Functional endoscopic sinus surgery

Functional endoscopic sinus surgery (FESS) is a type of paranasal sinus surgery performed intranasally using a rigid endoscope. Its primary objective is to restore physiological ventilation and mucociliary transport ¹.

Paranasal sinus imaging is crucial in preoperative planning and is also increasingly being used intraoperatively (image-guided surgical navigation) to help prevent complications and guide the surgeon.

Indications

Indications for endoscopic sinus surgery include:

• chronic or recurrent sinusitis despite appropriate medical treatment or previous surgical treatment
• sinonasal polyposis and antrochoanal polyps
• paranasal sinus mucoceles
• cerebrospinal fluid (CSF) leak closure
• choanal atresia repair
• foreign body removal
• epistaxis control

Certain ophthalmic procedures can also be carried out via endoscopic approach, including:

• orbital decompression (e.g. thyroid-associated orbitopathy)
• optic nerve decompression
• dacryocystorhinostomy

Contraindications

Endoscopy cannot satisfactorily correct certain conditions; in such cases, an open technique is used. These include:

• orbital abscess
• Pott puffy tumor
• certain sinonasal diseases and conditions, after failed endoscopic attempts (see e.g. Caldwell-Luc operation)

Radiographic features

CT

CT is the modality of choice for sinonasal surgery planning. A presurgical CT scan is now mandatory before every endoscopic sinus operation, in the interest of minimizing potential complications (see below).

An axial CT scan (1.5 mm slices or thinner) with coronal and sagittal reformations (3 mm slices or thinner) is performed for delineating both sinonasal anatomy and disease extent.

Anatomy 

Particular attention should be given to the following structures and anatomic variants, as failure to do so may result in serious complications ^3-5:

• ethmoid roof / cribriform plate dehiscence and asymmetry, skull base angle
• lamina papyracea dehiscence
• carotid canal dehiscence
• relationship of the optic nerve to air cells
• position of the anterior ethmoidal artery
• uncinate process attachments and relationships
• middle turbinate variants and attachments
• presence of infraorbital (Haller) and sphenoethmoidal (Onodi) air cells
• frontal recess configuration

Pathology

The Lund-Mackay score ⁶ is widely used for the radiologic staging of chronic rhinosinusitis.

Of note, CT cannot reliably differentiate between desiccated secretions and allergic fungal sinusitis (AFS), since both are hyperattenuating.

Technique

Endoscopic sinus surgery technique is based on the anterior-to-posterior approach of Messerklinger ⁹ and the posterior-to-anterior approach of Wigand for ethmoidectomy completion. In practice, most surgeons use a combination of both.

In summary, the procedure consists of the following steps ⁷, implemented as dictated by the patient's anatomy and extent and severity of disease:

• the patient is positioned, with their head to the right and the examiner on the patient's right
• diagnostic nasal endoscopy is performed with 30° rigid nasal endoscopes ⁸
  • a three-pass technique is used: the telescope is advanced along the nasal floor, toward the nasopharynx, and between the middle and inferior nasal conchae
• topical anesthetics are injected; general anesthesia is best used for the pediatric or anxious patient and for long procedures
• medialisation of the middle concha to expose the ostiomeatal complex
• uncinectomy: performed with a 0° endoscope
• maxillary antrostomy
• removal of the ethmoid bulla
• removal of the inferomedial part of the vertical middle concha basal lamella for entering the posterior ethmoidal sinus
• ethmoidectomy; it is important to stay low, so as not to breach the skull base
• identification of sphenoid face and posterior skull base
• skull base clearance posterior-to-anterior, with ethmoidal partition removal
• sphenoid sinusotomy / sphenoidotomy
• frontal sinusotomy; frontal work reserved for last, lest bleeding from frontal intervention obscures the sinonasal anatomy
• medialisation of the middle nasal concha and/or middle meatal spacer placement

Complications

In general, patient outcomes are excellent ² and complication rates are very low, especially in the hands of experienced surgeons.

Major complications

The rate of major complications is less than 0.5%. These include ¹⁰:

• internal carotid artery (ICA) injury
• skull base penetration with resultant intracranial hemorrhage, skull base fracture or cerebrospinal fluid leak
• blindness, either due to optic nerve injury or failure to promptly treat orbital hematoma
• massive epistaxis
• meningitis

Minor complications

• adhesions (synechiae)
• minor epistaxis
• nasolacrimal duct obstruction; treated with dacryocystorhinostomy
• anosmia or hyposmia; virtually all cases resolve

Failed FESS

Failed FESS consists of recurring symptoms following the procedure. It is most often due to recurrent disease, anatomical variants or incomplete surgery ^12,13

• middle turbinate lateralization: seen in ~30-78% of failed FESS
• incomplete surgery, including:
  • anterior or posterior ethmoidectomy (~31-74% of failed FESS)
  • uncinectomy (~37% of failed FESS)
  • retained agger nasi cell (~13-49% of failed FESS)
  • Onodi cell misidentified as the sphenoid sinus
• recurrent sinusitis: most often involves the frontal sinus and is due to persisting obstruction or postoperative scarring of the frontal sinus outflow tract

See also

• functional endoscopic sinus surgery variants (mnemonic)