapy, not a cure
• Ongoing topical steroids + saline irrigation required after FESS
• Recurrent disease is common, especially in CRSwNP - requires endoscopic surveillance
• ESS enables delivery of topical therapy into sinus cavities that would otherwise have no penetration (Cummings)
• Delay in surgery for CRS may adversely impact sinonasal outcomes and asthma prevalence (Cummings, UK studies)